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 unforeseen limit unforeseen aromatic

(Alkana) (Cycloalkanes) (Arena)

FROM p H 2 p +2 S. p H 2 p FROM p H 2 p -6

alkenes Polyens and Alkina

FROM p H 2 p Polynes S. p H 2 p -2

Fig. 1. Classification of organic compounds in the structure of the carbon skeleton

Classes of hydrocarbon derivatives on the availability of functional groups:

Halogen derivatives R-gal: CH 3 CH 2 Cl (chloroethane), with 6 H 5 Br (bromobenzene);

Alcohols and phenols R-it: CH 3 CH 2 it (ethanol), from 6 H 5 it (phenol);

Thiol R-SH: CH 3 CH 2 SN (ethanalty), with 6 H 5 SN (thiophenol);

Esters Simple R-O-R: CH 3 CH 2 -O-CH 2 CH 3 (diethyl ether),

complex R-co-O-R: CH 3 CH 2 coaxial 2 CH 3 (acetic acid ethyl ester);

Carbonyl compounds: Aldehydes R-SNO:

r-co-R ketones: CH 3 PIN 3 (propanone), from 6 H 5 pines 3 (methylphenylketon);

Carboxylic acids R-coxy: (acetic acid), (benzoic acid)

Sulfocuslotes R-SO 3 H: CH 3 SO 3 H (methanesulfonic acid), C 6 H 5 SO 3 H (benzenesulfonic acid)

Amines R-NH 2: CH 3 CH 2 NH 2 (ethylamine), CH 3 NHSH 3 (dimethylamine), from 6 H 5 NH 2 (aniline);

Nitro compound R-NO 2 CH 3 CH 2 NO 2 (nitroean), C 6 H 5 NO 2 (nitrobenzene);

Metallorganic (elementorganic) compounds: CH 3 CH 2 NA (ethyl nation).

A number of compounds similar in the structure of compounds with close chemical properties in which individual members of a series differ from each other only by the number of groups -CH 2 - is called homologous neara group - SN 2 - homologous difference . The members of the homologous series, the overwhelming majority of reactions are equally (the exception is only the first members of the series). Consequently, knowing the chemical reactions of only one member of the series, it is possible with a high degree of likelihood to assert that the same type of transformation is also with the rest of the homologous series.

For any homologous series, a general formula may be removed, reflecting the relationship between carbon and hydrogen atoms in the members of this series; Such. formula is called the general formula of the homologous series. So, S. p H 2 p +2 - Alkanov formula, with p H 2 p +1 ON aliphatic monatomic alcohols.

Nomenclature of organic compounds: trivial, rational and systematic nomenclature. Trivial nomenclature is a combination of historically established names. So, by the title it is immediately clear from where apple, amber or citric acid was isolated, which peeling acid (pyrolysis of grape acid) was obtained, the connoisseurs of the Greek language can easily guess that acetic acid is something sour, and the glycerin is sweet. As the synthesis of new organic compounds and the development of the theory of their structure, other nomenclatures were created, reflecting the structure of the compound (its belonging to a specific class).

The rational nomenclature is building the name of the compound on the basis of the structure of a simpler compound (the first member of the homologous series). SN 3 IS HE - Carbinol, CH 3 SN 2 IS HE - Methylcarbinol, CH 3 Sn (he)CH 3 - dimetalkarbinol, etc.

Nomenclature of Joupa (systematic nomenclature). According to the Nomenclature of the Jewberry (International Union on theoretical and Applied Chemistry), the names of hydrocarbons and their functional derivatives are based on the name of the appropriate hydrocarbon with the addition of prefixes and suffixes inherent in this homologous row.

To correctly (and definitely) to name the organic compound on the systematic nomenclature, it is necessary:

1) select the longest sequence of carbon atoms as the main carbon skeleton as the main carbon skeleton and give its name, paying attention to the degree of unsaturation of the compound;

2) to identify everything functional groups available in the compound;

3) to establish which group is older (see table), the name of this group is reflected in the title of the compound in the form of the sutvix and it is put at the end of the connection name; All other groups are given in the name of consoles;

4) to numbered carbon atoms of the main chain, giving the older group the smallest of the rooms;

5) list the prefixes in alphabetical order (at the same time multiplying consoles of di-, tri-, tetra-, etc. are not taken into account);

6) Make the full name of the connection.

Class of connections	Formula functional group		Suffix or ending
Carboxylic acids		Carboxy	Oboy acid
Sulfocislot			Sulfonic Acid

Aldehydes

		Hydroxy
		Mercapto-


	S≡≡≡≡.
Halogen derivatives	br, i, F, CL	Brom-, iodist-, fluoro-, chlorine	bromid, iiodide, -fluoride, chloride
Nitro compound

At the same time it must be remembered:

In the names of alcohols, aldehydes, ketones, carboxylic acids, amides, nitriles, sufifix halogenants, which determines the class, follows the suffix degree of unsaturation: for example, 2-buteral;

Compounds containing other functional groups are called hydrocarbon derivatives. The names of these functional groups are put as consoles before the name of the general hydrocarbon: for example, 1-chlorpropane.

The names of acid functional groups, such as a group of sulfonic acid or phosphine acid, are placed after the name of the hydrocarbon skeleton: for example, benzenesulfonic acid.

The derivatives of aldehydes and ketones are often called the name of the original carbonyl connection.

Carboxylic acid esters are called derivatives of generic acids. The ending of the acid is replaced by - ash: for example, methylpropionate is a methyl ether of propanco-acid.

In order to designate that the substituent is connected with the nitrogen atom of the source structure, use the capital letter n before the name of the substituent: N-methylaniline.

Those. It is necessary to start from the name of the source structure, for which it is absolutely necessary to know by heart the names of the first 10 members of the homologous series of alkanes (methane, ethane, propane, butane, pentane, hexane, heptane, octan, nonan, dean). Also, you need to know the names of the radicals formed from them - with the end of the end -ann it changes.

Consider the compound included in the preparations used to treat eye diseases:

CH 3 - C (CH 3) \u003d CH - CH 2 - CH 2 - C (CH 3) \u003d CH - SNO

The main generic structure is a chain of 8 carbon atoms, including an aldehyde group and both double bonds. Eight carbon atoms - Octan. But there are 2 double bonds - between the second and third atoms and between the sixth and seventh. One double bond - the end is oscillate to be replaced by nae, double bonds 2, it means to -dien, i.e. Octadyne, and at the beginning indicate their position, calling atoms with smaller numbers - 2.6-octadien. With the generic structure and accidentally figured out.

But in the compound there is an aldehyde group, this is not a hydrocarbon, and aldehyde, therefore add suffix -lm, without a number, it is always the first - 2.6-octadienal.

2 more substituents - methyl radicals in the 3rd and 7th atoms. So, as a result, we get: 3.7-dimethyl - 2.6-octadienal.

Lecture 15.

The theory of the structure of organic substances. Basic classes of organic compounds.

Organic chemistry -science engaged in the study of organic substances. Otherwise it can be defined as chemistry of carbon compounds. The latter occupies a special place in the Periodic system of D.I. REMEELEEVA by the diversity of compounds, which are known about 15 million, while the number of inorganic compounds is five hundred thousand. Organic substances are known to humanity for a long time, like sugar, vegetable and animal fats, coloring, fragrant and medicinal substances. Gradually, people learned by processing these substances to receive a variety of valuable organic products: wine, vinegar, soap, etc. Successes in organic chemistry rely on achievements in chemistry of protein substances, nucleic acids, vitamins, and others. Huge importance of organic chemistry has for the development of medicine, Since the overwhelming majority of drugs are organic compounds of not only natural origin, but also obtained mainly by synthesis. Exceptional significance high molecular weight Organic compounds (synthetic resins, plastics, fibers, synthetic rubbers, coloring substances, gerbecides, insecticides, fungicides, defolients ...). Great value of organic chemistry for the production of food and industrial goods.

Modern organic chemistry deeply penetrated into chemical processes occurring during the storage and processing of food products: processes of drying, barbing and washing oils, fermentation, bakery, digestion, drinking beverages, in the production of dairy products, etc. The discovery and study of enzymes, perfumery and cosmetic substances also played a big role.

One of the reasons for the greater diversity of organic compounds is the originality of their structure, which is manifested in the formation of carbon atoms of covalent bonds and chains, various types and length. At the same time, the number of linked carbon atoms in them can reach tens of thousands, and the configuration of carbon chains may be linear or cyclic. In the chain, in addition to carbon atoms, oxygen, nitrogen, sulfur, phosphorus, arsenic, silicon, tin, lead, titanium, iron, etc. can include oxygen, arsenic, silicon, tin, lead.

The manifestation of these properties is associated with several reasons. It was confirmed that the energy of the relationship with C - C and C - O comparable. Carbon has the ability to form three types of hybridization of orbitals: four SP 3 - hybrid orbitals, their orientation in the space tetrahedral and corresponds simple covalent bonds; Three hybrid SP 2 - orbitals located in the same plane in combination with a non-liberty orbital form double multiples communication (─c \u003d s─); Also, with the help of SP - hybrid orbitals of linear orientation and non-liberal orbitals between carbon atoms arise triple multiples Communications (─ C ≡ C ─). For this, such types of bonds of carbon atoms form not only with each other, but also with other elements. Thus, the modern theory of the structure of the substance explains not only a significant number of organic compounds, but also the influence of their chemical structure on the properties.

It also fully confirms the foundations theories of chemical structuredeveloped by the Great Russian scientist A.M. Butlerov. Its main provisions:

1) In organic molecules, atoms are connected to each other in a certain order according to their valence, which causes the structure of molecules;

2) the properties of organic compounds depend on nature and the number of atoms included in their composition, as well as on the chemical structure of molecules;

3) each chemical formula corresponds to a certain number of possible structures of isomers;

4) each organic compound has one formula and has certain properties;

5) In molecules, there is a mutual influence of atoms on each other.

Classes of organic compounds

According to the theory, organic compounds are divided into two rows - acyclic and cyclic compounds.

1. Aciclic compounds. (Alcans, alkenes) contain an open, unlocked carbon chain - direct or branched:

N n n n n n

│ │ │ │ │ │ │

N─ С─С─С─С н Н мас─С─С─Н

│ │ │ │ │ │ │

N n n n │ n

Normal Bhutan Isobutan (methylpropane)

2. a) alicyclic compounds - Compounds having closed (cyclic) carbon chains in molecules:

cyclobutane Cyclohexane

b) aromatic compoundsin the molecules of which there is a skeleton of benzene - a six-membered cycle with alternating simple and double connections (arena):

c) heterocyclic compounds - cyclic compounds containing nitrogen, sulfur, oxygen, phosphorus and some microelements, which are called heteroatoms.

furan Pyrrol Pyridin

In each row, organic substances are distributed by classes - hydrocarbons, alcohols, aldehydes, ketones, acids, ethers in accordance with the nature of the functional groups of their molecules.

There is also a classification according to the degree of saturation and by functional groups. According to the degree of saturation distinguish:

1. Male saturated - There are only single connections in the carbon skeleton.

─cms─

2. Unforeseen unsaturated - There are multiple (\u003d, ≡) communications in the carbon skeleton.

─c \u003d С─ ─С≡С

3. Aromatic - Disadvantaged cycles with ring pairing (4N + 2) π-electrons.

According to functional groups

1. Alcohols R-CH 2 OH

2. Phenols

3. Aldehydes R─COH ketones R─c─r

4. Carboxylic acids R─coh about

5. Essential esters R─coor 1

The theory of the structure of organic compounds

Since the opening of fire, a person has divided substances on combustible and non-combustible. The first group believed mainly products of plant and animal origin, and the second - mostly mineral origin. Thus, there was a certain connection between the ability of a substance to burn and afford it to the living and non-living world.

In 1867, Y. Berzelius proposed to call the compounds of the first group organic, and substances like water and salts, which are characteristic of inanimate nature, determined as inorganic.

Some organic substances in more or less pure form are known to a person from time immemorial (vinegar, many organic dyes). A number of organic compounds, such as urea, ethyl alcohol, "sulfur ether" were also obtained by alchemists. Very many substances, especially organic acids (oxal, lemon, dairy, etc.) and organic bases (alkaloids) were isolated from plants and animals in the second half of the XVIII century and the first years of the XIX century. This time should be considered the beginning of scientific organic chemistry.

v. Theory of Vitalism . In the XVIII century and the first quarter of the 19th century, the conviction was dominant that the chemistry of wildlife is fundamentally different from the chemistry of dead nature (mineral chemistry), and that the organisms are building their substances with the participation of special vitality, without which it is impossible to create them in the flask. That time was the time of domination vitalism - Teachings, considering life as a special phenomenon, submitting not to the laws of the universe, but the influence of special life forces.

The defender of the vitalism of the century used to be a stall, the founder of the theory of phlogiston. In his opinion, the chemists that matter with the most ordinary substances, to carry out their transformations that could not have the participation of life forces naturally could not.

The first doubts in the consistency of the vitalistic theory called the student of J. Britzeris German chemist F. Weller, who was synthesized from ammonium cyanate, unconditionally ranked inorganic substances, urea:

No need to overestimate the values \u200b\u200bof this work, because The urea is actually a rebuilt ammonium cyanate molecule, but, nevertheless, it is impossible to deny the value of the discovery of F. Piecele, because It contributed to the labeling of vitalism and inspired chemists on the synthesis of organic substances.

In 1845, A. Kolbe, a student F. Veler, made a synthesis of elements, i.e. Full synthesis, acetic acid. French chemist P. Bertlo got methyl and ethyl alcohols, methane. Nevertheless, it existed that the synthesis of such a complex substance, like sugar, will never be implemented. However, already in 1861, A. Butlers synthesized the sugar-like substance - methleenitian.

Simultaneously with these stages for organic chemistry, synthesis rapidly increased the total number of synthesized carbon-containing compounds not found in nature. So, in 1825, M. Faraday received benzene, ethylene, ethylene bromide and a number of benzene derivatives were also known. In 1842, N. Zinc from Nitrobenzene received Aninilin, and in the 50s of the same century, the first "aniline dyes" were synthesized from Anilin - Movein W. Perkin and Fuchsin. By the mid 50s of the 1950s. The vitalistic theory suffered the collapse finally.

v. Dualistic theory of J. Burtsellus . The basics of structural chemistry of organic substances laid Y. Burtsellius, who, after A. Lavoisier, distributed a quantitative analysis to organic objects and created to explain their nature dualistic (electrochemical) Theory is the first scientific theory in chemistry. According to Y. Burtsellius, an atom of an element is connected to oxygen due to the fact that it is electric, and oxygen electronegates; When connecting the charges are neutralized. J. Britzelius believed that his theory was also applied to organic chemistry, with the difference that in organic compounds radicals in oxides are more complex, for example, hydrocarbon. Otherwise this theory is also called " theory of complex radicals».

According to A. Lavoisier radicals of organic compounds consist of carbon, hydrogen and oxygen, to which in the case of substances of animal origin is added yet nitrogen and phosphorus.

v. Theory of radicals . The development of the theory of Bercelius became the theory of radicals. In 1810, J. Gay-Loussak noted that the CN group (cyanide group) can move from a compound into a compound, not separated by separate carbon and nitrogen atoms. Such groups began to call radicals.

Gradually, radicals began to consider how unchanging components of organic substances (similar to elements in inorganic compounds), which are transmitted in reactions from one connection to another. Some researchers, especially the German school (F. Veller, Y. Lubi), inspired by the opening of a series of new elements, were guided by the idea of \u200b\u200bfinding new radicals. In particular, they found the benzoyl radicals from 6 H 5 CO and acetyl CH 3 CO. By this time, it was also known that substances that are now called ethyl alcohol, diethyl ether, ethyl chloride and ethyl nitrite, contain a radical ethyl -С 2 H 5. The other method was identified and others were identified. radicals. Group of atoms remaining unchanged with various chemical transformations.

Multiple attempts to highlight the radicals in the free state turned out to be unsuccessful or carried out to erroneous results. So, before the establishment of the Law of the Avogadro Ethan, allocated by the reaction of Wuzza:

it was considered first with radical methyl - -CH 3, and only the subsequent determination of the molecular weight showed its twice-value.

The general recognition of the principle of unchanged radicals was shaken when the French chemist J. Dumas and his student O. Laurent opened the reaction metlepsy. Under the action of chlorine on organic compounds, chlorine comes into a substance so that one equivalent of hydrogen is removed from the substance, one equivalent of hydrogen in the form of chlorine-produced hydrogen is removed. In this case, the chemical character of the compound does not change. The contradiction with the theory of J. Burtzelius was striking: chlorine, "a negatively charged element", included in the place of "positive charged hydrogen", and the molecule not only persisted, but also did not change its chemical character. It turned out to be possible to replace hydrogen into other electronegative elements - halogens, oxygen, sulfur, etc., and the electrochemical dualistic theory of Y. Burtsellius collapsed. Obviously, it became that there are no unchanged radicals, and that in some reactions, the radicals are transferred to the newly formed molecules of the entire molecules, and in others are subject to change.

v. Type theory . Attempts to find something in common in the nature of organic molecules forced to abandon unsuccessful searches for an immutable part of the molecule and move to observations for its most modified part that we now call functional group. These observations led to type theories S. Gerar.

In alcohols and acids, S. Geraré saw the analogues of water in chloride hydrocarbons - analogs of hydrogen chloride, in alkanes - hydrogen, in newly open amines - ammonia.

Most supporters of the theory of types (S. Gerar, A. Kolbe, A. Kekule) proceeded from the fact that it is impossible to determine the structure of substances experimentally. They can only classify them. Depending on which reactions, the substance enters, the same organic compound can be attributed to different types. The theory with a large stretch classified a huge experienced material, and the possibility of targeted synthesis could not be speech. The organic chemistry in those years was presented, according to F. Weller, "... with a dormant forest, full of wonderful things, a huge thing without exit, without end, where you do not dare to penetrate." Further development of chemistry required the creation of a new, more progressive theory.

One of the disadvantages of the theory of types is the desire to lay all organic compounds in more or less formal schemes. The merit of this theory is to specify the concepts of homologous series and chemical functions, finally developed organic chemistry. Her role in the development of science is undoubted, because It led to the concept of valence and opened the way to the theory of the structure of organic compounds.

v. The theory of the structure of organic compounds . A number of studies preceded the emergence of the fundamental theory of the structure of organic compounds. Thus, A. Williamson in 1851 introduced the concept of so-called polyhydric radicals, that is, on radicals that can replace two or more hydrogen atoms. Thus, it became possible to attribute substances directly to two or more types, for example, aminoacetic acid can be attributed to the types of water and ammonia:

Such substances we now call heterofunctional compounds.

To comply with the consistency of carbon and oxygen valence, it turned out to be necessary to also adopt the existence of a double bond in ethylene (C \u003d C), in aldehydes and ketones (C \u003d O).

Scottish chemist L. Cooper offered a modern image of formulas in which the element sign supplied with a number of drops equal to his valence:

However, A. Kekule and L. Kupeur was still alien to the idea of \u200b\u200ban inseparable connection of the chemical and physical properties of molecules with its structure, a pronounced formula, the idea of \u200b\u200bthe uniqueness of this structure. A. Kekule admitted a description of the same compound by several different formulas, depending on which a set of reactions of this substance wanted to express the formula. Essentially, these were the so-called reaction formulas.

Basic provisions Theories of the structure of organic compounds A. Butlerov was made public in 1861. He himself belongs to the term structure or structure. The theory of Boutlerova was based on materialist ideas based on the atomistic teaching M. Lomonosov and D. Dalton. The essence of this theory is reduced to the following basic provisions:

1. The chemical nature of each complex molecule is determined by the nature of the components of its atoms, their number and chemical structure.

2. The chemical structure is a certain order of alternation of atoms in the molecule, the mutual influence of atoms to each other.

3. The chemical structure of substances determines their physical and chemical properties.

4. The study of the properties of substances allows to determine their chemical structure.

The chemical structure of A. Butlers called the sequence of atoms in the molecule. He pointed out how, on the basis of the study of chemical reactions of this substance, it is possible to establish its structure, which for each chemical individual is adequate. In accordance with this formula, it is possible to synthesize the connection data. The properties of a certain atom in the compound are primarily dependent on which the atom is associated with which the atom is associated. An example is the behavior of various hydrogen atoms in alcohols.

The theory of structure included and dissolved the theory of radicals, since any part of the molecule, turning in the reaction from one molecule to another, is a radical, but no longer possesses the prerogative. It has absorbed the theory of types, for those present in the molecule inorganic or containing carbon groups, leading their origin from water (hydroxyl -one), ammonia (amino group -NH 2), coalic acid (carboxyl -COOH), first and foremost determine chemical Behavior (function) of the molecule and made it similar to the behavior of the prototype.

The structural theory of the structure of organic compounds allowed to classify a huge experimental material and indicated the paths of targeted synthesis of organic substances.

It should be noted that the establishment of the structure of the substance is chemically carried out each time individually. Need confidence in the individuality of substances and knowledge of the quantitative elemental composition and molecular weight. If the composition of the compound and its molecular weight is known, you can derive the molecular formula. We give an example of the removal of structural formulas for substances with composition with 2 H 6 O.

The first substance reacts with sodium along the type of water, highlighting one hydrogen atom per sodium atom, and the sodium is part of the reaction product molecule instead of the exhausted hydrogen.

2C 2 H 6 O + 2NA → H 2 + 2C 2 H 5 ONA

A second sodium atom can not be introduced into the resulting connection. That is, it can be assumed that the substance contained a hydroxyl group and, highlighting it in the compound formula, the latter can be written as follows: from 2 H 5 it. This conclusion is confirmed by the fact that under action on the source of phosphorus bromide (III), the hydroxyl group leaves the molecule as an integer, turning to the phosphorus atom and replacing the bromine atom.

2C 2 H 5 OH + PBR 3 → 3C 2 H 5 BR + H 3 PO 3

It is an isomeric substance, i.e. having the same gross formula, does not react with the metallic sodium, and when interacting with the iodine hydrogen is decomposed by the equation:

C 2 H 6 O + HI → CH 3 I + CH 4 O.

From this we can conclude that in the source substance, two carbon atoms are not connected with each other, since the iodomodorod is not able to break the C-C-communication. It does not have a special hydrogen capable of replacing sodium. After breaking the molecule of this substance under the action of iodorodor, CH 4 O and CH 3 I are formed. The latter cannot be attributed to a different structure than the indicated below, since hydrogen, and iodine is monovalent.

The second of the substances formed, CH 4 O, behaves in the reaction not only with sodium, but also with phosphorus bromide (III), like ethyl alcohol.

2ch 4 O + 2NA → 2CH 3 ONA + H 2

3CH 4 O + PBR 3 → CH 3 BR + P (OH) 3

It is natural to assume that the iodomiculture broke the connection of two methyl groups carried out by an oxygen atom.

Indeed, under the action of one of the products of this reaction to the sodium derivative of the other, the synthesis of the source substance, isomeric ethyl alcohol, and confirm the structure of dimethyl ether accepted for it.

The first test stone of checking the theory of the structure of organic compounds was the synthesis of predicted but unknown at the time tert-Butyl alcohol and isobutylene, carried out by the author of the created theory and his student A. Zaitsev. Another student A. Butlerova - V. Markovnikov synthesized theoretically predicted isomaslane acid and based on its basis the mutual influence of atoms in the molecule.

The next stage in the development of theoretical issues is associated with the emergence of stereochemical ideas developed in the works of J. Vant-Gooff and J. Le Belya.

At the beginning of the twentieth century Representations of the electronic structure of atoms and molecules are laid. At the electronic level, the nature of the chemical bond and the reactivity of organic molecules is interpreted.

The creation of organic substance theory served as the basis of synthetic methods not only in the laboratory, but also in industry. Synthetic dyes, explosives and medicines arise. In organic synthesis, catalysts and high pressure are widely introduced.

In the field of organic synthesis, many natural substances (chlorophyll, vitamins, antibiotics, hormones) were obtained. The role of nucleic acids in the storage and transfer of heredity is revealed.

The solution of many issues in the structure of complex organic molecules has become effective due to the involvement of modern spectral methods.

Stalls g. (1659-1734) - German chemist and doctor. The creator of the theory of phlogistone is the first chemical theory, which allowed to commit to theoretical revival of alchemy.

Kolbe A. (1818 - 1884) is a German chemist, the creator of the theory of radicals. Synthesized a number of organic acids. Developed an electrochemical method for obtaining alkanes - the collee method.

Bertlo P. (1827-1907) - French chemist. One of the founders of organic chemistry. Fundamental work in the field of thermochemistry.

Faraday M. (1791-1867) - English physicist and chemist. One of the founders of the exercise on electromagnetism. Opened quantitative electrolysis laws. Research in the field of liquefied gases, glass, organic chemistry.

Perkin W. Art. (1838-1907) -Anglish chemist. Developed an industrial production of Moveina dyes, Alizhar. Opened the condensation reaction of aromatic aldehydes with carboxylic acid anhydrides ( reaction Perkin).

Würz Sh. (1817-1884) - French chemist studied Y. Libiha, Assistant J. Duma. Synthesized amines, phenols, ethylene glycol, lactic acid, conducted aldol and crotone condensation.

Duma J. (1800-1884) - French chemist. Created the theory of radicals. He opened the chlorination reaction, set the existence of a homologous series - a number of formic acid. Suggested a method for quantifying nitrogen.

Laurent O. (1807-1853) - French chemist. He studied coal resin products. Opened phthalic acid, indigo and naphthalene.

Kekule F. (1829 - 1896) - German chemist. The main works in the field of theoretical organic chemistry. Anthraquinone synthesized, triphenylmethane.

Cooper L. (1834 - 1891) - Scottish chemist, the main works are devoted to theoretical problems of chemistry.

Slide 1\u003e

Tasks lectures:

Educational:
- to form the concepts of the essence of the theory of the chemical structure of organic substances, based on the knowledge of students on the electronic structure of the atoms of the elements, their position in the periodic system D.I. Mendeleev, about the degree of oxidation, the nature of the chemical bond and the other main theoretical provisions:
  - the sequence of carbon atoms in the chain,
  - the mutual influence of atoms in the molecule,
  - the dependence of the properties of organic substances from the structure of molecules;
- form an idea of \u200b\u200bthe development of theories in organic chemistry;
- understand the concepts: isomers and isomeria;
- clarify the meaning of the structural formulas of Organism and their advantages over molecular;
- show the need and prerequisites for the creation of the theory of chemical structure;
- continue the formation of abstract design skills.
Developing:
- develop mental techniques of analysis, comparisons, generalizations;
- develop abstract thinking;
- train the attention of students in the perception of a large amount of material;
- sash the ability to analyze information and allocate the most important material.
Educational:
- for the purpose of patriotic and international education, the historical information about the life and activities of scientists will lead students.

DURING THE CLASSES

1. Organic part

- Greeting
- Preparation of students for lesson
- Getting information about missing.

2. Studying New

Lecture Plan:<Attachment 1 . Slide 2\u003e

I. Fruct theories:
- Vitalism;
- theory of radicals;
- Type theory.
II. Brief reference about the state of chemical science by the 60s of the XIX century. Conditions for the creation of the theory of chemical structure of substances:
- the need to create the theory;
- Background of the theory of chemical structure.
III. The essence of the theory of the chemical structure of organic substances A.M. Butlerova. The concept of isomerism and isomers.
IV. The value of the theory of the chemical structure of organic substances A.M. Butlerova and its development.

3. Task for the house:abstract, p. 2.

4. Lecture

I. Knowledge of organic substances accumulated gradually with deep antiquity, but as an independent science, organic chemistry arose only at the beginning of the XIX century. Registration of independence Org.Himy is associated with the name of the Swedish scientist Ya. Burtsellus<Attachment 1 . Slide 3\u003e. In 1808-1812 He issued his great guide in chemistry, in which initially intended to consider along with minerals and substances of animal and vegetable origin. But part of the tutorial dedicated to Organism, appeared only in 1827
The most significant difference between substances inorganic and organic Ya. Britzelius saw that the first can be obtained in laboratories with synthetic way, while the second allegedly formed only in living organisms under the action of some "vitality" - the chemical synonym "Soul", "Spirit", "divine origin" of living organisms and their components of their organic substances.
The theory explaining the formation of the organizational forces by the intervention of "vitality" was called vitalism. For some time it was popular. In the laboratory, only the simplest carbon-containing substances were able to synthesize, such as carbon dioxide - CO 2, calcium carbide - CAC 2, potassium cyanide - KCN.
Only in 1828 German scientist<Attachment 1 . Slide 4\u003e managed to obtain organic substance urea from inorganic salt - ammonium cyanate - NH 4 CNO.
NH 4 CNO - T -\u003e CO (NH 2) 2
In 1854, French scientist Bertlo<Attachment 1 . Slide 5\u003e received triglyceride. This led to the need to change the definition of organic chemistry.
Scientists tried on the basis of the composition and properties to solve the nature of organic substance molecules, sought to create a system that would associate together the scattered facts accumulated by the beginning of the XIX century.
The first attempt to create the theory, who sought to summarize the data having occurred about Organism, is related to the name of the French chemist J. Dyuma<Attachment 1 . Slide 6\u003e. It was an attempt to consider from a single point of view a rather large group of organizing connections, which we would call ethylene derivatives today. Org. Compounds turned out to be derived by some radical C 2 H 4 - Eterina:
C 2 H 4 * HCl - Ethyl chloride (solucasic Etherin)
The idea approached in this theory is an approach to org. Activity as consisting of 2 parts - subsequently formed the basis of the wider theory of radicals (Y. Berzelius, Y.Libih, F. Veller). This theory is based on the representation of the "dualistic structure" of substances. Ya. Burtsellius wrote: "Each org. An exercise consists of 2 constituent parts carrying the opposite electrical charge." One of these components, namely, a part of the electronegative, I.Bercelyus considered oxygen, the rest of the same part, actually organic, was supposed to be an electropositive radical.

The main provisions of the theory of radicals:<Attachment 1 . Slide 7\u003e

- The composition of organic substances includes radicals carrying a positive charge;
- radicals are always constant, are not subjected to changes, they change unchanged from one molecule to another;
- Radicals can exist in free form.

Gradually, the facts that contradict the theory of radical were accumulated in science. So J.Dume was replaced by hydrogen chlorine in hydrocarbon radicals. Scientists, adherents of the theory of radicals, seemed incredible that chlorine, charged negatively, played the role of hydrogen, charged positively. In 1834, J. Duma received a task to investigate an unpleasant incident during the Bala in the Palace of the French King: Candles with burning were distinguished by suffocating smoke. J.Dyuma found that the wax from which the candles were made, the manufacturer for bleach processed chlorine. In this case, chlorine was part of the wax molecule, replacing a portion of hydrogen contained in it. Sticky couples, who frightened royal guests, were chloride (HCl). In the future, J.Dume received trichloroacetic acid from acetic.
Thus, the electropositive hydrogen was replaced by an extremely electronegative element of chlorine, and the properties of the compound were almost not changed. Then J. Dyuma concluded that the approach to the dualistic approach should be the approach to the organizing compound as a whole.

The theory of radicals was gradually rejected, but it left a deep mark in organic chemistry:<Attachment 1 . Slide 8\u003e
- The concept of "radical" is firmly included in chemistry;
- It was faithful to approval about the possibility of the existence of radicals in free form, about the transition in the huge number of reactions of certain groups of atoms from one connection to another.

In the 40s XIX. The beginning of the teaching about homology was made, which allowed to find out some of the relationship between the composition and properties of the compounds. Homological rows are revealed, homologous difference, which made it possible to classify organic matter. The classification of HOLG.Sevistry based on homology led to the emergence of the theory of types (40-50s of the XIX century, Sh. Gerar, A.Kekule, etc.)<Attachment 1 . Slide 9\u003e

Essence of the theory of types<Attachment 1 . Slide 10\u003e

- The formation is based on an analogy in reactions between organic and some inorganic substances, adopted as types (types: hydrogen, water, ammonia, chloride, etc.). The hydrogen atoms on other groups of atoms in the type of substance, scientists predicted various derivatives. For example, the replacement of the hydrogen atom in the water molecule on the methyl radical leads to an alcohol molecule. Replacement of two hydrogen atoms - to the appearance of a simple ether molecule<Attachment 1 . Slide 11\u003e

Sh. Gerard directly spoke in connection with this that the formula of substances is only a reduced record of its reactions.

All org. Substances considered derivatives of the simplest inorganic substances - hydrogen, chloride, water, ammonia<Attachment 1 . Slide 12\u003e

<Attachment 1 . Slide 13\u003e

- organic substances molecules are a system consisting of atoms, the order of connection of which is unknown; The properties of compounds affect the combination of all molecule atoms;
- It is impossible to know the structure of the substance, since molecules are changed in the reaction process. The formula of the substance does not reflect the structure, but the reactions in which this substance. For each substance, you can write so much rational formulas, how many different types of transformations may experience a substance. The theory of types allowed the plurality of "rational formulas" for substances, depending on which reactions, they want to express these formulas.

Type theory played a big role in the development of organic chemistry <Attachment 1 . Slide 14\u003e

- allowed to predict and discover a number of substances;
- had a positive impact on the development of valence teachings;
- drew attention to the study of the chemical transformations of organic compounds, which made it possible to deeper the properties of substances, as well as the properties of predicted compounds;
- created the systematization of organic compounds perfect for that time.

We should not forget that in reality the theory arose and replaced each other not consistently, but existed simultaneously. Chemists often poorly understood each other. F.Veler in 1835 said that "Organic Chemistry Currently, can be crazy. It seems to me with a dormant forest full of wonderful things, huge without exit, without end, where you do not dare to penetrate ... ".

None of these theories became the theory of organic chemistry in the full sense of the word. The main reason for the failure of these ideas in their idealistic essence is: the inner structure of molecules was considered fundamentally unknowable, and any reasoning about it is a quantity.

We needed a new theory that would stand in materialistic positions. Such a theory appeared the theory of the chemical structure A.M. Butlerova <Attachment 1 . Slides 15, 16\u003e, which was created in 1861, all rational and valuable, which was in the theories of radicals and types, was further assimilated by the theory of chemical structure.

The need for the appearance of the theory dictated:<Attachment 1 . Slide 17\u003e

- increased requirements of industry to organic chemistry. It was necessary to provide the textile industry with dyes. In order to develop the food industry, it was necessary to improve the methods of processing agricultural products.
In connection with these tasks, new methods of organic matter synthesis began to be developed. However, scientists have serious difficulties in the scientific substantiation of these synthesis. For example, carbon valence in compounds with the help of old theory was impossible to explain the valence of carbon.
Carbon is known for us as an element of 4th valence (it was proven experimentally). But here it seems only in Methane CH 4 retains this valence. In this C 2 H 6 if you follow our ideas, carbon d.b. 3-valent, and in the propane of C 3 H 8 - fractional valence. (And we know that the valence must only be expressed by integers).
What is the same carbon valence in organic connections?

It was not clear why substances with the same composition exist, but different properties: C 6 H 12 O 6 is the molecular formula of glucose, but the same formula and fructose (sugar substance - the component of the honey).

Fruct theories could not explain the variety of organic substances. (Why carbon and hydrogen are two elements - can form such a large number of different connections?).

It was necessary to systematize the existing knowledge from a single point of view and develop a single chemical symbolism.

A scientifically based response to these questions gave the theory of the chemical structure of organic compounds created by the Russian scientist A.M. Butlerov.

Main premisespreparing the soil for the emergence of the theory of chemical building<Attachment 1 . Slide 18\u003e

- The doctrine of valence. In 1853, E. Frankland introduced the concept of valence, established valence for a number of metals, exploring metal organic compounds. Gradually, the concept of valence was distributed to many elements.

An important discovery for organic chemistry was a hypothesis about the ability of carbon atoms to the formation of chains (A. Kekule, A. Cooper).

One of the prerequisites was the development of the correct idea of \u200b\u200batoms and molecules. Up to the 2nd half of the 50s. XIX. There were no generally accepted criteria for determining the concepts: "Atom", "molecule", "atomic mass", "molecular weight". Only at the International Congress of Chemists in Karlsruhe (1860), these concepts were clearly defined, which predetermined the development of the theory of valence, the emergence of the theory of chemical structure.

The main provisions of the theory of the chemical structure A.M. Butlerova(1861)

A.M. Butlers formulated the most important ideas of the theory of the structure of organic compounds in the form of basic provisions that can be divided into 4 groups.<Attachment 1 . Slide 19\u003e

1. All atoms forming organic molecules are associated in a certain sequence according to their valence (i.e. molecule has a structure).

<Attachment 1 . Slides 19, 20\u003e

In accordance with these ideas, the valence of elements is conventionally depicted by dashes, for example, in methane CH 4.<Attachment 1 . Slide 20\u003e >

Such a schematic image of the structure of molecules is called structure formulas and structural formulas. Based on the provisions on the 4 valence of carbon and the ability of its atoms to form chains and cycles, the structural formulas of the Organization can be depicted as follows:<Attachment 1 . Slide 20\u003e

In these compounds, carbon tetravalenten. (Dash symbolizes a covalent bond, a pair of electrons).

2. The properties of the substance depend not only on what atoms and how many are included in the molecules, but also on the order of the compound of atoms in molecules. (I.e. properties depend on the structure) <Attachment 1 . Slide 19\u003e

This position of the theory of the structure of the Organism has explained, in particular, the phenomenon of isomerism. There are compounds that contain the same number of atoms of the same elements, but associated in various order. Such compounds have different properties and are called isomers.
The appearance of the existence of substances with the same composition, but a different structure and properties are called isomeria.<Attachment 1 . Slide 21\u003e

The existence of isomers of Organism explains their manifold. The phenomenon of isomerism was predicted and proved (experimentally) A.M. Butlerov on the example of Bhutan

For example, the composition with 4 H 10 corresponds to two structural formulas:<Attachment 1 . Slide 22\u003e

Miscellaneous interconnection of carbon atoms in u / in molecules appears only with Bhutan. The number of isomers increases with an increase in the number of carbon atoms in the appropriate hydrocarbon, for example, Pentan has three isomers, and the dean is seventy-five.

3. According to the properties of this substance, it is possible to determine the structure of its molecule, and in the structure of the molecule foresee the properties. <Attachment 1 . Slide 19\u003e

From the course of inorganic chemistry, it is known that the properties of inorganic substances depend on the structure of crystalline lattices. The distinctive properties of atoms from ions are explained by their structure. In the future, we will see that organic substances with the same molecular formulas, but different buildings differ not only in physical, but also by chemical properties.

4. Atoms and groups of atoms in the molecules of substances mutually affect each other.

<Attachment 1 . Slide 19\u003e

As it is already known, the properties of inorganic compounds containing hydroxochroups depend on which atoms are connected with atoms or non-metals. For example, hydroxochroup contain both bases and acids:<Attachment 1 . Slide 23\u003e

However, the properties of these substances are completely different. The reason for the various chemical character of the group is (in aqueous solution) is due to the influence of atoms associated with it and groups of atoms. With an increase in the non-metallic properties of the central atom, dissociation by the base type is weakened and dissociation by type of acid increases.

Organic compounds may also have different properties that depend on what atoms or groups of atoms are associated with hydroxyl groups.

The question of mutual injection of atoms A.M. Butlers disassembled in detail on April 17, 1879 at a meeting of Russian physico-chemical society. He said that if two different elements are associated with carbon, for example, CL and H, then "they do not depend on one of the other to the extent, as from carbon: there is no dependence between them, the connection that exists in the hydrochloric acid particle ... But does it follow from this that in the compound CH 2 Cl 2 between hydrogen and chlorine there is no dependence? I answer it with a decisive denial. "

As a specific example, it further leads to an increase in chlorine mobility when turning the CH 2 Cl group in COCL and speaks about this: "It is obvious that the character of the chlorine in the particle has changed under the influence of oxygen, although this last and not connected with chlorine directly."<Attachment 1 . Slide 23\u003e

The question of the mutual influence of directly non-linked atoms was the main theoretical rod of works by V.V. Morkovikov.

In the history of mankind, a relatively few scientists are known, the openings of which have worldwide importance. In the field of organic chemistry, such merits belong to A.M. Butlerov. According to the veryory of A.M. Theory Butlerova compared with periodic law.

The theory of the chemical structure A.M. Butlerova:<Attachment 1 . Slide 24\u003e

- allowed to systematize organic substances;
- answered all the questions arising by the time in organic chemistry (see above);
- allowed theoretically to foresee the existence of unknown substances, to find ways of their synthesis.

Almost 140 years have passed since the organic compounds of A.M. Butlerova but now the chemists of all countries use it in their works. The newest achievements of science replenish this theory, clarify and find all new confirmations of the correctness of its basic ideas.

The theory of chemical structure and today remains the foundation of organic chemistry.

THC organic compounds A.M. Butlerova made a significant contribution to the creation of a general scientific picture of the world, contributed to a dialectic - materialistic understanding of nature:<Attachment 1 . Slide 25\u003e

– the law of transition of quantitative changes to quality you can trace the example of alkanov:<Attachment 1 . Slide 25\u003e.

Only the number of carbon atoms changes.

– the law of unity and the struggle of the opposites traced on the phenomenon of isomeria<Attachment 1 . Slide 26\u003e

Unity - in the composition (the same) location in space.
The opposite is in the structure and properties (different sequence of arrangement of atoms).
These two substances coexist together.

– the law of denial denial - On isomeria.<Attachment 1 . Slide 27\u003e

Isomers coexisting deny each other by their existence.

Developing the theory, A.M. Butlers did not consider it absolute and unchanged. He argued that it should develop. THC organic compounds did not remain unchanged. Its further development went mainly in 2 interconnected areas:<Attachment 1 . Slide 28\u003e

Stereochemistry - the doctrine of the spatial structure of molecules.

The teaching on the electron structure of atoms (made it possible to understand the nature of the chemical bond of atoms, the essence of the mutual influence of atoms, explain the cause of the manifestation of various chemical properties).

The theory of the structure of organic compounds: Homology and isomerism (structural and spatial). Mutual influence of atoms in molecules

The theory of the chemical structure of organic compounds A. M. Butlerova

Similarly, for inorganic chemistry, the basis of development is the periodic law and the periodic system of chemical elements D. I. Mendeleev, the theory of the structure of organic compounds A. M. Butlerova has become fundamental to organic chemistry.

The main postulate of the theory of Butlerov is the Regulation on chemical structure of substanceunder which the order is understood, the sequence of the mutual connection of atoms into the molecule, i.e. chemical bond.

Under the chemical structure, the order of the compound of the atoms of chemical elements in the molecule according to their valence is understood.

This order can be displayed using structural formulas in which the valence of atoms are denoted by dashes: one child corresponds to a unit of valence of the atom of the chemical element. For example, for the organic substance of methane having a molecular formula $ CH_4 $, the structural formula looks like this:

The main provisions of the theory of A. M. Butlerova

Atoms in organic substances molecules are associated with each other according to their valence. Carbon in organic compounds is always four-tailed, and its atoms are capable of combating each other, forming various chains.
Properties of substances are determined not only by their qualitative and quantitative composition, but also by the order of the compound of atoms in the molecule, i.e. the chemical structure of the substance.
The properties of organic compounds depend not only on the composition of the substance and the order of the compound of atoms in its molecule, but also on the mutual influence of atoms and groups of atoms on each other.

The theory of the structure of organic compounds is a dynamic and developing teaching. As knowledge of the nature of the chemical bond, the effect of the electronic structure of organic substance molecules began to use, except Empirical and structural, electronic Formulas. In such formulas, the direction of displacement of electronic pairs in the molecule is indicated.

Quantum chemistry and chemistry of the structure of organic compounds confirmed the doctrine of the spatial direction of chemical ties ( cis and transisomeria), I studied the energy characteristics of mutual transitions in the isomers, allowed to judge the mutual influence of atoms in the molecules of various substances, created prerequisites for predicting the types of isomerism and the direction and mechanism of flowing chemical reactions.

Organic substances have a number of features:

All organic substances include carbon and hydrogen, so when burning, they form carbon dioxide and water.
Organic substances are complex and can have a huge molecular weight (proteins, fats, carbohydrates).
Organic substances can be positioned in the ranks of similar composition, structure and properties of homologs.
For organic substances is characteristic isomeria.

Isomerius and Homology of Organic Substances

The properties of organic substances depend not only on their composition, but also on the order of the compound of atoms in the molecule.

Isomeria - this is the appearance of the existence of various substances - isomers with the same qualitative and quantitative composition, i.e. with the same molecular formula.

There are two kinds of isomeria distinguish: structuraland spatial (stereoisomeria). Structural isomers differ from each other by the order of communication of atoms in the molecule; Stereoisomers - the arrangement of atoms in space with the same order of connections between them.

The following varieties of structural isomerism are distinguished: isomerism of the carbon skeleton, isomerism of the situation, isomericing of various classes of organic compounds (interclace isomerism).

Structural isomeria

Isomerius of carbon skeleton Determined by various orders of communication between carbon atoms forming the skeleton of the molecule. As already shown, two hydrocarbons correspond to the molecular formula $ s_4n_ (10) $: n-butane and isobutane. For hydrocarbon $ s_5n_ (12) $ three isomers are possible: Pentan, isopentane and non-foster:

$ CH_3-CH_2- (CH_2) ↙ (pentane) -CH_2-CH_3 $

With an increase in the number of carbon atoms in the molecule, the number of isomers increases rapidly. For hydrocarbon $ s_ (10) H_ (22) $ they are already $ 75, and for hydrocarbon $ s_ (20) H_ (44) $ - $ 366 $ 319.

Isomerius of the situation due to various positions of multiple communication, substituent, functional group with the same carbon skeleton of the molecule:

$ Ch_2 \u003d (ch-ch_2) ↙ (butene-1) -ch_3 $ $ ch_3- (ch \u003d ch) ↙ (butene-2) -ch_3 $

$ (Ch_3-ch_2-ch_2-oh) ↙ (n-propyl alcohol (propanol-1)) $

Isomerius of various classes of organic compounds (interclass isomeria) due to various position and combination of atoms in molecules of substances having the same molecular formula, but belonging to different classes. So, the molecular formula $ s_6n_ (12) $ corresponds to an unsaturated hydrocarbon hexene-1 and cyclic hydrocarbon Cyclohexane:

The isomers are a hydrocarbon belonging to alkins - butong 1 and a hydrocarbon with two double bonds in the Boutadien-1,3 chain:

$ CH≡C- (CH_2) ↙ (boudin-1) -ch_2 $ $ ch_2 \u003d (ch-ch) ↙ (butadiene-1,3) \u003d ch_2 $

Diethyl ether and butyl alcohol have the same molecular formula $ s_4n_ (10) about $:

$ (Ch_3ch_2och_2ch_3) ↙ (\\ text "diethyl ether") $ $ (ch_3ch_2ch_2ch_2oh) ↙ (\\ Text "n-butyl alcohol (butanol-1)") $

The structural isomers are aminoacetic acid and nitroethane, which correspond to the molecular formula $ s_2n_5no_2 $:

Isomers of this type contain various functional groups and belong to different classes of substances. Therefore, they differ in physical and chemical properties significantly more than carbon skeletal isomers or position isomers.

Spatial isomeria

Spatial isomeria It is divided into two types: geometric and optical. Geometric isomerism is characteristic of compounds containing double bonds, and cyclic compounds. Since the free rotation of the atoms around the double bond or in the cycle is not possible, the substituents can be located either one side of the double bond or cycle ( cis- Put), or on different directions ( trance-position). Designations cis and trance-usually refer to a pair of identical substituents:

Geometric isomers differ in physical and chemical properties.

Optical isomeria It occurs if the molecule is incompatible with its image in the mirror. This is possible when the carbon atom in the molecule has four different substituents. This atom is called asymmetric. An example of such a molecule is $ α α-α-monopropionic acid ($ α-$ -Anin) $ CH_3CH $ (NH_2) COOH $.

Molecule $ α $ -alanine None with any movement can coincide with its mirror reflection. Such spatial isomers are called Mirror, optical antipodes, or enantiomers. All physical and practically all chemical properties of such isomers are identical.

The study of optical isomerism is necessary when considering many reactions occurring in the body. Most of these reactions are under the action of enzymes - biological catalysts. The molecules of these substances should approach the molecules of the compounds to which they act as the key to the lock, therefore, the spatial structure, the relative position of the molecules and other spatial factors have great importance for the flow of these reactions. Such reactions are called stereoselective.

Most natural compounds are individual enantiomers, and their biological effects differ sharply from the properties of their optical antipodes obtained in the laboratory. A similar difference in biological activity is of great importance, as it is the basis of the most important property of all living organisms - metabolism.

Homological nearit is called a number of substances located in order of increasing their relative molecular masses similar to the structure and chemical properties, where each member differs from the previous on the homologous difference $ ch_2 $. For example: $ ch_4 $ - methane, $ C_2H_6 $ - ethane, $ C_3H_8 $ - propane, $ C_4H_ (10) $ - butane, etc.

Types of ties in organic substance molecules. Hybridization of carbon nuclear orbitals. Radical. Functional group.

Types of ties in organic substance molecules.

In organic compounds, carbon is always four sheets. In the excited state in its atom, a pair of $ 2s ^ 3 $ -Electrons and the transition of one of them on the p-orbital is:

Such an atom has four unpaired electrons and can take part in the formation of four covalent ties.

Based on the above electronic formula of the valence level of carbon atom, it would be possible to expect that it contains one $ S $ -Electron (spherical symmetric orbital) and three $ p $ -Electron, having mutually perpendicular orbitals ($ 2p_x, 2p_u, 2p_z $ - orbital). In reality, all four valence electron of carbon atom fully equivalent and the corners between their orbitals are equal to $ 109 ° 28 "$. In addition, calculations show that each of the four carbon chemical bonds in the methane molecule ($ CH_4 $) $ 25% $ is $ S- $ and $ 75% $ - $ P $ -Curry, i.e. occurs mixing $ s- $ and $ p- $ electron states.This phenomenon is called hybridization And mixed orbitals - hybrid.

The carbon atom in $ SP ^ 3 $ -Valent state has four orbital, each of which is one electron. In accordance with the theory of covalent bond, it has the ability to form four covalent bonds with atoms of any monovalent elements ($ CH_4, CHCl_3, CCl_4) or with other carbon atoms. Such connections are called $ σ $-combs. If the carbon atom has one $ C-C $ communication, then it is called primary ($ N_3c-sn_3 $), if two secondary ($ N_3c-sn_2-sn_3 $) if three tertiary (), and if four - quaternary ().

One of the characteristic features of carbon atoms is their ability to form chemical bonds due to the generalization of only $ p $ -electrons. Such connections are called $ π $ -soves. $ π $ -Connet in organic compound molecules are formed only in the presence of $ σ $-connections between atoms. Thus, in the ethylene molecule, $ n_2c \u003d CH_2 $ carbon atoms are associated with $ σ- $ and one $ π $ -Clecy, in an acetylene molecule $ ns \u003d CH $ - one $ σ- $ and two $ π $-connections. Chemical bonds formed with the participation of $ π $ -soves are called multiple (in ethylene molecule - double, in acetylene molecule - tripoe), and compounds with multiple connections - unsaturated.

Phenomenon $ SP ^ $ 3 -, $ SP ^ $ 2 - and $ Sp $ - hybridization of carbon atom.

In the formation of $ π $, the hybrid state of atomic orbitals of the carbon atom changes. Since the formation of $ π $ is comes at the expense of P-electrons, then in double-bond molecules, the electrons will have $ SP ^ 2 $ -Hybridization (there was $ SP ^ $ 3, but one P-electron is moving on $ π $ Orbital), and with triple - $ sp $ -Hymbridization (two P-electrons moved to $ π $ -orbital). The nature of hybridization changes the focus of $ σ $ -soves. If at $ SP ^ 3 $ -Hybridization, they form spatially branched structures ($ A $), then with $ SP ^ 2 $ -Hybridization, all atoms lie in the same plane and the angles between $ σ $-connections are $ 120 ° $ (b) , and with $ sp $-hybridization of the linear molecule (B):

At the same time, the axis $ π $ -rbitals are perpendicular to the axis $ σ $-deviation.

Both $ σ $ - and $ π $ is covalent, it means that they must be characterized by the length, energy, spatial orientation and polarity.

Characteristics of single and multiple bonds between atoms C.

Radical. Functional group.

One of the features of organic compounds is that in chemical reactions of their molecules are exchanged non-individual atoms, but atom groups. If this group of atoms consists only of carbon and hydrogen atoms, then it is called hydrocarbon radicalif it has atoms of other elements, then it is called functional group. For example, methyl ($ CH_3 $ -) and ethyl ($ s_2n_5 $ -) are hydrocarbon radicals, and an oxygroup (- $ it is $), aldehyde group ( ), nitro group (- $ no_2 $), etc. are functional groups of alcohols, aldehydes and nitrogen-containing compounds, respectively.

As a rule, the functional group defines the chemical properties of the organic compound and therefore is the basis of their classification.