Organic substances. Classes of organic substances

It is known that the properties of organic substances are determined by their composition and chemical structure. Therefore, it is not surprising that the classification of organic compounds is based on the theory of structure - the theory of L. M. Butlerov. Organic substances are classified according to the presence and order of connection of atoms in their molecules. The most durable and least changeable part of an organic substance molecule is its skeleton - a chain of carbon atoms. Depending on the order of connection of carbon atoms in this chain, substances are divided into acyclic, which do not contain closed chains of carbon atoms in molecules, and carbocyclic, which contain such chains (cycles) in molecules.
In addition to carbon and hydrogen atoms, molecules of organic substances can contain atoms of other chemical elements. Substances in whose molecules these so-called heteroatoms are included in a closed chain are classified as heterocyclic compounds.
Heteroatoms (oxygen, nitrogen, etc.) can be part of molecules and acyclic compounds, forming functional groups in them, for example, hydroxyl - OH, carbonyl, carboxyl, amino group -NH2.
Functional group- a group of atoms that determines the most characteristic chemical properties of a substance and its belonging to a certain class of compounds.

Hydrocarbons- These are compounds consisting only of hydrogen and carbon atoms.

Depending on the structure of the carbon chain, organic compounds are divided into open-chain compounds - acyclic (aliphatic) and cyclic- with a closed chain of atoms.

Cyclic ones are divided into two groups: carbocyclic compounds(cycles are formed only by carbon atoms) and heterocyclic(the cycles also include other atoms, such as oxygen, nitrogen, sulfur).

Carbocyclic compounds, in turn, include two series of compounds: alicyclic and aromatic.

Aromatic compounds, based on the structure of their molecules, have flat carbon-containing rings with a special closed system of p-electrons, forming a common π-system (a single π-electron cloud). Aromaticity is also characteristic of many heterocyclic compounds.

All other carbocyclic compounds belong to the alicyclic series.

Both acyclic (aliphatic) and cyclic hydrocarbons can contain multiple (double or triple) bonds. Such hydrocarbons are called unsaturated (unsaturated) in contrast to saturated (saturated), containing only single bonds.

Saturated aliphatic hydrocarbons called alkanes, they have the general formula C n H 2 n +2, where n is the number of carbon atoms. Their old name is often used today - paraffins.

Containing one double bond, got the name alkenes. They have the general formula C n H 2 n.

Unsaturated aliphatic hydrocarbonswith two double bonds called alkadienes

Unsaturated aliphatic hydrocarbonswith one triple bond called alkynes. Their general formula is C n H 2 n - 2.

Saturated alicyclic hydrocarbons - cycloalkanes, their general formula is C n H 2 n.

A special group of hydrocarbons, aromatic, or arenas(with a closed common π-electron system), known from the example of hydrocarbons with the general formula C n H 2 n -6.

Thus, if in their molecules one or more hydrogen atoms are replaced by other atoms or groups of atoms (halogens, hydroxyl groups, amino groups, etc.), hydrocarbon derivatives: halogen derivatives, oxygen-containing, nitrogen-containing and other organic compounds.

Halogen derivatives hydrocarbons can be considered as products of the replacement of one or more hydrogen atoms in hydrocarbons by halogen atoms. In accordance with this, saturated and unsaturated mono-, di-, tri- (in the general case poly-) halogen derivatives can exist.

General formula of monohalogen derivatives of saturated hydrocarbons:

and the composition is expressed by the formula

C n H 2 n +1 G,

where R is the remainder of a saturated hydrocarbon (alkane), a hydrocarbon radical (this designation is used further when considering other classes of organic substances), G is a halogen atom (F, Cl, Br, I).

Alcohols- derivatives of hydrocarbons in which one or more hydrogen atoms are replaced by hydroxyl groups.

Alcohols are called monatomic, if they have one hydroxyl group, and limiting if they are derivatives of alkanes.

General formula of saturated monohydric alcohols:

and their composition is expressed by the general formula:
C n H 2 n +1 OH or C n H 2 n +2 O

There are known examples of polyhydric alcohols, that is, those with several hydroxyl groups.

Phenols- derivatives of aromatic hydrocarbons (benzene series), in which one or more hydrogen atoms in the benzene ring are replaced by hydroxyl groups.

The simplest representative with the formula C 6 H 5 OH is called phenol.

Aldehydes and ketones- derivatives of hydrocarbons containing a carbonyl group of atoms (carbonyl).

In aldehyde molecules, one carbonyl bond connects with a hydrogen atom, the other with a hydrocarbon radical.

In the case of ketones, the carbonyl group is bonded to two (generally different) radicals.

The composition of saturated aldehydes and ketones is expressed by the formula C n H 2l O.

Carboxylic acids- hydrocarbon derivatives containing carboxyl groups (-COOH).

If there is one carboxyl group in an acid molecule, then the carboxylic acid is monobasic. General formula of saturated monobasic acids (R-COOH). Their composition is expressed by the formula C n H 2 n O 2.

Ethers are organic substances containing two hydrocarbon radicals connected by an oxygen atom: R-O-R or R 1 -O-R 2.

Radicals can be the same or different. The composition of ethers is expressed by the formula C n H 2 n +2 O

Esters- compounds formed by replacing the hydrogen atom of the carboxyl group in carboxylic acids with a hydrocarbon radical.

Nitro compounds- derivatives of hydrocarbons in which one or more hydrogen atoms are replaced by a nitro group -NO 2.

General formula of saturated mononitro compounds:

and the composition is expressed by the general formula

C n H 2 n +1 NO 2 .

Amines- compounds that are considered as derivatives of ammonia (NH 3), in which hydrogen atoms are replaced by hydrocarbon radicals.

Depending on the nature of the radical, amines can be aliphaticand aromatic.

Depending on the number of hydrogen atoms replaced by radicals, the following are distinguished:

Primary amines with the general formula: R-NNH 2

Secondary - with the general formula: R 1 -NН-R 2

Tertiary - with the general formula:

In a particular case, secondary and tertiary amines may have the same radicals.

Primary amines can also be considered as derivatives of hydrocarbons (alkanes), in which one hydrogen atom is replaced by an amino group -NH 2. The composition of saturated primary amines is expressed by the formula C n H 2 n +3 N.

Amino acids contain two functional groups connected to a hydrocarbon radical: an amino group -NH 2, and a carboxyl -COOH.

The composition of saturated amino acids containing one amino group and one carboxyl is expressed by the formula C n H 2 n +1 NO 2.

Other important organic compounds are known that have several different or identical functional groups, long linear chains connected to benzene rings. In such cases, a strict determination of whether a substance belongs to a specific class is impossible. These compounds are often classified into specific groups of substances: carbohydrates, proteins, nucleic acids, antibiotics, alkaloids, etc.

To name organic compounds, two nomenclatures are used: rational and systematic (IUPAC) and trivial names.

Compilation of names according to IUPAC nomenclature

1) The name of the compound is based on the root of the word, denoting a saturated hydrocarbon with the same number of atoms as the main chain.

2) A suffix is ​​added to the root, characterizing the degree of saturation:

An (ultimate, no multiple connections);
-ene (in the presence of a double bond);
-in (in the presence of a triple bond).

If there are several multiple bonds, then the suffix indicates the number of such bonds (-diene, -triene, etc.), and after the suffix the position of the multiple bond must be indicated in numbers, for example:
CH 3 –CH 2 –CH=CH 2 CH 3 –CH=CH–CH 3
butene-1 butene-2

CH 2 =CH–CH=CH2
butadiene-1,3

Groups such as nitro-, halogens, hydrocarbon radicals that are not included in the main chain are placed in the prefix. They are listed in alphabetical order. The position of the substituent is indicated by the number before the prefix.

The order of naming is as follows:

1. Find the longest chain of C atoms.

2. Number the carbon atoms of the main chain sequentially, starting from the end closest to the branch.

3. The name of the alkane is composed of the names of the side radicals, listed in alphabetical order, indicating the position in the main chain, and the name of the main chain.

Nomenclature of some organic substances (trivial and international)

Rice. 5. Friedrich Wöhler
(1800–1882)

Rice. 6. Alexander
Mikhailovich Butlerov
(1828–1886)

The essence of the theory of chemical structure they created can be formulated in the form of three propositions.
1. Atoms in molecules are connected in a certain order according to their valence, and carbon in organic compounds is tetravalent.
2. The properties of substances are determined not only by the qualitative and quantitative elemental composition, but also by the order of connections of atoms in molecules, i.e. chemical structure.
3. Atoms in molecules have a mutual influence on each other, which affects the properties of substances.
* German chemist. Conducted research in the field of inorganic and organic chemistry. He established the existence of the phenomenon of isomerism and for the first time carried out the synthesis of an organic substance (urea) from an inorganic one. Received some metals (aluminum, beryllium, etc.).
** Outstanding Russian chemist, author of the theory of chemical
structure of organic substances. Based onconcepts of structure explained the phenomenon of isomerism, predicted the existence of isomers of a number of substances and synthesized them for the first time. He was the first to synthesize a sugary substance. Founder of the school of Russian chemistryIkov, which included V.V. Markovnikov, A.M. Zaitsev, E.E. Vagner, A.E. Favorsky and others.

Today it seems incredible that until the middle of the 19th century, during the period of great discoveries in natural science, scientists had little understanding of the internal structure of matter. It was Butlerov who introduced the term “chemical structure,” meaning by it a system of chemical bonds between atoms in a molecule and their relative arrangement in space. Thanks to this understanding of the structure of the molecule, it became possible to explain the phenomenon of isomerism, predict the existence of unknown isomers, and correlate the properties of substances with their chemical structure. To illustrate the phenomenon of isomerism, we present the formulas and properties of two substances - ethyl alcohol and dimethyl ether, which have the same elemental composition C2H6O, but different chemical structures (Table 2).
table 2

Illustration of the dependence of the properties of a substancefrom its structure

The phenomenon of isomerism, very widespread in organic chemistry, is one of the reasons for the diversity of organic substances. Another reason for the diversity of organic substances is the unique ability of the carbon atom to form chemical bonds with each other, resulting in carbon chains
of various lengths and structures: unbranched, branched, closed. For example, four carbon atoms can form chains like this:

If we take into account that between two carbon atoms there can exist not only simple (single) C–C bonds, but also double C=C and triple C≡C, then the number of variants of carbon chains and, consequently, various organic substances increases significantly.
The classification of organic substances is also based on Butlerov’s theory of chemical structure. Depending on the atoms of which chemical elements are included in the molecule, all organic groups: hydrocarbons, oxygen-containing, nitrogen-containing compounds.
Hydrocarbons are organic compounds consisting only of carbon and hydrogen atoms.
Based on the structure of the carbon chain and the presence or absence of multiple bonds in it, all hydrocarbons are divided into several classes. These classes are presented in Diagram 2.
If a hydrocarbon does not contain multiple bonds and the chain of carbon atoms is not closed, it belongs, as you know, to the class of saturated hydrocarbons, or alkanes. The root of this word is of Arabic origin, and the suffix -an is present in the names of all hydrocarbons of this class.
Scheme 2

Classification of hydrocarbons

The presence of one double bond in a hydrocarbon molecule allows it to be classified as an alkene, and its relationship to this group of substances is emphasized
suffix -en in the name. The simplest alkene is ethylene, which has the formula CH2=CH2. There can be two C=C double bonds in a molecule; in this case, the substance belongs to the class of alkadienes.
Try to explain the meaning of the suffixes -diene. For example, 1,3 butadiene has the structural formula: CH2=CH–CH=CH2.
Hydrocarbons with a carbon-carbon triple bond in the molecule are called alkynes. The suffix -in indicates that a substance belongs to this class. The ancestor of the class of alkynes is acetylene (ethyne), the molecular formula of which is C2H2, and the structural formula is HC≡CH. From compounds with a closed carbon chain
The most important atoms are arenes - a special class of hydrocarbons, the name of the first representative of which you have probably heard is benzene C6H6, the structural formula of which is also known to every cultural person:

As you already understood, in addition to carbon and hydrogen, organic substances can contain atoms of other elements, primarily oxygen and nitrogen. Most often, the atoms of these elements in various combinations form groups, which are called functional.
A functional group is a group of atoms that determines the most characteristic chemical properties of a substance and its belonging to a certain class of compounds.
The main classes of organic compounds containing functional groups are presented in Scheme 3.
Scheme 3
Main classes of organic substances containing functional groups

The functional group –OH is called hydroxyl and determines membership in one of the most important classes of organic substances – alcohols.
The names of alcohols are formed using the suffix -ol. For example, the most famous representative of alcohols is ethyl alcohol, or ethanol, C2H5OH.
An oxygen atom can be linked to a carbon atom by a chemical double bond. The >C=O group is called carbonyl. The carbonyl group is part of several
functional groups, including aldehyde and carboxyl. Organic substances containing these functional groups are called aldehydes and carboxylic acids, respectively. The most well-known representatives of aldehydes are formaldehyde HCOH and acetaldehyde CH3SON. Everyone is probably familiar with acetic acid CH3COOH, the solution of which is called table vinegar. A distinctive structural feature of nitrogen-containing organic compounds, and, first of all, amines and amino acids, is the presence of the amino group –NH2 in their molecules.
The above classification of organic substances is also very relative. Just as one molecule (for example, alkadienes) can contain two multiple bonds, a substance can have two or even more functional groups. Thus, the structural units of the main carriers of life on earth - protein molecules - are amino acids. The molecules of these substances necessarily contain at least two functional groups - a carboxyl and amino group. The simplest amino acid is called glycine and has the formula:

Like amphoteric hydroxides, amino acids combine the properties of acids (due to the carboxyl group) and bases (due to the presence of an amino group in the molecule).
For the organization of life on Earth, the amphoteric properties of amino acids are of particular importance - due to the interaction of amino groups and carboxyl groups of amino acids.
lots are connected into polymer chains of proteins.
? 1. What are the main provisions of the theory of chemical structure of A.M. Butlerov. What role did this theory play in the development of organic chemistry?
2. What classes of hydrocarbons do you know? On what basis is this classification made?
3. What is the functional group of an organic compound? What functional groups can you name? What classes of organic compounds contain the named functional groups? Write down the general formulas of classes of compounds and the formulas of their representatives.
4. Define isomerism, write down the formulas of possible isomers for compounds of the composition C4H10O. Using various sources of information, name each of them and prepare a report about one of the compounds.
5. Classify substances whose formulas are: C6H6, C2H6, C2H4, HCOOH, CH3OH, C6H12O6, to the corresponding classes of organic compounds. Using various sources of information, name each of them and prepare a report about one of the compounds.
6. Structural formula of glucose: Which class of organic compounds would you classify this substance as? Why is it called a dual function compound?
7. Compare organic and inorganic amphoteric compounds.
8. Why are amino acids classified as compounds with dual functions? What role does this structural feature of amino acids play in the organization of life on Earth?
9. Prepare a message on the topic “Amino acids - the “building blocks” of life” using the Internet.
10. Give examples of the relativity of dividing organic compounds into certain classes. Draw parallels to similar relativity for inorganic compounds.

There are several definitions of what organic substances are and how they differ from another group of compounds - inorganic. One of the most common explanations comes from the name "hydrocarbons". Indeed, at the heart of all organic molecules are chains of carbon atoms bonded to hydrogen. There are also other elements called “organogenic”.

Organic chemistry before the discovery of urea

Since ancient times, people have used many natural substances and minerals: sulfur, gold, iron and copper ore, table salt. For the entire existence of science - from ancient times to the first half of the 19th century - scientists could not prove the connection between living and inanimate nature at the level of microscopic structure (atoms, molecules). It was believed that organic substances owe their appearance to a mythical life force - vitalism. There was a myth about the possibility of raising a human “homunculus”. To do this, it was necessary to put various waste products into a barrel and wait a certain time for the vital force to arise.

A crushing blow to vitalism was dealt by the work of Weller, who synthesized the organic substance urea from inorganic components. Thus, it was proven that there is no vital force, nature is one, organisms and inorganic compounds are formed by atoms of the same elements. The composition of urea was known before Weller’s work; studying this compound was not difficult in those years. The very fact of obtaining a substance characteristic of metabolism outside the body of an animal or human was remarkable.

Theory of A. M. Butlerov

The role of the Russian school of chemists in the development of science studying organic substances is great. Entire eras in the development of organic synthesis are associated with the names of Butlerov, Markovnikov, Zelinsky, and Lebedev. The founder of the theory of the structure of compounds is A. M. Butlerov. The famous chemist in the 60s of the 19th century explained the composition of organic substances, the reasons for the diversity of their structure, and revealed the relationship that exists between the composition, structure and properties of substances.

Based on Butlerov’s conclusions, it was possible not only to systematize knowledge about already existing organic compounds. It has become possible to predict the properties of substances not yet known to science and to create technological schemes for their production in industrial conditions. Many ideas of leading organic chemists are being fully realized today.

The oxidation of hydrocarbons produces new organic substances - representatives of other classes (aldehydes, ketones, alcohols, carboxylic acids). For example, large volumes of acetylene are used to produce acetic acid. Part of this reaction product is subsequently consumed to produce synthetic fibers. An acid solution (9% and 6%) is found in every home - this is ordinary vinegar. The oxidation of organic substances serves as the basis for the production of a very large number of compounds of industrial, agricultural, and medical importance.

Aromatic hydrocarbons

Aromaticity in molecules of organic substances is the presence of one or more benzene nuclei. A chain of 6 carbon atoms closes into a ring, a conjugated bond appears in it, therefore the properties of such hydrocarbons are not similar to other hydrocarbons.

Aromatic hydrocarbons (or arenes) are of great practical importance. Many of them are widely used: benzene, toluene, xylene. They are used as solvents and raw materials for the production of drugs, dyes, rubber, rubber and other products of organic synthesis.

Oxygen-containing compounds

A large group of organic substances contains oxygen atoms. They are part of the most active part of the molecule, its functional group. Alcohols contain one or more hydroxyl species -OH. Examples of alcohols: methanol, ethanol, glycerin. Carboxylic acids contain another functional particle - carboxyl (-COOOH).

Other oxygen-containing organic compounds are aldehydes and ketones. Carboxylic acids, alcohols and aldehydes are present in large quantities in various plant organs. They can be sources for obtaining natural products (acetic acid, ethyl alcohol, menthol).

Fats are compounds of carboxylic acids and the trihydric alcohol glycerol. In addition to alcohols and linear acids, there are organic compounds with a benzene ring and a functional group. Examples of aromatic alcohols: phenol, toluene.

Carbohydrates

The most important organic substances of the body that make up cells are proteins, enzymes, nucleic acids, carbohydrates and fats (lipids). Simple carbohydrates - monosaccharides - are found in cells in the form of ribose, deoxyribose, fructose and glucose. The last carbohydrate on this short list is the main metabolic substance in cells. Ribose and deoxyribose are components of ribonucleic and deoxyribonucleic acids (RNA and DNA).

When glucose molecules are broken down, energy is released that is necessary for life. First, it is stored during the formation of a kind of energy carrier - adenosine triphosphoric acid (ATP). This substance is transported in the blood and delivered to tissues and cells. With the sequential elimination of three phosphoric acid residues from adenosine, energy is released.

Fats

Lipids are substances of living organisms that have specific properties. They do not dissolve in water and are hydrophobic particles. The seeds and fruits of some plants, nervous tissue, liver, kidneys, and the blood of animals and humans are especially rich in substances of this class.

The skin of humans and animals contains many small sebaceous glands. The secretion they secrete is brought to the surface of the body, lubricates it, protects it from moisture loss and the penetration of microbes. The layer of subcutaneous fat protects internal organs from damage and serves as a reserve substance.

Squirrels

Proteins make up more than half of all organic substances in the cell; in some tissues their content reaches 80%. All types of proteins are characterized by high molecular weights and the presence of primary, secondary, tertiary and quaternary structures. When heated, they are destroyed - denaturation occurs. The primary structure is a huge chain of amino acids for the microcosm. Under the action of special enzymes in the digestive system of animals and humans, the protein macromolecule will break down into its component parts. They enter cells where the synthesis of organic substances occurs - other proteins specific to each living creature.

Enzymes and their role

Reactions in the cell proceed at a speed that is difficult to achieve under industrial conditions, thanks to catalysts - enzymes. There are enzymes that act only on proteins - lipases. Starch hydrolysis occurs with the participation of amylase. Lipases are needed to break down fats into their constituent parts. Processes involving enzymes occur in all living organisms. If a person does not have any enzyme in his cells, this affects his metabolism and overall health.

Nucleic acids

Substances, first discovered and isolated from cell nuclei, perform the function of transmitting hereditary characteristics. The main amount of DNA is contained in chromosomes, and RNA molecules are located in the cytoplasm. When DNA is reduplicated (doubling), it becomes possible to transfer hereditary information to germ cells - gametes. When they merge, the new organism receives genetic material from its parents.

Organic matter - These are compounds that contain a carbon atom. Even in the early stages of the development of chemistry, all substances were divided into two groups: mineral and organic. In those days, it was believed that in order to synthesize organic matter, it was necessary to have an unprecedented “vital force”, which is inherent only in living biological systems. Therefore, it is impossible to synthesize organic substances from mineral ones. And only at the beginning of the 19th century F. Weller refuted the existing opinion and synthesized urea from ammonium cyanate, that is, he obtained an organic substance from a mineral one. After which a number of scientists synthesized chloroform, aniline, acetate acid and many other chemical compounds.

Organic substances underlie the existence of living matter and are also the main food products for humans and animals. Most organic compounds are raw materials for various industries - food, chemical, light, pharmaceutical, etc.

Today, more than 30 million different organic compounds are known. Therefore, organic substances represent the most extensive class. The variety of organic compounds is associated with the unique properties and structure of Carbon. Neighboring carbon atoms are connected to each other by single or multiple (double, triple) bonds.

They are characterized by the presence of covalent bonds C-C, as well as polar covalent bonds C-N, C-O, C-Hal, C-metal, etc. Reactions involving organic substances have some features compared to mineral ones. Reactions of inorganic compounds usually involve ions. Often such reactions take place very quickly, sometimes instantly at the optimal temperature. Reactions with usually involve molecules. It should be said that in this case some covalent bonds are broken, while others are formed. As a rule, these reactions proceed much more slowly, and to speed them up it is necessary to increase the temperature or use a catalyst (acid or base).

How are organic substances formed in nature? Most organic compounds in nature are synthesized from carbon dioxide and water in the chlorophylls of green plants.

Classes of organic substances.

Based on the theory of O. Butlerov. Systematic classification is the foundation of scientific nomenclature, which makes it possible to name an organic substance based on the existing structural formula. The classification is based on two main features - the structure of the carbon skeleton, the number and placement of functional groups in the molecule.

The carbon skeleton is a part of an organic substance molecule that is stable in different ways. Depending on its structure, all organic substances are divided into groups.

Acyclic compounds include substances with a straight or branched carbon chain. Carbocyclic compounds include substances with cycles; they are divided into two subgroups - alicyclic and aromatic. Heterocyclic compounds are substances whose molecules are based on cycles, formed by carbon atoms and atoms of other chemical elements (Oxygen, Nitrogen, Sulfur), heteroatoms.

Organic substances are also classified according to the presence of functional groups that are part of the molecules. For example, classes of hydrocarbons (with the exception that there are no functional groups in their molecules), phenols, alcohols, ketones, aldehydes, amines, esters, carboxylic acids, etc. It should be remembered that each functional group (COOH, OH, NH2, SH, NH, NO) determines the physicochemical properties of a given compound.

Kazakh Humanitarian-Legal Innovative University

Department: Information technology and economics

On the topic: “Classification of organic compounds. Types of communication. Specific properties of organic compounds. Structural formulas. Isomerism."

Completed by: 1st year student, group E-124

Uvashov Azamat

Checked: Abylkasimova B. B

Semey 2010

1. Introduction

2. Classification of organic compounds

3. Types of communication

4. Structural formulas

5. Specific properties of organic compounds

6. Isomerism

Introduction

It is difficult to imagine progress in any area of ​​the economy without chemistry - in particular, without organic chemistry. All areas of the economy are connected with modern chemical science and technology.

Organic chemistry studies substances containing carbon, with the exception of carbon monoxide, carbon dioxide and carbonic acid salts (these compounds are closer in properties to inorganic compounds).

As a science, organic chemistry did not exist until the middle of the 18th century. By that time, three types of chemistry were distinguished: animal, plant and mineral chemistry. Animal chemistry studied the substances that make up animal organisms; vegetable– substances that make up plants; mineral- substances that are part of inanimate nature. This principle, however, did not allow the separation of organic substances from inorganic ones. For example, succinic acid belonged to the group of mineral substances, since it was obtained by distillation of fossil amber, potash was included in the group of plant substances, and calcium phosphate was included in the group of animal substances, since they were obtained by calcining, respectively, plant (wood) and animal (bone) materials .

In the first half of the 19th century, it was proposed to separate carbon compounds into an independent chemical discipline - organic chemistry.

Among scientists at that time it was dominant vitalistic a worldview according to which organic compounds are formed only in a living organism under the influence of a special, supernatural “vital force.” This meant that it was impossible to obtain organic substances by synthesis from inorganic ones, and that there was an insurmountable gap between organic and inorganic compounds. Vitalism became so entrenched in the minds of scientists that for a long time no attempts were made to synthesize organic substances. However, vitalism was refuted by practice, by chemical experiment.

The development of organic chemistry has now reached a level that allows us to begin solving such a fundamental problem of organic chemistry as the problem of the quantitative relationship between the structure of a substance and its properties, which can be any physical property, the biological activity of any strictly specified type, problems of this type are solved using mathematical methods.

Classification of organic compounds.

A huge number of organic compounds are classified taking into account the structure of the carbon chain (carbon skeleton) and the presence of functional groups in the molecule.

The diagram shows the classification of organic compounds depending on the structure of the carbon chain.

Hydrocarbons are taken as the basis for classification; they are considered basic compounds in organic chemistry. All other organic compounds are considered as their derivatives.

When classifying hydrocarbons, the structure of the carbon skeleton and the type of bonds connecting carbon atoms are taken into account.

I. ALIPHATIC (aleiphatos. Greek oil) hydrocarbons are linear or branched chains and do not contain cyclic fragments; they form two large groups.

1. Saturated or saturated hydrocarbons (so named because they are unable to attach anything) are chains of carbon atoms connected by simple bonds and surrounded by hydrogen atoms. In the case where the chain has branches, the prefix is ​​added to the name iso. The simplest saturated hydrocarbon is methane, and this is where a number of these compounds begin.

SATURATED HYDROCARBONS

VOLUMETRIC MODELS OF SATURATED HYDROCARBONS. The valences of carbon are directed to the vertices of the mental tetrahedron; as a result, chains of saturated hydrocarbons are not straight, but broken lines.

The main sources of saturated hydrocarbons are oil and natural gas. The reactivity of saturated hydrocarbons is very low; they can only react with the most aggressive substances, for example, halogens or nitric acid. When saturated hydrocarbons are heated above 450 C° without air access, C-C bonds are broken and compounds with a shortened carbon chain are formed. High temperature exposure in the presence of oxygen leads to their complete combustion to CO 2 and water, which allows them to be effectively used as gaseous (methane - propane) or liquid motor fuel (octane).

When one or more hydrogen atoms are replaced by any functional (i.e., capable of subsequent transformations) group, the corresponding hydrocarbon derivatives are formed. Compounds containing the C-OH group are called alcohols, HC=O - aldehydes, COOH - carboxylic acids (the word “carboxylic” is added to distinguish them from ordinary mineral acids, for example, hydrochloric or sulfuric). A compound may simultaneously contain various functional groups, for example, COOH and NH 2; such compounds are called amino acids. The introduction of halogens or nitro groups into the hydrocarbon composition leads, respectively, to halogen or nitro derivatives.

UNSATURATED HYDROCARBONS in the form of volumetric models. The valencies of two carbon atoms connected by a double bond are located in the same plane, which can be observed at certain angles of rotation, at which point the rotation of the molecules stops.

The most typical thing for unsaturated hydrocarbons is the addition of a multiple bond, which makes it possible to synthesize a variety of organic compounds on their basis.

ALICYCLIC HYDROCARBONS. Due to the specific orientation of the bonds at the carbon atom, the cyclohexane molecule is not a flat, but a curved cycle - in the shape of a chair (/ - /), which is clearly visible at certain angles of rotation (at this moment the rotation of the molecules stops)

In addition to those shown above, there are other options for connecting cyclic fragments, for example, they can have one common atom (so-called spirocyclic compounds), or connect in such a way that two or more atoms are common to both cycles (bicyclic compounds), when combining three and more cycles, the formation of hydrocarbon frameworks is also possible.

HETEROCYCLIC COMPOUNDS. Their names were formed historically, for example, furan received its name from furan aldehyde - furfural, obtained from bran ( lat. furfur - bran). For all the compounds shown, addition reactions are difficult, but substitution reactions are quite easy. Thus, these are aromatic compounds of the non-benzene type.

The aromatic nature of these compounds is confirmed by the flat structure of the cycles, which is clearly noticeable at the moment when their rotation is suspended

The diversity of compounds of this class is further increased due to the fact that the heterocycle may contain two or more heteroatoms in the ring

TYPES OF COMMUNICATION

Chemical bond- this is the interaction of particles (atoms, ions) carried out by exchanging electrons. There are several types of communication.
When answering this question, we should dwell in detail on the characteristics of covalent and ionic bonds.
A covalent bond is formed as a result of the sharing of electrons (to form common electron pairs), which occurs during the overlap of electron clouds. The formation of a covalent bond involves the electron clouds of two atoms.
There are two main types of covalent bonds:

a) non-polar and b) polar.

a) A covalent nonpolar bond is formed between nonmetal atoms of the same chemical element. Simple substances, for example O 2, have such a connection; N 2; C 12. You can give a diagram of the formation of a hydrogen molecule: (in the diagram, electrons are indicated by dots).
b) A polar covalent bond is formed between atoms of different nonmetals.

The formation of a covalent polar bond in the HC1 molecule can be schematically represented as follows:

The total electron density is shifted towards chlorine, resulting in a partial negative charge on the chlorine atom and a partial positive charge on the hydrogen atom. Thus, the molecule becomes polar:

Ionic is the bond between ions, i.e., charged particles formed from an atom or group of atoms as a result of the addition or loss of electrons. Ionic bonding is characteristic of salts and alkalis.

It is better to consider the essence of ionic bonding using the example of the formation of sodium chloride. Sodium, as an alkali metal, tends to donate an electron located in the outer electron layer. Chlorine, on the contrary, tends to attach one electron to itself. As a result, sodium donates its electron to chlorine. As a result, oppositely charged particles are formed - Na + and Cl - ions, which are attracted to each other. When answering, you should pay attention to the fact that substances consisting of ions are formed by typical metals and non-metals. They are ionic crystalline substances, that is, substances whose crystals are formed by ions rather than molecules.

After considering each type of communication, we should move on to their comparative characteristics.

What is common to covalent nonpolar, polar and ionic bonds is the participation of external electrons, which are also called valence electrons, in the formation of the bond. The difference lies in the extent to which the electrons involved in the formation of the bond become common. If these electrons belong equally to both atoms, then the covalent bond is nonpolar; if these electrons are biased towards one atom more than the other, then the bond is polar covalent. If the electrons involved in the formation of a bond belong to one atom, then the bond is ionic.

Metallic bond is a bond between ion-atoms in the crystal lattice of metals and alloys, carried out due to the attraction of freely moving (along the crystal) electrons (Mg, Fe).

All of the above differences in the mechanism of bond formation explain the difference in the properties of substances with different types of bonds.

STRUCTURAL FORMULA

Structural formula is a type of chemical formula that graphically describes the arrangement and bonding order of atoms in a compound, expressed on a plane. Bonds in structural formulas are indicated by valence dashes.

Structural formulas are often used where bonds with hydrogen atoms are not indicated by valence dashes (type 2). In another type of structural formula (skeletal), used for large molecules in organic chemistry, the hydrogen atoms associated with carbon atoms are not indicated and the carbon atoms are not designated (type 3).

Coordination bonds, hydrogen bonds, molecular stereochemistry, delocalized bonds, charge localization, etc. are also indicated using different types of symbols used in structural formulas.

SPECIFIC PROPERTIES OF ORGANIC COMPOUNDS

The reactions of organic compounds have some specific features. Reactions of inorganic compounds usually involve ions; these reactions occur very quickly, sometimes instantly at normal temperatures. Reactions in organic compounds usually involve molecules; in this case, some covalent bonds are broken, while others are formed. Such reactions proceed more slowly than ionic ones (for example, tens of hours), and to speed them up it is often necessary to increase the temperature or add a catalyst. The most commonly used catalysts are acids and bases. Typically, not one but several reactions occur, so that the yield of the desired product is very often less than 50%. In this regard, in organic chemistry they do not use chemical equations, but reaction schemes without indicating stoichiometric ratios.

Reactions of organic compounds can occur in very complex ways and do not necessarily correspond to the simplest relative notation. Typically, a simple stoichiometric reaction actually occurs in several successive steps. Carbocations R+, carbanions R-, free radicals, carbenes: CX2, radical cations (for example, radical anions (for example, Ar)) and other unstable particles that live for fractions of a second can appear as intermediates in multi-stage processes. the description of all the changes that occur at the molecular level in the process of converting reactants into products is called a reaction mechanism.

The study of the influence of the structure of organic compounds on the mechanism of their reactions is studied by physical organic chemistry, the foundations of which were laid by K. Ingold, Robinson and L. Hammett (1930s).

Reactions of organic compounds can be classified depending on the method of breaking and forming bonds, the method of excitation of the reaction, its molecularity, etc.

ISOMERIA

ISOMERIA (Greek isos - same, meros - part) is one of the most important concepts in chemistry, mainly in organic chemistry. Substances may have the same composition and molecular weight, but different structures and compounds containing the same elements in the same quantity, but differing in the spatial arrangement of atoms or groups of atoms, are called isomers. Isomerism is one of the reasons that organic compounds are so numerous and varied.

Isomerism was first discovered by J. Liebig in 1823, who established that silver salts of fulminate and isocyanic acids: Ag-O-N=C and Ag-N=C=O have the same composition, but different properties. The term “Isomerism” was introduced in 1830 by I. Berzelius, who suggested that differences in the properties of compounds of the same composition arise due to the fact that the atoms in the molecule are arranged in a different order. The idea of ​​isomerism was finally formed after A.M. Butlerov created the theory of chemical structure (1860s). Based on this theory, he proposed that there should be four different butanols. By the time the theory was created, only one butanol was known (CH 3) 2 CHCH 2 OH, obtained from plant materials.

The subsequent synthesis of all butanol isomers and determination of their properties became convincing confirmation of the theory.

According to the modern definition, two compounds of the same composition are considered isomers if their molecules cannot be combined in space so that they completely coincide. Combination, as a rule, is done mentally; in complex cases, spatial models or calculation methods are used. There are several reasons for isomerism.

Structural isomerism

As a rule, it is caused by differences in the structure of the hydrocarbon skeleton or unequal arrangement of functional groups or multiple bonds.

Isomerism of the hydrocarbon skeleton. Saturated hydrocarbons containing from one to three carbon atoms (methane, ethane, propane) have no isomers. For a compound with four carbon atoms C 4 H 10 (butane), two isomers are possible, for pentane C 5 H 12 - three isomers, for hexane C 6 H 14 - five

As the number of carbon atoms in a hydrocarbon molecule increases, the number of possible isomers increases dramatically. For heptane C 7 H 16 there are nine isomers, for the hydrocarbon C 14 H 30 there are 1885 isomers, for the hydrocarbon C 20 H 42 there are over 366,000.

In complex cases, the question of whether two compounds are isomers is resolved using various rotations around the valence bonds (simple bonds allow this, which to a certain extent corresponds to their physical properties). After moving individual fragments of the molecule (without breaking the bonds), one molecule is superimposed on another. If two molecules are completely identical, then these are not isomers, but the same compound:

Isomers that differ in skeletal structure usually have different physical properties (melting point, boiling point, etc.), which makes it possible to separate one from the other. This type of isomerism also exists in aromatic hydrocarbons.