Mutual influence of atoms in molecules of organic compounds and methods of its transmission. Mutual influence of atoms in molecules of organic substances

Target: study of the electronic structure of organic compounds and methods of transmitting the mutual influence of atoms in their molecules.

Plan:

Inductive effect

Types of pairing.

Aromaticity of organic compounds

Mesomeric effect (conjugation effect)

1. Inductive effect

A molecule of an organic compound is a collection of atoms connected in a certain order by covalent bonds. In this case, bonded atoms can differ in electronegativity (E.O.).

Electronegativity– the ability of an atom to attract the electron density of another atom to effect a chemical bond.

The larger the E.O. of a given element, the more strongly it attracts bonding electrons. The values ​​of E.O. were established by the American chemist L. Pauling and this series is called the Pauling scale.

The EO of a carbon atom depends on the state of its hybridization, because carbon atoms located in different types of hybridization differ from each other in EO and this depends on the proportion of the s-cloud in a given type of hybridization. For example, the C atom in the state of sp 3 hybridization has the lowest EO. since the p-cloud accounts for the least amount of the s-cloud. Greater E.O. possesses the C atom in sp-hybridization.

All atoms that make up a molecule are in mutual communication with each other and experience mutual influence. This influence is transmitted through covalent bonds using electronic effects.

One of the properties of a covalent bond is a certain mobility of electron density. It is capable of shifting towards the atom with greater E, O.

Polarity A covalent bond is an uneven distribution of electron density between bonded atoms.

The presence of a polar bond in a molecule affects the state of neighboring bonds. They are influenced by polar bonding and their electron density also shifts towards more EO. atom, i.e. the electronic effect is transferred.

The shift of electron density along a chain of ϭ bonds is called inductive effect and is denoted by I.

The inductive effect is transmitted through the circuit with attenuation, because when a ϭ-bond is formed, a large amount of energy is released and it is poorly polarized, and therefore the inductive effect manifests itself to a greater extent on one or two bonds. The direction of shift of the electron density of all ϭ bonds is indicated by straight arrows.→

For example: CH 3 δ +< → CH 2 δ +< → CH 2 δ +< →Cl δ - Э.О. Сl >E.O. WITH

СH 3 δ +< → CH 2 δ +< → CH 2 δ +< →OH δ - Э.О. ОН >E.O. WITH

An atom or group of atoms that shifts the electron density of a ϭ-bond from a carbon atom to itself is called electron-withdrawing substituents and exhibit a negative inductive effect (- I-Effect).

They are halogens (Cl, Br, I), OH -, NH 2 -, COOH, COH, NO 2, SO 3 H, etc.

An atom or group of atoms that donates electron density is called electron-donating substituents and exhibit a positive inductive effect (+ I-Effect).

I-effect exhibit aliphatic hydrocarbon radicals, CH 3, C 2 H 5, etc.

The inductive effect also manifests itself in the case when the bonded carbon atoms differ in their state of hybridization. For example, in a propene molecule, the CH 3 group exhibits a +I effect, since the carbon atom in it is in the sp 3 hybrid state, and the carbon atoms at the double bond are in the sp 2 hybrid state and exhibit greater electronegativity, therefore they exhibit -I- effect and are electron acceptors.

A molecule of an organic compound is a collection of atoms linked in a certain order, usually by covalent bonds. In this case, bonded atoms can differ in size electronegativity. Quantities electronegativities largely determine such important bond characteristics as polarity and strength (energy of formation). In turn, the polarity and strength of bonds in a molecule, to a large extent, determine the ability of the molecule to enter into certain chemical reactions.

Electronegativityof a carbon atom depends on the state of its hybridization. This is due to the share s— orbitals in a hybrid orbital: it is smaller than y sp 3 - and more for sp 2 - and sp -hybrid atoms.

All the atoms that make up a molecule are interconnected and mutually influenced. This influence is transmitted mainly through a system of covalent bonds, using the so-called electronic effects.

Electronic effects called the shift in electron density in a molecule under the influence of substituents./>

Atoms connected by a polar bond carry partial charges, denoted by the Greek letter delta ( d ). Atom "pulling" electron densitys—connection in its direction, acquires a negative charge d -. When considering a pair of atoms linked by a covalent bond, the more electronegative atom is called electron acceptor. His partner s -bond will accordingly have an equal-magnitude electron density deficit, i.e. partial positive charge d +, will be called electron donor.

Shift of electron density along the chains—connections are called inductive effect and is designated I.

The inductive effect is transmitted through the circuit with attenuation. The direction of shift of the electron density of alls—connections are indicated by straight arrows.

Depending on whether the electron density moves away from the carbon atom in question or approaches it, the inductive effect is called negative (- I ) or positive (+I). The sign and magnitude of the inductive effect are determined by differences in electronegativity between the carbon atom in question and the group causing it.

Electron-withdrawing substituents, i.e. an atom or group of atoms that shifts electron densitys—bonds from a carbon atom to itself exhibit negative inductive effect (- I-effect).

Electrodonorsubstituents, i.e. an atom or group of atoms that shifts electron density to a carbon atom away from itself exhibits positive inductive effect(+I-effect).

The I-effect is exhibited by aliphatic hydrocarbon radicals, i.e. alkyl radicals (methyl, ethyl, etc.). Most functional groups exhibit − I -effect: halogens, amino group, hydroxyl, carbonyl, carboxyl groups.

The inductive effect also manifests itself in the case when the bonded carbon atoms differ in their state of hybridization.

When the inductive effect of a methyl group is transferred to a double bond, its influence is first experienced by the mobilep— connection.

The influence of the substituent on the distribution of electron density transmitted throughp—connections are called mesomeric effect (M). The mesomeric effect can also be negative and positive. In structural formulas it is depicted as a curved arrow starting at the center of the electron density and ending at the place where the electron density shifts.

The presence of electronic effects leads to a redistribution of electron density in the molecule and the appearance of partial charges on individual atoms. This determines the reactivity of the molecule.

Organic chemistry- a branch of chemistry in which carbon compounds, their structure, properties, and interconversions are studied.

The very name of the discipline - “organic chemistry” - arose quite a long time ago. The reason for this lies in the fact that most of the carbon compounds encountered by researchers at the initial stage of the development of chemical science were of plant or animal origin. However, as an exception, individual carbon compounds are classified as inorganic. For example, carbon oxides, carbonic acid, carbonates, bicarbonates, hydrogen cyanide and some others are considered to be inorganic substances.

Currently, just under 30 million different organic substances are known, and this list is constantly growing. Such a huge number of organic compounds is associated primarily with the following specific properties of carbon:

1) carbon atoms can be connected to each other in chains of arbitrary length;

2) not only a sequential (linear) connection of carbon atoms with each other is possible, but also a branched and even cyclic one;

3) different types of bonds between carbon atoms are possible, namely single, double and triple. Moreover, the valence of carbon in organic compounds is always four.

In addition, the wide variety of organic compounds is also facilitated by the fact that carbon atoms are able to form bonds with atoms of many other chemical elements, for example, hydrogen, oxygen, nitrogen, phosphorus, sulfur, and halogens. In this case, hydrogen, oxygen and nitrogen are most common.

It should be noted that for quite a long time organic chemistry represented a “dark forest” for scientists. For some time, the theory of vitalism was even popular in science, according to which organic substances cannot be obtained “artificially”, i.e. outside of living matter. However, the theory of vitalism did not last very long, due to the fact that one after another substances were discovered whose synthesis is possible outside living organisms.

Researchers were perplexed by the fact that many organic substances have the same qualitative and quantitative composition, but often have completely different physical and chemical properties. For example, dimethyl ether and ethyl alcohol have exactly the same elemental composition, but under normal conditions dimethyl ether is a gas, and ethyl alcohol is a liquid. In addition, dimethyl ether does not react with sodium, but ethyl alcohol reacts with it, releasing hydrogen gas.

Researchers of the 19th century put forward many assumptions regarding how organic substances were structured. Significantly important assumptions were put forward by the German scientist F.A. Kekule, who was the first to express the idea that atoms of different chemical elements have specific valence values, and carbon atoms in organic compounds are tetravalent and are capable of combining with each other to form chains. Later, starting from Kekule’s assumptions, the Russian scientist Alexander Mikhailovich Butlerov developed a theory of the structure of organic compounds, which has not lost its relevance in our time. Let's consider the main provisions of this theory:

1) all atoms in molecules of organic substances are connected to each other in a certain sequence in accordance with their valency. Carbon atoms have a constant valency of four and can form chains of different structures with each other;

2) the physical and chemical properties of any organic substance depend not only on the composition of its molecules, but also on the order in which the atoms in this molecule are connected to each other;

3) individual atoms, as well as groups of atoms in a molecule, influence each other. This mutual influence is reflected in the physical and chemical properties of the compounds;

4) by studying the physical and chemical properties of an organic compound, its structure can be established. The opposite is also true - knowing the structure of the molecule of a particular substance, you can predict its properties.

Just as D.I. Mendelev’s periodic law became the scientific foundation of inorganic chemistry, the theory of the structure of organic substances by A.M. Butlerov actually became the starting point in the development of organic chemistry as a science. It should be noted that after the creation of Butlerov’s theory of structure, organic chemistry began its development at a very rapid pace.

Isomerism and homology

According to the second position of Butlerov’s theory, the properties of organic substances depend not only on the qualitative and quantitative composition of the molecules, but also on the order in which the atoms in these molecules are connected to each other.

In this regard, the phenomenon of isomerism is widespread among organic substances.

Isomerism is a phenomenon when different substances have exactly the same molecular composition, i.e. same molecular formula.

Very often, isomers differ greatly in physical and chemical properties. For example:

Types of isomerism

Structural isomerism

a) Isomerism of the carbon skeleton

b) Positional isomerism:

multiple connection

deputies:

functional groups:

c) Interclass isomerism:

Interclass isomerism occurs when compounds that are isomers belong to different classes of organic compounds.

Spatial isomerism

Spatial isomerism is a phenomenon when different substances with the same order of attachment of atoms to each other differ from each other by a fixed-different position of atoms or groups of atoms in space.

There are two types of spatial isomerism - geometric and optical. Tasks on optical isomerism are not found on the Unified State Exam, so we will consider only geometric ones.

If the molecule of a compound contains a double C=C bond or a ring, sometimes in such cases the phenomenon of geometric or cis-trans-isomerism.

For example, this type of isomerism is possible for butene-2. Its meaning is that the double bond between carbon atoms actually has a planar structure, and the substituents on these carbon atoms can be fixedly located either above or below this plane:

When identical substituents are on the same side of the plane they say that it is cis-isomer, and when they are different - trance-isomer.

On in the form of structural formulas cis- And trance-isomers (using butene-2 ​​as an example) are depicted as follows:

Note that geometric isomerism is impossible if at least one carbon atom at the double bond has two identical substituents. For example, cis-trans- isomerism is not possible for propene:

Propen does not have cis-trans-isomers, since one of the carbon atoms at the double bond has two identical “substituents” (hydrogen atoms)

As you can see from the illustration above, if we swap places between the methyl radical and the hydrogen atom located at the second carbon atom, on opposite sides of the plane, we get the same molecule that we just looked at from the other side.

The influence of atoms and groups of atoms on each other in molecules of organic compounds

The concept of chemical structure as a sequence of atoms connected to each other was significantly expanded with the advent of electronic theory. From the standpoint of this theory, it is possible to explain how atoms and groups of atoms in a molecule influence each other.

There are two possible ways in which one part of a molecule influences another:

1) Inductive effect

2) Mesomeric effect

Inductive effect

To demonstrate this phenomenon, let us take as an example the 1-chloropropane molecule (CH 3 CH 2 CH 2 Cl). The bond between carbon and chlorine atoms is polar because chlorine has a much higher electronegativity compared to carbon. As a result of the shift of electron density from the carbon atom to the chlorine atom, a partial positive charge (δ+) is formed on the carbon atom, and a partial negative charge (δ-) is formed on the chlorine atom:

The shift in electron density from one atom to another is often indicated by an arrow pointing towards the more electronegative atom:

However, an interesting point is that, in addition to the shift in electron density from the first carbon atom to the chlorine atom, there is also a shift, but to a slightly lesser extent, from the second carbon atom to the first, as well as from the third to the second:

This shift in electron density along a chain of σ bonds is called the inductive effect ( I). This effect fades away with distance from the influencing group and practically does not appear after 3 σ bonds.

In the case where an atom or group of atoms has greater electronegativity compared to carbon atoms, such substituents are said to have a negative inductive effect (- I). Thus, in the example discussed above, the chlorine atom has a negative inductive effect. In addition to chlorine, the following substituents have a negative inductive effect:

–F, –Cl, –Br, –I, –OH, –NH 2 , –CN, –NO 2 , –COH, –COOH

If the electronegativity of an atom or group of atoms is less than the electronegativity of a carbon atom, there is actually a transfer of electron density from such substituents to the carbon atoms. In this case, they say that the substituent has a positive inductive effect (+ I) (is electron donor).

So, substituents with + I-the effect is saturated hydrocarbon radicals. At the same time, the expression + I-effect increases with lengthening of the hydrocarbon radical:

–CH 3 , –C 2 H 5 , –C 3 H 7 , –C 4 H 9

It should be noted that carbon atoms located in different valence states also have different electronegativity. Carbon atoms in the sp 2 -hybridized state have greater electronegativity compared to carbon atoms in the sp 2 -hybridized state, which, in turn, are more electronegative than carbon atoms in the sp 3 -hybridized state.

Mesomeric effect (M), or conjugation effect, is the influence of a substituent transmitted through a system of conjugated π bonds.

The sign of the mesomeric effect is determined according to the same principle as the sign of the inductive effect. If a substituent increases the electron density in a conjugated system, it has a positive mesomeric effect (+ M) and is electron-donating. Double carbon-carbon bonds and substituents containing a lone electron pair: -NH 2 , -OH, halogens have a positive mesomeric effect.

Negative mesomeric effect (– M) have substituents that withdraw electron density from the conjugated system, while the electron density in the system decreases.

The following groups have a negative mesomeric effect:

–NO 2 , –COOH, –SO 3 H, -COH, >C=O

Due to the redistribution of electron density due to mesomeric and inductive effects in the molecule, partial positive or negative charges appear on some atoms, which is reflected in the chemical properties of the substance.

Graphically, the mesomeric effect is shown by a curved arrow that begins at the center of the electron density and ends where the electron density shifts. For example, in a vinyl chloride molecule, the mesomeric effect occurs when the lone electron pair of the chlorine atom couples with the electrons of the π bond between the carbon atoms. Thus, as a result of this, a partial positive charge appears on the chlorine atom, and the mobile π-electron cloud, under the influence of an electron pair, is shifted towards the outermost carbon atom, on which a partial negative charge arises as a result:

If a molecule has alternating single and double bonds, then the molecule is said to contain a conjugated π-electron system. An interesting property of such a system is that the mesomeric effect in it does not fade.

The atoms that make up a molecule experience mutual influence, transmitted through electronic and spatial effects. Electronic effects characterize the ability of substituents to transmit their influence along a chain of covalently bonded atoms. The influence of substituents can be transmitted both through chemical bonds and through space.

A.Inductive effect

One of the properties of a covalent bond is the possibility of shifting the electron density of the bond towards one of the partners.

In a propyl chloride molecule, the chlorine atom induces a partial positive charge on the carbon atom associated with it. This charge induces a smaller positive charge on the next carbon atom, which induces an even smaller positive charge on the next atom, and so on.

+ + + -

CH 3  CH 2  CH 2  Cl

The ability of a substituent to displace electrons along -bonds is called inductive effect. The inductive effect (I-effect) is of the nature of an electrostatic effect; it is transmitted along the communication line and leads to the appearance of fractional charges. Electron-withdrawing groups have negative inductive effect (-I), and electron-donating ones - positive inductive effect (+I). Electron-withdrawing groups include F, Cl, Br, NH 2, OH, CHO, COOH, COOR, CN and NO 2. Electron-donating groups include metal atoms and alkyl groups.

The inductive effect is transmitted through a chain of -bonds with gradual attenuation and, as a rule, after three or four bonds it no longer appears. Graphically, the I-effect is indicated by an arrow at the end of the valence line, pointing towards the more electronegative atom. The direction of bond polarization can be established using the Pauling electronegativity scale of elements (Table 1). The direction of the inductive effect of the substituent is qualitatively assessed by comparing it with the practically nonpolar C–H bond and assuming the I-effect of the hydrogen atom to be equal to zero.

For example, in a propene molecule, the carbon atom of the methyl group located in sp 3 -hybrid state, less electronegative than sp 2 -hybridized carbon atoms of the double bond. Therefore, the methyl group acts as an electron donor and the p-bond is primarily affected by it. The shift in electron density of a p-bond is indicated by a curved arrow, as shown in the example of propene:

The positive inductive effect of alkyl groups increases when moving from the methyl group to the primary groups and then to the secondary and tertiary groups.

Inductive effects reach their greatest significance when an atom or group of atoms has a full charge. A particularly strong shift in electron density is caused by ions, which extends far along the chain.

NH 3 + (-I-effect) H 2 O + (-I-effect) O − (+I-effect)

B. Measurable effect

The mesomeric effect, or conjugation effect (M-effect), is the transfer of the electronic influence of substituents through a conjugated system.

A substituent can introduce a -bond (,-conjugation) or R-AO, which can be either vacant or occupied by one electron or lone pair of electrons ( R,-conjugation). The mesomeric effect reflects the fact that R The -orbitals of the substituent, overlapping with the orbitals of the  bonds, form a delocalized orbital of lower energy. Unlike the inductive effect, the mesomeric effect is transmitted through conjugate systems without attenuation.

The displacement of -electrons or lone pairs in conjugated systems is called mesomeric effect. Electron-donating groups have a positive mesomeric effect (+M). These include substituents containing a heteroatom with a lone pair of electrons or having a negative charge:

vinyl methyl ether aniline phenoxide ion

Electron-withdrawing groups that polarize the conjugated system in the opposite direction are characterized by a negative mesomeric effect (_M) (oxygen in the propenal). These include substituents containing multiple bonds of a carbon atom with a more electronegative heteroatom:

propenal (acrolein) benzoic acid benzonitrile

The inductive and mesomeric effects of the substituent do not necessarily coincide in direction. When assessing the influence of a substituent on the distribution of electron density in a molecule, it is necessary to take into account the resulting effect of these effects. With rare exceptions (halogen atoms), the mesomeric effect prevails over the inductive effect.

Delocalized electron density in a molecule can be achieved with the participation of electrons and -bonds. The lateral overlap of -bond orbitals with neighboring -orbitals is called superconjugation. The superconjugation effect is denoted by the symbol M h . The designation of this effect is illustrated using propene as an example.

Ex. 15. P exert electronic effects in the molecules of the following compounds: (a) propyl chloride, (b) 1-nitropropane, (c) ethanol, (d) propyllithium,

(e) ethanamine, (f) benzaldehyde, (g) acrylonitrile, (h) phenol, (i) methyl benzoate.

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;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">lectures on organic chemistry for students of the pediatric faculty

;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">Lecture 2

;font-family:"Times New Roman";text-decoration:underline" xml:lang="ru-RU" lang="ru-RU">Topic: Mutual influence of atoms in molecules of organic compounds

;text-decoration:underline" xml:lang="ru-RU" lang="ru-RU">Target:" xml:lang="ru-RU" lang="ru-RU">" xml:lang="ru-RU" lang="ru-RU">study of the electronic structure of organic compounds and methods of transmitting the mutual influence of atoms in their molecules.

;font-family:"Times New Roman";text-decoration:underline" xml:lang="ru-RU" lang="ru-RU">Plan:

1. ;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">Inductive effect
2. ;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">Types of pairing.
3. ;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">Aromaticity of organic compounds
4. ;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">Mesomeric effect (conjugation effect)

1. ;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">Inductive effect

;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">A molecule of an organic compound is a collection of atoms connected in a certain order by covalent bonds. Moreover, the bonded atoms may differ in electronegativity value (E.O.).

• ;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU"> Electronegativity;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU"> the ability of an atom to attract the electron density of another atom to effect a chemical bond.

;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">The greater the EO value of a given element, the more strongly it attracts bonding electrons. EO values. were established by the American chemist L. Pauling and this series is called the Pauling scale.

;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">E. O. of a carbon atom depends on the state of its hybridization, since carbon atoms located in different types of hybridization differ from each other in E.O. and this depends on the proportion;font-family:"Times New Roman"" xml:lang="en-US" lang="en-US">s;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">-clouds in this type of hybridization. For example, atom C is in the state;font-family:"Times New Roman"" xml:lang="en-US" lang="en-US">sp;font-family:"Times New Roman";vertical-align:super" xml:lang="ru-RU" lang="ru-RU">3;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">-hybridization has the lowest EO since the p-cloud accounts for the least;font-family:"Times New Roman"" xml:lang="en-US" lang="en-US">s;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">-clouds. Atom C in the;font-family:"Times New Roman"" xml:lang="en-US" lang="en-US">sp;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">- hybridization.

;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">All the atoms that make up the molecule are in mutual connection with each other and experience mutual influence. This influence is transmitted through covalent connections using electronic effects.

;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">One ​​of the properties of a covalent bond is a certain mobility of electron density. It is capable of shifting towards an atom with higher E, O .

• ;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">Polarity;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">covalent bond is an uneven distribution of electron density between bonded atoms.

;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">The presence of a polar bond in a molecule affects the state of neighboring bonds. They are influenced by the polar bond, and their electron density also shifts towards a more EO of the atom, i.e. the electronic effect is transferred.

• ;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU"> The shift of electron density along a chain of ϭ-bonds is called;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">inductive effect;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU"> and is designated;font-family:"Times New Roman"" xml:lang="en-US" lang="en-US">I;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">.

;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">The inductive effect is transmitted through the circuit with attenuation, since when a ϭ-bond is formed, a large amount of energy is released and it is poorly polarized and therefore the inductive effect manifests itself to a greater extent on one or two bonds.The direction of the shift in the electron density of all ϭ-bonds is indicated by straight arrows.→

;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">For example: C;font-family:"Times New Roman"" xml:lang="en-US" lang="en-US">H;font-family:"Times New Roman";vertical-align:sub" xml:lang="ru-RU" lang="ru-RU">3;font-family:"Times New Roman";vertical-align:super" xml:lang="en-US" lang="en-US">δ;font-family:"Times New Roman";vertical-align:super" xml:lang="ru-RU" lang="ru-RU">+< ;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU"> →;font-family:"Times New Roman"" xml:lang="en-US" lang="en-US">CH;font-family:"Times New Roman";vertical-align:sub" xml:lang="ru-RU" lang="ru-RU">2;font-family:"Times New Roman";vertical-align:super" xml:lang="en-US" lang="en-US">δ;font-family:"Times New Roman";vertical-align:super" xml:lang="ru-RU" lang="ru-RU">+< ;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU"> →;font-family:"Times New Roman"" xml:lang="en-US" lang="en-US">CH;font-family:"Times New Roman";vertical-align:sub" xml:lang="ru-RU" lang="ru-RU">2;font-family:"Times New Roman";vertical-align:super" xml:lang="en-US" lang="en-US">δ;font-family:"Times New Roman";vertical-align:super" xml:lang="ru-RU" lang="ru-RU">+< ;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU"> →;font-family:"Times New Roman"" xml:lang="en-US" lang="en-US">Cl;font-family:"Times New Roman";vertical-align:super" xml:lang="en-US" lang="en-US">δ;font-family:"Times New Roman";vertical-align:super" xml:lang="ru-RU" lang="ru-RU">-;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU"> E.O. S;font-family:"Times New Roman"" xml:lang="en-US" lang="en-US">l;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU"> > E.O. S

;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">С;font-family:"Times New Roman"" xml:lang="en-US" lang="en-US">H;font-family:"Times New Roman";vertical-align:sub" xml:lang="ru-RU" lang="ru-RU">3;font-family:"Times New Roman";vertical-align:super" xml:lang="en-US" lang="en-US">δ;font-family:"Times New Roman";vertical-align:super" xml:lang="ru-RU" lang="ru-RU">+< ;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU"> →;font-family:"Times New Roman"" xml:lang="en-US" lang="en-US">CH;font-family:"Times New Roman";vertical-align:sub" xml:lang="ru-RU" lang="ru-RU">2;font-family:"Times New Roman";vertical-align:super" xml:lang="en-US" lang="en-US">δ;font-family:"Times New Roman";vertical-align:super" xml:lang="ru-RU" lang="ru-RU">+< ;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU"> →;font-family:"Times New Roman"" xml:lang="en-US" lang="en-US">CH;font-family:"Times New Roman";vertical-align:sub" xml:lang="ru-RU" lang="ru-RU">2;font-family:"Times New Roman";vertical-align:super" xml:lang="en-US" lang="en-US">δ;font-family:"Times New Roman";vertical-align:super" xml:lang="ru-RU" lang="ru-RU">+< ;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU"> →;font-family:"Times New Roman"" xml:lang="en-US" lang="en-US">OH;font-family:"Times New Roman";vertical-align:super" xml:lang="en-US" lang="en-US">δ;font-family:"Times New Roman";vertical-align:super" xml:lang="ru-RU" lang="ru-RU">-;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">E.O. ON > E.O. S

• ;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">An atom or group of atoms that shifts the electron density of a ϭ bond from a carbon atom to itself is called;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">electron-withdrawing substituents;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">and exhibit a negative inductive effect;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">(-;font-family:"Times New Roman"" xml:lang="en-US" lang="en-US">I;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">-effect).

;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">Imi;font-family:"Times New Roman"" xml:lang="en-US" lang="en-US">;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">are;font-family:"Times New Roman"" xml:lang="en-US" lang="en-US">;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">halogens;font-family:"Times New Roman"" xml:lang="en-US" lang="en-US"> (Cl, Br, I), OH;font-family:"Times New Roman";vertical-align:super" xml:lang="en-US" lang="en-US">-;font-family:"Times New Roman"" xml:lang="en-US" lang="en-US">, NH;font-family:"Times New Roman";vertical-align:sub" xml:lang="en-US" lang="en-US">2;font-family:"Times New Roman";vertical-align:super" xml:lang="en-US" lang="en-US">-;font-family:"Times New Roman"" xml:lang="en-US" lang="en-US">, COOH, COH, NO;font-family:"Times New Roman";vertical-align:sub" xml:lang="en-US" lang="en-US">2;font-family:"Times New Roman"" xml:lang="en-US" lang="en-US">, SO;font-family:"Times New Roman";vertical-align:sub" xml:lang="en-US" lang="en-US">3;font-family:"Times New Roman"" xml:lang="en-US" lang="en-US">H and others.

• ;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">An atom or group of atoms that donates electron density is called;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">electron-donating substituents;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">and exhibit a positive inductive effect;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">(+;font-family:"Times New Roman"" xml:lang="en-US" lang="en-US">I;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">-effect).

;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">+;font-family:"Times New Roman"" xml:lang="en-US" lang="en-US">I;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">-effect;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">show aliphatic hydrocarbon radicals, CH;font-family:"Times New Roman";vertical-align:sub" xml:lang="ru-RU" lang="ru-RU">3;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">, C;font-family:"Times New Roman";vertical-align:sub" xml:lang="ru-RU" lang="ru-RU">2;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">Н;font-family:"Times New Roman";vertical-align:sub" xml:lang="ru-RU" lang="ru-RU">5;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU"> etc.

;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">The inductive effect also manifests itself in the case when the bonded carbon atoms differ in the state of hybridization. For example, in the propene molecule the group CH;font-family:"Times New Roman";vertical-align:sub" xml:lang="ru-RU" lang="ru-RU">3;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU"> shows +;font-family:"Times New Roman"" xml:lang="en-US" lang="en-US">I;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">-effect, since the carbon atom in it is in;font-family:"Times New Roman"" xml:lang="en-US" lang="en-US">sp;font-family:"Times New Roman";vertical-align:super" xml:lang="ru-RU" lang="ru-RU">3;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">-hybrid state, and the carbon atoms at the double bond are in;font-family:"Times New Roman"" xml:lang="en-US" lang="en-US">sp;font-family:"Times New Roman";vertical-align:super" xml:lang="ru-RU" lang="ru-RU">2;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">-hybrid state and exhibit greater electronegativity, therefore they exhibit -;font-family:"Times New Roman"" xml:lang="en-US" lang="en-US">I;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">-effect and are electron acceptors." xml:lang="ru-RU" lang="ru-RU">

;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">propene-1

1. ;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">Conjugated systems. Types of conjugation.

;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">The most important factor determining the chemical properties of a molecule is the distribution of electron density in it. The nature of the distribution depends on the mutual influence of atoms .

;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">It was previously shown that in molecules having only ϭ-bonds, the mutual influence of atoms in the case of their different E ,O. is carried out through the inductive effect. In molecules, which are conjugated systems, the action of another effect is manifested;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">mesomeric,;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">or;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU"> conjugation effect.

• ;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">The influence of a substituent transmitted through a conjugate system of π bonds is called;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">mesomeric effect (M).

;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">Before talking about the mesomeric effect, it is necessary to examine the issue of conjugated systems.

;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">Conjugation is found in the molecules of many organic compounds (alkadienes, aromatic hydrocarbons, carboxylic acids, urea, etc.).

;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">Compounds with an alternating arrangement of double bonds form conjugated systems.

• ;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">Conjugation;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">formation of a single electron cloud as a result of the interaction of non-hybridized particles;font-family:"Times New Roman";vertical-align:sub" xml:lang="en-US" lang="en-US">z;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">- orbitals in a molecule with alternating double and single bonds.

;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">The simplest conjugated compound is butadiene-1,3. All four carbon atoms in the molecule of butadiene-1,3 are located able;font-family:"Times New Roman"" xml:lang="en-US" lang="en-US">sp;font-family:"Times New Roman";vertical-align:super" xml:lang="ru-RU" lang="ru-RU">2;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">-

;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">hybridization. All these atoms lie in the same plane and make up the σ-skeleton of the molecule (see figure).

;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">The unhybridized p orbitals of each carbon atom are located perpendicular to this plane and parallel to each other. This creates conditions for their mutual overlap. The overlap of these orbitals occurs not only between the atoms C-1 and C-2 and C-3 and C-4, but also partially between the atoms C-2 and C-3. When four p;font-family:"Times New Roman";vertical-align:sub" xml:lang="en-US" lang="en-US">z;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">-orbitals, a single π-electron cloud is formed, i.e.;font-family:"Times New Roman";text-decoration:underline" xml:lang="ru-RU" lang="ru-RU">pairing;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU"> two double bonds. This type of conjugation is called;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">π, π-conjugation;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">, because the orbitals of π bonds interact. The conjugation chain can include a large number of double bonds. The longer it is , the greater the delocalization of π-electrons and the more stable the molecule. In a conjugated system, π-electrons no longer belong to certain bonds, they;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">delocalized;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">i.e., they are evenly distributed throughout the molecule. The delocalization of π-electrons in a conjugated system is accompanied by the release of energy, which is called;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">conjugation energy.;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU"> Such molecules are more stable than systems with isolated double bonds. This is explained by the fact that the energy of such molecules is lower. As a result of the delocalization of electrons during the formation of a conjugated system, a partial alignment of bond lengths occurs: the single bond becomes shorter, and the double bond becomes longer.

;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">The conjugation system can also include heteroatoms. Examples of π,π-conjugated systems with a heteroatom in the chain are α and β unsaturated carbonyl compounds, for example in acrolein (propen-2-al) CH;font-family:"Times New Roman";vertical-align:sub" xml:lang="ru-RU" lang="ru-RU">2;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU"> = CH CH = O.

;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">The coupling chain includes three;font-family:"Times New Roman"" xml:lang="en-US" lang="en-US">sp;font-family:"Times New Roman";vertical-align:super" xml:lang="ru-RU" lang="ru-RU">2;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">-hybridized carbon atom and oxygen atom, each of which contributes one p-electron to a single π-system .

;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">р,π-conjugation.;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">In p,π-conjugated systems, atoms with a lone donor electron pair take part in the formation of conjugation. These can be : Cl, O, N,;font-family:"Times New Roman"" xml:lang="en-US" lang="en-US">S;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU"> etc. Such compounds include halides, ethers, acetamides, carbocations. In the molecules of these compounds double conjugation occurs bonds with the p-orbital of a heteroatom. A delocalized three-center bond is formed by overlapping two p-orbitals;font-family:"Times New Roman"" xml:lang="en-US" lang="en-US">sp;font-family:"Times New Roman";vertical-align:super" xml:lang="ru-RU" lang="ru-RU">2;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">-hybridized carbon atom and one p-orbital of a heteroatom with a pair of electrons.

;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">

;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">The formation of a similar bond can be shown in the amide group, which is an important structural fragment of peptides and proteins. The amide group of the acetamide molecule includes two heteroatoms nitrogen and oxygen.P, π-conjugation involves the π-electrons of the polarized double bond of the carbonyl group and the donor electron pair of the nitrogen atom.

;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU"> р, π-conjugation

;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU"> Conjugation can also occur in cyclic systems. These primarily include arenas and their derivatives. The simplest representative is benzene All carbon atoms in a benzene molecule are in;font-family:"Times New Roman"" xml:lang="en-US" lang="en-US">sp;font-family:"Times New Roman";vertical-align:super" xml:lang="ru-RU" lang="ru-RU">2;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">-hybridization. Six;font-family:"Times New Roman"" xml:lang="en-US" lang="en-US">sp;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">-hybrid clouds form the framework of benzene. All ϭ-bonds (C C and C H) lie in one plane. Six nonhydridized p-orbitals are located perpendicular to the plane of the molecule and parallel to each other. Each p-orbital can equally overlap with two neighboring p-orbitals. As a result of such overlap, a single delocalized π-system arises, in which the highest electron density is located above and below the plane of the ϭ-skeleton and covers all carbon atoms of the ring. The π-electron density is evenly distributed throughout the cyclic system. All bonds between carbon atoms have the same length (0.139 nm), intermediate between the lengths of single and double bonds.

" xml:lang="ru-RU" lang="ru-RU">

1. ;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">Aromaticity

" xml:lang="ru-RU" lang="ru-RU">This concept, which includes various properties of aromatic compounds, was introduced by the German physicist E. Hückel (1931).

" xml:lang="ru-RU" lang="ru-RU">Aromaticity conditions:

• " xml:lang="ru-RU" lang="ru-RU">flat closed loop
• " xml:lang="ru-RU" lang="ru-RU">all C atoms are in" xml:lang="en-US" lang="en-US">sp;vertical-align:super" xml:lang="ru-RU" lang="ru-RU">2" xml:lang="ru-RU" lang="ru-RU"> hybridization
• " xml:lang="ru-RU" lang="ru-RU">a single conjugate system of all atoms of the cycle is formed
• " xml:lang="ru-RU" lang="ru-RU">Hückel's rule is fulfilled: “4" xml:lang="en-US" lang="en-US">n" xml:lang="ru-RU" lang="ru-RU">+2;font-family:"Symbol"" xml:lang="ru-RU" lang="ru-RU">" xml:lang="ru-RU" lang="ru-RU">-electrons, where" xml:lang="en-US" lang="en-US">n" xml:lang="ru-RU" lang="ru-RU"> = 1, 2, 3..." xml:lang="-none-" lang="-none-">" xml:lang="ru-RU" lang="ru-RU">”

;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">The simplest representative of aromatic hydrocarbons is benzene. It satisfies" xml:lang="ru-RU" lang="ru-RU">i;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">et all four aromaticity conditions.

;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">Hückel's rule: 4;font-family:"Times New Roman"" xml:lang="en-US" lang="en-US">n;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">+2 = 6,;font-family:"Times New Roman"" xml:lang="en-US" lang="en-US">n;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU"> = 1.

;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">Naphthalene

;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">Naphthalene aromatic compound ;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">Hückel's rule: 4;font-family:"Times New Roman"" xml:lang="en-US" lang="en-US">n;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">+2 = 10,;font-family:"Times New Roman"" xml:lang="en-US" lang="en-US">n;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU"> = 2.

;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">Pir" xml:lang="ru-RU" lang="ru-RU">and;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">din

;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">Pyridine aromatic heterocyclic ;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">с" xml:lang="ru-RU" lang="ru-RU">o;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">unity.

1. ;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">Mesomeric effect

;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">Unlike non-conjugated systems in which the electronic influence of substituents is transmitted through ϭ-bonds (inductive effect), in conjugated systems the π-electrons of delocalized covalent bonds play the main role in the transmission of electronic influence.The effect manifested in a shift in the electron density of the delocalized (conjugated) π-system is called the conjugation effect or mesomeric effect.

• ;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">Mesomeric effect (+M, -M);font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU"> transfer of the electronic influence of the deputy through the associated system.

;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">In this case, the substituent becomes part of the conjugated system. It can introduce a π bond (carbonyl, carboxyl, nitro group, sulfo group, etc.), a lone pair of electrons of a heteroatom (halogens, amino, hydroxyl groups), vacant or filled with one or two electrons of p-orbitals. Denoted by the letter M and from" xml:lang="ru-RU" lang="ru-RU">o;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">curved arrow The mesomeric effect can be “+” or “”.

• ;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">Substituents that increase the electron density in a conjugated system exhibit a positive mesomeric effect. They contain atoms with a lone electron pair or negative charge and are capable of transferring their electrons to a common conjugate system, i.e. they are;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">electron donors. (ED);font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">. They direct reactions;font-family:"Times New Roman"" xml:lang="en-US" lang="en-US">S;font-family:"Times New Roman";vertical-align:sub" xml:lang="en-US" lang="en-US">E;font-family:"Times New Roman";vertical-align:sub" xml:lang="ru-RU" lang="ru-RU">;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">in positions 2,4,6 and are called;font-family:"Times New Roman";text-decoration:underline" xml:lang="ru-RU" lang="ru-RU">orientations;font-family:"Times New Roman";text-decoration:underline" xml:lang="en-US" lang="en-US">I;font-family:"Times New Roman";text-decoration:underline" xml:lang="ru-RU" lang="ru-RU"> kind

;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">ED Examples:

;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">A substituent that attracts electrons from a conjugated system exhibits M and is called;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">electron acceptor (EA;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">). These are substituents that have two" xml:lang="ru-RU" lang="ru-RU">th;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">new connection

;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">benzaldehyde

;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">Table 1;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">Electronic effects of substituents

;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">Deputies	;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">Orientants in C;font-family:"Times New Roman";vertical-align:sub" xml:lang="ru-RU" lang="ru-RU">6;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">Н;font-family:"Times New Roman";vertical-align:sub" xml:lang="ru-RU" lang="ru-RU">5;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">-;font-family:"Times New Roman"" xml:lang="en-US" lang="en-US">R	;font-family:"Times New Roman"" xml:lang="en-US" lang="en-US">I	;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">M
;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">A;font-family:"Times New Roman"" xml:lang="en-US" lang="en-US">lk;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU"> (;font-family:"Times New Roman"" xml:lang="en-US" lang="en-US">R;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">-): CH;font-family:"Times New Roman";vertical-align:sub" xml:lang="ru-RU" lang="ru-RU">3;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">-, C;font-family:"Times New Roman";vertical-align:sub" xml:lang="ru-RU" lang="ru-RU">2;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">Н;font-family:"Times New Roman";vertical-align:sub" xml:lang="ru-RU" lang="ru-RU">5;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">-...	;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">Orientants ;font-family:"Times New Roman"" xml:lang="en-US" lang="en-US">I;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU"> sort: ;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">send ED ;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">alternates ;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">in ortho- and para- ;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">position" xml:lang="ru-RU" lang="ru-RU">е;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">nia	;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">+
;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">Н;font-family:"Times New Roman";vertical-align:sub" xml:lang="ru-RU" lang="ru-RU">2;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">,;font-family:"Times New Roman"" xml:lang="en-US" lang="en-US">N;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">Н;font-family:"Times New Roman"" xml:lang="en-US" lang="en-US">R;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">,;font-family:"Times New Roman"" xml:lang="en-US" lang="en-US">NR;font-family:"Times New Roman";vertical-align:sub" xml:lang="ru-RU" lang="ru-RU">2		;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">	;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">+
;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">Н, Н,;font-family:"Times New Roman"" xml:lang="en-US" lang="en-US">R		;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">	;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">+
;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">Н;font-family:"Times New Roman"" xml:lang="en-US" lang="en-US">L		;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">	;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">+
	;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">Orientants ;font-family:"Times New Roman"" xml:lang="en-US" lang="en-US">II;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU"> kind: direct ;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">з" xml:lang="ru-RU" lang="ru-RU">a;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">replacements in meta- ;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">p" xml:lang="ru-RU" lang="ru-RU">o;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">positions	;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">	;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">

;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">Recommended reading

;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">Main

;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">1.;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">Luzin A. P., Zurabyan S. E.,;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">N. A. Tyukavkina, Organic chemistry (textbook for students of secondary pharmaceutical and medical institutions), 2002. P.42-46, 124-128.

;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">Additional

1. ;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">Egorov A. S., Shatskaya K. P.;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU"> Chemistry. Allowance tutor for applicants to universities
2. ;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">Kuzmenko N. E., Eremin V. V., Popkov V. A.;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU"> Beginnings of Chemistry M., 1998. P. 57-61.
3. ;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">Ryle S. A., Smith K., Ward R.;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">. Fundamentals of organic chemistry for students of biological and medical specialties M.: Mir, 1983.

;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">4. Lectures by teachers.

Rice. ;font-family:"Times New Roman"" xml:lang="-none-" lang="-none-">Formation of a conjugated system in the 1,3-butadiene molecule

;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">SN;font-family:"Times New Roman";vertical-align:sub" xml:lang="ru-RU" lang="ru-RU">2;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">= CH O CH;font-family:"Times New Roman";vertical-align:sub" xml:lang="ru-RU" lang="ru-RU">3

;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">Vinyl methyl ether

;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">The combination of six ϭ-bonds with a single π-system is called;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">aromatic connection.;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">A cycle of six carbon atoms linked by an aromatic bond is called;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">benzene ring;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">, or;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">benzene ring.

;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">р, π-conjugation

;font-family:"Times New Roman"" xml:lang="ru-RU" lang="ru-RU">EA