1. Basic provisions of the theory of chemical structure A.M. Butlerova
1. Atoms in molecules are connected to each other in a certain sequence according to their valences. The sequence of interatomic bonds in the molecule is called its chemical structure and is reflected in one structural formula (structure formula).
2. The chemical structure can be installed by chemical methods. (Currently used modern physical methods).
3. The properties of substances depend on their chemical structure.
4. According to the properties of this substance, it is possible to determine the structure of its molecule, and on the structure of the molecule - to foresee properties.
5. Atoms and groups of atoms in the molecule have a mutual influence on each other.
The organic compound molecule is a combination of atoms associated in a certain order, as a rule, covalent bonds. In this case, the associated atoms may vary by electronegability. Electric negativeness values \u200b\u200blargely determine such essential communication characteristics as polarity and strength (Education Energy). In turn, the polarity and strength of bonds in the molecule, to a large extent, determine the possibilities of the molecule to enter into certain chemical reactions.
Electricity of carbon atom depends on the state of its hybridization. This is due to the fraction of the S-orbital in the hybrid orbital: it is less in SP3- and more in SP2 and SP-hybrid atoms.
All components of the molecule atoms are in relationships and experience mutual influence. This effect is transmitted mainly through a system of covalent bonds, with the help of so-called electronic effects.
Electronic effects refer to the displacement of electron density in the molecule under the influence of substituents.
Atoms associated with polar bonds are partial charges denoted by the Greek letter "Delta" (D). Atom, "delaying" electronic density of S-communication in its direction, acquires a negative charge D-. When considering a pair of atoms associated with a covalent bond, a more electronegative atom is called an electron-coceptor. His partner for S-Communication will respectively will have an equal deficit of electronic density, i.e. A partial positive D + charge will be called an electronone.
The displacement of the electronic density according to the S-links circuit is called inductive effect and is indicated by I.
2. Isomeria - The existence of compounds (mainly organic) is the same by elemental composition and molecular weight, but different in physical and chemical properties. Such compounds are called isomers.
Structural isomeria - The result of differences in the chemical structure. To this type include:
The isomerism of the carbon skeleton, due to various orders of communication of carbon atoms. The simplest example is butane CH3-CH2-CH2-CH3 and isobutane (CH3) 3CH. Other examples: anthracene and phenantrene (formula I and II, respectively), cyclobutane and methylcyclopropane (III and IV).
Valentine isomeria is a special type of structural isomerism, in which the isomers can be translated into each other only due to the redistribution of links. For example, benzene valence isomers (V) are bicyclohexa-2,5-diode (VI, "Benzole Dewar"), the probe (VII, Benzole Ladenburg), benzvalen (VIII).
The isomerism of the functional group - differs in the nature of the functional group; For example, ethanol (CH3-CH2-OH) and dimethyl ether (CH3-O-CH3).
Isomerius of the situation- type of structural isomerism, characterized by the difference in the position of the same functional groups or double ties with the same carbon skeleton. Example: 2-chlorobutaneic acid and 4-chlorobutaneic acid.
Enantiomers (optical isomers, mirror isomers) are pairs of optical antipodes - substances characterized by opposite on the sign and the same by the rotations of the plane of the polarization of light when identity of all other physical and chemical properties (with the exception of reactions with others. Optically active substances and physical properties in chiral Medium). The necessary and sufficient cause of optical antipodes is the affiliation of the molecule to one of the following point symmetry groups: CN, DN, T, O or I (chirality). Most often we are talking about an asymmetric carbon atom, that is, about the atom associated with four different substituents.
3. sP³ hybridization -It occurs when mixing one S- and three P-orbitals. Four identical orbitals arise, located relative to each other under the tetrahedral angles of 109 ° 28 '(109.47 °), length 0.154 nm.
For carbon atom and other elements of the 2nd period, this process occurs according to the scheme:
2S + 2PX + 2PY + 2PZ \u003d 4 (2SP3)
Alkana(saturated hydrocarbons, paraffins, aliphatic compounds) - acyclic hydrocarbons of linear or branched structure containing only simple bonds and forming a homologous series with a general formula CNH2N + 2 . Chemical structure alkin(The order of compounds of atoms in molecules) of the simplest alkanes - methane, ethane and propane - show their structural formulas, shown in Section 2. From these formulas it is clear that there are two types of chemical ties in alkanes:
C-C and Sn. Communication C-C is a covalent non-polar. Communication C - H is a covalent weaklyolar, because Carbon and hydrogen are close by electronegativity
Not participating in hybridization P-orbital located perpendicular to the plane Σ-ties, Used to form π-bond with other atoms. Such carbon geometry is characteristic of graphite, phenol, etc.
Valenny corner - angle formed by the directions of chemical bonds emanating from one atom. Knowledge of valence angles is necessary to determine the geometry of molecules. Valence angles depend on the individual characteristics of the attached atoms and on the hybridization of atomic orbitals of the central atom. For simple molecules, the valence angle, as well as other geometric parameters of the molecule, can be calculated by the methods of quantum chemistry. They are experimentally determined from the values \u200b\u200bof the moments of inertia of molecules obtained by analyzing their rotational spectra (see infrared spectroscopy, molecular spectra, microwave spectroscopy). The valence angle of complex molecules is determined by the methods of diffraction structural analysis.
4. SP2 hybridization (flat trigonal) One S- and two P-orbitals are mixed, and three equivalent SP2-hybrid orbitals are formed, located in the same plane at an angle of 120 ° (highlighted in blue). They can form three σ-bonds. The third p-orbital remains non-mentioned and oriented perpendicular to the plane of the location of hybrid orbitals. This R-AO participates in the formation of π-communication . For the elements of the 2nd period, the SP2 hybridization process occurs according to the scheme:
2s + 2px + 2py \u003d 3 (2SP2)
The second valence state of the carbon atom. There are organic substances in which carbon atom is not associated with four, but with three neighboring atoms, while remaining quadricular
5. SP-hybridization (linear) One S- and one p-orbital is mixed, forming two equivalent SP orbitals located at an angle of 180, i.e. on one axis. Hybrid SP-orbitals participate in the formation of two σ-links. Two p-orbitals are not hybridized and are located in mutually perpendicular planes. -Evubitals form two π-connections in connections.
For the elements of the 2nd period, SP-hybridization occurs according to the scheme:
2S + 2px \u003d 2 (2SP)
2PY- and 2PZ-AO do not change.
Acetylene- Unsaturated hydrocarbon C2H2. It has a triple connection between carbon atoms, belongs to the class of alkins
Carbon atoms in acetylene SP-hybridized. They are associated with one way in two, Max. The densities of thecom are located in two mutually perpendicular areas, forming cylindrich. voltage density; Outside of N. atoms
Methylacetyle(Propin, Allilene) CH3C \u003d CH. By chemical M.-typical representative of acetylene hydrocarbons. Easily joins the electroph effect, nucleoph. and radical joining on triple communication, for example When completing Methanol forms methyl-isopropenyl ether.
6. Types of Communication -Metal communication, covalent bond, ion connection, hydrogen bond
Ion communication - Durable chemical bonds formed between atoms with a large difference in electrical negotiations, in which the total electronic pair completely passes to the atom with greater electronegitability. An example is the CSF connection, in which the "degree of ionicity" is 97%.
the extreme case of polarization of covalent polar communication. It is formed between typical metal and non-metallol. At the same time, the electrons of the metal completely switch to nonmetal. The ions are formed.
If the chemical bond is formed between atoms, which have a very large difference in electronegate (EO\u003e 1.7 by Pauling), the total electronic pair fully moves to the atom with greater EO. The result is the formation of the combination of oppositely charged ions.
Covalent communication (atomic communication, homeopolar communication) - chemical bond formed by overlapping (socialization) pairs of valence electronic clouds. Providing communication electronic clouds (electrons) are called a common electronic pair.
A simple covalent bond is formed from two unpaired valence electrons, one from each atom:
As a result of the socialization of electrons form a completed energy level. The connection is formed if their total energy at this level will be less than in the initial state (and the difference in energy will not be different as the communication energy).
Filling atomic electrons (at the edges) and molecular (in the center) orbitals in the H2 molecule. The vertical axis corresponds to the energy level, the electrons are indicated by the arrows reflecting their backs.
According to the theory of molecular orbitals, the overlapping of two atomic orbitals leads in the simplest case to the formation of two molecular orbitals (MO): binding MO and anti-binding (loose) MO. Common electrons are located at a lower binding energy of MO.
7. Alkana - acyclic hydrocarbons of a linear or branched structure containing only simple bonds and forming a homologous series with a general formula CNH2N + 2.
Alkans are saturated hydrocarbons and contain the maximum possible number of hydrogen atoms. Each carbon atom in alkanan molecules is in the state of SP³ hybridization - all 4 hybrid orbital atoms with equal in form and energy, 4 electronic clouds are directed at the top of the tetrahedron at the angles of 109 ° 28. "Due to single bonds between atoms with possibly free rotation around carbon tie. Type of carbon bond - σ-bonds, links are low-polar and poorly polarizes. The length of the carbon bond is 0.154 nm.
The isomerism of limiting hydrocarbons is due to the simplest type of structural isomerism - a carbon skeleton isomeria. Homological The difference is -ch2-. Alkaans, the number of carbon atoms in which are more than three, have isomers. The number of these isomers increases at a huge rate as the number of carbon atoms increases. For alkanes with n \u003d 1 ... 12, the number of isomers is 1, 1, 1, 2, 3, 5, 9, 18, 35, 75, 159, 355.
Nomenclature -Rational. One of the carbon chains atoms is selected, it is considered substituted methane and the name of alkyl1alkyl2 alkyl3 alkyl4metan is constructed relative to it.
Obtaining. Restoration of halogen derivatives of alkanes. Restoration of alcohols. Restoration of carbonyl compounds. Hydrogenation of unsaturated hydrocarbons. Synthesis Kolbe. Gasification of solid fuel. Nurez reaction. Synthesis Fisher-Tropsch.
8. Alkana Have low chemical activity. This is explained by the fact that single C-H and C-C communication are relatively durable and difficult to destroy them.
Reactions of radical substitution.
Halogenation of alkanov proceeds along the radical mechanism. To initiate the reaction, a mixture of alkane and halogen is necessary to irradiate UV light or heat. Methane chlorination does not stop at the stage of obtaining methyl chloride (if equimolar amounts of chlorine and methane are taken), and leads to the formation of all possible substitution products, from methyl chloride to tetrachloroupar.
Nitching (Konovalov reaction)
Alkans react with a 10% nitric acid solution or nitrogen oxide N2O4 in the gas phase with the formation of nitro-producing:
RH + HNO3 \u003d RNO2 + H2O
All available data indicate a free radical mechanism. As a result of the reaction, mixtures of products are formed.
Oxidation reactions. Combustion
The main chemical property of limit hydrocarbons that determine their use as fuel is a combustion reaction. Example: CH4 + 2O2 → CO2 + 2H2O + Q
In the event of a lack of oxygen, instead of carbon dioxide, carbon black gas is obtained or coal (depending on the concentration of oxygen).
In the general case, the burning reaction equation for any CXHY hydrocarbon can be written in the following form: CXHY + (X + 0,5Y) O2 → XCO2 + 0,5yH2O
Catalytic oxidation
Alcohols, aldehydes, carboxylic acids can be formed.
Thermal transformations of alkanans. Decomposition
The decomposition reactions occur only under the influence of large temperatures. An increase in temperature leads to a rupture of carbon bonds and the formation of free radicals.
Examples: CH4 → C + 2H2 (T\u003e 1000 ° C); C2H6 → 2C + 3H2
Cracking
When heated above 500 ° C, alkanes are subjected to pyrolytic decomposition to form a complex mixture of products, the composition and the ratio of which depend on the temperature and reaction time.
Dehydrification
Education alkene and hydrogen release
Conditions of the flow: 400 - 600 ° C, catalysts - Pt, Ni, Al2O3, CR2O3; C2H6 → C2H4 + H2
Isomerization -Under the action of a catalyst (for example. AlCl3) isomerization of alkane, for example:
butane (C4H10) interacting with aluminum chloride (AlCl3) turns from n-butane into 2-methylpropane.
Conversion methane
CH4 + H2O → CO + H2 - ni catalyst ("CO + H2" "Synthesis gas")
With mangartee-acid potassium (KMNO4) and bromine water (BR2), alkanes do not interact.
9. Allas (otherwise olefins or ethylene hydrocarbons) - acyclic unsaturated hydrocarbons containing one double bond between carbon atoms forming a homologous row with a general formula CNH2N. The carbon atoms at double bond are in a state of hybridization SP², and have a valence angle of 120 °. The simplest alkene is Ethen (C2H4). According to the IUPAC nomenclature, the names of alkenes are formed from the names of the corresponding alkanes by replacing the suffix "-an" on "-En"; The dual connection position is indicated by the Arabic digit.
Alkenes, the number of carbon atoms in which are more than three, have isomers. For alkenes, the isomerism of the carbon skeleton, the position of the double bond, inter-odd and spatial. Ethen (ethylene) C2H4, propnc3h6, buten4h8, pentenc5h10, hexenc6h12,
Methods for obtaining alkenes -The main industrial method of obtaining alkenes is a catalytic and high-temperature cracking of petroleum and natural gas hydrocarbons. To produce lower alkenes, the reaction of the dehydration of the corresponding alcohols is also used.
In laboratory practice, the method of dehydration of alcohols is usually used in the presence of strong mineral acids, dehydrolageening and the dehydrogenation of the corresponding halogen derivatives; Synthesis of Hoffman, Chugaev, Wittig and Cope.
10. Chemical properties of alkenes Alkenes are chemically active. Their chemical properties are largely determined by the presence of a double bond. For alkenes, the reaction of the electrophile addition and the reaction of radical attachment is most characteristic. The reactions of nucleophilic additions typically require a strong nucleophile and are not typical for alkenes.
The peculiarity of alkenes is also the reaction of cycloading and metathesis.
Alkenes are easily entering the oxidation reaction, hydrogenated with strong reducing agents or hydrogen under the action of catalysts to alkanes, as well as capable of allyl radical substitution.
Reactions of electrophile attachment.In these reactions, the attacking particle is the electrophile. Strong article: Electrophile connection reactions
Halogenation of alkenesextending in the absence of radical reaction initiators is a typical reaction of electrophile attachment. It is carried out in the medium of non-polar inert solvents (for example: CCL4):
The reaction of the halogenation of stereospecificant - the addition occurs from the opposite sides relative to the plane of the alkene molecule
Hydroalogenation.The electrophile attachment of halogen farming to alkenes occurs according to the rule of Markovnikov:
Hydroporization.The addition occurs is multiparted with the formation of an intermediate cyclic activated complex, and the addition of boron occurs against the Markovnikov rule - to the most hydrogenated carbon atom
Hydration.The reaction of water connection to alkens flows in the presence of sulfuric acid
Alkylation.The addition of alkanans to alkenes in the presence of an acid catalyst (HF or H2SO4) at low temperatures leads to the formation of hydrocarbon with a larger molecular weight and is often used in industry
11. Alkina (otherwise, acetylene hydrocarbons) - hydrocarbons containing a triple bond between carbon atoms, with the general formula CNH2N-2. Carbon atoms with triple bond are in a state of SP hybridization.
For alkins, attachment reaction is characteristic. Unlike alkenes, which are characterized by the reaction of electrophile addition, alkina can also enter into a nucleophilic attachment reaction. This is due to a significant S-character of communication and, as a result, increased electronegithium carbon atom. In addition, the high mobility of the hydrogen atom with a triple bond determines the acidic properties of alkins in reactions of substitution.
The main industrial how to receive Acetylene is an electro- or thermocracing of methane, pyrolysis of natural gas and carbide method
12. Dien hydrocarbons (dienes), unsaturated hydrocarbons with two double bonds. Aliophatic. Dianes sn2n_2 called. Alicyclic. Sn2n_4 - cycloalkalidians. The article discusses dial hydrocarbons with conjugate double bonds [conjugate dienes; See Table]. Deenes with isolated double bonds by chemical. C-you in Osn. Do not differ from olefins. Oh Soch. With cumulated double connections, see Allen. In diene hydrocarbons, all four carbon atoms of the conjugate system have SP2 hybridization and lie in the same plane. Four p-electrons (one by one carbon atom) are combined, forming four P-molecular orbital (two binding - occupied and two baking-free - free), from which only the lowest is delocalized by all carbon atoms. Partial delocalization of p-electrons causes the conjugation effect manifested in a decrease in the energy of the system (by 13-17 kJ / mol compared to the system of isolated double bonds), align the interatomic distances: the double bonds are somewhat longer (0.135 nm), and simple - shorter (0,146 nm) than in molecules without conjugation (acc. 0.133 and 0.154 nm), increase polarizability, exaltation of molecular refraction, etc. Effects. Dien hydrocarbons exist in the form of two conformations, passing into each other, and the S-trans form is more stable
13. Alcohols Called compounds containing one or more hydroxyl groups. According to them, alcohols are divided into monoatomy, ductomy, trochatomic, etc. Length of ties and valence angles in methyl alcohol.
For alcohols there are several ways of their name. In the modern nomenclature of the Jewak for the name of the alcohol to the name of the hydrocarbon, the end "Ol" is added. The longest chain containing a functional one-group is numbered from that end to which the hydroxyl group is closest, and the substituents are designated in the prefix.
Getting. Hydration of alkenes. In the interaction of alkenes with dilute aqueous solutions, the main product is alcohol.
Hydroxyimercury-Demmerization of alkenes. This reaction is not accompanied by regrouping and leads to the formation of individual alcohols. The reaction direction complies with the rule of Markovnikov, the reaction is carried out under mild conditions with the outputs close to quantitative.
Helporing of alkenes and subsequent oxidation Boranans with a solution of hydrogen peroxide in an alkaline medium leads, ultimately, to the Antimemknikovsky product of water to double-bond.
Restoration of aldehydes and ketones of lithium aluminum hydride or sodium borohydride
LiAlh4 and Nabh4 reduce aldehydes to primary alcohols, and ketones to secondary, and sodium borohydride is preferable due to greater safety in circulation: it can be used even in water and alcohol solutions. Alumohydride lithium reacts with water and with an alcohol with an explosion and decomposes with an explosion when heated above 120 ° in a dry state.
Restoration of esters and carboxylic acids to primary alcohols.Primary alcohols are formed when restoring esters and carboxylic acids by aluminohydride lithium in the air or THF. It is especially convenient for preparative terms for the restoration of lithium aluminum hydride esters. It should be noted that sodium borohydride does not restore the ester and carboxyl group. This allows the selective restoration of the carbonyl group with NABH4 in the presence of ester and carboxyl groups. Outputs of recovery products are rarely below 80%. Lithium borohydride in contrast to NABH4 restores the esters to the andpervilic alcohols.
14. Multiatomic alcohols. Glycerol - Chemical connection with the HOCH2CH (OH) -CH2OH or C3H5 (OH) 3 formula (OH) 3. The simplest representative of triple alcohols. It is a viscous transparent liquid. It is easy to form in the hydrolysis of natural (plant or animals) fat and oils (triglycerides), for the first time Carl Shelele was obtained in 1779 when the fats were washed.
Physical properties. Glycerol - colorless, viscous, hygroscopic fluid, unlimited soluble in water. Sweet taste, why and got his name (glycos - sweet). Many substances are well dissolved.
Chemical properties Glycerin is typical for polyatomic alcohols. The weight of glycerol with halogen hydrogen or phosphorus halides leads to the formation of mono- and digalohyenhydrins. Gliserine is eaterified by carbon and mineral acids with the formation of appropriate ethers. Thus, with nitric acid, glycerin forms trinitrate - nitroglycerin (obtained in 1847. Askanio Sobero (English)), which is currently used in the production of smokeless powder.
With dehydration, it forms acrolein:
HOCH2CH (OH) -CH2OH H2C \u003d CH-CHO + 2 H2O,
Ethylene glycol, HO-CH2-CH2-OH is the simplest representative of polyhydric alcohols. In purified form, it is a transparent colorless liquid slightly oily consistency. There is no smell and has a sweet taste. Toxic. The entry of ethylene glycol or its solutions can lead to irreversible changes in the body and to death.
In industry ethylene glycol obtained by hydration Ethylene oxide at 10 atm and 190-200 ° C or at 1 at and 50-100 ° C in the presence of 0.1-0.5% sulfur (or orthophosphoric) acid reaching 90% of the output. By the on-site products are diethylene glycol, triethylene glycol and a slight amount of higher polymer generics of ethylene glycol.
15. Aldehydes - alcohol, deprived of hydrogen; Organic compounds containing a carbonyl group (C \u003d O) with one substituent.
Aldehydes and ketones are very similar, the difference lies in the fact that the latter have two deputies with a carbonyl group. The polarization of the double bond "carbon-oxygen" on the principle of mesomeric conjugation allows you to write down the following resonant structures:
Such a separation of charges is confirmed by physical research methods and largely determines the reaction capacity of aldehydes as pronounced electrophils. In general, the chemical properties of the aldehydes are similar to ketone, however, the aldehydes exhibit greater activity, which is associated with greater polarization of communication. In addition, for aldehydides, the reaction is characterized, not characterized for ketones, for example, hydration in aqueous solution: from methanal due to even greater polarization of communication - complete, and other aldehydes - partial:
Rc (O) H → RC (OH) 2H, where R - H, any alkyl or aryl radical.
The simplest aldehydes have a sharp characteristic smell (for example, benzaldehyde - almond smell).
Under the action of hydroxylamine turn into oxime: CH3Cly + NH2OH \u003d CH3C (\u003d NOH) H + H2O
Formaldehyde (from lat. Formica - ant), Aldehyde, CH2O, The first member of the homologous series of aliphatic aldehydes; Colorless gas with a sharp smell, well-soluble in water and alcohol, Tkip - 19 ° C. In industry F. is obtained by oxidation of methyl alcohol or methane air oxygen. F. It is easily polymerized (especially at temperatures up to 100 ° C), so it is stored, transported and used mainly in the form of formalin and solid low molecular weight polymers - trioxane (see trioximetylene) and paraform (see paraformaldehyde).
F. very reactive; Many reactions underlie the industrial methods for obtaining a number of important products. So, when interacting with Ammonia F. forms urotropin (see hexamethylenetetramine), with urea-urea-formaldehyde resins, with melamine - melamine-formaldehyde resins, with phenol - phenol-formaldehyde resins (see phenol-aldehyde resins), with phenol - and naphthalene sulfonic acids - flushing substances, with the coteten - B-Popiocton. F. is also used to obtain a polyvinyl formal (see polyvinyl acetal), isoprene, pentaeryritis, medicinal substances, dyes, for skin tossing, like a disinfectant and deodorizing agent. Polymerization of F. receive polyformaldehyde. F. Toxic; The maximum permissible concentration in the air is 0.001 mg / l.
Acetaldehyde, acetic Aldehyde, CH3CHO, organic compound, colorless liquid with a sharp smell; Boiling point 20,8 ° C. The melting point is 124 ° C, a density of 783 kg / m3 "is mixed in all respects with water, alcohol, ether. Metaldehyde (CH3CHO) 4. When heated both polymers in the presence of sulfuric acid, A.
One of the main known methods for receipt A. It consists in connecting water to acetylene in the presence of mercury salts at a temperature of about 95 ° C
16. Ketones - These are organic substances, in the molecules of which the carbonyl group is associated with two hydrocarbon radicals.
The general formula of ketones: R1-CO-R2. Among other carbonyl compounds, the presence of two carbon atoms in the ketones directly related to the carbonyl group, distinguishes them from carboxylic acids and their derivatives, as well as aldehydes.
Physical properties.Ketones are volatile fluids or low-melting solids that are well mixed with water. The impossibility of the formation of intermolecular hydrogen bonds causes a slightly large volatility than those of alcohols and carboxylic acids with the same molecular weight.
Synthesis methods. Oxidation of secondary alcohols.
From the tertiary pellsofers of the rearrangement of Cryga.
Cyclictakes can be obtained by the cyclization of the rusts.
Aromatic ketones can be obtained by Friedel-Krafts reaction
Chemical properties.There are three main types of ketone reactions.
The first is associated with a nucleophilic attack on carbonyl carbonyl carbon atom. For example, the interaction of ketones with cyanide anion or metallorganic connections. The same type (nucleophilic accession) includes the interaction of the carbonyl group with alcohols, leading to acetals and semi-aotic.
Interaction with alcohols:
CH3COCH3 + 2C2H5OH → C2H5-O-C (CH3) 2-O-C2H5
with reagents Grignar:
C2H5-C (O) -C2H5 + C2H5MGI → (C2H5) 3OMGI → (C2H5) 3OH, Tertiary alcohol. Reactions with aldehydes, and especially with methanal go noticeably more active, while the secondary alcohols are formed with aldehydes, and with methanal - primary.
Ketones also react with nitrogenous bases, for example, with ammonia and primary amines to form imine:
CH3-C (O) -CH3 + CH3NH2 → CH3-C (N-CH3) -CH3 + H2O
The second type of reaction is the deprotonation of the beta-carbon atom, with respect to the carbonyl group. The resulting carbanion is stabilized due to the conjugation with the carbonyl group, the ease of removal of the proton increases, therefore carbonyl compounds are relatively strong Sn acids.
Third - coordination of electrophils at a different pair of an oxygen atom, for example, Lewis acids such as AlCl3
To a separate type of reaction can be attributed to the restoration of ketones - Eternation on Leicaren with the outputs close to quantitative.
17. Create 15 and 16 questions.
18. Monoxide Limit Carboxylic Acid (single-axis saturated carboxylic acids) - carboxylic acids in which the saturated hydrocarbon radical is connected to one carboxyl group -COOH. All of them have the general formula CNH2N + 1COOH, where n \u003d 0, 1, 2, ...
Nomenclature. The systematic names of single-axis limit carboxylic acids are given by the name of the corresponding alkane with the addition of suffix and the words of the acid.
The skeleton isomeria in the hydrocarbon radical manifests itself, starting with butanic acid, which has two isomers:
CH3-CH2-CH2-COOH n-butanic acid; CH3-CH (CH3) -COOH 2-methylpropane acid.
Interclative isomerism is manifested, starting with acetic acid:
CH3-COH acetic acid; H-COO-CH3 methyl formate (Methyl ether of formic acid); HO-CH2-COH hydroxyetanal (hydroxyuxous aldehyde); HO-CHO-CH2 hydroxyethylene oxide.
19. Essentials - organic compounds, carbon or mineral derivatives, in which the hydroxyl group -OH acid function is replaced by the alcohol residue. They differ from these ethers in which two hydrocarbon radicals are connected by an oxygen atom (R1-O-R2).
Fat, or triglycerides - natural organic compounds, complete glycerol ethers and monolay fatty acids; Part lipids are included in the lipid class. Along with carbohydrates and proteins, fats are one of the main components of animal, plants and microorganisms. Liquid fats of plant origin are usually called oils - just like butter.
Carboxylic acids - The class of organic compounds whose molecules contain one or more functional carboxyl groups -COOH. Sour properties are explained by the fact that this group can relatively easily split the proton. Over rare exceptions, carboxylic acids are weak. For example, in acetic acid CH3COOH escort constant is 1.75 · 10-5. Di- and tricarboxylic acids are stronger than monocarbonic.
Fat is a good thermal insulator, so many warm-blooded animals are postponed in subcutaneous adipose tissue, reducing heat loss. A particularly thick subcutaneous fat layer is characteristic of aqueous mammals (whale, walrus, etc.). At the same time, animals living in a hot climate (camels, carcans) fat reserves are deposited on
Structural function
Phospholipids constitute the basis of the bilayer of cell membranes, cholesterol - membrane yield regulators. At Archey, the membranes include derivatives of isoprene hydrocarbons. Waxes form a cuticle on the surface of the above-ground organs (leaves and young shoots) of plants. They also produce many insects (so, the bees build copies of them, and the Chervers and the shields form protective covers).
Regulatory
Vitamins - Lipids (A, D, E)
Hormonal (steroids, eikosanoids, prostaglandins and others.)
Cofackers (Dolichol)
Signal Molecules (Digliciserides, Jasmonic Acid; MP3 Cascade)
Protective (amortization)
The thick layer of fat protects the internal organs of many animals from damage during shocks (for example, Syvuchi with a mass of up to tons can jump onto a rocky coast with a height of 4-5 m).
20-21-22. Simple unsteady acids - derivatives of unsaturated hydrocarbons, in which one hydrogen atom is substituted with a carboxyl group.
Nomenclature, isomeria. In the group of unsaturated acids, empirical names are most often used: CH2 \u003d CH-coton - acrylic (propnas) acid, CH2 \u003d C (CH3) -Oson - methacryl (2-methylpropane) acid. Isomerius in a group of unspecified mono-abnormal acids is associated with:
a) isomeria of a carbon skeleton; b) the position of the double bond; c) cis-trans isomeria.
Methods for getting.one. Dehydrogalogenation of halogen-substituted acids:
CH3-CH2-SNSL-coxy --- koh (concluded) ---\u003e CH3-CH \u003d CH-coxy
2. Oxycoslot dehydration: but-CH2-CH2-coxy -\u003e CH2 \u003d CH-coxy
Physical properties. Lower unsaturated acids - liquids soluble in water, with a strong sharp odor; Higher - solid, non-soluble substances, odorless.
Chemical properties Unfoluble carboxylic acids are due to both the properties of the carboxyl group and the properties of the double bond. Specific properties have acids with a double-connected double-connected group located from the carboxyl group - alpha, beta-unsteady acids. In these acids, the addition of halogen breeding and hydration go against the rules of Markovnikov: CH2 \u003d CH-coo + NBR -\u003e CH2VR-CH2-coxy
Under careful oxidation, dioxic acids are formed: CH2 \u003d CH-coo + [O] + H20 -\u003e But-CH2-CH (OH) -Oson
With an energetic oxidation, a double bond is rupture and a mixture of different products are formed by which the dual connection position can be installed. Oleic acid C17H33Son - one of the most important higher non-precious acids. It is a colorless liquid, hardens in the cold. Its structural formula: CH3- (CH2) 7-CH \u003d CH (CH2) 7-coxy.
23. Two-axis limiting carboxylic acids (Two-axis saturated carboxylic acids) - carboxylic acids in which the saturated hydrocarbon radical is connected to two carboxyl groups -COOH. All of them have a general formula HOOC (CH2) NCOOH, where n \u003d 0, 1, 2, ...
Nomenclature. The systematic names of the two-axis limit carboxylic acids are given by the name of the corresponding alkane with the addition of suffix-person and the words of the acid.
The skeleton isomerism in the hydrocarbon radical manifests itself, starting with the butteric acid, which has two isomers:
HOOC-CH2-CH2-COOH H-butdanic acid (ethane-1,2-dicarboxylic acid);
CH3-CH (COOH) -COOH ethane-1,1-dicarboxylic acid.
24-25. Oxycycles (hydroxycarboxylic acids) , have in a molecule along with a carboxyl group - COOH hydroxyl group - OH, for example Hoch2Cooh (glycolic acid). It is contained in plant and animal organisms (dairy, lemon, wine and other acids).
Distribution in nature
Oxyc acids are very widespread; So, wine, lemon, apple, dairy and other acids belong to oxyc acids, and their name reflects the primary natural source in which this substance was found.
Methods of synthesis
The reformat reaction is the method of synthesizing the esters of β-hydroxycarboxylic acids.
"Fruit Acid". Many oxycycles obtained use in cosmetics as keratolithics. Title, however, marketers have changed a little - for greater attractiveness in cosmetology they are often called "fruit acids".
26-27. Oxyc acids (alcoholic acid ), double-function connections, simultaneously alcohols and acids containing and water residue and carboxyl group. It depends on the situation he relates to the coxy (next to one, two, three places) is distinguished by A-, /? -, u-, b-oxic acids. For obtaining O., there are many methods that are essential from the bone cautious oxidation of glycols: CH3.CH (OH). SN2.On + 02 \u003d CH3. . SN (OH). washing oxyminitriles CH3.CH (OH) .cn - * CH3.SN (OH). Halogen exchange in haloidisloids on it: CH2S1.Cono + Kon \u003d CH2 (OH). Andone + + ks1, action HN02 on amino acids: CH2 (NH2). Soam + HN02 \u003d CH2 (OH) + N2 + + H20. In the animal organism, hydroxy acids are formed during deamination (see) amino acids, when oxidizing fatty Kt (see acetone bodies, protein metabolism), with glycolize (see), fermentation (see) and others. Chem. processes. Oxycycles dense liquids or crystalline. Substances. In chemical About O. react and like alcohols and how to-you: give eg both simple and sophisticated esters; With the action of halogen compounds of phosphorus, it is replaced by a halogen; Halojondogenic K-you react only with alcohol. Coxy \u003d 2N20 + CH2.O.o (glycolide); S.O. SN2 / Zh., Highlighting the water, form unforeseen k-you: CH2 (OH). SN2.Con- H20 \u003d CH2: CH. .Con; U- and d-oxic acids form anhydrides - lactones: CH3.CH (OH). SN2.Sn2.Cono \u003d \u003d H2O + CH3.Sn2.Sn2.Co. O. Widespread in animal and vegetable organisms. Representatives of aliphatic ah. are gli-pants acid, CN2On.Oson (oxyuxus-naya), lactic acid; From /? - oxyc acid hydraulic, CH2On.Sn2Cone, / 9-hydroxy oil acid; Uth. Unknown in free form, since losing water, go to lactones. Among the bible O. Essential importance is an apple to-one (oxijan-naya); Soone. SNON. SN2.Cono, widespread in plants; He has left rotation in weak solutions, right in strong; Synthetic k-ta is notable. Two-axis four-heed acids include wine acids (dioxijanter). From other O.-lemon, but.z. SN2. . (Sleep) (coxy). Then2.Cono, is very common in the plant world (in wine - historia, lemon) and found in an animal organism (in milk); In the form of iron, iron is used in medicine. From aromatic O. (phenolocuslot) in medicine, salicylic acid, halmic acid and their derivatives are important; Phenis-Love ester salicylic K-you (Salol), Sul-Fosalicyl K-TA, C6H3. Oh.s03h.coh (reagent for protein), acetylsalicyl K-TA (aspirin). In plants there are many different O. aromatic series, to the derivatives of the to-rye belong among other tubils that have important technical significance. About biol. The meaning of individual O. and on the methods of their quantitative determination, see. Acetone bodies, bro-glycolysis, deamination, blood, lactic acid, urine, muscle, beta (^) - oxymalaic acid.
28-29. In the ammonia molecule to sequentially replace hydrogen atoms with hydrocarbon radicals, then compounds are obtained that relate to the class of amines. Accordingly, the amines are primary (RNH2), secondary (R2NH), tertiary (R3N). Group -NH2 is called an amino group.
There are aliphatic, aromatic, alicyclic and heterocyclic amines depending on which radicals are associated with a nitrogen atom.
The construction of the names of amines is carried out by adding the amino attachment to the name of the corresponding hydrocarbon (primary amines) or the end of the-amin to the listed names of the radicals associated with the nitrogen atom (for any amines).
Methods of obtaining.1. Hofman reaction. One of the first methods for obtaining primary amines - alkylation of ammonia alkyl halides . 2. Zinin reaction - A convenient way to obtain aromatic amines when restoring aromatic nitro compounds. As reducing agents are used: h2 (on the catalyst). Sometimes hydrogen is generated directly at the moment of the reaction, for which metals (zinc, iron) diluted with acid are treated.
Physical properties of amines.The presence of a mean-free e-pair at the nitrogen atom causes higher boiling temperatures than that of the corresponding alkans. Amines have an unpleasant sharp smell. At room temperature and atmospheric pressure, the first representatives of a number of primary amines - gases, rather soluble in water. With an increase in the carbon radical, the boiling point rises and the solubility in water is reduced.
Chemical properties of amines. The main properties of amines
The amines are grounds, since the nitrogen atom can provide an electron pair for the formation of communication with the electron-drum particles according to the donor-acceptor mechanism (compliance with the definition of basic Lewis base). Therefore, amines, as well as ammonia, can interact with acids and water, connecting the proton to the formation of appropriate ammonium salts.
Ammonium salts are well soluble in water, but poorly dissolved in organic solvents. Amic solutions of amines have an alkaline reaction.
The main properties of amines depend on the nature of the substituents. In particular, aromatic amines - weaker bases than aliphatic, because The free electron pair of nitrogen enters into a conjugation with the -system of the aromatic nucleus, which reduces the electron density on the nitrogen atom (-M-effect). On the contrary, the alkyl group is a good donor of electron density (+ i-effect).
Oxidation of amines. The combustion of amines is accompanied by the formation of carbon dioxide, nitrogen and water: 4Ch3NH2 + 9O2 \u003d 4CO2 + 2N2 + 10N2O
Aromatic amines are spontaneously oxidized in air. So, aniline will quickly boil in air due to oxidation.
The addition of alkyl halides Amina attach halogens with salt formation
The interaction of amines with nitrogenic acid is of great importance to the reaction of diazotization of primary aromatic amines under the action of nitrate acid obtained by in situ by sodium nitrite reaction with hydrochloric acid.
Primary aliphatic amines with a nitrate acid reaction form alcohols, and secondary aliphatic and aromatic amines give N-nitrogen derivatives: R-NH2 + NanO2 + NSl \u003d R-OH + N2 + NaCl + H2O; NH + Nano2 + HCl \u003d R2N-N \u003d O + NaCl + H2O
In aromatic amines, the amino group facilitates replacement in ortho and para-positions of the benzene ring. Therefore, the halogenation of aniline occurs quickly and in the absence of catalysts, and the three atoms of hydrogen of the benzene ring are replaced, and a white precipitate of 2,4,6-tribromanyline falls out:
This reaction of bromine water is used as a high-quality reaction to aniline.
Application
Amines are used in the pharmaceutical industry and organic synthesis (CH3NH2, (CH3) 2NH, (C2H5) 2NH, etc.); in the production of nylon (NH2- (CH2) 6-NH2 - hexamethylenediamine); As raw materials for the production of dyes and plastics (anilin).
30. Amino acids (aminocarboxylic acids) - organic compounds, in the molecule of which are at the same time contained carboxyl and amine groups. Amino acids can be considered as derivatives of carboxylic acids, in which one or more hydrogen atoms are replaced by amine groups.
Common chemical properties.1. Amino acids can exhibit both acidic properties caused by the presence in their molecules of the carboxyl group -COOH and the main properties caused by the amino group -NH2. Amino acid solutions in water due to the properties of buffer solutions.
Zwitter-ion is called an amino acid molecule, in which the amino group is represented in the form of -NH3 +, and the carboxy group is in the form of -COO-. Such a molecule has a significant dipole moment at zero total charge. It is from such molecules that the crystals of most amino acids were built.
Some amino acids have several amino groups and carboxyl groups. For these amino acids, it is difficult to talk about some particular Zwitter-ion.
2. An important feature of amino acids is their ability to polycondensation leading to the formation of polyamides, including peptides, proteins and nylon-66.
3. The isoelectric point of amino acids is called the pH value at which the maximum proportion of amino acid molecules has a zero charge. With such a pH of the amino acid, the least mobile in the electric field, and this property can be used to separate amino acids, as well as proteins and peptides.
4. Amino acids can usually enter into all reactions characteristic of carboxylic acids and amines.
Optical isomeria. All incoming alive organisms of α-amino acids, except for glycine, contain an asymmetric carbon atom (threonine and isoleucine contain two asymmetric atoms) and possess optical activity. Almost all in the nature of α-amino acids have a L-shape, and only L-amino acids are included in the proteins synthesized on ribosomes.
This feature of "living" amino acids is very difficult to explain, since in reactions between optically inactive substances or racemates (which, apparently, organic molecules on ancient land were presented) L and D-forms are formed in the same quantities. Maybe. The choice of one of the forms (L or D) is simply the result of a random coincidence: the first molecules from which the matrix synthesis was able to begin, possess a certain form, and it was to them "adapted" the corresponding enzymes.
31. Amino acids are organic amphoteric compounds. They contain two functional groups of the opposite as part of the molecule: an amino group with basic properties and a carboxyl group with acidic properties. Amino acids react with both acids and bases:
H2N-CH2-coxy + HCl → CL [H3N-CH2-SON],
H2N-CH2-coxy + NaOH → H2N-CH2-Coona + H2O.
When the amino acids dissolve in water, the carboxyl group clears the hydrogen ion, which can join the amino group. In this case, the inner salt is formed, the molecule of which is a bipolar ion:
H2N-CH2-coo + H3N-CH2-SO-.
Amic solutions of amino acids have a neutral, alkaline or acidic medium depending on the number of functional groups. Thus, glutamic acid forms an acidic solution (two groups -Oson, one -NH2), lysine-alkaline (one group -Oson, two -NH2).
Like primary amines, amino acids react with nitrate acid, while the amino group turns into a hydroxoy group, and the amino acid - in hydroxy acid: H2N-CH (R) -COOH + HNO2 → HO-CH (R) -COOH + N2 + H2O
Measuring the volume of highlighted nitrogen allows you to determine the amount of amino acid (Van Sladen method).
Amino acids can react with alcohols in the presence of gaseous chloride chloride, turning into a complex ether (more precisely, in the chloride salt of ether): H2N-CH (R) -COOH + R "OH H2N-CH (R) -COOR" + H2O.
Amino acid esters do not have a bipolar structure and are volatile compounds. The most important property of amino acids is their ability to condensation with the formation of peptides.
32. Carboxyl group Combines two functional groups - carbonyl \u003d CO and hydroxyl -OH, mutually affecting each other.
The acid properties of carboxylic acids are due to the displacement of electron density to carbonyl oxygen and caused by this additional (compared to alcohols) of the polarization of the O-N communication.
In an aqueous solution, carboxylic acids dissociate to ions: R-COOH \u003d R-COO- + H +
Water solubility and high boiling points acids are due to the formation of intermolecular hydrogen bonds.
Amino group is a monovalent group -NH2, ammonia residue (NH3). The amino group is contained in many organic compounds - amines, amino acids, aminospirts, etc. Compounds containing a group -NH2 have, as a rule, the basic nature caused by the presence of a mean-free electronic pair on the nitrogen atom.
In the electrophilic reactions in the aromatic compounds of the amino group, the first kind orientant is the orientant. Activates the ortho and parasol in the benzene ring.
33. Polycondensation - The process of synthesizing polymers from polyfunctional (most often bifunctional) compounds, usually accompanied by the release of low molecular weight by-products (water, alcohols, etc.) in the interaction of functional groups.
The molecular weight of the polymer formed in the polycondensation process depends on the ratio of the source components, the reaction conditions.
In the polycondensation reaction, it can be used as one monomer with two different functional groups: for example, poly-ε-caproamide synthesis (nylon-6, kapron) from ε-aminocaproic acid and two monomers carrying various functional groups, for example, nylon synthesis 66 polycondensation of adipic acid and hexamethylenediamine; At the same time, polymers of linear structure are formed (linear polycondensation, see Fig. 1). In case the monomer (or monomers) bear more than two functional groups, cross-linked polymers of three-dimensional mesh structure (three-dimensional polycondensation) are formed. In order to obtain such polymers to the mixture of monomers, the "crosslinking" polyfunctional components are often added.
The mansion is the reaction of the synthesis of polymers from cyclic monomers using the cycle disclosure mechanism - addition, for example, nylon-6 synthesis from caprolactam (cyclic amide ε-aminocaproic acid); Despite the fact that the release of a low molecular weight fragment does not occur, such reactions are more common to polycondensation.
Peptide communication - The type of amide communication arising from the formation of proteins and peptides as a result of the interaction of the α-amino hydro group (-nh2) of one amino acid with an α-carboxyl group (-son) of another amino acid.
the C-N ile in the peptide bond is partially characterized by a double, which manifests itself, in particular, in a decrease in its length to 1.32 Angstrom. This causes the following properties:
4 coupling atoms (C, N, O and H) and 2 α-carbon are in the same plane. R-groups of amino acids and hydrogens with α-carbon are outside this plane.
H and O in peptide bonds, as well as α-carcristers of two amino acids transoriented (trans-isomer is more stable). In the case of L-amino acids, which takes place in all natural proteins and peptides, R-groups are also transoriented.
Rotation around communication C-N is impossible, it is possible to rotate around C-due to communication.
peptides (Greek πεπτος - nutritious) - a family of substances whose molecules are constructed from α-amino acid residues connected to a chain peptide (amide) bonds -c (O) NH-.
34. Proteins (proteins, polypeptides) - High molecular weight organic substances consisting of amino acid peptide bonds connected into a chain. In living organisms, the amino acid composition of proteins is determined by the genetic code, in most cases 20 standard amino acids are used in the synthesis. Many of their combinations give a wide variety of properties of proteins molecules. In addition, the amino acids in the protein are often subjected to post-translation modifications that may occur before the protein begins to perform its function, and during its "work" in the cell. Often in living organisms, several protein molecules form complex complexes, for example, a photosynthetic complex.
In order to understand the intricate laying (architectonics) of a protein macromolecule, you should consider in it several levels of organization. The primary, the most simple structure is the polypeptide chain, that is, the amino acid threads associated with the peptide bonds. In the primary structure, all links between amino acids are covalent and, therefore, durable. The next, higher level of organization is a secondary structure when the protein thread is spinled in the form of a spiral. There are hydrogen bonds on one twist of spiral groups, and -NH2 groups on another twist. They arise on the basis of hydrogen, which is most often between two negative atoms. Hydrogen bonds are weaker than covalent, but with a large number of them provide a sufficiently strong structure. The amino acid thread (polypeptide) is further coagulated, forming a tangle, or fibril or globulus, for each protein specific. Thus, a complex configuration occurs, called the tertiary structure. Its determination is usually produced using the X-ray structural analysis method, which allows you to establish a position in the space of atoms and groups of atoms in crystals and complex compounds.
Communication supporting the tertiary structure of the protein is also weak. They arise, in particular, due to hydrophobic interactions. These are the forces of attraction between non-polar molecules or between non-polar sections of molecules in the aquatic environment. The hydrophobic residues of some amino acids in the aqueous solution are close, "sticking out" and stabilize, thus, the structure of the protein. In addition to the hydrophobic forces, in maintaining the tertiary structure of the protein, electrostatic bonds are played between electronegative and electropositant radicals of amino acid residues. The tertiary structure is also supported by a small number of covalent disulfide -S-S-S-bonds arising between the sulfur atoms of sulfur-containing amino acids. I must say that both tertiary; The protein structure is not the ultimate. The protein macromolecule is often connected to the macromolecules of the same protein or molecules of other proteins. For example, a complex hemoglobin molecule - protein located in red blood cells consists of four macromolecules of globins: two alpha chains and two beta chains, each of which is connected to iron-containing gem. As a result of their association, a functioning hemoglobin molecule is formed. Only in such packaging, hemoglobin works full, that is, it is capable of carrying oxygen. Due to the combination of several protein molecules, a quaternary structure is formed among themselves. If peptide chains are laid in the form of a ball, then such proteins are called globular. If the polypeptide chains are laid in the beams of the threads, they are called fibrillar proteins. Starting from the secondary structure, the spatial device (conformation) of the protein macromolecules, as we found out, is mainly maintained by weak chemical bonds. Under the influence of external factors (change in temperature, salt composition of the medium, pH, under the action of radiation and other factors), weak bonds stabilizing the macromolecule, and the structure of the protein, and therefore its properties change. This process is called denaturation. The gap of part of weak bonds, changes in the conformation and protein properties occur under the action of physiological factors (for example, under the action of hormones). Thus, protein properties are governed: enzymes, receptors, conveyors. These changes in the protein structure are usually easily reversible. A large number of weak bonds leads to denaturation of a protein, which can be irreversible (for example, coagulation of egg protein when boiling eggs). Sometimes the protein denaturation has a biological meaning. For example, the spider allocates the droplet of the secret and sticks it to some kind of support. Then, continuing to distinguish the secret, it slightly pulls the string, and this weak tension is enough so that the protein is denatured, it turned out of the soluble form to the insoluble, and the thread acquired strength.
35-36. Monosaccharides (from Greek Monos: the only, Sacchar: sugar), - organic compounds, one of the main groups of carbohydrates; The simplest form of sugar; are usually colorless, soluble in water, transparent solids. Some monosaccharides possess a sweet taste. Monosaccharides are standard blocks, of which disaccharides are synthesized (such as sucrose) and polysaccharides (such as cellulose and starch), contain hydroxyl groups and aldehyde (aldose) or a keto group (ketosis). Each carbon atom with which the hydroxyl group is connected (except for the first and last) is chiral, giving the beginning to many isomeric forms. For example, galactose and glucose - aldo-boxose, but have various chemical and physical properties. Monosaccharides, like all carbohydrates, contain only 3 elements (C, O, H).
Monosaccharides are divided on triosis, tetroza, pentoses, hexoses, etc. (3, 4, 5, 6, etc., carbon atoms in the chain); Natural monosaccharides with a carbon chain containing more than 9 carbon atoms are not detected. Monosaccharides containing a 5-membered cycle are called furanosum, 6-membered with pranodes.
Isomeria.For monosaccharides containing N asymmetric carbon atoms, the existence of 2n stereoisomers (see isomeria) is possible.
38. Chemical properties.Monosaccharides come into chemical reactions peculiar to carbonyl and hydroxyl groups. The characteristic feature of monosaccharides is the ability to exist in open (acyclic) and cyclic forms and produce derivatives of each of the forms. Most monomoses are cyclized in an aqueous solution with the formation of hemiacetals or hemiquates (depending on whether they are alcohol or ketosis) between alcohol and carbonyl group of the same sugar. Glucose, for example, easily forms semi-aotic, connecting its C1 and O5 to form a 6-membered ring, called Pyranoside. The same reaction may occur between C1 and O4 to form a 5-membered furanoside.
Monosaccharides in nature.Monosaccharides are part of complex carbohydrates (glycosides, oligosaccharides, polysaccharides) and mixed carbohydrate-containing biopolymers (glycoproteins, glycolipids, etc.). At the same time, monosaccharides are connected with each other and with a restless part of the molecule with glycosidic bonds. In hydrolysis, under the action of acids or enzymes, these bonds can rush with the release of monosaccharides. In nature, free monosaccharides, with the exception of D-glucose and D-fructose, are rare. Biosynthesis of monosaccharides from carbon dioxide and water occurs in plants (see photosynthesis); With the participation of activated monosaccharide derivatives - nucleosidediffosfatshares - occurs, as a rule, the biosynthesis of complex carbohydrates. The decay of monosaccharides in the body (for example, alcohol fermentation, glycoliz) is accompanied by excretion of energy.
Application.Some free monosaccharides and their derivatives (for example, glucose, fructose and its diphosphate, etc.) are used in the food industry and medicine.
37. Glucose (C6H12O6) ("Grape Sugar", dextrose) occurs in the juice of many fruits and berries, including grapes, which there was a name for this type of sugar. It is a six-fat sugar (hexose).
Physical properties. The white crystalline substance of a sweet taste, well-soluble in water, is not soluble on the air, poorly soluble in alcohol.
The structure of the molecule
CH2 (OH) -CH (OH) -CH (OH) -CH (OH) -CH (OH) -C \u003d O
Glucose can exist in the form of cycles (α and β glucose).
α and β glucose
Glucose transition from Fisher's projection in Haworth Projection.Glucose is the final product of the hydrolysis of most disaccharides and polysaccharides.
Biological role.Glucose is the main product of photosynthesis, is formed in the Calvin cycle.
In the human body and animal glucose is the main and most universal source of energy to ensure metabolic processes. All cells of animals organism have the ability to absorb glucose. At the same time, the ability to use other energy sources - for example, free fatty acids and glycerin, fructose or milk acid - not all organism cells have, but only some of their types.
Transportation of glucose from the external environment Inside the animal cell is carried out by actively transmembrane transfer using a special protein molecule - the carrier (transporter) hexosis.
Glucose in cells may be subjected to glycolize in order to obtain energy in the form of ATP. The first enzyme in the glycolysis chain is hexokinas. The activity of cell hexochinase is under the controlling influence of hormones - so, insulin sharply increases the hexokinase activity and, consequently, the utilization of glucose by cells, and glucocorticoids reduce the hexokinase activity.
Many of the glucose sources of energy can be directly converted to the liver in glucose - for example, lactic acid, many free fatty acids and glycerin, or free amino acids, primarily the simplest of them, such as Alanine. The process of forming glucose in the liver from other compounds is called glukegenesis.
Those energy sources for which there is no way of direct biochemical transformation into glucose can be used by liver cells to generate ATP and subsequent energy supply of glucosegenesis processes, milk-acid residuisa, or energy supply of the gas coating polysaccharide stock process from glucose monomers. From glycogen, by simple splitting, glucose is easily produced.
Due to the exceptional importance of maintaining a stable blood glucose level, a person and many other animals have a complex system of hormonal regulation of carbohydrate exchange parameters. When oxidizing 1 gram of glucose to carbon dioxide and water, 17.6 kJ of energy is distinguished. The repaid maximum "potential energy" in the glucose molecule in the form of the degree of oxidation -4 carbon atom (C-4) may decrease in metabolic processes to C + 4 (in the CO2 molecule). Its restoration to the previous level can carry out autotrophic.
Fructose, or fruit sugar C6H12O6 - Monosaccharide, which is freely present in almost all sweet berries and fruits. Many prefer to replace sugar non-synthetic preparations, but natural fructose.
Unlike glucose, which serves a universal source of energy, fructose is not absorbed by insulin-dependent tissues. It is almost completely absorbed and metabolized by the cells of the liver. Practically no other cells of the human body (except spermatozoa) cannot use fructose. In fructose liver cells phosphorylated, and then split into triosis, which is either used for the synthesis of fatty acids, which can lead to obesity, as well as to increase the level of triglycerides (which, in turn, increases the risk of atherosclerosis), or is used to synthesize glycogen ( Partially also turns into glucose during gluconeogenesis). However, the conversion of fructose into glucose is a complex multistage process, and the ability of the liver to process fructose is limited. The question is whether to include fructose into the diet of diabetics, as insulin is not required for her assimilation, intensively investigated in recent years.
Although a healthy man fructose does not increase (or increases slightly) blood glucose level, in patients with fructose diabetes often leads to an increase in glucose level. On the other hand, due to the lack of glucose in cells, fat can be burned in the organisms of diabetics, leading to the depletion of fat stocks. In this case, fructose, which is easily turning into fat and does not require insulin, can be used to restore them. The advantage of fructose is that the sweet taste can be given a dish with relatively small amounts of fructose, since with equal caloric content (380 kcal / 100 g) it is 1.2-1.8 times sweeter. However, as research shows, fructose consumers do not reduce food calorics, instead they eat sweeter dishes.
39. Oligosaccharida - these are oligomers consisting of several (no more than 20) monomers - monosaccharides, in contrast to polysaccharides consisting of dozens, hundreds or thousands of monosaccharides; - Compounds constructed from several monosaccharide residues (from 2 to 10), interconnected by glycosidic bond.
A very important and widespread private case of oligosaccharides are disaccharides - dimers consisting of two monosaccharide molecules.
You can also talk about three, tetra-, etc. Saccharide.
40. Disaccharides - The general name of the subclass of oligosaccharides, in which the molecule consists of two monomers - monosaccharides. Disaccharides are formed as a result of the condensation reaction between two monosaccharides, usually hexoses. Condensation reaction involves removing water. The relationship between monosaccharides arising from the condensation reaction is called a glycosidic bond. This connection is formed between the 1st and 4th carbon atoms of neighboring monosaccharide units (1,4-glycoside).
The condensation process may be repeated for the countless number of times, resulting in huge polysaccharide molecules. After connecting monosaccharide units, they are called residues. The most common disaccharides are lactose and sucrose.
Mutarota (from the lat. Muto-changing and rotatio - rotation), change the magnitude of Optic. Rotation of p-mards of optically active compounds due to their epimerization. It is characteristic of monosaccharides, restoring oligosaccharides, lactones, etc. Mutarization can be catalyzed by acids and bases. In the case of glucose, muterization is due to the establishment of equilibrium: in the equilibrium state there are 38% of the air shapes and 62% of beta-shapes. Paris. Aldehyde form is contained in a negligible concentration. Advantages, the formation of B-forms is explained by the fact that it is more thermodynamically stable.
The reaction of the "silver mirror" and "copper mirror" is characteristic of aldehydes
1) Reaction of "Silver Mirror", Education on the walls of the AG Sediment
2) the reaction of the "copper mirror", the loss of red sediment CU2O
40. In turn, disaccharides arising in some cases hydrolysis of polysaccharides (Maltosis with starch hydrolysis, cellulose hydrolysis) or existing in the body in free form (lactose, sucrose, trehalosis, etc.), hydrolyzed at the catalytic effects of OS and P-glycosidases to individual monosaccharides. All glycosidases, with the exception of the track (OT, OMROGALOS-glucohydrshgaz), are distinguished by a wide range of specificity, accelerating the hydrolysis of almost any glycosi-doves, which are derived or another A- or (3-monosaccharide. So, A-glucosidase accelerates the hydrolysis reaction of glucoside, including maltose; p-glshkosidase - p-glucoside, including cellobiosa; in galactosidase - in galactosides and among them lactose, etc. Examples of action A and p-glucosidases were previously shown
41. In accordance with the failure chemical structure of Disaccharida Type of track-vines (glycoside-glycosides) and Maltose type (glycoside-glucose) have substantially different chemical properties: the first do not give any reactions inherent to the aldehyde or ketone group, that is not oxidized, they are not restored, do not form an ozon, not Polycooutation reaction (not rational), do not mutimate, etc. For maltose-type disaccharides, all mentioned reactions, on the contrary, are very characteristic. The reason for this difference is quite understandable from the above-described type of disaccharides and properties of monosaccharide residues included in their composition. It lies in the fact that only in disaccharides of the Maltose type, a ring-paging tautomeria is possible, as a result of which a free aldehyde or ketone group is formed, manifesting its characteristic properties.
According to alcohol hydroxyls, both types of disaccharides give the same reactions: form simple and sacred ether, interact with metal oxide hydrates.
In nature, there is a large number of disaccharides; The essential zpacchapie among them is mentioned above Tregaloz and Maltose, as well as sucrose, cellobiosis and lactose.
42. Malto (from English Malt - malt) - malt sugar, natural disaccharide, consisting of two glucose residues; It is contained in large quantities in the sprouted grains (malt) barley, rye and other grains; It was also discovered in tomatoes, in pollen and nectar of a row of plants. M. Easy soluble in water, has a sweet taste; It is reducing sugar, as it has an unsubstituted semi-aceteal hydroxyl group. Bosynthesis M. from B-D-glucopyranosyl phosphate and D-glucose is known only in some types of bacteria. In the animal and plant organisms, M. is formed during the enzymatic cleavage of starch and glycogen (see amylases). The splitting of M. up to two glucose residues occurs as a result of the action of the enzyme A-glucosidase, or moaltase, which is contained in the digestive juices of animals and humans, in the sprouted grain, in mold mushrooms and yeast. The genetically determined absence of this enzyme in the mucous membrane of the human intestinal leads to the congenital intolerance of M. - severe disease, requiring exceptions from the diet M., starch and glycogen or addition to the Falthaza enzyme.
When the boiling of maltose with dilute acid and under the action of the maltase enzyme hydrolyzed (two C6H12O6 glucose molecules are formed). Maltose is easily absorbed by the human body. Molecular weight - 342.32 tons of melting- 108 (anhydrous)
43. Lactose (from lat. Lactis - milk) C12N22O11 - the carbohydrate group of disaccharides is contained in milk and dairy products. Lactose molecule consists of remnants of glucose and galactose molecules. Lactose is sometimes called milk sugar.
Chemical properties.When boiling with dilute acid, the lactose hydrolysis occurs.
Get lactose from milk serum.
Application.Used for the preparation of nutrient media, for example, in the production of penicillin. Used as an auxiliary substance (filler) in the pharmaceutical industry.
Lactose is obtained by lactulose - a valuable preparation for the treatment of intestinal disorders, such as constipation.
44. Sakharoza C12H22O11, or beet sugar, reed sugar, in everyday life sugar - disaccharide, consisting of two monosaccharides - α-glucose and β-fructose.
Sakhares is quite common in nature by Disacharid, it is found in many fruits, fruits and berries. Especially great sucrose content in sugar binding and sugar cane, which are used for industrial food sugar production.
Sacraosis has high solubility. In the chemical ratio of fructose is rather inert, that is. When moving from one place to another is almost not involved in metabolism. Sometimes sucrose is postponed as a spare nutrient.
Sakharoza, falling into the intestines, quickly hydrolyzed alpha-glucosidase of the small intestine on glucose and fructose, which are then absorbed into the blood. Alfa-glucosidase inhibitors, such as acarbosis, inhibit the splitting and suction of sucrose, as well as other carbohydrates, hydrolyzed alpha-glucosidase, in particular, starch. It is used in the treatment of type 2 diabetes mellitus. Synonyms: alpha-D-glucopyranosyl-beta-D-fructofuranoside, beet sugar, cane sugar.
Chemical and physical properties.Molecular weight 342.3 AE.M. Gross formula (Hill system): C12H22O11. Taste sweetish. Solubility (grams per 100 grams): in water 179 (0 ° C) and 487 (100 ° C), in ethanol 0.9 (20 ° C). A little solvent in methanol. Not soluble in diethyl ether. Density of 1.5879 g / cm3 (15 ° C). Specific rotation for sodium D-line: 66.53 (water; 35 g / 100g; 20 ° C). When cooling with liquid air, after lighting the bright light, the sucrose crystals phosphoresize. Does not show reducing properties - does not react with the tolls reagent and the Feling reagent. The presence of hydroxyl groups in the sucrose molecule is easily confirmed by the reaction with hydroxides of metals. If the sucrose solution is pouring the copper (II) hydroxide, a bright blue solution of copper sacharat is formed. There is no aldehyde group in sucrose: when heated with ammonia solution of silver oxide (I), it does not give a "silver mirror", when heated with copper hydroxide (II) does not form red copper oxide (I). From among the isomers of sucrose having a molecular formula C12N22O11, maltose and lactose can be allocated.
The reaction of sucrose with water.If you boil a solution of sucrose with several drops of hydrochloric or sulfuric acid and neutralize the acid by alkali, and then heat the solution, then molecules with aldehyde groups appear, which restore copper (II) hydroxide to copper (I) oxide. This reaction shows that sucrose with a catalytic action of an acid is hydrolyzed, as a result of which glucose and fructose are formed: C12N22O11 + H2O → C6H12O6 + C6H12O6
Natural and anthropogenic sources.It is contained in sugar cane, sugar beet (up to 28% dry matter), plant juices and fruits (for example, birch, cock, melons and carrots). The source of sucrose - from beet or cane is determined by the ratio of the content of stable carbon isotopes 12c and 13c. Sugar beet has a C3-mechanism for the assimilation of carbon dioxide (through phosphoglycerolic acid) and preferably absorbs the isotope 12c; Sugar cane has a C4-mechanism of absorption of carbon dioxide (through oxalacetic acid) and preferably absorbs the isotope 13c.
45. Cellobiosis - a carbohydrate from a group of disaccharides, consisting of two glucose residues connected by (β-glucoside bond; the main structural unit of cellulose.
White crystalline substance, well soluble in water. For cellobiosis, the reaction with the participation of aldehyde (semi-acetal) group and hydroxyl groups is characterized. In acid hydrolysis or under the action of the enzyme β-glucosidase, the cellobiosis is splitted with the formation of 2 glucose molecules.
It is obtained by cellobiosis with partial hydrolysis of cellulose. In the free form of cellobiosis is contained in the juice of some trees.
46. \u200b\u200bPolysaccharides - The general name of the class of complex high molecular carbohydrates, whose molecules consist of dozens, hundreds or thousands of monomers - monosaccharides.
Polysaccharides are necessary for the vital activity of animals and vegetable organisms. They are one of the main sources of energy generated by the metabolism of the body. They take part in immune processes, ensure the adhesion of cells in tissues, are the main mass of organic matter in the biosphere.
A variety of biological activity of polysaccharides of plant origin was established: antibiotic, antiviral, antitumor, antidial [source not specified 236 days]. Polysaccharides of plant origin perform a large role in reducing lipemia and precomposition of blood vessels due to the ability to give complexes with proteins and plasma lipo proteids.
Polyesaccharides include, in particular:
dextrin - polysaccharide, product of starch hydrolysis;
starch is the main polysaccharide, laid as an energy margin in plant organisms;
glycogen - polysaccharide, delayed, as an energy margin in animal cells, but occurs in small quantities and in plant tissues;
cellulose - the main structural polysaccharide of the cell walls of plants;
galaktomannans - spare polysaccharides of some plants of the bean family, such as guaran and gum of the horn tree;
glucomananan - Polysaccharide, obtained from the tuber conn, consists of alternating glucose links and mannose, soluble food fiber, which reduces appetite;
amyloid is used in the production of parchment paper.
Cellulose (from lat. Cellula - cell, the same as the fiber) - [C6H7O2 (OH) 3] n, polysaccharide; The main component of the cell shells of all higher plants.
Cellulose consists of remnants of glucose molecules, which is formed in acid hydrolysis of cellulose:
(C6H10O5) N + NH2O -\u003e NC6H12O6
Cellulose is long threads containing 300-2500 glucose residues, without side branches. These threads are interconnected by a multitude of hydrogen bonds, which gives cellulose greater mechanical strength. In mammals (as well as most other animals) there are no enzymes capable of cleaving cellulose. However, many herbivore animals (for example, chewing) have in the digestive path of the symbiotic bacteria that split and help the owners to absorb this polysaccharide.
The industrial pulp method is obtained by cooking on cellulose factories of incoming industrial complexes (combines). By type of reagents used, the following cellulose cooking methods are distinguished:
Sulphite. The cooking solution contains sulfuric acid and its salt, such as sodium hydrosulfite. This method is used to produce cellulose from low-grade wood: spruce, fir.
Alkaline:
Natron. Sodium hydroxide solution is used. A typus method can be obtained cellulose from hardwood wood and annual plants.
Sulphate. The most common method today. A solution containing hydroxide and sodium sulphide is used as a reagent, and called white liquor. The method received its name from sodium sulfate, from which sulphide for white liquor is obtained on cellulose combines. The method is suitable for producing pulp from any type of plant raw materials. The disadvantage of it is the allocation of a large number of ill-smelling sulfur compounds: methylmercaptan, dimethyl sulfide, etc. As a result of adverse reactions.
The technical cellulose obtained after cooking contains various impurities: lignin, hemicellulose. If the cellulose is intended for chemical processing (for example, to produce artificial fibers), it is subjected to refining - treatment with cold or hot alkalo alkalo solution to remove hemicellulose.
To remove residual lignin and giving cellulose whiteness, its bleach is carried out. Traditional chlorine bleach includes two steps:
processing chlorine - for the destruction of lignin macromolecules;
approaching alkali - to extract the resulting lignin destruction products.
47. Starch - Amilosa and amylopectin polysaccharides, whose monomer is alpha-glucose. Starch, synthesized by different plants under the action of light (photosynthesis) has several different compositions and the structure of the grain.
Biological properties.Starch, being one of the products of photosynthesis, is widespread in nature. For plants, it is a reserve of nutrients and is mainly in fruits, seeds and tubers. The most richly starch grain grain of cereal plants: rice (up to 86%), wheat (up to 75%), corn (up to 72%), as well as potato tubers (up to 24%).
For the human body, starch, along with sucrose, serves as the main supplier of carbohydrates - one of the most important components of food. Under the action of starch enzymes is hydrolyzed to glucose, which is oxidized in cells to carbon dioxide and water with the release of energy necessary for the functioning of a living organism.
Biosynthesis.Part of glucose generated in green plants with photosynthesis, turns into starch:
6CO2 + 6H2O → C6H12O6 + 6O2
nC6H12O6 (glucose) → (C6H10O5) N + NH2O
In general, it can be written as 6NCO2 + 5NH2O → (C6H10O5) N 6NO2.
Starch as a backup nutrition accumulates in tubers, fruits, plant seeds. So in the potato tubers is contained up to 24% starch, in the wheat grains - up to 64%, rice - 75%, corn - 70%.
Glycogen - Polysaccharideformed by glucose residues; The main spare carbohydrate of man and animals. Glycogen (also sometimes called animal starch, despite the inaccuracy of this term) is the main form of glucose storage in animal cells. It is postponed in the form of granules in cytoplasm in many types of cells (mainly liver and muscles). Glycogen forms an energy reserve that can be quickly mobilized if necessary, fill the sudden lack of glucose. The glycogen margin, however, is not so extinguishing in calories per gram, as a stock of triglycerides (fats). Only glycogen, stored in liver cells (hepatocytes) can be recycled in glucose to feed the entire body, while hepatocytes are able to accumulate up to 8 percent of their weight in the form of glycogen, which is the maximum concentration among all types of cells. The total weight of glycogen in the liver can reach 100-120 grams in adults. In the muscles, glycogen is processed in glucose exclusively for local consumption and accumulates in much smaller concentrations (no more than 1% of the total mass of the muscles), at the same time its total muscular supply may exceed the margin accumulated in hepatocytes. Not a large number of Glycogen is discovered in the kidneys, and even less - in certain types of brain cells (glial) and white blood cells.
48. Hitin (C8H13O5N) (FR. Chitine, from Greek. Chiton: Chiton - clothes, leather, shell) - a natural compound from a group of nitrogen-containing polysaccharides. Chemical title: Poly-N-acetyl-D-glucose-2-amine, polymer from N-acetylglucosamine residue, interconnected B- (1.4) -Hlikosoidal bonds. The main component of the exoskeleton (cuticle) of arthropods and a number of other invertebrates is included in the cell wall of mushrooms and bacteria.
Distribution in nature.Hitin is one of the most common polysaccharides - every year about 10 gigaton chitin is formed every year on earth in living organisms and decomposes.
Performs protective and reference functions, providing the rigidity of the cells - is contained in the cell walls of mushrooms.
The main component of the exoskeleton of arthropods.
Also, chitin is formed in the organisms of many other animals - a variety of worms, intestinal and so on.
In all organisms that produce and use chitin, it is not in its pure form, but in a complex with other polysaccharides, and very often associated with proteins. Despite the fact that chitin is a substance, very close in structure, physicochemical properties and biological roles for cellulose, in organisms forming cellulose (plants, some bacteria) chitin failed.
Chemistry chitin.In the natural form of chitins of different organisms, they differ slightly from each other in composition and properties. Molecular weight of chitin reaches 260,000.
Chitin is not soluble in water, resistant to dilute acids, alkalis, alcohol, and other organic solvents. Soluble in concentrated solutions of some salts (zinc chloride, lithium thiocyanate, calcium salts).
When heated with concentrated solutions of mineral acids is collapsed (hydrolyzed), cleaving acetyl groups.
Practical use.One of the chitin derivatives obtained from it in an industrial method is chitosan. Raw materials for obtaining it serve as crustacean shells (Krill, Kamchatka Crab), as well as microbiological synthesis products.
49. Aromatic hydrocarbons, Organic compounds consisting of carbon and hydrogen and containing benzene kernels. The simplest and most important representatives of A. y. - benzene (i) and its homologues: methylbenzene, or toluene (II), dimethylbenzene, or xylene, etc. K. Benzol derivatives with unsaturated side chains, such as styrene (III), also belong. There are a lot of A.. with several benzene nuclei in a molecule, for example diphenylmethane (IV), DiPhenyl C6H5-C6H5, in which both benzene nuclei are directly related; in naphthalene (V), both cycles have 2 common carbon atoms; Such hydrocarbons are called A. y. with condensed cores.
Benzole C6H6, PHH) - organic chemical compound, colorless liquid with a pleasant sweet odor. Aromatic hydrocarbon. Benzene is part of gasoline, is widely used in industry, is the initial raw material for the production of drugs, various plastics, synthetic rubber, dyes. Although benzene is part of crude oil, on an industrial scale it is synthesized from its other components. Toxic, carcinogen.
Homologies - Compounds belonging to one class, but differing from each other in the composition of the integer number of CH2 groups. The combination of all homologues forms a homologous row.
Physical properties.Colorless liquid with a peculiar odor. Melting point \u003d 5.5 ° C, Boiling point \u003d 80.1 ° C, density \u003d 0.879 g / cm³, molecular weight \u003d 78.11 g / mol. Like all hydrocarbons, benzene burns and forms a lot of soot. With air, it forms explosive mixtures, mixed with ether, gasoline and other organic solvents, with water forms azeotropic mixture with a boiling point of 69.25 ° C. The solubility in water is 1.79 g / l (at 25 ° C).
Structure.Benzole in composition refers to unsaturated hydrocarbons (Homological series CNH2N-6), but in contrast to hydrocarbons of ethylene C2H4 exhibits properties inherent in saturated hydrocarbons under rigid conditions, but the benzene reactions are more inclined. Such a "behavior" of benzene is explained by its special structure: the presence in the structure of a conjugate 6π-electron cloud. The current presentation of the electronic nature of the bonds in Benzole is based on the hypothesis of Linus Pauling, which suggested depicting a benzene molecule in the form of a hexagon with an inscribed circumference, thereby emphasizing the absence of fixed double bonds and the presence of a single electronic cloud covering all six carbon atoms of the cycle.
50. Aromatic compounds (arena) - cyclic organic compounds that have an aromatic system of ties in their composition. They may have rich or unsaturated side chains.
The most important aromatic hydrocarbons include benzene C6H6 and its homologues: toluene C6H5SNZ, xylene C6H4 (SNZ) 2, etc.; Naphthalene C10H8, Anthracene C14N10 and their derivatives. Distinctive chemical properties - increased stability of the aromatic nucleus and the tendency to reactions to substitution. The main source of obtaining aromatic hydrocarbons serve a coal tar, oil and petroleum products. Synthetic methods of obtaining are of great importance. Aromatic hydrocarbons - source products for producing ketones, aldehydes and acids of aromatic rows, as well as many other substances. There are also heterocyclic arenas, among which are most often found in pure form and in the form of compounds - pyridine, pyrrole, furan and thiophene, indole, purin, quinoline.
Also, Borazol ("inorganic benzene") has aromaticity, but its properties differ significantly from the properties of organic arena.
Electrophilic reaction " (Eng. Substitution Electrophilic Reaction) - reactions of substitution in which the attack carries out the electrophile particle, charged positively or having a deficit of electrons. In the formation of a new connection, the outgoing particle - the electrophage is cleaved without its electronic pair. The most popular outgoing group is the proton H +.
51-52. The reactions of aromatic electrophilic replacement
For aromatic systems, there is a single mechanism of electrophilic substitution - SEAR. The SE1 mechanism (by analogy with the SN1 mechanism), it is extremely rare, and SE2 (corresponding by the analogy of SN2) is not found at all.
SEAR reaction mechanism or the reaction of aromatic electrophilic substitution (eng. Substitution Electrophilic Aromatic) is the most common and most important among the reactions of substitution of aromatic compounds and consists of two stages. At the first stage, the attachment of the electrophila occurs, on the second - the cleavage of electrophigh.
During the reaction, an intermediate positively charged intermediate (in Figure 2B) is formed. It is called Intermediat Wuelanda, anonymous ion or σ-complex. This complex is usually very reactive and easily stabilized, quickly cleaving the cation. The limiting step in the overwhelming majority of SEAR reactions is the first stage.
Reaction rate \u003d K **
As an attacking particle, there are usually relatively weak electrophils, therefore, in most cases, the SEAR reaction proceeds under the action of a catalyst - Lewis acids. More often than others are used by AlCl3, FECL3, FeBr3, ZnCl2.
In this case, the reaction mechanism is as follows (on the example of chlorination of benzene, FECL3 catalyst):
1. On the first stage, the catalyst interacts with an attacking particle to form an active electrical agent
In the second stage, in fact, the SEAR mechanism is implemented
53. Heterocyclic compounds (heterocycles) - organic compounds containing cycles in which, along with carbon, the atoms of other elements are also included. It can be considered as carbocyclic compounds with hetero-plates (heteroatoms) in the cycle. The most diverse and well studied aromatic nitrogen-containing heterocyclic compounds. Limit cases of heterocyclic compounds - compounds that do not contain carbon atoms in the cycle, for example, pentazole.
Pyrrole.- Aromatic five-membered nitrogen heterocycle, has weak major properties. It is contained in bone oil (which is obtained with dry distillation of bones), as well as in a coal currency. Pyrrolone rings are part of the porphyrins - chlorophyll plants, hemoglobins and cytochromes and a number of other biologically important compounds.
Building and properties.Pyrrole is a colorless liquid resembling the smell of chloroform, slowly darkening during air standing. It is slightly hygroscopic, slightly soluble in water and is well soluble in most organic solvents. Pyrrola's structure suggested in 1870 by Bayer, based on its oxidation with chromium acid in maleinimide and the formation of it with a distillation of succinimide with zinc dust.
Acidity and metallization.Pyrrole is weak NH acid (PKa 17.5 in water) and reacts with alkaline metals and their amides in liquid ammonia or inert solvents with deprotonation by position 1 and the formation of appropriate salts. The reaction with the reactivities of Grignar, at which N-magnesium salts are formed. N-substituted pyrrolas react with butyl and phenyllium, meticulous in the α-position.
54. Indoil (Benzo [B] Pyrrol), they say. m. 117.18; Beszvest. crystals with a weak smell of naphthalene; t. pl. 52.5 ° C, t. Kip. 254 ° C; D456 1,0718; Running under force. up to 150 ° C; m 7.03.10-30 kl.m (benzene, 25 ° С); distilled with water vapor, diethyl ether and NH3; well suited. in org. R-Ryteli, hot water, liquid NH3. The molecule has a flat configuration.
Indole is a weak base (RKA -2.4). During protonation, the 3H-indole (F-la i) cation is formed, which is commercially. With a neutral indole molecule gives dimer (II). As a weak K-TA (PKA 17), indole with Na in liquid NH3 forms N-sodiumindol, with a con at 130 ° C - N-potassiumindol. It has aromatic. Mow. Electrophe Replacement goes ch. arr. To position 3., the nitration is usually carried out by benzoylntitom, sulphing - pyridin sulfotryoid, bromination - dioxandibromide, chlorination - SO2Cl2, alkylation - active alkyl halides. Acetylation in acetic k-those also goes to position 3, at a presence. CH3COONA - in position 1; In acetic anhydride, 1,3-diacetylindol is formed. Indol easily joins the double bond A, B-unefprecedable ketones and nitriles.
Aminomethylation (mannich) in mild conditions flows to position 1, in rigid - in position 3. Replacement in the benzene ring (premix. In position 4 and 6) is only in acidic environments with a blocked position 3. at a presence. H2O2, Načislot or the Indol light is oxidized into indoxyl, then then turning. in trimer or indigo. The stringent oxidation under the action of O3, MNO2 leads to a breaking of a pyrrole ring with the formation of 2-formamp-benzaldehyde. In the hydrogenation of indole hydrogen in mild conditions, a pyrrole ring is restored, in more hard - and benzene.
Indol is contained in the essential oils of jasmine and citrus, is part of Kam.-ug. resin. Indol Ring - Fragment of Molecules Important Pri. compounds (eg tryptophan, serotonin, melatonin, buffotonin). The indole is usually isolated from the naphthalene fraction Kam. --ug. Resins or are obtained by dehydrogenation of O-ethylleniline with the last. Cooling the resulting product. Indole and its derivatives are also synthesized by the cyclization of the arylhydrasons of carbonyl compounds. (Fisher's Rocation), Primary. Arylamines with A-halogen or a-hydroxycarbonyl compounds. (Bishler's Rocation) and others. The indole core is part of the indole alkaloids. Indole-fixator itself smell in perfumes; Its derivatives are used in the production of biologically active compound. (hormones, halucinogen) and lek. CP-B (eg, indoor, indomethacin).
55. Imidazole. - organic compound of the heterocycle class, a five-membered cycle with two nitrogen atoms and three carbon atoms in the cycle, is isometrine pyrazole.
Properties.In unsubstituted imidazole positions 4 and 5 (carbon atoms) are equivalent, due to the Tautomeria. Aromatic, reacts with diazonia salts (combination). It is noticing and sulphised only in an acidic medium to position 4, halogens in an alkaline medium are joined by position 2, in acidic - by position 4. Easily alkylated and acylated by imminent N, reveals the cycle when interacting with solutions of strong acids and peroxides. Catalyzes hydrolysis of hard-fired esters and amides carboxylic acids.
On the basis of imidazole produce a large number of different ionic liquids.
Methods of receipt.From ortho-phenylenediamine through benzimidazole and 4.5-imidazoledicarboxylic acid.
The interaction of glyoxal (sorveless aldehyde) with ammonia and formaldehyde.
Biological role.The imidazol cycle is part of an indispensable ashidin amino acid. Structural fragment of histamine, purine bases, dibazole.
56. Pyridine - a six-membered aromatic heterocycle with one nitrogen atom, a colorless liquid with a sharp unpleasant odor; Mixed with water and organic solvents. Pyridine is a weak base, gives salts with strong mineral acids, easily forms double salts and complex compounds.
Getting.The main source for obtaining pyridine is a coal tar.
Chemical properties.Pyridine shows properties characteristic of tertiary amines: forms N-oxides, N-alkylpyridinium salts, is able to act as a sigma donor ligand.
At the same time, pyridine has obvious aromatic properties. However, the presence of a nitrogen atom in the ring leads to a serious redistribution of electron density, which leads to a strong decrease in pyridine activity in the reaction of electrical aromatic substitution. In such reactions, predominantly meta-position ring react.
For pyridine, the reaction of aromatic nucleophilic substitution is characterized, which take place predominantly by ortho-steam the positions of the ring. Such a reactivity indicates the electronic nature of the pyridine ring, which can be generalized in the following empirical rule: the reactivity of pyridine as an aromatic compound approximately corresponds to the reactivity of nitrobenzene.
Application.Used in the synthesis of dyes, medicinal substances, insecticides, in analytical chemistry, as a solvent of many organic and some inorganic substances, for denaturing alcohol.
Safety.Pyridine toxic, acts on the nervous system, the skin.
57. Biological role.Nicotinic acid is a pyridine derivative. It is absorbed in the stomach and duodenalist, and then subjected to amination, resulting in nicotinoamide, which in the body in the complex with proteins is formed more than 80 enzymes. This is the main physiological role of vitamin B5. Thus, nicotinic acid is part of such important redox enzymes as dehydrogenesis, catalyzing hydrogen from oxidizing organic substances. Thus, the hydrogen is taken in this way, these enzymes further transmit the further-reducing enzymes, which include riboflavin. In addition, in the body of mammals from nicotinamide (niacin) and nicotinic acid, pyridine nucleotides are formed, which serve as coenzymes over and NADF. The lack of these precursors in animals causes Pellagru - a disease that manifests symptoms from the skin, the gastrointestinal tract and the nervous system (dermatitis, diarrhea, dementia). As coenzymes over and NADF, nicotinic acid predecessors are involved in many oxidative and reduced reactions catalyzing dehydrogenases. The biological effect of nicotine acid is manifested in the form of stimulation of the secretory function of the stomach and the digestive glands (in its presence in the stomach, the concentration of free hydrochloric acid increases). Under the influence of vitamin B5 there is an increase in glycogen biosynthesis and a reduction in hyperglycemia, an increase in the detoxifying liver function, the expansion of blood vessels, improved blood microcirculation.
There is a connection between nicotine acid and sulfur-containing amino acids. Increased excretion with urine methylnicotamide during protein deficiency is normalized by inclusion in the diet of sulfur-containing amino acids. At the same time, the content of phosphopyrinucleotides in the liver is normalized.
58. Pyrimidine (C4N2H4, Pyrimidine, 1,3- or M-diazine, Miazin) is a heterocyclic compound having a flat molecule, the simplest representative of 1.3-diazines.
Physical properties.Pyrimidine - colorless crystals with a characteristic smell.
Chemical properties.Molecular weight of pyrimidine 80.09 g / mol. Pyrimidine shows the properties of a weak two-cylinder base, since nitrogen atoms can attach protons due to donor-acceptor communications, acquiring a positive charge. The reactivity in the electrophyl substitution reactions in pyrimidine is reduced due to a decrease in the electron density in the positions of 2,46, caused by the presence of two nitrogen atoms in the cycle. The substitution becomes possible only in the presence of electron-sized substituents and is sent to the least deactivated position 5. However, in contrast, pyrimidine is active with respect to nucleophilic reagents that attack 2, 4 and 6 carbon atoms in the cycle.
Getting.Pyrimidine is obtained by the restoration of halogenated pyrimidine derivatives. Or from the 2.4,6-trichlorine pyrimidine obtained by the processing of barbituric acid chloroxide.
Pyrimidine derivatives Widely common in wildlife, where they are involved in many important biological processes. In particular, such derivatives as cytosine, Timin, Uracil is part of nucleotides, which are structural units of nucleic acids, the pyrimidine kernel is part of some vitamins of the group B, in particular B1, coenzymes and antibiotics.
59. Purin (C5N4H4, PURINE) - heterocyclic compound, the simplest representative of imidazopyrimidines.
Pyrin derivatives play an important role in the chemistry of natural compounds (purine bases of DNA and RNA; NAD coenzyment; alkaloids, caffeine, theophylline and theobromine; toxins, saxicoxin and related compounds; uric acid) and, due to this, in pharmaceutics.
Adenin- nitrogenous base, amino derivatives of purine (6-aminopurine). Forms two hydrogen bonds with Uracil and Timin (complementarity).
Physical properties.Adenin is colorless crystals that melt at a temperature of 360-365 C. It has a characteristic maximum absorption (λmax) at 266 MMK (pH 7) with a molar extinction coefficient (εmax) 13500.
Chemical formula C5H5N5, Molecular weight 135.14 g / mol. Adenin shows the basic properties (PKA1 \u003d 4.15; PKA2 \u003d 9.8). When interacting with nitric acid, adenin loses an amino group, turning into hypoxanthin (6-oxypurine). In aqueous solutions, crystallizes in crystal hydrate with three water molecules.
Solubility.Well soluble in water, especially hot, with a decrease in water temperature, the solubility of adenine in it drops. Easy to soluble in alcohol, in chloroform, ether, as well as in acids and alkalis - not soluble.
Prevalence and significance in nature.Adenin is part of many vital for living organisms of compounds, such as: adenosine, adenosinephosphotasis, adenosine phosphoric acids, nucleic acids, adenine nucleotides, etc. In the form of these compounds, adenin is widespread in wildlife.
Guanian- A nitrogen base, amino derivatives (6-oxy-2-aminoinurin), is an integral part of nucleic acids. In DNA, the replication and transcription forms three hydrogen bonds with cytosine (complementarity). First allocated from Guano.
Physical properties.Colorless, amorphous crystalline powder. Melting point 365 ° C. Huanin solution in HCl fluoresce. In alkaline and acidic mediums, two absorption maxima (λmax) in the ultraviolet spectrum: at 275 and 248 MMK (pH 2) and 246 and 273 MMK (pH 11).
Chemical properties.Chemical formula - C5H5N5O, molecular weight - 151.15 g / mol. Manifests basic properties, pka1 \u003d 3.3; pka2 \u003d 9.2; PKA3 \u003d 12.3. Reacts with acids and alkalis to form salts.
Solubility.Well soluble in acids and alkalis, poorly soluble on the air, alcohol, ammonia and neutral solutions insoluble in water .
Qualitative reactions.To determine the guanine, it is precipitated by metaphosphor and picric acids, with diazosulfonic acid in the Na2Co3 solution gives red staining.
Distribution in nature and value.Included in nucleic acids.
60. Nucleosides - These are glycosylamines containing a nitrogenous base associated with sugar (ribose or deoxyribose).
Nucleosides can be phosphorylated by cell kinases along the primary alcohol sugar group, while the corresponding nucleotides are formed.
Nucleotides - Nucleoside phosphor esters, nucleoside phosphates. Free nucleotides, in particular ATP, CAMF, ADP, play an important role in energy and information intracellular processes, as well as components of nucleic acids and many coenzymes.
Nucleotides are esters of nucleosides and phosphoric acids. Nucleosides, in turn, are N-glycosides containing a heterocyclic fragment associated with a nitrogen atom with a C-1 atom of the sugar residue.
The structure of nucleotides.In nature, nucleotides are the most common nucleotides, which are β-n-glycosides of purines or pyrimidines and pentosis - D-ribose or D-2-ribose. Depending on the structure of pentoses, ribonucleotides and deoxyribonucleotides are distinguished, which are monomers of molecules of complex biological polymers (polynucleotides) - respectively, RNA or DNA.
The phosphate residue in nucleotides usually forms the ester bond with 2 "-, 3" - or 5 "-gidroxyl groups of ribonucleosides, in the case of 2" -deoxinucleosides, 3 "- or 5" -hydroxyl groups are esterified.
Compounds consisting of two nucleotide molecules are called dinucleotides, of three-trinucleotides, from a small number - oligonucleotides, and from many - polynucleotides, or nucleic acids.
Nucleotide names are abbreviations in the form of standard three-or four-letter codes.
If the abbreviation begins with the lowercase letter "d" (eng. D), it means that deoxyribonucleotide is meant; The absence of the letter "D" means ribonucleotide. If the abbreviation begins with the lowercase letter "C" (eng. C), it means we are talking about the cyclic form of a nucleotide (for example, CAMF).
The first capital letter of the abbreviation indicates a specific nitrogen base or a group of possible nucleic bases, the second letter - by the amount of phosphoric acid residues in the structure (M - mono-d - d -, T - three-), and the third capital letter - always the letter F ("-Phosphate"; English P).
Latin and Russian codes for nucleic grounds:
A - A: adenine; G - g: Guanin; C - C: cytosine; T - T: Timin (5-methyluracyl) is not found in RNA, it takes a place of Uracil to DNA; U - U: Uracil, does not occur in DNA, it takes a place of thymine in RNA.
The first originated at the beginning of the XIX century. theory of radicals (J. Gay Lussak, F. Veller, Y. Libih). Radicals were named groups of atoms, moving unchanged with chemical reactions from a single connection to another. Such a concept about radicals has been preserved, but most of the provisions of the theory of radicals were incorrect.
According to type theories (Sh. Gerard) All organic substances can be divided into types corresponding to certain inorganic substances. For example, R-Oh alcohols and ethers of R-O-R were considered as representatives of the type of H-OH water, in which hydrogen atoms are substituted with radicals. The theory of types created a classification of organic substances, some principles of which are currently applied.
The modern theory of the structure of organic compounds was created by an outstanding Russian scientist A.M. Butlerov.
The main provisions of the structure of the structure of organic compounds A.M. Butlerova
1. Atoms in the molecule are arranged in a certain sequence according to their valence. The valence of carbon atom in organic compounds is four.
2. The properties of substances depend not only on what atoms and in what quantities are included in the molecule, but also on what order they are interconnected.
3. Atoms or groups of atoms included in the molecule mutually affect each other, from which the chemical activity and the reactivity of molecules depend.
4. The study of the properties of substances allows to determine their chemical structure.
The mutual influence of neighboring atoms in molecules is the most important property of organic compounds. This effect is transmitted or on the circuit of simple bonds or by chain of conjugate (alternating) simple and double bonds.
Classification of organic compounds Based on the analysis of two aspects of the structure of molecules - the structure of the carbon skeleton and the availability of functional groups.
Organic compounds
Hydrocarbons heterocyclic compounds
Extremely
delica ticked
Aliphatic carbocyclic
Limit unsaturated alicyclic aromatic
(Alkana) (Cycloalkanes) (Arena)
FROM PH 2 p+2 S. PH 2 p FROM PH 2 p-6
End of work -
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All the themes of this section:
Alkenes alkadien alkina
SPN2P SPN2P-2 SPN2P-2 Fig. 1. Classification of organic compounds on the structure
Electronic structure of carbon atom. Hybridization.
For the valence electronic layer of an atom with the inlet subgroup of the fourth group of the second period of the periodic table D. I. Mendeleev, the main quantum number n \u003d 2, side (orbital
Conjugated systems
There are two types of conjugate systems (and conjugation). 1. P, P-pairing - electrons are delocalized
Topic 3. Chemical structure and isomerism of organic compounds
Isomerius of organic compounds. If two or more individual substances have the same quantitative composition (molecular formula), but differ from each other
Conformations of organic molecules
The turn around the S-C S-C is performed relatively easily, the hydrocarbon chain can take different forms. Conformational forms easily go into each other and therefore are not different
Conformations of cyclic compounds.
Cyclopentane. In a five-membered cycle in a flat form, the valence angles are equal to 108 °, which is close to the normal value for a SP3-hybrid atom. Therefore, in a flat cyclopentane, in contrast to the cycle
Configuration isomers
These are stereoisomers with different arrangements around certain atoms of other atoms, radicals or functional groups in space relative to each other. Discern the concepts of diastere
The overall characteristics of the reactions of organic compounds.
Acidness and basicity of organic compounds. To assess the acidity and baseness of organic compounds, two theories are the most important - the theory of Brenstead and theory
The bases of Brensted are neutral molecules or ions capable of attaching a proton (proton acceptors).
Acidness and basicity are not absolute, but relative properties of compounds: Acid properties are detected only in the presence of the base; Basic properties - only in the presence of ki
General characteristics of organic compound reactions
Most organic reactions include several consecutive (elementary) stages. A detailed description of the combination of these stages is called the mechanism. Reaction mechanism -
Selectivity reactions
In many cases, several unequal reactionary centers are present in the organic compound. Depending on the structure of the reaction products, they are talking about the regional selectivity, chemoselectivity and
Radical reactions.
Chlorine reacts with limit hydrocarbons only under the influence of light, heating or in the presence of catalysts, and all hydrogen atoms are sequentially replaced: CH4
Reactions of electrophile joining
Unsaturated hydrocarbons - alkenes, cycloalkens, alkadians and alkins - exhibit the ability to reactions to attachment, as they contain double or triple ties. More important in vivo is double
And elimination in a saturated carbon atom
Nucleophilic replacement reactions in a SP3-hybridized carbon atom: heterolithic reactions due to the polarization of S- Communication carbon - heteroatom (halogenopro
The reactions of nucleophilic replacement with the participation of a SP2-hybridized carbon atom.
The mechanism of reactions of this type will look at the example of the interaction of carboxylic acids with alcohols (esterification reaction). In the carboxyl group, the acid is realized by p, the pairing, as a pair of ele
Nucleophilic replacement reactions in a row of carboxylic acids.
Only with purely formal positions can be considered a carboxyl group as a combination of carbonyl and hydroxyl functions. In fact, their mutual influence on each other is such that fully and
Organic compounds.
Redox reactions (OSR) occupy a large place in organic chemistry. ORZ for life processes are essential. With their help the body satisfy
Participating in the processes of life
The overwhelming majority of organic substances involved in metabolic processes are compounds with two and more functional groups. Such connections are customary to classify.
Double phenols
Double phenols - pyrocatechin, resorcin, hydroquinone - are included in many natural compounds. All of them give characteristic staining with iron chloride. Pirocatechin (O-Dihydroxybenzene, catecho
Dicarboxylic and unsaturated carboxylic acids.
Carboxylic acids containing one carboxyl group in their composition are called monasons, two - two-axis, so far dicarboxylic acids - white crystalline substances possessing
Aminospirts
2-aminoethanol (ethanolamine, collamin) - the structural component of complex lipids, is formed by opening the intense three-mended cycles of ethylene oxide and ethylenemine ammonia or water, respectively
Hydroxy and amino acids.
Hydroxy acid contains in the molecule at the same time hydroxyl and carboxyl groups, amino acids - carboxyl and amino group. Depending on the location of hydroxy- or amino group
Oxocuslotes
Oxocuslots - compounds containing at the same time carboxyl and aldehyde (or ketone) group. In accordance with this, aldehydiscoslotes and ketokislotes are distinguished. Simpled aldegiadis
Heterofunctional benzene derivatives as medicinal products.
The last decades are characterized by the emergence of many new drugs and drugs. At the same time, some groups of previously known drugs continue to maintain
Topic 10. Biologically important heterocyclic compounds
Heterocyclic compounds (heterocycles) - compounds comprising in a cycle one or more atoms other than carbon (heteroatoms). Heterocyclic systems underlie with
Theme 11. Amino acids, peptides, proteins
The structure and properties of amino acids and peptides. Amino acids - compounds, in the molecules of which are at the same time there are amino and carboxyl groups. Natural A-amine
The spatial structure of polypeptides and proteins
For high molecular weight polypeptides and proteins, along with the primary structure, higher levels of organization are characterized, which is customary to be called secondary, tertiary and quaternary structures.
Topic 12. Carbohydrates: mono, di- and polysaccharides
Carbohydrates are divided into simple (monosaccharides) and complex (polysaccharides). Monosaccharides (monozia). These are heteropolifunctional compounds containing carbonyl and several g
Topic 13. Nucleotides and nucleic acids
Nucleic acids (polynucleotides) are biopolymers whose monomer units are nucleotides. Nucleotide is a three-component structure consisting
Nucleosides.
Heterocyclic bases form N-glycosides with D-ribose or 2-deoxy-d-ribose. In nucleic acid chemistry, such N-glycosides are called nucleosides. D-ribose and 2-deoxy-d -Rebosis in
Nucleotides.
Nucleotides are called nucleoside phosphates. Phosphoric acid usually esterifies alcohol hydroxyl at C-5 "or C-3" in the residue of ribose or deoxyribose (a nitrogen base atoms
Steroids
Steroids are widespread in nature, perform a variety of functions in the body. By now, about 20,000 steroids are known; More than 100 of them applied in medicine. Steroids have
Steroid hormones
Hormones - biologically active substances resulting from the activities of the domestic secretion glands and participating in the regulation of metabolism and physiological functions in the body.
Sterina
As a rule, cells are very rich in sterols. Depending on the source of the selection, the hydrodes (from animals) are distinguished, phytosterols (from plants), micoserines (from mushrooms) and sterols of microorganisms. IN
Bile acids
In the liver of sterile, in particular, cholesterol is converted into bile acids. Aliphatic side chain at C17 in bile acids, hydrocarbon derivatives of Kolan, consists of 5 carbon atoms
Terpene and terpenoids
Under this name, a number of hydrocarbons and their oxygen-containing derivatives - alcohols, aldehydes and ketones, a carbon skeleton of which are built of two, three or more isoprene units are built. Ourselves
Vitamins
Vitamins are usually called organic substances, the presence of which in small quantities in human food and animals is necessary for their normal life activity. This is a classic OPR.
Long-soluble vitamins
Vitamin A refers to sesquiterpets, contained in oil, milk, egg yolk, fish oil; Pork fat and margarine does not contain it. It is vitamin growth; disadvantaged in fodder
Water soluble vitamins
At the end of the last century, thousands of sailors in the Japanese courts suffered, and many of them died to the painful death from the Mysterious Disease of Bury Bury. One of the riddles of Bury Take was that sailors on with
Topic: the main provisions of the theory of the structure of organic compounds A. M. Butlerova.
The theory of the chemical structure of organic compounds, nominated by A. M. Butlerov in the second half of the last century (1861), was confirmed by the works of many scientists, including the students of Butlerov and themselves. It turned out to be possible on its basis to explain many phenomena, until that pore did not have interpretation:, homology, the manifestation of carbon atoms of four-grams in organic substances. The theory performed its predictive function: on its basis, scientists predicted the existence of unknown even compounds, described the properties and opened them. So, in 1862-1864. A. M. Butlers considered propyl, butyl and amyl alcohols, determined the number of possible isomers and derived the formula of these substances. The existence of them later was experimentally proven, and some of the isomers synthesized the bootlers himself.
During the XX century. The provisions of the theory of the chemical structure of chemical compounds were developed on the basis of new views spreading in science: the theory of the structure of the atom, the theory of chemical bond, ideas about the mechanisms of chemical reactions. Currently, this theory has a universal nature, that is, it is fair not only for organic substances, but also for inorganic.
First position. Atoms in molecules are connected in a certain order in accordance with their valence. Carbon in all organic and in most inorganic compounds four ruby.
Obviously, the latter part of the first position of the theory is easy to explain that in compounds, carbon atoms are in an excited state:
tourgeal carbon atoms can be connected to each other, forming various chains:
The order of the compound of carbon atoms in molecules may be different and depends on the type of covalent chemical bond between carbon atoms - single or multiple (double and triple):
This provision explains the phenomenon.
Substances having the same composition, but a different chemical or spatial structure, and, consequently, different properties are called isomers.
Main types:
Structural isomerism, in which substances differ by the order of communication of atoms in molecules: carbon skeleton
Third position. Properties of substances depend on the mutual influence of atoms in molecules.
For example, in acetic acid, only one of the four hydrogen atoms come into the reaction with alkali. Based on this, it can be assumed that only one hydrogen atom is associated with oxygen:
On the other hand, from the structural formula of acetic acid, it is possible to conclude about the presence of one moving hydrogen atom in it, that is, its monasondness.The main directions of development of the theory of the structure of chemical compounds and its value.
In times, A. M. Butlerova in organic chemistry was widely used
empirical (molecular) and structural formulas. The latter reflect the order of the compound of atoms in the molecule according to their valence, which is denoted by dashes.
For ease of recording, abbreviated structural formulas are often used, in which dashes denote only links between carbon or carbon and oxygen atoms.
And fibers, products of which are used in technique, everyday life, medicine, agriculture. The value of the theory of chemical structure A. M. Butlerova for organic chemistry can be compared with the value of the periodic law and the periodic system of chemical elements D. I. Mendeleev for inorganic chemistry. No wonder in both theories so much in common in the ways of their formation, development directions and general scientific value.
As science took shape at the beginning of the XIX century, when the Swedish scientist J. Ya. Burtsellius first introduced the concept of organic substances and organic chemistry. The first theory in organic chemistry is the theory of radicals. The chemicals found that in the chemical transformations of a group of several atoms, a single substance is unchanged from the molecule into a molecule of another substance, just as the atoms of elements move from the molecule to the molecule. Such "unchangeable" groups of atoms and received the name of radicals.
However, not all scientists agreed with the theory of radicals. Many generally rejected the idea of \u200b\u200batomotic - representations about the complex structure of the molecule and the existence of an atom as its component. What is indisputable in our days is not the slightest doubt, in the XIX century. It was the subject of fierce disputes.
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But some people used by a person were not synthesized them, because they were obtained from living organisms or plants. These substances called organic.Organic substances failed to synthesize in the laboratory. At the beginning of the nineteenth century, such a doctrine as Vitalyism (VITA - life) was actively developed, according to which organic substances arise only thanks to the "life force" and it is impossible to create their "artificial way".
But there was time and science developed, new facts about organic substances appeared, which were contrary to the existing theory of the Vitalists.
In 1824, the German scientist F. Vylerfor the first time in the history of chemical science synthesized oxalic acid – Organic substance from inorganic substances (dicyan and water):
(CN) 2 + 4H 2 O → COOH - COOH + 2NH 3
In 1828, Völler heated a cyanomonic sodium with sulfur ammonium and synthesized urea - Product of liveliness of animal organisms:
Naocn + (NH 4) 2 SO 4 → NH 4 OCN → NH 2 OCNH 2
These discoveries played an important role in the development of science in general, and chemistry in particular. Chemical scientists began to gradually move away from the vitalistic teaching, and the principle of dividing substances into organic and inorganic discovered their inconsistency.
Currently substances Still divide on organic and inorganic,but the criterion of separation is already a bit different.
Organic called substancescontaining carbon in its composition, they are also called carbon compounds. Such compounds are about 3 million, the rest of the same compounds about 300 thousand.
Substances that carbon is not included, called inorganicand. But there are exceptions to the general classification: there are a number of compounds that include carbon, but they relate to inorganic substances (oxide and carbon dioxide, servo carbon, coal acid and its salts). All of them in composition and properties they are similar to inorganic compounds.
During the study of organic substances, new difficulties appeared: on the basis of theories about inorganic substances, it is impossible to reveal the patterns of the structure of organic compounds, to explain the valence of carbon. Carbon in different compounds had various valence.
In 1861, Russian scientist A.M. Butlers for the first time the synthesis received a sugar substance.
When studying hydrocarbons, A.M. Butlersi realized that they constitute a completely special class of chemicals. Analyzing their structure and properties, the scientist revealed several patterns. They laid the basis created by him chemical building theory.
1. The molecule of any organic matter is not random, the atoms in molecules are connected to each other in a certain sequence according to their valenneys. Carbon in organic compounds are always quadricula.
2. The sequence of interatomic bonds in the molecule is called the ephythmic structure reflected by one structural formula (structure formula).
3. The chemical structure can be installed by chemical methods. (Currently used modern physical methods).
4. Properties of substances depend not only on the composition of the molecules of the substance, but from their chemical structure (sequence of the compound of the atoms of the elements).
5. According to the properties of this substance, it is possible to determine the structure of its molecule, and on the structure of the molecule – anticipate properties.
6. Atoms and groups of atoms in the molecule have a mutual influence on each other.
This theory has become a scientific foundation for organic chemistry and accelerated its development. Relying on the provisions of the theory, A.M. Butlers described and explained the phenomenon isomeria, predicted the existence of various isomers and first got some of them.
Consider the chemical structure of ethane – C 2 H 6. Denoticing the valence of the elements of the fuses, depicting the ethane molecule in the order of the compound of atoms, that is, we will write a structural formula. According to A.M. Theory Butlerova, it will have the following form:
Hydrogen and carbon atoms are associated with one particle, hydrogen valence is equal to one, and carbon – Four. Two carbon atoms are interconnected by carbon bond – Carbon (S. – FROM). Carbon ability to form with – C-bond is understandable, based on the chemical properties of carbon. On the outer electronic layer at the carbon atom, four electrons, the ability to give electrons is the same as to attach the missing. Therefore, carbon most often forms compounds with a covalent bond, that is, due to the formation of electronic pairs with other atoms, including carbon atoms with each other.
This is one of the reasons for the diversity of organic compounds.
The compounds that have the same composition, but different buildings are called isomers. Isomeriya phenomenon – One of the reasons for the variety of organic compounds
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