Chemical structure of the molecule It is the most characteristic and unique side of it, since it defines its general properties (mechanical, physical, chemical and biochemical). Any change in the chemical structure of the molecule entails a change in its properties. In the case of minor structural changes made to one molecule, there are small changes in its properties (usually affects physical properties), if the molecule has experienced deep structural changes, then its properties (especially chemical) will be deeply changed.

For example, alpha-aminopropionic acid (alpha alanine) has the following structure:

Alpha Alanine

What we see are:

1. The presence of certain atoms (C, N, O, N),
2. a certain number of atoms belonging to each class, which are associated in a certain order;

All these constructive features A number of properties of alpha-alanine are determined, such as: solid aggregate state, boiling point 295 ° C, water solubility, optical activity, chemical properties of amino acids, etc.

In the presence of an amino group with another carbon atom (i.e., a minor structural change occurred), which corresponds to beta-alanine:

Beta-alanine

General chemical properties remain characteristic of amino acids, but the boiling point is already 200 ° C and there is no optical activity.

If, for example, two atoms in this molecule are connected by an N atom in the following order (deep structural change):

then educated substance - 1-nitropropane in its physical and chemical properties It is absolutely not similar to amino acids: 1-nitro-propane is a yellow liquid, with a boiling point of 131 ° C, insoluble in water.

In this way, The relationship "Structure-Property" allows you to describe the general properties of a substance with a known structure and, on the contrary, allows you to find chemical structure Substances, knowing its general properties.

General principles of the structure of the structure of organic compounds

In the essence of the definition of the structure of the organic compound, the following principles are followed from the connection between their structure and properties:

a) organic substances, in analytically pure state, have the same composition, regardless of the method of their preparation;

b) organic substances, in analytically pure condition, has permanent physicochemical properties;

c) Organic substances with constant composition and properties, has only one unique structure.

In 1861, the Grand Russian scientist A. M. Butlerov In his article "On the chemical structure of the substance", the basic idea of \u200b\u200bthe theory of the chemical structure, which consists in the influence of the method of communication of atoms in the organic matter on its properties. He generalized all the knowledge and ideas about the structure of chemical compounds in the structure of the structure organic compounds.

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

briefly be outlined as follows:

1. In the organic compound molecule, atoms are associated in a certain sequence, which determines its structure.
2. The carbon atom in the composition of organic compounds has a valence equal to four.
3. With the same composition of the molecules, several options for connecting atoms of this molecule are possible. Such compounds that have one composition, but various buildings were named with isomers, and a similar phenomenon - isomeria.
4. Knowing the structure of an organic compound can be predicted its properties; Knowing the properties of the organic compound can be predicted its structure.
5. Atoms forming the molecule are subject to mutual influence, which determines their reactivity. The directly related atoms have a greater impact on each other, the influence of non-linked atoms is much weaker.

Student A.M. Butlerova - V. V. Markovnikov continued to study the issue of mutual influence of atoms, which was reflected in 1869 in his dissertation work "Materials on the issues of mutual influence of atoms in chemical compounds".

Merit A.M. Butlerova and the value of the theory of chemical structure is exceptionally large in chemical synthesis. It has been able to predict the basic properties of organic compounds, to anticipate their synthesis. Due to the theory of chemical structure, the chemists first appreciated the molecule as an ordered system with a strict order of communication between atoms. And at present the main provisions of the theory of Butlerov, despite changes and clarifications, underlie the current theoretical ideas of organic chemistry.

Categories ,

The chemical nature of organic compounds, properties that distinguish them from unorganic compounds, as well as their diversity, found an explanation in the formulated butcher in 1861. Theory of the chemical structure (see § 38).

According to this theory, the properties of compounds are determined by their qualitative and quantitative composition, the chemical structure, i.e., the sequential order of the compound between the formation molecule between the molecule and their mutual influence. The theory of the structure of organic compounds, developed and supplemented with the latest views in the field of chemistry and physics of atoms and molecules, especially the views on the spatial structure of molecules, on the nature of chemical bonds and the nature of the mutual influence of atoms, is the theoretical basis of organic chemistry.

In the modern theory of the structure of organic compounds, the following are the following provisions.

1. All features of organic compounds are determined primarily by the properties of the carbon element.

In accordance with the place that carbon occupies in the periodic system, in the external electron layer of its atom (-female) there are four electrons. It does not show a pronounced tendency to give or attach electrons, in this respect, the intermediate position between metals and non-metals and is characterized by a sharply pronounced ability to form covalent bonds. The structure of the outer electronic layer of carbon atom can be represented by the following schemes:

An excited carbon atom can participate in the formation of four covalent bonds. Therefore, in the overwhelming majority of its compounds, carbon exhibits covalently equal to four.

So, the simplest organic compound hydrocarbon methane has a composition. It can be depicted in structure (a) or electron-structural (or electronic) (b) formulas:

The electronic formula shows that carbon atom in methane molecule has a stable eight-electron outer sheath (electron octet), and hydrogen atoms are a steady two-electron sheath (electronic doublet).

All four carbon covalent bonds in methane (and in other similar compounds) are equivalent and symmetrically directed in space. The carbon atom is as it were in the center of the tetrahedron (the correct tetrahedral pyramid), and the four atoms connected to it (in the case of methane - four atoms of the tetrahedra vertices (Fig. 120). The corners between the directions of any pair of links (valence angles of carbon) are the same and amount to 109 ° 28.

This is due to the fact that in the carbon atom, when it forms covalent bonds with four other atoms, from one S- and three p-orbitals as a result of the hybridization, four symmetrically arranged hybrid-satellite, elongated in the direction to the vertices of the tetrahedron.

Fig. 120. Tetrahedral model of methane molecule.

Fig. 121. Scheme of formation - connections in methane molecule.

As a result of overlapping-hybrid electronic carbon clouds with electronic clouds of other atoms (in methane with ball clouds, hydrogen atoms) formed four tetrahedral covalent-means offices (Fig. 121; see also p. 131).

The tetrahedral structure of methane molecule is visually expressed by its spatial models - ball (Fig. 122) or segment (Fig. 123). White balls (segments) depict hydrogen atoms, black - carbon. The ball model characterizes only the mutual spatial arrangement of atoms, segmental - gives, in addition, an idea of \u200b\u200brelative interatomic distances (distances between nuclei. As shown in Fig. 122, the methane structural formula can be considered as a projection of its spatial model on the drawing plane.

2. The exceptional property of carbon, due to the diversity of organic compounds, is the ability of its atoms to be connected by durable covalent bonds with each other, forming carbon chains of almost unlimited length

The valence of carbon atoms that did not go to the mutual compound are used to attach other atoms or groups (in hydrocarbons - to attach hydrogen).

Thus, hydrocarbons Ethan and propane contain chains, respectively, from two and three carbon atoms.

Fig. 122. Ball model of methane molecule.

Fig. 123. Segment model of methane molecule.

Their structure expresses the following structural and electronic formulas:

Known compounds containing hundreds and more carbon atoms in chains.

Building a carbon chain by one carbon atom leads to an increase in the composition on the group. Such a quantitative change in the composition leads to a new compound, which has several other properties, i.e., already qualitatively different from the initial compound; However, the overall nature of the compounds persists. So, except for methane hydrocarbons, ethane, propane exist Bhutan, pentane, etc. Thus, in a huge manifold organic substances Rows of the same type of connections can be isolated, in which each subsequent member differs from the previous one. Such rows are called homologous rows, their members in relation to each other are homologues, and the existence of such series is called the phenomenon of homology.

Consequently, hydrocarbons methane, stage, propane, butane, etc. - Homologists of the same number, which is called a number of marginal, or saturated, hydrocarbons (alkanov) or, according to the first representative, is a number of methane.

Due to the tetrahedral orientation of carbon bonds, its atoms included in the chain are not located on a straight line, but zigzag, and, due to the possibility of rotating atoms around the axis of the communication, the chain in space can take various forms (conformations):

Such a structure of the chains makes it possible to climb the terminal (b) or other non-adjacent carbon atoms (B); As a result of the occurrence of communication between these atoms, carbon chains may be closed in rings (cycles), for example:

Thus, the variety of organic compounds is determined by the fact that with the same number of carbon atoms in the molecule, compounds with an open, unlocked chain of carbon atoms, as well as substances whose molecules contain cycles (cyclic compounds).

3. Covalent bonds between carbon atoms formed by one pair of generalized electrons are called simple (or ordinary) bonds.

The relationship between carbon atoms can be carried out not one, but by two or three common pairs of electrons. Then there are chains with multiple - double or triple bonds; These links can be depicted as follows:

The simplest compounds containing multiple bonds are ethylene hydrocarbons (with double bond) and acetylene (with a triple bond):

Hydrocarbons with multiple connections are called unsaturated or unsaturated. Ethylene and acetylene are the first representatives of two homologous series - ethylene and acetylene hydrocarbons.

Fig. 124. Education scheme - Communications in the ethane molecule.

A simple covalent bond (or C: C), formed by overlapping two-hybrid electronic clouds along the line connecting the centers of atoms (along the axis of the communication), such as, for example, in ethane (Fig. 124), is a -C. (see § 42 ). Communications are also - comments - they are formed by overlapping on the axis of communication - a hybrid cloud of an atom with and a ball cloud -electron atom N.

The nature of multiple carbon-carbon ties is somewhat different. Thus, in an ethylene molecule in the formation of a double covalent bond (or) in each of the carbon atoms in hybridization, one-cite is involved and only two p-orbntal (-Hybridization); One of the p-orbitals of each atom with not hybridizes. As a result, three-hybrid electronic clouds are formed, which are involved in the formation of three-beds. In total, five connections (four and one) molecule are ethylene; All of them are located in the same plane at corners of about 120 ° to each other (Fig. 125).

Thus, one of the electronic pairs in connection is carried out, and the second is formed by P-electrons that are not involved in hybridization; Their clouds preserve the form of the volume eight, are oriented perpendicular to the plane in which there are connections, and overlap over and under this plane (Fig. 126), forming-§ 42).

Fig. 125. The scheme of formation in the ethylene molecule.

Fig. 126. Scheme of Education - Options in the ethylene molecule.

Consequently, the double bond with \u003d C is a combination of one and one-connections.

Triple bond (or) is a combination of one-means and two-beds. For example, when acetylene molecule is formed in each of the carbon atoms in hybridization, one-ibntal is involved and only one p-orbital (-gibridization); As a result, two-hybrid electronic clouds are formed involved in the formation of two-beds. The clouds of two P-electrons of each atom with do not hybridize, retain their configuration and participate in the formation of two-beds. Thus, in acetylene, there are only three-bonds (one and two), directed along one straight line, and two -roads oriented in two mutually perpendicular planes (Fig. 127).

Multiple (i.e. double and triple) communications in reactions are easily converted into simple; Triple first goes into double, and the last one is in a simple. This is due to their high reactivity and takes place when attaching any atoms to a pair of carbon atoms associated with a multiple bond.

The transition of multiple connections into simple is explained by the fact that usually have a smaller strength and therefore greater lability compared to -ols. When forming, the P-electronic clouds with parallel axes overlap to a much lesser extent than electronic clouds overlapping along the link axis (i.e. hybrid, -electronic or oriented P-electronic clouds oriented by the axis).

Fig. 127. Scheme of formation-means in acetylene molecule.

Fig. 128. Models of ethylene molecule: and - ball; B - segmental.

Multiple communication is stronger than simple. Thus, the energy break energy is, connections, and the relationship only.

From the above, it follows that in the formulas two drops of three in connection and one dash from two in connection express communication less durable than a simple connection.

In fig. 128 and 129 presents ball and segment spatial models of compounds with dual (ethylene) and with triple (acetylene) bonds.

4. The theory of structure explained numerous cases of isomerism of organic compounds.

Chains from carbon atoms can be unbranched or branched:

Thus, the composition has three limiting hydrocarbons (pentane) with a different circuit structure - one with a unbranched chain (normal structure) and two with branched (isothing):

The composition has three unforeseen hydrocarbons. Two normal builds, but isomeric than the position of the double bond and one - iso-building:

Fig. 129. Models of acetylene molecule: and ball; B - segmental.

Two cyclic hydrocarbons, also have a composition and isomeric to each other by the magnitude of the cycle:

At one and the same composition, compounds may differ in structure due to various positions in the carbon chain and other, not carbon, atoms, for example:

The isomerism may be due not only to various orders of compound of atoms. There are several types of spatial isomerism (stereoisometry), which consists in the fact that the corresponding isomers (stereoisomers) with the same composition and the order of the compound of atoms are distinguished by the different arrangement of atoms (or groups of atoms) in space.

So, if there is a carbon atom in the compound, associated with four different atoms or groups of atoms (asymmetric atom), then two spatial-isomeric forms of such a compound are possible. In fig. 130 Two tetrahedral models of lactic acid are presented, in which an asymmetric carbon atom (it is marked with an asterisk in the formula) is located in the center of the tetrahedron. It is easy to note that these models cannot be combined in space: they are constructed mirrors and display the spatial configuration of the molecules of two different substances (in this example of lactic acids), which differ in some physical, and mainly by biological properties. Such isomeria is called mirror stereoisomeria, and the corresponding isomers are mirror isomers.

Fig. 130. Tetrahedral models of molecules of mirror isomers of lactic acid.

The difference in the spatial structure of mirror isomers can also be represented using the structural formulas, in which the various location of atomic groups is shown at an asymmetric atom; For example, for shown in Fig. 130 mirror isomers of lactic acid:

As already indicated, carbon atoms; connected by double bond, lie in one plane with four connections connecting them with other atoms; The angles between the directions of these connections are approximately the same (Fig. 126). When various atoms or groups are connected to each of the carbon atoms, various atoms or groups are connected, the so-called geometric stereoisomeria, or cis-trans isomeria, is possible. An example is the spatial geometric isomers of dichloroethylene

In the molecules of one isomer, chlorine atoms are located on one side of the double bond, and in the other molecules - along different sides. The first configuration is called cis-, the second trans-configuration. Geometric isomers differ from each other in physical and chemical properties.

The existence of them is due to the fact that the double bond eliminates the possibility of free rotation of the connected atoms around the axis of the communication (such rotation requires a break-break; see Fig. 126).

5. Mutual influence in organic substance molecules show first of all atoms directly related to each other. In this case, it is determined by the nature of the chemical bond between them, the degree of difference in their relative electronegativity and, consequently, the degree of polarity of communication.

For example, judging by the total formulas, then in the methane molecule and in the methyl alcohol molecule, all four hydrogen atoms must have the same properties. But, as will be shown further, in methyl alcohol, one of the hydrogen atoms is capable of substituting with an alkaline metal, while hydrogen atoms do not exist in methane. This is explained by the fact that in alcohol, the hydrogen atom is directly connected with carbon, but with oxygen

In the above structural formulas, the arrows on the lines of bonds are conditionally shown the displacement of pairs of electrons forming a covalent bond, due to various electronegability, atoms. In methane, such a displacement in connection is small, since carbon electrorence (2.5) only slightly exceeds the electronegability of hydrogen Table. 6, p. 118). At the same time, the methane molecule is symmetrical. In the alcohol molecule, the connection is significantly polarized, because oxygen (electrothricate 3.5) is much more delayed by an electronic pair; Therefore, a hydrogen atom connected to an oxygen atom acquires greater mobility, i.e. it is easier to leave in the form of a proton.

In organic molecules, the mutual influence of atoms that are not directly related to each other is also important. Thus, in methyl alcohol, under the influence of oxygen, the reactivity is increasing not only atom of hydrogen associated with oxygen, but also hydrogen atoms, directly with oxygen non-associated, and connected to carbon. Due to this, methyl alcohol is quite easily oxidized, while methane is relatively resistant to the action of oxidizers. This is due to the fact that the oxygen of the hydroxyl group significantly densites a pair of electrons in connection connecting it with carbon, the electronegability of which is less.

As a result, the effectary charge of the carbon atom becomes more positive, which causes an additional displacement of the electrons pair of electrons as well in relations in methyl alcohol, compare "to the same connections in the methane molecule. Under the action of oxidants, N atoms associated with the same carbon atom with which the group is connected is much easier than in hydrocarbons, they are detached and combined with oxygen, forming water. In this case, the carbon atom associated with the group is subjected to further oxidation (see § 171).

The mutual influence of atoms, directly with each other not related, can be transmitted by a significant distance along the carbon atom chains and is explained by the displacement of the density of electronic clouds throughout the molecule under the influence of the various electronegability of atoms or groups. The mutual influence can be transmitted through the space surrounding the molecule - as a result of overlapping electronic clouds of convergent atoms.

By the first half of the XIX century, an enormous actual material was accumulated in organic chemistry, the further study of which was hampered by the absence of any systematic basis. Since the 20s of the XIX century, replacing each other theories apply to the generalized description of the structure of organic compounds began to appear. One of them was the theory of types developed in the years of the French scientist Sh. Gerarm. According to this theory, all organic compounds were considered as derivatives of the simplest inorganic substances adopted for types. Gerarm

Shortly before the appearance of the structure of the structure of A. M. Butlerova by the German chemist F.A. Kekule (1857) was developed in relation to organic compounds the theory of valence, which established such facts as four-grams of carbon atom and its ability to form carbon chains due to a compound with carbon atoms. M. ButlerovaF.A. Kekule

The theoretical developments of the Dobtlerian period made a certain contribution to the cognition of the structure of organic compounds. But none of the early theories was universal. And only A.M. Butlerov managed to create such a logically completed theory of the structure, which to this day serves as a scientific basis of organic chemistry. Theory of the structure of A.M. Butlerova is based on a materialistic approach to the real molecule and proceeds from the possibility of the cognition of its structure experimentally. A.M. Butlers in the establishment of the structure of substances attached fundamental importance to chemical reactions. Theory of the structure of A.M. Butlerova not only explained already known facts, its scientific importance was to predict the existence of new organic compounds.. Butlerov A.M. Butlerova A.M. Butlerova.m. Butlerova

Isomers are substances that have the same molecular formula, but a different chemical structure, and therefore possess different properties. The genuine explanation of Isomeria received only in the second half of 19 B based on the theory of the chemical structure A.M. Butlerova (structural isomeria) and stereochemical teachings Ya. Vant-Gooff (spatial isomeria). G. Vant-Gooff

Formulanation Number of Isomers CH 4 Methane1 C4H6C4H6 Ethan1 C3H8C3H8 Propane1 C 4 H 10 Butane2 C 5 H 12 Pentane3 C 6 H 14 Hexane5 C 7 H 16 Heptane9 C 8 H 18 Octan18 C 9 H 20 Nonan35 C 10 H 22 Dean75 C 11 H 24 Undekan159 C 12 H 26 DODECAN 355 C 13 H 28 Tridekan802 C 14 H 30 Tetrakan1 858 C 15 H 32 pentadecan4 347 C 20 H 42 EKOSAN C 25 H 52 Pentacham C 30 H 62 Triakontan C 40 H 82 Tetracotan

The structural is the isomers corresponding to various structural formulas of organic compounds (with different orders of compound of atoms). Spatial isomers have the same substituents for each carbon atom and differ only mutual location in space.

Spatial isomers (stereoisomers). Stereoisomers can be divided into two types: geometric isomers and optical isomers. Geometric isomerism is characteristic of compounds containing a double bond or cycle. In such molecules it is often possible to carry out a conditional plane in such a way that the substituents in different carbon atoms may turn out to be one direction (cis-) or by different directions (trans-) from this plane. If the change in the orientation of these substituents relative to the plane is possible only due to the rupture of one of the chemical bonds, they say the presence of geometric isomers. Geometric isomers are distinguished by their physical and chemical properties.

A new way of obtaining optical isomers of organic molecules was opened when Alice turned out to be in his own, but "lubricant" room, it was surprised: the room seems to be similar, but still quite different. Similarly, mirror isomers of chemical molecules are different: outwardly similar, but behave differently. The most important area of \u200b\u200borganic chemistry is the separation and synthesis of these mirror options. (Illustration of John Tenanel to Lewis Carroll's book "Alice in the Looking Game")

American scientists have learned how to obtain optical isomers of compounds based on aldehydes, finally implementing an important reaction, over which chemists worked for many years. In the experiment, they combined two catalysts working according to various principles. As a result of the joint action of these catalysts, two active organic molecules are formed, which are combined into the desired substance. The example of this reaction shows the possibility of synthesizing a whole class of biologically important organic compounds.

Now at least 130 organic synthesis reactions are already known, in which more or less clean chiral isomers are obtained. If the catalyst itself has chiral properties, then an optically active product will be obtained from an optically inactive substrate. This rule was derived at the beginning of the 20th century and remains basic today. The principle of the sample action of the catalyst in relation to optical isomers is similar to a handshake: the catalyst "conveniently" is born only with one of the chiral isomers, therefore it is preferable only one of the reactions. By the way, the term "chiral" occurred from the Greek Chéir hand.

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):

Second position. The properties of substances depend not only on their qualitative and quantitative composition, but also from the structure of their molecules.

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

Positions of multiple relations:

substituents

positions of functional groups

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 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.

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\u200binseparable communication of chemical and physical properties Molecules with its structure, expressed 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.