Chemistry theory of the structure of organic compounds. Theory of the structure of chemical compounds A

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:

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 first appeared at the beginning of the 19th century. radical theory(J. Gay-Lussac, F. Wehler, J. Liebig). Radicals are groups of atoms that pass without change during chemical reactions from one compound to another. This concept of radicals has been preserved, but most other provisions of the theory of radicals turned out to be incorrect.

According to type theories(C. Gerard) all organic substances can be divided into types corresponding to certain inorganic substances. For example, alcohols R-OH and ethers R-O-R were considered to be representatives of the water type H-OH, in which the hydrogen atoms are replaced by radicals. The theory of types created a classification of organic substances, some of the principles of which are used today.

The modern theory of the structure of organic compounds was created by the outstanding Russian scientist A.M. Butlerov.

Basic principles of the theory of the structure of organic compounds A.M. Butlerov

1. Atoms in a molecule are arranged in a certain sequence according to their valence. The valency of the carbon atom in organic compounds is four.

2. The properties of substances depend not only on which atoms and in what quantities are included in the molecule, but also on the order in which they are connected to each other.

3. Atoms or groups of atoms that make up a molecule mutually influence each other, which determines the chemical activity and reactivity of the molecules.

4. Studying the properties of substances allows us to determine their chemical structure.

The mutual influence of neighboring atoms in molecules is the most important property of organic compounds. This influence is transmitted either through a chain of simple bonds or through a chain of conjugated (alternating) simple and double bonds.

Classification of organic compounds is based on the analysis of two aspects of the structure of molecules - the structure of the carbon skeleton and the presence of functional groups.

Organic compounds

Hydrocarbons Heterocyclic compounds

Limit- Unprecedent- Aroma-

efficient practical

Aliphatic Carbocyclic

Ultimate Unsaturated Alicyclic Aromatic

(Alkanes) (Cycloalkanes) (Arenas)

WITH P H 2 P+2 C P H 2 P WITH P H 2 P-6

End of work -

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Alkenes Alkadienes Alkynes
SpN2p SpN2p-2 SpN2p-2 Fig. 1. Classification of organic compounds by structure

Electronic structure of the carbon atom. Hybridization.
For the valence electron layer of the C atom, located in the main subgroup of the fourth group of the second period of D. I. Mendeleev’s Periodic Table, the main quantum number n = 2, secondary (orbital

Conjugate systems
There are two types of conjugate systems (and couplings). 1. p, p-conjugation - electrons are delocalized

TOPIC 3. Chemical structure and isomerism of organic compounds
Isomerism of organic compounds. If two or more individual substances have the same quantitative composition (molecular formula), but differ from each other in

Conformations of organic molecules
Rotation around the C–C s-bond is relatively easy, and the hydrocarbon chain can take different shapes. Conformational forms easily transform into each other and therefore are not different compounds

Conformations of cyclic compounds.
Cyclopentane. The five-membered ring in flat form has bond angles of 108°, which is close to the normal value for an sp3 hybrid atom. Therefore, in flat cyclopentane, in contrast to the cycle

Configuration isomers
These are stereoisomers with different arrangements around certain atoms of other atoms, radicals or functional groups in space relative to each other. There are concepts of diastere

General characteristics of reactions of organic compounds.
Acidity and basicity of organic compounds. To assess the acidity and basicity of organic compounds, two theories are of greatest importance - the Brønsted theory and theo

Bronsted bases are neutral molecules or ions that can accept a proton (proton acceptors).
Acidity and basicity are not absolute, but relative properties of compounds: acidic properties are found only in the presence of a base; basic properties - only in the presence of ki

General characteristics of reactions of organic compounds
Most organic reactions involve several sequential (elementary) steps. A detailed description of the totality of these stages is called a mechanism. Reaction mechanism -

Selectivity of reactions
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Radical reactions.
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Electrophilic addition reactions
Unsaturated hydrocarbons - alkenes, cycloalkenes, alkadienes and alkynes - exhibit the ability to undergo addition reactions, since they contain double or triple bonds. More important in vivo is twofold

And elimination from a saturated carbon atom
Nucleophilic substitution reactions at an sp3-hybridized carbon atom: heterolytic reactions caused by the polarization of the s-bond carbon - heteroatom (halogenopro

Nucleophilic substitution reactions involving the sp2-hybridized carbon atom.
Let us consider the mechanism of reactions of this type using the example of the interaction of carboxylic acids with alcohols (esterification reaction). In the carboxyl group of an acid, p,p-conjugation occurs, since the pair is

Nucleophilic substitution reactions in the series of carboxylic acids.
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Organic compounds.
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Participating in life processes
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Amino alcohols
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Hydroxy and amino acids.
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Steroid hormones
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Sterols
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The chemical structure of a substance is the order of connection of atoms in molecules. Mutual influence of atoms and atomic groups in a molecule. In this case, the tetravalency of carbon atoms and the monovalency of hydrogen atoms are strictly observed. The properties of substances depend not only on the qualitative and quantitative composition, but also on the order of connection of atoms in the molecule, the phenomenon of isomerism.

§1.3. Basic principles of the theory of the chemical structure of organic compounds by A.M. Butlerov. The chemical structure of a substance is the order of connection of atoms in molecules. Dependence of the properties of substances on the chemical structure of molecules. Mutual influence of atoms and atomic groups in a molecule.
By the sixties of the last century, organic chemistry had accumulated a huge amount of factual material that required explanation. Against the background of the continuous accumulation of experimental facts, the insufficiency of theoretical concepts of organic chemistry was especially acute. Theory lagged behind practice and experiment. This lag had a painful impact on the progress of experimental research in laboratories; Chemists conducted their research largely at random, blindly, often without understanding the nature of the substances they synthesized and the essence of the reactions that led to their formation. Organic chemistry, as Wöhler aptly put it, resembled a dense forest full of wonderful things, a huge thicket with no exit, no end. “Organic chemistry is like a dense forest, which is easy to enter but impossible to get out.” So, apparently, it was destined that it was Kazan that gave the world a compass with which it is not scary to enter the “Dense Forest of Organic Chemistry”. And this compass, which is still used today, is Butlerov’s theory of chemical structure. From the 60s of the last century to this day, any textbook in the world on organic chemistry begins with the postulates of the theory of the Great Russian chemist Alexander Mikhailovich Butlerov.
Basic principles of the theory of chemical structure A.M. Butlerov
1st position
Atoms in molecules are connected to each other in a certain sequence according to their valences. The sequence of interatomic bonds in a molecule is called its chemical structure and is reflected by one structural formula (structure formula).

This provision applies to the structure of the molecules of all substances. In the molecules of saturated hydrocarbons, carbon atoms combine with each other to form chains. In this case, the tetravalency of carbon atoms and the monovalency of hydrogen atoms are strictly observed.

2nd position. The properties of substances depend not only on the qualitative and quantitative composition, but also on the order of connection of atoms in the molecule(isomerism phenomenon).
Studying the structure of hydrocarbon molecules, A. M. Butlerov came to the conclusion that these substances, starting with butane (C 4 N 10 ), a different order of connection of atoms is possible with the same composition of molecules. Thus, in butane, a double arrangement of carbon atoms is possible: in the form of a straight (unbranched) and a branched chain.

These substances have the same molecular formula, but different structural formulas and different properties (boiling point). Therefore, these are different substances. Such substances are called isomers.

And the phenomenon in which several substances can exist that have the same composition and the same molecular weight, but differ in molecular structure and properties, is called the phenomenon isomerism. Moreover, with an increase in the number of carbon atoms in hydrocarbon molecules, the number of isomers increases. For example, there are 75 isomers (different substances) corresponding to the formula C 10 N 22 , and 1858 isomers with formula C 14 N 30 .

For composition C 5 H 12 The following isomers can exist (there are three of them) -

3rd position. Based on the properties of a given substance, one can determine the structure of its molecule, and based on its structure, one can predict its properties.Proof of this proposition. This proposition can be proven using the example of inorganic chemistry.
Example. If this substance changes the color of violet litmus to pink, interacts with metals standing before hydrogen, with basic oxides, bases, then we can assume that this substance belongs to the class of acids, i.e. contains hydrogen atoms and an acid residue. And, conversely, if this substance belongs to the class of acids, then it exhibits the above properties. For example: N 2 S O 4 - sulfuric acid

4th position. Atoms and groups of atoms in the molecules of substances mutually influence each other.
Proof of this point

This position can be proven using the example of inorganic chemistry. To do this, we need to compare the properties of aqueous solutions NH 3, HC1, N 2 O (indicator action). In all three cases, the substances contain hydrogen atoms, but they are connected to different atoms, which have different effects on the hydrogen atoms, so the properties of the substances are different.
Butlerov's theory was the scientific foundation of organic chemistry and contributed to its rapid development. Based on the provisions of the theory, A.M. Butlerov explained the phenomenon of isomerism, predicted the existence of various isomers and obtained some of them for the first time.
In the fall of 1850, Butlerov passed the exams for a master's degree in chemistry and immediately began his doctoral dissertation “On Essential Oils,” which he defended early next year.

On February 17, 1858, Butlerov made a report at the Paris Chemical Society, where he first outlined his theoretical ideas about the structure of matter. His report aroused general interest and lively debate: “The ability of atoms to connect with each other is different. Particularly interesting in this regard is carbon, which, according to August Kekule, is tetravalent,” Butlerov said in his report. connections."

No one has expressed such thoughts until now. Perhaps the time has come, Butlerov continued, when our research should become the basis of a new theory of the chemical structure of substances. This theory will be distinguished by the accuracy of mathematical laws and will allow one to predict the properties of organic compounds.”

A few years later, during his second trip abroad, Butlerov presented the theory he had created for discussion. He made a report at the 36th Congress of German naturalists and doctors in Speyer. The congress took place in September 1861. He made a presentation to the chemical section. The topic had a more than modest title - “Something about the chemical structure of bodies.” In the report, Butlerov expressed the main provisions of his theory of the structure of organic compounds.
Works of A.M. Butlerov

Office of A.M. Butlerov

The theory of chemical structure made it possible to explain many facts that had accumulated in organic chemistry at the beginning of the second half of the 19th century, and proved that with the help of chemical methods (synthesis, decomposition and other reactions) it was possible to establish the order of connection of atoms in molecules (this thereby proved the possibility of knowing the structure substances);

She introduced something new into atomic-molecular science (the order of atoms in molecules, the mutual influence of atoms, the dependence of properties on the structure of the molecules of a substance). The theory considered the molecules of matter as an ordered system endowed with the dynamics of interacting atoms. In this regard, atomic-molecular science received its further development, which was of great importance for the science of chemistry;

Made it possible to foresee the properties of organic compounds based on structure, synthesize new substances, adhering to the plan;

Allowed us to explain the diversity of organic compounds;

It gave a powerful impetus to the synthesis of organic compounds and the development of the organic synthesis industry (synthesis of alcohols, ethers, dyes, medicinal substances, etc.).

Having developed the theory and confirmed its correctness by the synthesis of new compounds A.M. Butlerov did not consider the theory absolute and unchangeable. He argued that it must develop, and foresaw that this development would proceed by resolving contradictions between theoretical knowledge and emerging new facts.

The theory of chemical structure, as predicted by A.M. Butlerov, did not remain unchanged. Its further development proceeded mainly in two interrelated directions.

The first of them was predicted by A.M. Butlerov himself

He believed that science in the future would be able to establish not only the order of connection of atoms in a molecule, but also their spatial arrangement. The study of the spatial structure of molecules, called stereochemistry (Greek “stereos” - spatial), entered science in the 80s of the last century. It made it possible to explain and predict new facts that did not fit into the framework of previous theoretical concepts.
The second direction is associated with the application in organic chemistry of the doctrine of the electronic structure of atoms, developed in physics of the twentieth century. This doctrine made it possible to understand the nature of the chemical bond of atoms, to clarify the essence of their mutual influence, and to explain the reason for the manifestation of certain chemical properties by a substance.

Structural formulas, detailed and brief

Reasons for the diversity of organic compounds

Carbon atoms form single (simple), double and triple bonds:

There are homological series:

Isomers:

PAGE \* MERGEFORMAT 1

The first appeared at the beginning of the 19th century. radical theory(J. Gay-Lussac, F. Wehler, J. Liebig). Radicals are groups of atoms that pass without change during chemical reactions from one compound to another. This concept of radicals has been preserved, but most other provisions of the theory of radicals turned out to be incorrect.

According to type theories(C. Gerard) all organic substances can be divided into types corresponding to certain inorganic substances. For example, alcohols R-OH and ethers R-O-R were considered to be representatives of the water type H-OH, in which the hydrogen atoms are replaced by radicals. The theory of types created a classification of organic substances, some of the principles of which are used today.

The modern theory of the structure of organic compounds was created by the outstanding Russian scientist A.M. Butlerov.

Basic principles of the theory of the structure of organic compounds by A.M. Butlerov

1. Atoms in a molecule are arranged in a certain sequence according to their valence. The valency of the carbon atom in organic compounds is four.

2. The properties of substances depend not only on which atoms and in what quantities are included in the molecule, but also on the order in which they are connected to each other.

3. Atoms or groups of atoms that make up a molecule mutually influence each other, which determines the chemical activity and reactivity of the molecules.

4. Studying the properties of substances allows us to determine their chemical structure.

The mutual influence of neighboring atoms in molecules is the most important property of organic compounds. This influence is transmitted either through a chain of simple bonds or through a chain of conjugated (alternating) simple and double bonds.

Classification of organic compounds is based on the analysis of two aspects of the structure of molecules - the structure of the carbon skeleton and the presence of functional groups.

Organic compounds

Hydrocarbons Heterocyclic compounds

Limit- Unprecedent- Aroma-

efficient practical

Aliphatic Carbocyclic

Ultimate Unsaturated Ultimate Unsaturated Aromatic

(Alkanes) (Cycloalkanes) (Arenas)

WITH P H 2 P+2 C P H 2 P WITH P H 2 P -6

alkenes, polyenes and alkynes

WITH P H 2 P polyines C P H 2 P -2

Rice. 1. Classification of organic compounds according to the structure of the carbon skeleton

Classes of hydrocarbon derivatives based on the presence of functional groups:

Halogen derivatives R–Gal: CH 3 CH 2 Cl (chloroethane), C 6 H 5 Br (bromobenzene);

Alcohols and phenols R–OH: CH 3 CH 2 OH (ethanol), C 6 H 5 OH (phenol);

Thiols R–SH: CH 3 CH 2 SH (ethanethiol), C 6 H 5 SH (thiophenol);

Ethers R–O–R: CH 3 CH 2 –O–CH 2 CH 3 (diethyl ether),

complex R–CO–O–R: CH 3 CH 2 COOCH 2 CH 3 (ethyl acetic acid);

Carbonyl compounds: aldehydes R–CHO:

ketones R–СО–R: CH 3 COCH 3 (propanone), C 6 H 5 COCH 3 (methyl phenylketone);

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

Sulfonic acids R–SO 3 H: CH 3 SO 3 H (methanesulfonic acid), C 6 H 5 SO 3 H (benzenesulfonic acid)

Amines R–NH 2: CH 3 CH 2 NH 2 (ethylamine), CH 3 NHCH 3 (dimethylamine), C 6 H 5 NH 2 (aniline);

Nitro compounds R–NO 2 CH 3 CH 2 NO 2 (nitroethane), C 6 H 5 NO 2 (nitrobenzene);

Organometallic (organoelement) compounds: CH 3 CH 2 Na (ethyl sodium).

A series of compounds similar in structure, possessing similar chemical properties, in which individual members of the series differ from each other only in the number of -CH 2 - groups, is called homologous series, and the -CH 2 group is a homological difference . For members of a homologous series, the vast majority of reactions proceed in the same way (with the exception of only the first members of the series). Consequently, knowing the chemical reactions of only one member of the series, it can be stated with a high degree of probability that the same type of transformation occurs with the remaining members of the homologous series.

For any homologous series, a general formula can be derived that reflects the relationship between the carbon and hydrogen atoms of the members of this series; like this the formula is called general formula of the homologous series. Yes, S P H 2 P+2 – formula of alkanes, C P H 2 P+1 OH – aliphatic monohydric alcohols.

Nomenclature of organic compounds: trivial, rational and systematic nomenclature. Trivial nomenclature is a collection of historically established names. So, from the name it is immediately clear where malic, succinic or citric acid was isolated, how pyruvic acid was obtained (pyrolysis of grape acid), connoisseurs of the Greek language will easily guess that acetic acid is something sour, and glycerin is sweet. As new organic compounds were synthesized and the theory of their structure developed, other nomenclatures were created that reflected the structure of the compound (its belonging to a certain class).

Rational nomenclature constructs the name of a compound based on the structure of a simpler compound (the first member of a homologous series). CH 3 HE– carbinol, CH 3 CH 2 HE– methylcarbinol, CH 3 CH(OH) CH 3 – dimethylcarbinol, etc.

IUPAC nomenclature (systematic nomenclature). According to IUPAC (International Union of Pure and Applied Chemistry) nomenclature, the names of hydrocarbons and their functional derivatives are based on the name of the corresponding hydrocarbon with the addition of prefixes and suffixes inherent in this homologous series.

To correctly (and unambiguously) name an organic compound using systematic nomenclature, you must:

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

2) identify All functional groups present in the compound;

3) establish which group is senior (see table), the name of this group is reflected in the name of the compound in the form of a suffix and it is placed at the end of the name of the compound; all other groups are given in the name in the form of prefixes;

4) number the carbon atoms of the main chain, giving the highest group the lowest number;

5) list the prefixes in alphabetical order (in this case, multiplying prefixes di-, tri-, tetra-, etc. are not taken into account);

6) write down the full name of the compound.

It is necessary to remember:

In the names of alcohols, aldehydes, ketones, carboxylic acids, amides, nitriles, acid halides, the suffix defining the class follows the suffix of the degree of unsaturation: for example, 2-butenal;

Compounds containing other functional groups are called hydrocarbon derivatives. The names of these functional groups are placed as prefixes before the name of the parent hydrocarbon: for example, 1-chloropropane.

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

Derivatives of aldehydes and ketones are often named after the parent carbonyl compound.

Esters of carboxylic acids are called derivatives of parent acids. The ending –oic acid is replaced by –oate: for example, methyl propionate is the methyl ester of propanoic acid.

To indicate that the substituent is bonded to the nitrogen atom of the parent structure, use a capital letter N before the name of the substituent: N-methylaniline.

Those. you need to start with the name of the parent structure, for which it is absolutely necessary to know by heart the names of the first 10 members of the homologous series of alkanes (methane, ethane, propane, butane, pentane, hexane, heptane, octane, nonane, decane). You also need to know the names of the radicals formed from them - in this case, the ending -an changes to -il.

Consider a compound that is part of drugs used to treat eye diseases:

CH 3 – C(CH 3) = CH – CH 2 – CH 2 – C(CH 3) = CH – CHO

The basic parent structure is a chain of 8 carbon atoms, including an aldehyde group and both double bonds. Eight carbon atoms are octane. But there are 2 double bonds - between the second and third atoms and between the sixth and seventh. One double bond - the ending -an must be replaced with -ene, there are 2 double bonds, which means -diene, i.e. octadiene, and at the beginning we indicate their position, naming the atoms with lower numbers - 2,6-octadiene. We have dealt with the original structure and indefiniteness.

But the compound contains an aldehyde group, it is not a hydrocarbon, but an aldehyde, so we add the suffix -al, without a number, it is always the first - 2,6-octadienal.

Another 2 substituents are methyl radicals at the 3rd and 7th atoms. So, in the end we get: 3,7-dimethyl - 2,6-octadienal.

The largest event in the development of organic chemistry was the creation in 1961 by the great Russian scientist A.M. Butlerov's theory of the chemical structure of organic compounds.

Before A.M. Butlerov considered it impossible to know the structure of a molecule, that is, the order of chemical bonds between atoms. Many scientists even denied the reality of atoms and molecules.

A.M. Butlerov denied this opinion. He proceeded from the correct materialistic and philosophical ideas about the reality of the existence of atoms and molecules, about the possibility of knowing the chemical bond of atoms in a molecule. He showed that the structure of a molecule can be established experimentally by studying the chemical transformations of a substance. Conversely, knowing the structure of the molecule, one can deduce the chemical properties of the compound.

The theory of chemical structure explains the diversity of organic compounds. It is due to the ability of tetravalent carbon to form carbon chains and rings, combine with atoms of other elements and the presence of isomerism in the chemical structure of organic compounds. This theory laid the scientific foundations of organic chemistry and explained its most important laws. The basic principles of his theory A.M. Butlerov outlined it in his report “On the theory of chemical structure.”

The main principles of the theory of structure are as follows:

1) in molecules, atoms are connected to each other in a certain sequence in accordance with their valency. The order in which the atoms bond is called chemical structure;

2) the properties of a substance depend not only on which atoms and in what quantity are included in its molecule, but also on the order in which they are connected to each other, i.e., on the chemical structure of the molecule;

3) atoms or groups of atoms that form a molecule mutually influence each other.

In the theory of chemical structure, much attention is paid to the mutual influence of atoms and groups of atoms in a molecule.

Chemical formulas that depict the order of connection of atoms in molecules are called structural formulas or structure formulas.

The importance of the theory of chemical structure of A.M. Butlerova:

1) is the most important part of the theoretical foundation of organic chemistry;

2) in importance it can be compared with the Periodic Table of Elements by D.I. Mendeleev;

3) it made it possible to systematize a huge amount of practical material;

4) made it possible to predict in advance the existence of new substances, as well as indicate ways to obtain them.

The theory of chemical structure serves as the guiding basis for all research in organic chemistry.

5. Isomerism. Electronic structure of atoms of elements of short periods. Chemical bond

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

Isomers are substances that have the same composition and the same molar mass, but different molecular structures, and therefore have different properties.

Scientific significance of the theory of chemical structure:

1) deepens understanding of matter;

2) indicates the path to knowledge of the internal structure of molecules;

3) makes it possible to understand the facts accumulated in chemistry; predict the existence of new substances and find ways to synthesize them.

With all this, the theory greatly contributed to the further development of organic chemistry and the chemical industry.

The German scientist A. Kekule expressed the idea of ​​connecting carbon atoms with each other in a chain.

The doctrine of the electronic structure of atoms.

Features of the doctrine of the electronic structure of atoms: 1) made it possible to understand the nature of the chemical bond of atoms; 2) find out the essence of the mutual influence of atoms.

State of electrons in atoms and structure of electron shells.

Electron clouds are areas with the highest probability of electron presence, which differ in their shape, size, and direction in space.

In an atom hydrogen A single electron, when moving, forms a negatively charged cloud of spherical (spherical) shape.

S electrons are electrons that form a spherical cloud.

A hydrogen atom has one s electron.

In an atom helium– two s-electrons.

Features of the helium atom: 1) clouds of the same spherical shape; 2) the highest density is equally distant from the core; 3) electron clouds are combined; 4) form a common two-electron cloud.

Features of the lithium atom: 1) has two electronic layers; 2) has a spherical cloud, but is significantly larger in size than the internal two-electron cloud; 3) the electron of the second layer is weaker attracted to the nucleus than the first two; 4) easily captured by other atoms in redox reactions; 5) has an s-electron.

Features of the beryllium atom: 1) the fourth electron is the s-electron; 2) the spherical cloud is combined with the cloud of the third electron; 3) there are two paired s-electrons in the inner layer and two paired s-electrons in the outer layer.

The more electron clouds overlap when atoms join together, the more energy is released and the stronger the chemical bond.