Theory of the chemical structure of organic compounds. Classification of organic substances. Organic compounds and their classification

The simplest classification is this. that all known substances are divided into inorganic and organic. Organic substances include hydrocarbons and their derivatives. All other substances are inorganic.

Inorganic substances according to composition they are divided into simple and complex.

Simple substances consist of atoms of one chemical element and are divided into metals, nonmetals, and noble gases. Complex substances consist of atoms of different elements chemically bonded to each other.

Complex inorganic substances are classified according to their composition and properties as follows: the most important classes: oxides, bases, acids, amphoteric hydroxides, salts.

  • Oxides- This complex substances, consisting of two chemical elements, one of which is oxygen with an oxidation state (-2). The general formula of oxides is: E m O n, where m is the number of atoms of the element E, and n is the number of oxygen atoms. Oxides, in turn, are classified into salt-forming and non-salt-forming. Salt-forming compounds are divided into basic, amphoteric, and acidic, which correspond to bases, amphoteric hydroxides, and acids, respectively.
  • Basic oxides are metal oxides in oxidation states +1 and +2. These include:
    • metal oxides of the main subgroup of the first group ( alkali metals) Li-Fr
    • metal oxides of the main subgroup of the second group ( Mg and alkaline earth metals) Mg-Ra
    • transition metal oxides in lower oxidation states
  • Acidic oxides-form nonmetals with CO. more than +2 and metals with S.O. from +5 to +7 (SO 2, SeO 2, P 2 O 5, As 2 O 3, CO 2, SiO 2, CrO 3 and Mn 2 O 7). Exception: NO oxides 2 and ClO 2 there are no corresponding acidic hydroxides, but they are considered acidic.
  • Amphoteric oxides-formed by amphoteric metals with S.O. +2, +3, +4 (BeO, Cr 2 O 3, ZnO, Al 2 O 3, GeO 2, SnO 2 and PbO).
  • Non-salt-forming oxides- non-metal oxides with CO+1, +2 (CO, NO, N 2 O, SiO).
  • Reasons- these are complex substances consisting of metal atoms and one or more hydroxyl groups (-OH). The general formula of the bases is: M(OH) y, where y is the number of hydroxyl groups equal to the oxidation state of the metal M (usually +1 and +2). Bases are divided into soluble (alkalis) and insoluble.
  • Acids-(acid hydroxides) are complex substances consisting of hydrogen atoms that can be replaced by metal atoms and acidic residues. The general formula of acids: H x Ac, where Ac is the acidic residue (from the English “acid” - acid), x is the number of hydrogen atoms equal to the charge of the ion of the acidic residue.
  • Amphoteric hydroxides- these are complex substances that exhibit both the properties of acids and the properties of bases. Therefore, the formulas of amphoteric hydroxides can be written in both acid and base form.
  • Salts- these are complex substances consisting of metal cations and anions of acid residues. This definition applies to medium salts.
  • Medium salts- these are the products of complete replacement of hydrogen atoms in an acid molecule with metal atoms or complete replacement of hydroxo groups in a base molecule with acidic residues.
  • Acid salts- hydrogen atoms in the acid are partially replaced by metal atoms. They are obtained by neutralizing a base with an excess of acid. To correctly name sour salt, it is necessary to add the prefix hydro- or dihydro- to the name of a normal salt, depending on the number of hydrogen atoms included in the acid salt. For example, KHCO 3 is potassium bicarbonate, KH 2 PO 4 is potassium dihydrogen orthophosphate. It must be remembered that acid salts can only form two or more basic acids.
  • Basic salts- hydroxo groups of the base (OH −) are partially replaced by acidic residues. To name basic salt, it is necessary to add the prefix hydroxo- or dihydroxo- to the name of a normal salt, depending on the number of OH groups included in the salt. For example, (CuOH) 2 CO 3 is copper (II) hydroxycarbonate. It must be remembered that basic salts can only form bases containing two or more hydroxo groups.
  • Double salts- they contain two different cations; they are obtained by crystallization from a mixed solution of salts with different cations, but the same anions. For example, KAl(SO 4) 2, KNaSO 4.
  • Mixed salts- they contain two different anions. For example, Ca(OCl)Cl.
  • Hydrate salts (crystalline hydrates) - they contain molecules of water of crystallization. Example: Na 2 SO 4 10H 2 O.

Classification of organic substances

Compounds consisting only of hydrogen and carbon atoms are called hydrocarbons. Before starting this section, remember, to simplify the recording, chemists do not write carbons and hydrogens in chains, but do not forget that carbon forms four bonds, and if in the figure carbon is connected by two bonds, then it is connected to hydrogens by two more, although the latter is not specified:

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 are divided into two groups: carbocyclic connections and heterocyclic.

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

Aromatic compounds The molecular structure is based on flat carbon-containing rings with a special closed system of π-electrons. forming a common π-system (a single π-electron cloud).

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

Pi bond (π bond) – a covalent bond formed by overlapping p-atomic orbitals. Unlike sigma coupling, which is accomplished by overlapping s-atomic orbitals along the line of atomic bonding, pi bonds occur when p-atomic orbitals on either side of the line of atomic bonding overlap.

In the case of the formation of an aromatic system, for example, benzene C6H6, each of the six carbon atoms is in a state of sp2 hybridization and forms three sigma bonds with bond angles of 120 °. The fourth p-electron of each carbon atom is oriented perpendicular to the plane of the benzene ring. In general, a single bond appears that extends to all carbon atoms of the benzene ring. Two regions of high electron density pi bonds are formed on either side of the sigma bond plane. With such a bond, all carbon atoms in the benzene molecule become equivalent and, therefore, such a system is more stable than a system with three localized double bonds.

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

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

Saturated alicyclic hydrocarbons are cycloalkanes, their general formula is C n H 2n:

We looked at the classification of hydrocarbons. But if in these molecules one or larger number hydrogen atoms are replaced by other atoms or groups of atoms (halogens, hydroxyl groups, amino groups, etc.), hydrocarbon derivatives are formed: halogen derivatives, oxygen-containing, nitrogen-containing and other organic compounds.

Atoms or groups of atoms that determine the most characteristic properties of this class of substances are called functional groups.

Hydrocarbons and their derivatives with the same functional group form homologous series.

A homologous series is a series of compounds belonging to the same class (homologs), differing from each other in composition by an integer number of -CH 2 - groups (homologous difference), having a similar structure and, therefore, similar chemical properties.

The similarity of the chemical properties of homologues greatly simplifies the study of organic compounds.

Substituted hydrocarbons

  • Halogenated hydrocarbons can be considered as products of the replacement of one or more hydrogen atoms by halogen atoms in hydrocarbons. In accordance with this, there may be saturated and unsaturated mono-, li-, tri- (in general, poly-) halogen derivatives. The general formula of halogen derivatives of saturated hydrocarbons is R-G. Oxygen-containing organic substances include alcohols, phenols, aldehydes, ketones, carboxylic acids , simple and esters.
  • Alcohols- derivatives of hydrocarbons in which one or more hydrogen atoms are replaced by hydroxyl groups. Alcohols are called monohydric if they have one hydroxyl group, and saturated if they are derivatives of alkanes. The general formula of saturated monohydric alcohols is R-OH.
  • Phenols- derivatives of aromatic hydrocarbons (benzene series), in which one or more hydrogen atoms in the benzene ring are replaced by hydroxyl groups.
  • Aldehydes and ketones- derivatives of hydrocarbons containing a carbonyl group of atoms (carbonyl). In aldehyde molecules, one carbonyl bond is connected to a hydrogen atom, the other to a hydrocarbon radical. In the case of ketones, the carbonyl group is connected to two (generally different) radicals.
  • Ethers are organic substances containing two hydrocarbon radicals connected by an oxygen atom: R=O-R or R-O-R 2. The radicals can be the same or different. The composition of ethers is expressed by the formula C n H 2n +2O.
  • 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.
  • Amines- compounds that are considered as derivatives of ammonia, in which the hydrogen atoms are replaced by hydrocarbon radicals. Depending on the nature of the radical, amines can be aliphatic. Depending on the number of hydrogen atoms replaced by radicals, primary, secondary, and tertiary amines are distinguished. 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. Amino acids contain two functional groups connected to a hydrocarbon radical - the amino group -NH 2 and the carboxyl -COOH.

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. Currently, many compounds are also known that can be classified as both organic and inorganic. They are called organoelement compounds. Some of them can be considered as hydrocarbon derivatives.

Nomenclature

There are 2 nomenclatures used to name organic compounds: rational and systematic (IUPAC) and trivial names.


Compiling 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);

En (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

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.


The procedure for compiling the name

Chemical language, which includes chemical symbolism (including chemical formulas) as one of its most specific parts, is an important active means of cognition of chemistry and therefore requires clear and conscious use.

Chemical formulas- these are conventional images of the composition and structure of chemically individual substances using chemical symbols, indices and other signs. When studying the composition, chemical, electronic and spatial structure of substances, their physical and chemical properties, isomerism and other phenomena, chemical formulas of different types are used.

Especially many types of formulas (simple, molecular, structural, projection, conformational, etc.) are used in the study of substances of molecular structure - most organic substances and a relatively small part inorganic substances under normal conditions. Significantly fewer types of formulas (the simplest) are used in the study of non-molecular compounds, the structure of which is more clearly reflected by ball-and-stick models and diagrams of crystal structures or their unit cells.


Drawing up complete and brief structural formulas of hydrocarbons

Example:

Draw up a complete and brief structural formula of propane C 3 H 8.

Solution:

1. Write 3 carbon atoms in a line and connect them with bonds:

S–S–S

2. Add dashes (bonds) so that each carbon atom has 4 bonds:

4. Write down a brief structural formula:

CH 3 –CH 2 –CH 3

Solubility table

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 property, 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.

Organic compounds

Acyclic (aliphatic)

(open circuit connections)

Cyclic

(closed circuit connections)

Saturated (ultimate)

Unsaturated (unsaturated)

Carbocyclic (the cycle consists only of carbon atoms)

Heterocyclic (the cycle consists of carbon atoms and other elements)

Alicyclic (aliphatic cyclic)

Aromatic

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 valencies 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 valences 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 increases further 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 overall 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 a 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 note that substances consisting of ions are formed by typical metals and non-metals. They are ionic crystalline substances, i.e. 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 - bond between ion-atoms in crystal lattice 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 connections.

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).

By using different types symbols used in structural formulas also indicate coordination bonds, hydrogen bonds, stereochemistry of molecules, delocalized bonds, charge localization, etc.

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; while alone covalent bonds are torn, and 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, and 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 intermediate compounds in multi-stage processes. Detailed Description All the changes that occur at the molecular level in the process of converting reactants into products is called the 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) – one of the most important concepts in chemistry, mainly organic. Substances may have the same composition and molecular weight, but different structure 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 concept of isomerism was finally formed after A.M. Butlerov created the theory 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 C7H16 there are nine isomers, for the hydrocarbon C14H30 there are 1885 isomers, for the hydrocarbon C20H42 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 allowing the bonds to break), 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 allows you to separate one from the other. This type of isomerism also exists in aromatic hydrocarbons.

The classification of organic substances is even more complex. This is due to a number of reasons: the extreme abundance of organic compounds, the complexity and diversity of their structure, and the very history of the study of carbon compounds.
Indeed, before mid-19th V. Organic chemistry, in the figurative expression of F. Wöhler*, seemed to be “a dense forest full of amazing things, a boundless thicket from which you cannot get out, into which you do not dare to penetrate.” Only with the advent of the “dense forest” theory of the chemical structure of organic compounds in 1861
organic chemistry began to transform into a regular park flooded with sunlight with a strict grid of alleys and paths. The authors of this theory were an outstanding international trio of chemists: our compatriot A.M. Butlerov**, the German F.A. Kekule and the Englishman A. Cooper.

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 double chemical bond. The >C=O group is called carbonyl. The carbonyl group is part of several
functional groups, including aldehyde and carboxyl. Organic matter containing these functional groups are called aldehydes and carboxylic acids, respectively. Most famous representatives 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 for classes of compounds and the formulas for their representatives.
4. Define isomerism, write down the formulas of possible isomers for compounds of the composition C4H10O. By using various sources information, give names to each of them and prepare a message about one of the connections.
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.

When moving from inorganic to organic chemistry, one can see how the classification of organic and inorganic substances differs. The world of organic compounds has a variety and many options. The classification of organic substances not only helps to understand this abundance, but also provides a clear scientific basis for their study.

The theory of chemical structure was chosen as the basis for class distribution. The basis of the study of organics is work with the largest class, which is usually called the main class for organic substances - hydrocarbons. Other representatives of the organic world are considered as their derivatives. Indeed, when studying their structure, it is not difficult to notice that the synthesis of these substances occurs by replacing (replacing) one, and sometimes several hydrogen units in the hydrocarbon structure with atoms of other chemical elements, and sometimes with entire radical branches.

The classification of organic substances took hydrocarbons as a basis also because of the simplicity of their composition, and the hydrocarbon component is the most significant part of most known organic compounds. Today, of all the known organics related to the world, compounds built on the basis have a significant predominance. All other substances are either in the minority, allowing them to be classified as exceptions to the general rule, or are so unstable that their production is difficult even in our time.

Classification of organic substances by dividing them into separate groups and classes allows us to distinguish two large organic classes of acyclic and cyclic compounds. Their very name allows us to draw a conclusion about the type of structure of the molecule. In the first case, it is a chain of hydrocarbon units, and in the second, the molecule is a ring.

Acyclic compounds can have branches or form a simple chain. Among the names of these substances you can find the expression “fatty or aliphatic hydrocarbons”. They can be saturated (ethane, isobutane, or unsaturated (ethylene, acetylene, isoprene), depending on the type of bonding of some carbon units.

The classification of organic substances belonging to cyclic compounds implies their further division into the group of carbocyclic and the group of heterocyclic hydrocarbons.

Carbocyclic “rings” are made up of carbon atoms only. They can be alicyclic (saturated and unsaturated), and also be aromatic carbocyclic compounds. In alicyclic compounds, the two ends of the carbon chain simply join together, but aromatic compounds have a so-called benzene ring in their structure, which has a significant effect on their properties.

In heterocyclic substances, atoms of other substances can be found; nitrogen most often performs this function.

The next component that affects the properties of organic substances is the presence of a functional group.

For halogenated hydrocarbons, one or even several halogen atoms can act as a functional group. Alcohols obtain their properties due to the presence of hydroxo groups. For aldehydes, a characteristic feature is the presence of aldehyde groups, for ketones - carbonyl groups. Carboxylic acids differ in that they contain carboxyl groups, and amines have an amino group. Nitro compounds are characterized by the presence of a nitro group.

The variety of types of hydrocarbons, as well as their properties, is based on a very different type of combination. For example, the composition of one molecule may include two or more identical, and sometimes different, functional groups, determining the specific properties of this substance (glycerol).

A table that can easily be compiled based on the information presented in the text of this article will provide greater clarity for considering the issue (classification of organic substances).

All substances that contain a carbon atom, other than carbonates, carbides, cyanides, thiocyanates and carbonic acid, are organic compounds. This means that they are capable of being created by living organisms from carbon atoms through enzymatic or other reactions. Today, many organic substances can be synthesized artificially, which allows the development of medicine and pharmacology, as well as the creation of high-strength polymer and composite materials.

Classification of organic compounds

Organic compounds are the most numerous class of substances. There are about 20 types of substances here. They differ in chemical properties and differ in physical qualities. Their melting point, mass, volatility and solubility, as well as their state of aggregation under normal conditions are also different. Among them:

  • hydrocarbons (alkanes, alkynes, alkenes, alkadienes, cycloalkanes, aromatic hydrocarbons);
  • aldehydes;
  • ketones;
  • alcohols (dihydric, monohydric, polyhydric);
  • ethers;
  • esters;
  • carboxylic acids;
  • amines;
  • amino acids;
  • carbohydrates;
  • fats;
  • proteins;
  • biopolymers and synthetic polymers.

This classification reflects the characteristics of the chemical structure and the presence of specific atomic groups that determine the difference in the properties of a particular substance. IN general view classification based on the configuration of the carbon skeleton, which does not take into account the characteristics of chemical interactions, looks different. According to its provisions, organic compounds are divided into:

  • aliphatic compounds;
  • aromatics;
  • heterocyclic substances.

These classes of organic compounds may have isomers in different groups substances. The properties of isomers are different, although their atomic composition may be the same. This follows from the provisions laid down by A.M. Butlerov. Also, the theory of the structure of organic compounds is the guiding basis for all research in organic chemistry. It is placed on the same level as Mendeleev's Periodic Law.

The very concept of chemical structure was introduced by A.M. Butlerov. It appeared in the history of chemistry on September 19, 1861. Previously, there were different opinions in science, and some scientists completely denied the existence of molecules and atoms. Therefore, there was no order in organic and inorganic chemistry. Moreover, there were no patterns by which one could judge the properties of specific substances. At the same time, there were compounds that, with the same composition, exhibited different properties.

The statements of A.M. Butlerov largely directed the development of chemistry in the right direction and created a very solid foundation for it. Through it, it was possible to systematize the accumulated facts, namely, the chemical or physical properties of certain substances, the patterns of their entry into reactions, etc. Even predicting the routes to obtain compounds and the presence of some general properties became possible thanks to this theory. And most importantly, A.M. Butlerov showed that the structure of the molecule of a substance can be explained from the point of view of electrical interactions.

Logic of the theory of the structure of organic substances

Since before 1861 many in chemistry rejected the existence of an atom or molecule, the theory of organic compounds became a revolutionary proposal for the scientific world. And since A. M. Butlerov himself proceeds only from materialistic conclusions, he managed to refute philosophical ideas about organic matter.

He was able to show that the molecular structure can be recognized experimentally through chemical reactions. For example, the composition of any carbohydrate can be determined by burning a certain amount of it and counting the resulting water and carbon dioxide. The amount of nitrogen in an amine molecule is also calculated during combustion by measuring the volume of gases and isolating the chemical amount of molecular nitrogen.

If we consider Butlerov's judgments about structure-dependent chemical structure in the opposite direction, a new conclusion arises. Namely: knowing the chemical structure and composition of a substance, one can empirically assume its properties. But most importantly, Butlerov explained that in organic matter there is a huge number of substances that exhibit different properties, but have the same composition.

General provisions of the theory

Considering and studying organic compounds, A. M. Butlerov derived some of the most important principles. He combined them into a theory explaining the structure of chemical substances of organic origin. The theory is as follows:

  • in molecules of organic substances, atoms are connected to each other in a strictly defined sequence, which depends on valence;
  • chemical structure is the immediate order according to which atoms in organic molecules are connected;
  • the chemical structure determines the presence of the properties of an organic compound;
  • depending on the structure of molecules with the same quantitative composition, different properties of the substance may appear;
  • all atomic groups involved in the formation of a chemical compound have a mutual influence on each other.

All classes of organic compounds are built according to the principles of this theory. Having laid the foundations, A. M. Butlerov was able to expand chemistry as a field of science. He explained that due to the fact that in organic substances carbon exhibits a valence of four, the diversity of these compounds is determined. The presence of many active atomic groups determines whether a substance belongs to a certain class. And it is precisely due to the presence of specific atomic groups (radicals) that physical and chemical properties appear.

Hydrocarbons and their derivatives

These organic compounds of carbon and hydrogen are the simplest in composition among all the substances in the group. They are represented by a subclass of alkanes and cycloalkanes (saturated hydrocarbons), alkenes, alkadienes and alkatrienes, alkynes (unsaturated hydrocarbons), as well as a subclass of aromatic substances. In alkanes, all carbon atoms are connected only by a single S-S connection yu, because of which not a single H atom can be built into the hydrocarbon composition.

In unsaturated hydrocarbons, hydrogen can be incorporated at the site of the double C=C bond. Also, the C-C bond can be triple (alkynes). This allows these substances to enter into many reactions involving the reduction or addition of radicals. For the convenience of studying their ability to react, all other substances are considered to be derivatives of one of the classes of hydrocarbons.

Alcohols

Alcohols are organic chemical compounds that are more complex than hydrocarbons. They are synthesized as a result of enzymatic reactions in living cells. The most typical example is the synthesis of ethanol from glucose as a result of fermentation.

In industry, alcohols are obtained from halogen derivatives of hydrocarbons. As a result of the replacement of the halogen atom with a hydroxyl group, alcohols are formed. Monohydric alcohols contain only one hydroxyl group, polyhydric alcohols contain two or more. An example of a dihydric alcohol is ethylene glycol. Polyhydric alcohol is glycerin. The general formula of alcohols is R-OH (R is the carbon chain).

Aldehydes and ketones

After alcohols enter into reactions of organic compounds associated with the abstraction of hydrogen from the alcohol (hydroxyl) group, the double bond between oxygen and carbon closes. If this reaction proceeds through the alcohol group located at the terminal carbon atom, it results in the formation of an aldehyde. If the carbon atom with the alcohol is not located at the end of the carbon chain, then the result of the dehydration reaction is the production of a ketone. The general formula of ketones is R-CO-R, aldehydes R-COH (R is the hydrocarbon radical of the chain).

Esters (simple and complex)

The chemical structure of organic compounds of this class is complicated. Ethers are considered to be reaction products between two alcohol molecules. When water is removed from them, a compound is formed sample R-O-R. Reaction mechanism: abstraction of a hydrogen proton from one alcohol and a hydroxyl group from another alcohol.

Esters are reaction products between an alcohol and an organic carboxylic acid. Reaction mechanism: elimination of water from the alcohol and carbon group of both molecules. Hydrogen is separated from the acid (at the hydroxyl group), and the OH group itself is separated from the alcohol. The resulting compound is depicted as R-CO-O-R, where the beech R denotes the radicals - the remaining parts of the carbon chain.

Carboxylic acids and amines

Carboxylic acids are special substances that play an important role in the functioning of the cell. The chemical structure of organic compounds is as follows: a hydrocarbon radical (R) with a carboxyl group (-COOH) attached to it. The carboxyl group can only be located at the outermost carbon atom, because the valency of C in the (-COOH) group is 4.

Amines are simpler compounds that are derivatives of hydrocarbons. Here, at any carbon atom there is an amine radical (-NH2). There are primary amines in which a group (-NH2) is attached to one carbon (general formula R-NH2). In secondary amines, nitrogen combines with two carbon atoms (formula R-NH-R). In tertiary amines, nitrogen is connected to three carbon atoms (R3N), where p is a radical, a carbon chain.

Amino acids

Amino acids are complex compounds that exhibit the properties of both amines and acids of organic origin. There are several types of them, depending on the location of the amine group in relation to the carboxyl group. The most important are alpha amino acids. Here the amine group is located at the carbon atom to which the carboxyl group is attached. This allows the creation of a peptide bond and the synthesis of proteins.

Carbohydrates and fats

Carbohydrates are aldehyde alcohols or keto alcohols. These are compounds with a linear or cyclic structure, as well as polymers (starch, cellulose and others). Their most important role in the cell is structural and energetic. Fats, or rather lipids, perform the same functions, only they participate in other biochemical processes. From the point of view of chemical structure, fat is an ester of organic acids and glycerol.