The classification of organic substances is the basis for the study of organic chemistry. The Wonderful World of Organics

In the history of the development of organic chemistry, two periods are distinguished: empirical (from the middle of the 17th to the end of the 18th century), in which the knowledge of organic substances, methods for their isolation and processing took place empirically, and analytical (the end of the 18th - the middle of the 19th century), associated with the emergence of methods for establishing composition of organic matter. During the analytical period, it was found that all organic substances contain carbon. Among other elements that make up organic compounds, hydrogen, nitrogen, sulfur, oxygen and phosphorus were found.

Of great importance in the history of organic chemistry is the structural period (second half of the 19th - early 20th centuries), marked by the birth of the scientific theory of the structure of organic compounds, the founder of which was A.M. Butlerov.

The main provisions of the theory of the structure of organic compounds:

atoms in molecules are interconnected in a certain order by chemical bonds in accordance with their valency. Carbon in all organic compounds is tetravalent;
the properties of substances depend not only on their qualitative and quantitative composition, but also on the order in which atoms are combined;
atoms in a molecule mutually influence each other.

The order of connection of atoms in a molecule is described by a structural formula in which chemical bonds are represented by dashes.

Characteristic properties of organic substances

There are several important properties that distinguish organic compounds into a separate, unlike any other class of chemical compounds:

Organic compounds are usually gases, liquids, or low-melting solids, in contrast to inorganic compounds, which are mostly solids with a high melting point.
Organic compounds are mostly built covalently, and inorganic compounds - ionically.
The different topology of the formation of bonds between the atoms that form organic compounds (primarily carbon atoms) leads to the appearance of isomers - compounds that have the same composition and molecular weight, but have different physicochemical properties. This phenomenon is called isomerism.
The phenomenon of homology is the existence of series of organic compounds in which the formula of any two neighbors of the series (homologues) differs by the same group - the homological difference CH 2 . Organic matter burns.

Classification of organic substances

The classification takes as a basis two important features - the structure of the carbon skeleton and the presence of functional groups in the molecule.

In the molecules of organic substances, carbon atoms combine with each other, forming the so-called. carbon skeleton or chain. Chains are open and closed (cyclic), open chains can be unbranched (normal) and branched:

According to the structure of the carbon skeleton, there are:

- alicyclic organic substances having an open carbon chain, both branched and unbranched. For example,

CH 3 -CH 2 -CH 2 -CH 3 (butane)

CH 3 -CH (CH 3) -CH 3 (isobutane)

- carbocyclic organic substances in which the carbon chain is closed in a cycle (ring). For example,

- heterocyclic organic compounds containing in the cycle not only carbon atoms, but also atoms of other elements, most often nitrogen, oxygen or sulfur:

A functional group is an atom or group of non-hydrocarbon atoms that determines whether a compound belongs to a particular class. The sign according to which an organic substance belongs to one class or another is the nature of the functional group (Table 1).

Table 1. Functional groups and classes.

Compounds may contain more than one functional group. If these groups are the same, then the compounds are called polyfunctional, for example, chloroform, glycerol. Compounds containing various functional groups are called heterofunctional, they can be simultaneously attributed to several classes of compounds, for example, lactic acid can be considered as a carboxylic acid and as an alcohol, and colamine as an amine and an alcohol.

With the development of chemical science and the emergence of a large number of new chemical compounds, the need to develop and adopt a naming system understandable to scientists all over the world, i.e. . Next, we give an overview of the main nomenclatures of organic compounds.

Trivial nomenclature

In the origins of the development of organic chemistry, new compounds were attributed trivial names, i.e. names that have developed historically and are often associated with the method of obtaining them, their appearance and even taste, etc. Such a nomenclature of organic compounds is called trivial. The table below shows some of the compounds that have retained their names to this day.

Rational nomenclature

With the expansion of the list of organic compounds, it became necessary to associate their name with the Base of Rational Nomenclature of Organic Compounds is the name of the simplest organic compound. For example:

However, more complex organic compounds cannot be assigned names in this way. In this case, the compounds should be named according to the rules of IUPAC systematic nomenclature.

IUPAC systematic nomenclature

IUPAC (IUPAC) - International Union of Pure and Applied Chemistry (International Union of Pure and Applied Chemistry).

IN this case When naming compounds, one should take into account the location of carbon atoms in the molecule and structural elements. The most commonly used is the substitutional nomenclature of organic compounds, i.e. the basic basis of the molecule is distinguished, in which hydrogen atoms are replaced by some structural units or atoms.

Before you start building the names of compounds, we advise you to learn the names numeric prefixes, roots and suffixes used in IUPAC nomenclature.

As well as the names of functional groups:

Numerals are used to indicate the number of multiple bonds and functional groups:

Limit hydrocarbon radicals:

Unsaturated hydrocarbon radicals:

Aromatic hydrocarbon radicals:

Rules for constructing the name of an organic compound according to the IUPAC nomenclature:

Select the main chain of the molecule

Determine all functional groups present and their precedence

Determine the presence of multiple bonds

Number the main chain, and the numbering should start from the end of the chain closest to the senior group. If there are several such possibilities, the chain is numbered so that either the multiple bond or another substituent present in the molecule receives the minimum number.

Carbocyclic compounds are numbered starting from the carbon atom associated with the highest characteristic group. If there are two or more substituents, they try to number the chain so that the substituents have the minimum numbers.

Create a connection name:

- Determine the basis of the name of the compound that makes up the root of the word, which denotes a saturated hydrocarbon with the same number of atoms as the main chain.

- After the stem of the name, a suffix follows, showing the degree of saturation and the number of multiple bonds. For example, - tetraene, diene. In the absence of multiple bonds, use the suffix - sk.

- Then, also the name of the senior functional group.

— This is followed by a listing of the alternates in alphabetical order, indicating their location in Arabic numerals. For example, - 5-isobutyl, - 3-fluorine. In the presence of several identical substituents, their number and position are indicated, for example, 2,5 - dibromo-, 1,4,8-trimethy-.

It should be noted that numbers are separated from words by a hyphen, and between themselves by commas.

As example Let's name the following connection:

1. Choose main circuit, which must include senior group- COON.

Define others functional groups: - OH, - Cl, - SH, - NH 2.

Multiple bonds No.

2. We number the main chain starting with the older group.

3. The number of atoms in the main chain is 12. Name basis

10-amino-6-hydroxy-7-chloro-9-sulfanyl-methyl ester of dodecanoic acid.

10-amino-6-hydroxy-7-chloro-9-sulfanyl-methyldodecanoate

Nomenclature of optical isomers

In some classes of compounds, such as aldehydes, hydroxy and amino acids, the mutual arrangement of substituents is indicated by D, L- nomenclature. letter D denote the configuration of the dextrorotatory isomer, L- left-handed.

At the core D,L-the nomenclature of organic compounds are Fischer projections:

α-amino acids and α-hydroxy acids isolate the "oxy-acid key", i.e. upper parts of their projection formulas. If the hydroxyl (amino-) group is located on the right, then this D-isomer, left L-isomer.

For example, the tartaric acid shown below has D- configuration by oxy-acid key:

to determine isomer configurations sugars isolate the "glycerin key", i.e. compare the lower parts (lower asymmetric carbon atom) of the projection formula of sugar with the lower part of the projection formula of glyceraldehyde.

The designation of the sugar configuration and the direction of rotation is similar to the configuration of glyceraldehyde, i.e. D– the configuration corresponds to the location of the hydroxyl group is located on the right, L configurations on the left.

For example, below is D-glucose.

2) R-, S-nomenclature (Kahn, Ingold and Prelog nomenclature)

In this case, the substituents at the asymmetric carbon atom are arranged in order of precedence. Optical isomers are designated R And S, and the racemate RS.

To describe the connection configuration according to R,S-nomenclature proceed as follows:

All substituents on the asymmetric carbon atom are determined.
The seniority of the deputies is determined, i.e. compare their atomic masses. The rules for determining the seniority series are the same as when using the E/Z nomenclature of geometric isomers.
The substituents are oriented in space so that the junior substituent (usually hydrogen) is in the corner furthest from the observer.
The configuration is determined by the location of the remaining substituents. If the movement from the senior to the middle and then to the junior deputy (i.e., in order of decreasing seniority) is carried out clockwise, then this is the R configuration, counterclockwise - the S-configuration.

The table below lists the deputies in ascending order of precedence:

Categories ,

In the past, scientists divided all substances in nature into conditionally inanimate and living ones, including the animal and plant kingdoms among the latter. Substances of the first group are called mineral. And those that entered the second, began to be called organic substances.

What is meant by this? The class of organic substances is the most extensive among all chemical compounds known to modern scientists. The question of which substances are organic can be answered as follows - these are chemical compounds that include carbon.

Please note that not all carbon-containing compounds are organic. For example, corbides and carbonates, carbonic acid and cyanides, carbon oxides are not among them.

Why are there so many organic substances?

The answer to this question lies in the properties of carbon. This element is curious in that it is able to form chains from its atoms. And at the same time, the carbon bond is very stable.

In addition, in organic compounds, it exhibits a high valence (IV), i.e. the ability to form chemical bonds with other substances. And not only single, but also double and even triple (otherwise - multiples). As the bond multiplicity increases, the chain of atoms becomes shorter, and the bond stability increases.

And carbon is endowed with the ability to form linear, flat and three-dimensional structures.

That is why organic substances in nature are so diverse. You can easily check it yourself: stand in front of a mirror and carefully look at your reflection. Each of us is a walking textbook on organic chemistry. Think about it: at least 30% of the mass of each of your cells is organic compounds. The proteins that built your body. Carbohydrates, which serve as "fuel" and a source of energy. Fats that store energy reserves. Hormones that control organ function and even your behavior. Enzymes that start chemical reactions within you. And even the "source code," the strands of DNA, are all carbon-based organic compounds.

Composition of organic substances

As we said at the very beginning, the main building material for organic matter is carbon. And practically any elements, combining with carbon, can form organic compounds.

In nature, most often in the composition of organic substances are hydrogen, oxygen, nitrogen, sulfur and phosphorus.

The structure of organic substances

The diversity of organic substances on the planet and the diversity of their structure can be explained by the characteristic features of carbon atoms.

You remember that carbon atoms are able to form very strong bonds with each other, connecting in chains. The result is stable molecules. The way carbon atoms are connected in a chain (arranged in a zigzag pattern) is one of the key features of its structure. Carbon can combine both into open chains and into closed (cyclic) chains.

It is also important that the structure of chemicals directly affects their chemical properties. A significant role is also played by how atoms and groups of atoms in a molecule affect each other.

Due to the peculiarities of the structure, the number of carbon compounds of the same type goes to tens and hundreds. For example, we can consider hydrogen compounds of carbon: methane, ethane, propane, butane, etc.

For example, methane - CH 4. Such a combination of hydrogen with carbon under normal conditions is in a gaseous state of aggregation. When oxygen appears in the composition, a liquid is formed - methyl alcohol CH 3 OH.

Not only substances with different qualitative composition (as in the example above) exhibit different properties, but substances of the same qualitative composition are also capable of this. An example is the different ability of methane CH 4 and ethylene C 2 H 4 to react with bromine and chlorine. Methane is capable of such reactions only when heated or under ultraviolet light. And ethylene reacts even without lighting and heating.

Consider this option: the qualitative composition of chemical compounds is the same, the quantitative is different. Then the chemical properties of the compounds are different. As in the case of acetylene C 2 H 2 and benzene C 6 H 6.

Not the last role in this variety is played by such properties of organic substances, "tied" to their structure, as isomerism and homology.

Imagine that you have two seemingly identical substances - the same composition and the same molecular formula to describe them. But the structure of these substances is fundamentally different, hence the difference in chemical and physical properties. For example, the molecular formula C 4 H 10 can be written for two different substances: butane and isobutane.

We are talking about isomers- compounds that have the same composition and molecular weight. But the atoms in their molecules are located in a different order (branched and unbranched structure).

Concerning homology- this is a characteristic of such a carbon chain in which each next member can be obtained by adding one CH 2 group to the previous one. Each homologous series can be expressed by one general formula. And knowing the formula, it is easy to determine the composition of any of the members of the series. For example, methane homologues are described by the formula C n H 2n+2 .

As the “homologous difference” CH 2 is added, the bond between the atoms of the substance is strengthened. Let's take the homologous series of methane: its first four members are gases (methane, ethane, propane, butane), the next six are liquids (pentane, hexane, heptane, octane, nonane, decane), and then substances in the solid state of aggregation follow (pentadecane, eicosan, etc.). And the stronger the bond between carbon atoms, the higher the molecular weight, boiling and melting points of substances.

What classes of organic substances exist?

Organic substances of biological origin include:

proteins;
carbohydrates;
nucleic acids;
lipids.

The first three points can also be called biological polymers.

A more detailed classification of organic chemicals covers substances not only of biological origin.

The hydrocarbons are:

acyclic compounds:
- saturated hydrocarbons (alkanes);
- unsaturated hydrocarbons:
  - alkenes;
  - alkynes;
  - alkadienes.
cyclic compounds:
- carbocyclic compounds:
  - alicyclic;
  - aromatic.
- heterocyclic compounds.

There are also other classes of organic compounds in which carbon combines with substances other than hydrogen:

alcohols and phenols;
aldehydes and ketones;
carboxylic acids;
esters;
lipids;
carbohydrates:
- monosaccharides;
- oligosaccharides;
- polysaccharides.
- mucopolysaccharides.
amines;
amino acids;
proteins;
nucleic acids.

Formulas of organic substances by classes

Examples of organic substances

As you remember, in the human body, various kinds of organic substances are the basis of the foundations. These are our tissues and fluids, hormones and pigments, enzymes and ATP, and much more.

In the bodies of humans and animals, proteins and fats are prioritized (half of the dry weight of an animal cell is protein). In plants (about 80% of the dry mass of the cell) - for carbohydrates, primarily complex - polysaccharides. Including for cellulose (without which there would be no paper), starch.

Let's talk about some of them in more detail.

For example, about carbohydrates. If it were possible to take and measure the masses of all organic substances on the planet, it would be carbohydrates that would win this competition.

They serve as a source of energy in the body, are building materials for cells, and also carry out the supply of substances. Plants use starch for this purpose, and glycogen for animals.

In addition, carbohydrates are very diverse. For example, simple carbohydrates. The most common monosaccharides in nature are pentoses (including deoxyribose, which is part of DNA) and hexoses (glucose, which is well known to you).

Like bricks, at a large construction site of nature, polysaccharides are built from thousands and thousands of monosaccharides. Without them, more precisely, without cellulose, starch, there would be no plants. Yes, and animals without glycogen, lactose and chitin would have a hard time.

Let's look carefully at squirrels. Nature is the greatest master of mosaics and puzzles: from just 20 amino acids, 5 million types of proteins are formed in the human body. Proteins also have many vital functions. For example, construction, regulation of processes in the body, blood coagulation (there are separate proteins for this), movement, transport of certain substances in the body, they are also a source of energy, in the form of enzymes they act as a catalyst for reactions, provide protection. Antibodies play an important role in protecting the body from negative external influences. And if a discord occurs in the fine tuning of the body, antibodies, instead of destroying external enemies, can act as aggressors to their own organs and tissues of the body.

Proteins are also divided into simple (proteins) and complex (proteins). And they have properties inherent only to them: denaturation (destruction, which you have noticed more than once when you boiled a hard-boiled egg) and renaturation (this property is widely used in the manufacture of antibiotics, food concentrates, etc.).

Let's not ignore and lipids(fats). In our body, they serve as a reserve source of energy. As solvents, they help the course of biochemical reactions. Participate in the construction of the body - for example, in the formation of cell membranes.

And a few more words about such curious organic compounds as hormones. They are involved in biochemical reactions and metabolism. These small hormones make men men (testosterone) and women women (estrogen). They make us happy or sad (thyroid hormones play an important role in mood swings, and endorphins give a feeling of happiness). And they even determine whether we are “owls” or “larks”. Whether you're ready to study late or prefer to get up early and do your homework before school, it's not just your daily routine that decides, but some adrenal hormones as well.

Conclusion

The world of organic matter is truly amazing. It is enough to delve into its study just a little to take your breath away from the feeling of kinship with all life on Earth. Two legs, four or roots instead of legs - we are all united by the magic of mother nature's chemical laboratory. It causes carbon atoms to join in chains, react and create thousands of such diverse chemical compounds.

You now have a short guide to organic chemistry. Of course, not all possible information is presented here. Some points you may have to clarify on your own. But you can always use the route we have planned for your independent research.

You can also use the definition of organic matter, classification and general formulas of organic compounds and general information about them in the article to prepare for chemistry classes at school.

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organic matter - these are compounds that have a carbon atom in their composition. 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 is necessary to have an unprecedented "life force", which is inherent only in living biosystems. Therefore, it is impossible to carry out the synthesis of organic substances from minerals. 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 organic matter from mineral matter. After that, 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 for humans and animals. Most organic compounds are raw materials for various industries - food, chemical, light, pharmaceutical, etc.

Today, more than 30 million various 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 linked by single or multiple (double, triple) bonds.

They are characterized by the presence of C-C covalent bonds, as well as polar covalent bonds C-N, C-O, C-Hal, C-metal, etc. Reactions that take place with the participation of organic substances have some features in comparison with mineral ones. In the reactions of inorganic compounds, as a rule, ions participate. Often such reactions pass very quickly, sometimes instantly at the optimum temperature. Molecules are usually involved in reactions with. 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 in order to accelerate them, it is necessary to increase the temperature or use a catalyst (acid or base).

How are organic compounds formed in nature? Most of the 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 organic matter 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 the molecule of organic matter 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, the classes of hydrocarbons (the exception is 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 this compound.

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

inorganic substances divided by composition into simple and complex.

Simple substances consist of atoms of one chemical element and are divided into metals, non-metals, noble gases. Compounds are made up of atoms of different elements that are chemically bonded to each other.

Complex inorganic substances according to their composition and properties are divided into the following major classes: oxides, bases, acids, amphoteric hydroxides, salts.

oxides- these are 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 substances are divided into basic, amphoteric, acidic, which correspond to bases, amphoteric hydroxides, 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
Acid oxides- form non-metals with S.O. 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: for NO oxides 2 and ClO 2 there are no corresponding acid 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- oxides of non-metals with С.О.+1, +2 (СО, NO, N 2 O, SiO).
Foundations- these are complex substances consisting of metal atoms and one or more hydroxo groups (-OH). The general formula of the bases is: M (OH) y, where y is the number of hydroxo groups equal to the oxidation state of the metal M (usually +1 and +2). Bases are divided into soluble (alkali) and insoluble.
acids- (acid hydroxides) are complex substances consisting of hydrogen atoms that can be replaced by metal atoms, and acid residues. The general formula of acids: H x Ac, where Ac is an acid residue (from the English "acid" - acid), x is the number of hydrogen atoms equal to the charge of the ion of the acid residue.
Amphoteric hydroxides are complex substances that exhibit both the properties of acids and the properties of bases. Therefore, the formulas of amphoteric hydroxides can be written both in the form of acids and in the form of bases.
salt- 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 the complete replacement of hydrogen atoms in the acid molecule by metal atoms or the complete replacement of hydroxo groups in the base molecule by 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 an acid. To properly name acid salt, it is necessary to add the prefix hydro- or dihydro- to the name of the normal salt, depending on the number of hydrogen atoms that make up the acid salt. For example, KHCO 3 is potassium bicarbonate, KH 2 PO 4 is potassium dihydroorthophosphate. 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 the normal salt, depending on the number of OH groups that make up the salt. For example, (CuOH) 2 CO 3 is copper (II) hydroxocarbonate. It must be remembered that basic salts can only form bases containing two or more hydroxo groups.
double salts- in their composition there are 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- in their composition there are two different anions. For example, Ca(OCl)Cl.
Hydrate salts (crystal hydrates) - they include molecules of crystallization water. Example: Na 2 SO 4 10H 2 O.

Classification of organic substances

Compounds containing only hydrogen and carbon atoms are called hydrocarbons. Before starting this section, remember, to simplify the record, chemists do not paint carbons and hydrogens in chains, but do not forget that carbon forms four bonds, and if in the figure carbon is bound by two bonds, then it is bound by two more bonds to hydrogens, although the last and not indicated:

Depending on the structure of the carbon chain, organic compounds are divided into compounds with an open chain - 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 compounds: alicyclic And aromatic.

aromatic compounds the structure of molecules is based on flat carbon-containing cycles 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. These hydrocarbons are called unlimited(unsaturated), as opposed to marginal(saturated) containing only single bonds.

Pi-bond (π-bond) - a covalent bond formed by the overlap of p-atomic orbitals. In contrast to the sigma bond, which occurs when s-atomic orbitals overlap along the atomic bond line, pi bonds occur when p-atomic orbitals overlap on either side of the atomic bond line.

In the case of the formation of an aromatic system, for example, benzene C6H6, each of the six carbon atoms is in the 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 arises, extending to all carbon atoms of the benzene ring. Two regions of pi bonds of high electron density are formed on both sides of the plane of sigma bonds. 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.

Limit 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 C n H 2n - 2

Limit alicyclic hydrocarbons - cycloalkanes, their general formula is C n H 2n:

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

The atoms or groups of atoms that determine the most characteristic properties of a given class of substances are called functional groups.

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

A homologous series is a series of compounds belonging to the same class (homologues), 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

Halogen derivatives of hydrocarbons can be considered as products of substitution in hydrocarbons of one or more hydrogen atoms by halogen atoms. In accordance with this, saturated and unsaturated mono-, li-, tri- (generally poly-) halogen derivatives can exist. , ethers 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: 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 goes to the connection 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.
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 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 as well as 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 - an amino group -NH 2 and a carboxyl -COOH.

Other important organic compounds are known that have several different or identical functional groups, long linear chains associated with benzene rings. In such cases, a strict definition of whether a substance belongs to a particular class is impossible. These compounds are often isolated into specific groups of substances: carbohydrates, proteins, nucleic acids, antibiotics, alkaloids, etc. At present, 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 derivatives of hydrocarbons.

Nomenclature

Two nomenclature is used to name organic compounds - rational and systematic (IUPAC) and trivial names.

Compilation of names according to the IUPAC nomenclature:

1) The basis of the name of the compound is 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 (limiting, no multiple bonds);

Yong (in the presence of a double bond);

Ying (in the presence of a triple bond).

If there are several multiple bonds, then the number of such bonds (-diene, -triene, etc.) is indicated in the suffix, and after the suffix, the position of the multiple bond must be indicated in numbers, for example:

CH 3 -CH 2 -CH \u003d CH 2 CH 3 -CH \u003d CH -CH 3

butene-1 butene-2

CH 2 \u003d CH - CH \u003d CH 2

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

The title order is as follows:

1. Find the longest chain of C atoms.

2. Sequentially number the carbon atoms of the main chain, starting from the end closest to the branch.

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

Naming order

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

Chemical formulas- these are conditional images of the composition and structure of chemically individual substances through 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 various types are used.

Especially many types of formulas (the simplest, molecular, structural, projection, conformational, etc.) are used in the study of substances of molecular structure - most organic substances and a relatively small part of inorganic substances under ordinary conditions. Significantly fewer types of formulas (the simplest ones) 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.