Names

Organic chemistry for dummies: history, concepts

a branch of chemical science that studies hydrocarbons substances containing carbon and hydrogen, as well as various derivatives of these compounds, including atoms of oxygen, nitrogen and halogens. All such compounds are called organic.

Organic chemistry arose in the process of studying those substances that were extracted from plant and animal organisms, consisting mostly of organic compounds. This is what determined the purely historical name of such compounds (organism organic). Some technologies of organic chemistry arose in ancient times, for example, alcoholic and acetic acid fermentation, the use of organic dyes indigo and alizarin, leather tanning processes, etc. For a long time, chemists only knew how to isolate and analyze organic compounds, but could not obtain them artificially, As a result, the belief arose that organic compounds could only be produced by living organisms. Starting from the second half of the 19th century. methods of organic synthesis began to develop intensively, which made it possible to gradually overcome the established misconception. For the first time, the synthesis of organic compounds in the laboratory was carried out by F. Wöhler ne (during the period 1824-1828), by hydrolyzing cyanogen he obtained oxalic acid, previously isolated from plants, and by heating ammonium cyanate due to the rearrangement of the molecule ( cm. ISOMERIA) received urea, a waste product of living organisms (Fig. 1).

Rice. 1. FIRST SYNTHESIS OF ORGANIC COMPOUNDS

Many of the compounds found in living organisms can now be produced in the laboratory, and chemists are constantly obtaining organic compounds not found in nature.

The emergence of organic chemistry as an independent science occurred in the mid-19th century, when, thanks to the efforts of chemists, ideas about the structure of organic compounds began to form. The most noticeable role was played by the works of E. Frankland (defined the concept of valency), F. Kekule (established the tetravalency of carbon and the structure of benzene), A. Cooper (proposed the symbol of the valence line that connects atoms when depicting structural formulas, which is still used today), A.M. Butlerov (created a theory of chemical structure, which is based on the position that the properties of a compound are determined not only by its composition, but also by the order in which the atoms are connected).

The next important stage in the development of organic chemistry is associated with the work of J. Van't Hoff, who changed the very way of thinking of chemists, proposing to move from a flat image of structural formulas to the spatial arrangement of atoms in a molecule, as a result, chemists began to consider molecules as volumetric bodies.

Ideas about the nature of chemical bonds in organic compounds were first formulated by G. Lewis, who suggested that atoms in a molecule are connected by electrons: a pair of generalized electrons creates a simple bond, and two or three pairs form a double and triple bond, respectively. By considering the distribution of electron density in molecules (for example, its displacement under the influence of electronegative atoms O, Cl, etc.), chemists were able to explain the reactivity of many compounds, i.e. the possibility of their participation in certain reactions.

Taking into account the properties of the electron determined by quantum mechanics led to the development of quantum chemistry, using the concept of molecular orbitals. Now quantum chemistry, which has demonstrated its predictive power in many examples, is successfully collaborating with experimental organic chemistry.

A small group of carbon compounds is not classified as organic: carbonic acid and its salts (carbonates), hydrocyanic acid HCN and its salts (cyanides), metal carbides and some other carbon compounds that are studied in inorganic chemistry.

The main feature of organic chemistry is the exceptional variety of compounds that arose due to the ability of carbon atoms to combine with each other in almost unlimited quantities, forming molecules in the form of chains and cycles. Even greater diversity is achieved through the inclusion of oxygen, nitrogen, etc. atoms between the carbon atoms. The phenomenon of isomerism, due to which molecules with the same composition can have different structures, further increases the diversity of organic compounds. More than 10 million organic compounds are now known, and their number increases annually by 200-300 thousand.

Classification of organic compounds. 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 not able to attach anything) are chains of carbon atoms connected by simple bonds and surrounded by hydrogen atoms (Fig. 1). 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.

Rice. 2. SATURATED HYDROCARBONS

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 (Fig. 3).

Rice. 4. EXAMPLES OF SATURATED HYDROCARBONS with functional groups

All hydrocarbon derivatives shown form large groups of organic compounds: alcohols, aldehydes, acids, halogen derivatives, etc. Since the hydrocarbon part of the molecule has very low reactivity, the chemical behavior of such compounds is determined by the chemical properties of the functional groups OH, -COOH, -Cl, -NO2, etc.

2. Unsaturated hydrocarbons have the same main chain structure options as saturated ones, but contain double or triple bonds between carbon atoms (Fig. 6). The simplest unsaturated hydrocarbon is ethylene.

Rice. 6. UNSATURATED HYDROCARBONS

Most typical for unsaturated hydrocarbons is addition via a multiple bond (Fig. 8), which makes it possible to synthesize a variety of organic compounds on their basis.

Rice. 8. ADDING REAGENTS to unsaturated compounds via multiple bonds

Another important property of compounds with double bonds is their ability to polymerize (Fig. 9), the double bonds open, resulting in the formation of long hydrocarbon chains.

Rice. 9. POLYMERIZATION OF ETHYLENE

The introduction of the previously mentioned functional groups into the composition of unsaturated hydrocarbons, as in the case of saturated hydrocarbons, leads to the corresponding derivatives, which also form large groups of corresponding organic compounds - unsaturated alcohols, aldehydes, etc. (Fig. 10).

Rice. 10. UNSATURATED HYDROCARBONS with functional groups

For the compounds shown, simplified names are given; the exact position in the molecule of multiple bonds and functional groups is indicated in the name of the compound, which is compiled according to specially developed rules.

The chemical behavior of such compounds is determined by both the properties of multiple bonds and the properties of functional groups.

II. CARBOCYCLIC HYDROCARBONS contain cyclic fragments formed only by carbon atoms. They form two large groups.

1. Alicyclic (i.e. both aliphatic and cyclic at the same time) hydrocarbons. In these compounds, cyclic fragments can contain both simple and multiple bonds; in addition, the compounds can contain several cyclic fragments; the prefix “cyclo” is added to the name of these compounds; the simplest alicyclic compound is cyclopropane (Fig. 12).

Rice. 12. ALICYCLIC HYDROCARBONS

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 (Fig. 14).

Rice. 14. CYCLE CONNECTION OPTIONS in alicyclic compounds: spirocycles, bicycles and frameworks. The names of spiro- and bicyclic compounds indicate the aliphatic hydrocarbon that contains the same total number carbon atoms, for example, the spiro cycle shown in the figure contains eight carbon atoms, so its name is based on the word “octane”. In adamantane, the atoms are arranged in the same way as in crystal lattice diamond, which determined its name ( Greek adamantos diamond)

Many mono- and bicyclic alicyclic hydrocarbons, as well as adamantane derivatives, are part of oil; their general name is naphthenes.

In terms of their chemical properties, alicyclic hydrocarbons are close to the corresponding aliphatic compounds, however, they have an additional property associated with their cyclic structure: small rings (36-membered) are capable of opening, adding some reagents (Fig. 15).

Rice. 15. REACTIONS OF ALICYCLIC HYDROCARBONS, occurring with the opening of the cycle

The introduction of various functional groups into the composition of alicyclic hydrocarbons leads to the corresponding derivatives: alcohols, ketones, etc. (Fig. 16).

Rice. 16. ALICYCLIC HYDROCARBONS with functional groups

2. The second large group of carbocyclic compounds is formed by aromatic hydrocarbons benzene type, i.e. containing one or more benzene rings (there are also aromatic compounds of the non-benzene type ( cm. AROMATICITY). Moreover, they may also contain fragments of saturated or unsaturated hydrocarbon chains (Fig. 18).

Rice. 18. AROMATIC HYDROCARBONS.

There is a group of compounds in which the benzene rings are, as it were, soldered together; these are the so-called condensed aromatic compounds (Fig. 20).

Rice. 20. CONDENSED AROMATIC COMPOUNDS

Many aromatic compounds, including condensed ones (naphthalene and its derivatives), are part of oil; the second source of these compounds is coal tar.

Benzene rings are not characterized by addition reactions, which take place with great difficulty and under harsh conditions; the most typical reactions for them are substitution reactions of hydrogen atoms (Fig. 21).

Rice. 21. SUBSTITUTION REACTIONS hydrogen atoms in the aromatic ring.

In addition to the functional groups (halogen, nitro and acetyl groups) attached to the benzene ring (Fig. 21), other groups can also be introduced, resulting in corresponding derivatives of aromatic compounds (Fig. 22), forming large classes of organic compounds - phenols, aromatic amines, etc.

Rice. 22. AROMATIC COMPOUNDS with functional groups. Compounds in which the ne-OH group is connected to a carbon atom in the aromatic ring are called phenols, in contrast to aliphatic compounds, where such compounds are called alcohols.

III. HETEROCYCLIC HYDROCARBONS contain in the cycle (in addition to carbon atoms) various heteroatoms: O, N, S. The cycles can be of different sizes, contain both simple and multiple bonds, as well as hydrocarbon substituents attached to the heterocycle. There are options when the heterocycle is “fused” to the benzene ring (Fig. 24).

Rice. 24. 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 diversity of compounds of this class increases further due to the fact that the heterocycle can contain two or more heteroatoms in the ring (Fig. 26).

Rice. 26. HETEROCYCLES with two or more heteroatoms.

Just like the previously considered aliphatic, alicyclic and aromatic hydrocarbons, heterocycles can contain various functional groups (-OH, -COOH, -NH 2, etc.), and the heteroatom in the ring in some cases can also be considered as functional group, since it is able to take part in the corresponding transformations (Fig. 27).

Rice. 27. HETEROATOM N as a functional group. In the name of the last compound, the letter “N” indicates which atom the methyl group is attached to.

Reactions of organic chemistry. Unlike reactions in inorganic chemistry, where ions react at high speed (sometimes instantaneously), reactions of organic compounds usually involve molecules containing covalent bonds. As a result, all interactions proceed much more slowly than in the case of ionic compounds (sometimes tens of hours), often at elevated temperatures and in the presence of substances accelerating the process - catalysts. Many reactions proceed through intermediate steps or in several parallel directions, which leads to a noticeable decrease in the yield of the desired compound. Therefore, when describing reactions, instead of equations with numerical coefficients (which is traditionally accepted in inorganic chemistry), reaction schemes are often used without indicating stoichiometric ratios.

The names of large classes of organic reactions are often associated with chemical nature the active reagent or the type of organic group introduced into the compound:

a) halogenation introduction of a halogen atom (Fig. 8, first reaction scheme),

b) hydrochlorination, i.e. exposure to HCl (Fig. 8, second reaction scheme)

c) nitration introduction of the nitro group NO 2 (Fig. 21, second direction of the reaction)

d) metalation introduction of a metal atom (Fig. 27, first stage)

a) alkylation introduction of an alkyl group (Fig. 27, second stage)

b) acylation introduction of the acyl group RC(O)- (Fig. 27, second stage)

Sometimes the name of the reaction indicates the features of the rearrangement of the molecule, for example, cyclization ring formation, decyclization ring opening (Fig. 15).

A large class is formed by condensation reactions ( lat. condensatio compaction, thickening), in which the formation of new C-C bonds occurs with the simultaneous formation of easily removable inorganic or organic compounds. Condensation accompanied by the release of water is called dehydration. Condensation processes can also occur intramolecularly, that is, within one molecule (Fig. 28).

Rice. 28. CONDENSATION REACTIONS

In the condensation of benzene (Fig. 28), the role of functional groups is played by C-H fragments.

The classification of organic reactions is not strict, for example, shown in Fig. 28 intramolecular condensation of maleic acid can also be attributed to cyclization reactions, and condensation of benzene to dehydrogenation.

There are intramolecular reactions, somewhat different from condensation processes, when a fragment (molecule) is cleaved off as an easily removable compound without the obvious participation of functional groups. Such reactions are called elimination ( lat. eliminare expel), while new connections are formed (Fig. 29).

Rice. 29. ELIMINATION REACTIONS

Options are possible when several types of transformations are realized together, which is shown below using the example of a compound in which different types of processes occur when heated. During thermal condensation of mucus acid (Fig. 30), intramolecular dehydration and subsequent elimination of CO 2 take place.

Rice. 30. CONVERSION OF MUCICOAL ACID(obtained from acorn syrup) into pyrosmucic acid, so named because it is obtained by heating mucus. Pyroslitic acid is a heterocyclic compound of furan with an attached functional (carboxyl) group. During the reaction they break apart S-O connections, С-Н and new ones are formed S-N connections and S-S.

There are reactions in which the molecule is rearranged without changing its composition ( cm. ISOMERIZATION).

Research methods in organic chemistry. Modern organic chemistry, in addition to elemental analysis, uses many physical methods research. Complex mixtures of substances are separated into their constituent components using chromatography, which is based on the movement of solutions or vapors of substances through a sorbent layer. Infrared spectroscopy transmission of infrared (thermal) rays through a solution or through a thin layer of a substance allows one to determine the presence of certain molecular fragments in a substance, for example, groups C 6 H 5, C=O, NH 2, etc.

Ultraviolet spectroscopy, also called electronic, carries information about the electronic state of the molecule; it is sensitive to the presence of multiple bonds and aromatic fragments in the substance. Analysis of crystalline substances using X-rays (X-ray diffraction analysis) gives a three-dimensional picture of the arrangement of atoms in the molecule, similar to those, which is shown in the animated drawings above, in other words, allows you to see the structure of the molecule with your own eyes.

Spectral method nuclear magnetic resonance, based on the resonant interaction of the magnetic moments of nuclei with the external magnetic field, makes it possible to distinguish atoms of one element, for example, hydrogen, located in different fragments of the molecule (in the hydrocarbon skeleton, in the hydroxyl, carboxyl or amino group), and also to determine their quantitative ratio. A similar analysis is also possible for nuclei C, N, F, etc. All these modern physical methods have led to intensive research in organic chemistry; it has become possible to quickly solve problems that previously took for many years.

Some sections of organic chemistry have emerged as large independent areas, for example, the chemistry of natural substances, medicines, dyes, polymer chemistry. In the middle of the 20th century. The chemistry of organoelement compounds began to develop as an independent discipline that studies substances containing a C-E bond, where the symbol E denotes any element (except carbon, hydrogen, oxygen, nitrogen and halogens). There have been great advances in biochemistry, which studies the synthesis and transformations of organic substances occurring in living organisms. The development of all these areas is based on the general laws of organic chemistry.

Modern industrial organic synthesis includes a wide range of different processes these are, first of all, large-scale production oil and gas refining and the production of motor fuels, solvents, coolants, lubricating oils, in addition, the synthesis of polymers, synthetic fibers, various resins for coatings, adhesives and enamels. Small-scale production includes the production of medicines, vitamins, dyes, food additives and aromatic substances.

Mikhail Levitsky

LITERATURE Karrer P. Organic chemistry course, trans. from German, GNTI Khimlit, L., 1962
Cram D., Hammond J. Organic chemistry, trans. from English, Mir, M., 1964

If you have entered the university, but by this time have not understood this difficult science, we are ready to reveal a few secrets to you and help you study organic chemistry from scratch (for dummies). All you have to do is read and listen.

Basics of organic chemistry

Organic chemistry is distinguished as a separate subtype due to the fact that the object of its study is everything that contains carbon.

Organic chemistry is a branch of chemistry that deals with the study of carbon compounds, the structure of such compounds, their properties and methods of joining.

As it turned out, carbon most often forms compounds with the following elements - H, N, O, S, P. By the way, these elements are called organogens.

Organic compounds, the number of which today reaches 20 million, are very important for the full existence of all living organisms. However, no one doubted it, otherwise the person would have simply thrown the study of this unknown into the back burner.

The goals, methods and theoretical concepts of organic chemistry are presented as follows:

Separation of fossil, animal or plant materials into individual substances;
Purification and synthesis of various compounds;
Identification of the structure of substances;
Determination of the mechanics of chemical reactions;
Finding the relationship between the structure and properties of organic substances.

A little history of organic chemistry

You may not believe it, but back in ancient times, the inhabitants of Rome and Egypt understood something about chemistry.

As we know, they used natural dyes. And often they had to use not a ready-made natural dye, but extract it by isolating it from a whole plant (for example, alizarin and indigo contained in plants).

We can also remember the culture of drinking alcohol. The secrets of producing alcoholic beverages are known in every nation. Moreover, many ancient peoples knew recipes for preparing “ hot water» from starch- and sugar-containing products.

This went on for many, many years, and only in the 16th and 17th centuries did some changes and small discoveries begin.

In the 18th century, a certain Scheele learned to isolate malic, tartaric, oxalic, lactic, gallic and citric acid.

Then it became clear to everyone that the products that had been isolated from plant or animal raw materials had a lot of common features. At the same time, they were very different from inorganic compounds. Therefore, the servants of science urgently needed to highlight them in separate class This is how the term “organic chemistry” appeared.

Despite the fact that organic chemistry itself as a science appeared only in 1828 (it was then that Mr. Wöhler managed to isolate urea by evaporating ammonium cyanate), in 1807 Berzelius introduced the first term into the nomenclature in organic chemistry for dummies:

The branch of chemistry that studies substances obtained from organisms.

The next important step in the development of organic chemistry is the theory of valence, proposed in 1857 by Kekule and Cooper, and the theory of chemical structure of Mr. Butlerov from 1861. Even then, scientists began to discover that carbon was tetravalent and capable of forming chains.

In general, since then, science has regularly experienced shocks and excitement thanks to new theories, discoveries of chains and compounds, which allowed the active development of organic chemistry.

Science itself emerged due to the fact that scientific and technological progress was unable to stand still. He went on and on, demanding new solutions. And when there was no longer enough coal tar in industry, people simply had to create a new organic synthesis, which over time grew into the discovery of an incredibly important substance, which to this day is more expensive than gold - oil. By the way, it was thanks to organic chemistry that its “daughter” was born - a subscience that was called “petrochemistry”.

But this is a completely different story that you can study for yourself. Next, we invite you to watch a popular science video about organic chemistry for dummies:

Well, if you have no time and urgently need help professionals, you always know where to find them.

ORGANIC CHEMISTRY

Basic concepts of organic chemistry

Organic chemistry – is the branch of chemistry that studies carbon compounds. Carbon stands out among all elements in that its atoms can bond with each other in long chains or cycles. It is this property that allows carbon to form millions of compounds that are studied in organic chemistry.

Theory of chemical structure by A. M. Butlerov.

The modern theory of the structure of molecules explains both the huge number of organic compounds and the dependence of the properties of these compounds on their chemical structure. It also fully confirms the basic principles of the theory of chemical structure developed by the outstanding Russian scientist A.M. Butlerov.

The main provisions of this theory (sometimes called structural):

1) atoms in molecules are connected to each other in a certain order by chemical bonds according to their valency;

2) the properties of a substance are determined not only by its qualitative composition, but also by its structure and mutual influence of atoms.

3) by the properties of a substance one can determine its structure, and by its structure - properties.

An important consequence of the theory of structure was the conclusion that every organic compound must have one chemical formula reflecting its structure. This conclusion theoretically substantiated the already well-known phenomenon isomerism, - the existence of substances with the same molecular composition, but having different properties.

Isomers– substances that are identical in composition but different in structure

Structural formulas. The existence of isomers required the use of not only simple molecular formulas, but also structural formulas reflecting the bond order of the atoms in the molecule of each isomer. In structural formulas, a covalent bond is indicated by a dash. Each dash represents a common electron pair that links atoms in a molecule.

Structural formula - conventional representation of the structure of a substance, taking into account chemical bonds.

Classification of organic compounds.

To classify organic compounds by type and construct their names, it is customary to distinguish the carbon skeleton and functional groups in the molecule of an organic compound.

Carbon skeleton represents a sequence of chemically bonded carbon atoms.

Types of Carbon Skeletons. Carbon skeletons are divided into acyclic(not containing loops) , cyclic and heterocyclic.

In a heterocyclic skeleton, one or more atoms other than carbon are included in the carbon cycle. Within the carbon skeletons themselves, individual carbon atoms must be classified according to the number of carbon atoms chemically bonded to them. If a given carbon atom is bonded to one carbon atom, then it is called primary, with two - secondary, three - tertiary and four - quaternary.

Since carbon atoms can form not only single, but also multiple (double and triple) bonds with each other, then compounds containing only single C––C bonds are called saturated, compounds with multiple bonds are called unsaturated.

Hydrocarbons– compounds in which carbon atoms are bonded only to hydrogen atoms.

Hydrocarbons are recognized as parent compounds in organic chemistry. Various compounds are considered as hydrocarbon derivatives obtained by introducing functional groups into them.

Functional groups. Most organic compounds, in addition to carbon and hydrogen atoms, contain atoms of other elements (not included in the skeleton). These atoms or their groups, which largely determine the chemical and physical properties of organic compounds, are called functional groups.

The functional group turns out to be the final sign by which compounds belong to one class or another.

The most important functional groups

Functional groups		Connection class
designation	Name	Connection class
F, -Cl, - Br, - I		halogenated hydrocarbons
	hydroxyl	alcohols, phenols
	carbonyl	aldehydes, ketones
	carboxyl	carboxylic acids
	amino group
	nitro group	nitro compounds

Homologous series. To describe organic compounds, the concept of homologous series is useful. Homologous series form compounds that differ from each other by the -CH 2 - group and have similar chemical properties. CH 2 groups are called homological difference .

An example of a homologous series is a series of saturated hydrocarbons (alkanes). Its simplest representative is methane CH 4. Homologues of methane are: ethane C 2 H 6, propane C 3 H 8, butane C 4 H 10, pentane C 5 H 12, hexane C 6 H 14, heptane C 7 H 16, etc. The formula of any subsequent homologue can be obtained by adding a homologous difference to the formula of the previous hydrocarbon.

The composition of the molecules of all members of the homologous series can be expressed by one general formula. For the considered homologous series of saturated hydrocarbons, this formula will be C n H 2n+2, where n is the number of carbon atoms.

Nomenclature of organic compounds. Currently, the systematic nomenclature of IUPAC (IUPAC - International Union of Pure and Applied Chemistry) is recognized.

According to IUPAC rules, the name of an organic compound is constructed from the name of the main chain, which forms the root of the word, and the names of the functions used as prefixes or suffixes.

To correctly construct the name, it is necessary to select the main chain and number the carbon atoms in it.

The numbering of carbon atoms in the main chain begins from the end of the chain closer to which the senior group is located. If there are several such possibilities, then the numbering is carried out in such a way that either the multiple bond or another substituent present in the molecule receives the lowest number.

In carbocyclic compounds, numbering begins from the carbon atom at which the highest characteristic group is located. If it is impossible to choose an unambiguous numbering, then the cycle is numbered so that the substituents have the lowest numbers.

In the group of cyclic hydrocarbons, aromatic hydrocarbons are especially distinguished, which are characterized by the presence of a benzene ring in the molecule. Some well-known representatives of aromatic hydrocarbons and their derivatives have trivial names, the use of which is permitted by IUPAC rules: benzene, toluene, phenol, benzoic acid.

The C 6 H 5 - radical formed from benzene is called phenyl, not benzyl. Benzyl is the C 6 H 5 CH 2 - radical formed from toluene.

Naming an organic compound. The name of the compound is based on the root word denoting saturated hydrocarbon with the same number of atoms as the main chain ( met-, et-, prop-, but-, pent: hex- etc.). Then follows a suffix characterizing the degree of saturation, -an, if there are no multiple bonds in the molecule, -en in the presence of double bonds and -in for triple bonds (eg pentane, pentene, pentine). If there are several multiple bonds in a molecule, then the suffix indicates the number of such bonds: - di en, - three en, and after the suffix the position of the multiple bond must be indicated in Arabic numerals (for example, butene-1, butene-2, butadiene-1,3):

Next, the suffix contains the name of the oldest characteristic group in the molecule, indicating its position with a number. Other substituents are designated using prefixes. Moreover, they are listed not in order of seniority, but alphabetically. The position of the substituent is indicated by the number before the prefix, for example: 3 -methyl; 2 -chlorine, etc. If a molecule has several identical substituents, then before the name of the corresponding group their number is indicated with a word (for example, di methyl-, trichlor-, etc.). All numbers in the names of molecules are separated from words by a hyphen, and from each other by commas. Hydrocarbon radicals have their own names.

Saturated hydrocarbon radicals:

Unsaturated hydrocarbon radicals:

Aromatic hydrocarbon radicals:

Let's take the following connection as an example:

1) The choice of chain is unambiguous, therefore, the root of the word is pent; followed by the suffix − en, indicating the presence of a multiple connection;

2) the numbering order ensures that the senior group (-OH) has the smallest number;

3) the full name of the compound ends with a suffix indicating senior group(in this case the suffix is ol indicates the presence of a hydroxyl group); The position of the double bond and hydroxyl group is indicated by numbers.

Therefore, the given compound is called penten-4-ol-2.

Trivial nomenclature is a collection of unsystematic historical names of organic compounds (example: acetone, acetic acid, formaldehyde, etc.).

Isomerism.

It was shown above that the ability of carbon atoms to form four covalent bonds, including with other carbon atoms, opens up the possibility of the existence of several compounds of the same elemental composition - isomers. All isomers are divided into two large classes - structural isomers and spatial isomers.

Structural are called isomers with different orders of atoms.

Spatial isomers have identical substituents on each carbon atom and they differ only in their relative location in space.

Structural isomers. In accordance with the above classification of organic compounds by type, three groups are distinguished among structural isomers:

1) compounds differing in carbon skeletons:

2) compounds that differ in the position of the substituent or multiple bond in the molecule:

3) compounds containing various functional groups and belonging to various classes of organic compounds:

Spatial isomers(stereoisomers). Stereoisomers can be divided into two types: geometric isomers and optical isomers.

Geometric isomerism characteristic of compounds containing a double bond or ring. In such molecules it is often possible to draw a conventional plane in such a way that the substituents on different carbon atoms can be on the same side (cis-) or on opposite sides (trans-) of this plane. If a change in the orientation of these substituents relative to the plane is possible only due to the breaking of one of the chemical bonds, then they speak of the presence of geometric isomers. Geometric isomers differ in their physical and chemical properties.

Mutual influence of atoms in a molecule.

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

Electronic effects are called shifts in electron density in a molecule under the influence of substituents.

Atoms connected by a polar bond carry partial charges, denoted by the Greek letter delta (δ). An atom that “pulls” the electron density of the δ bond in its direction acquires a negative charge δ − . When considering a pair of atoms linked by a covalent bond, the more electronegative atom is called the electron acceptor. Its partner in the δ bond will accordingly have an electron density deficit of equal magnitude, i.e., a partial positive charge δ +, and will be called an electron donor.

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

The inductive effect is transmitted through the circuit with attenuation. The direction of shift of the electron density of all σ bonds is indicated by straight arrows.

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

Electron-withdrawing substituents, i.e. an atom or group of atoms that shifts the electron density of a σ bond from a carbon atom exhibits a negative inductive effect (−I effect).

Electron-donating substituents, i.e. an atom or group of atoms that shift electron density to a carbon atom, exhibit a positive inductive effect (+I-effect).

The I-effect is exhibited by aliphatic hydrocarbon radicals, i.e. alkyl radicals (methyl, ethyl, etc.).

Most functional groups exhibit an -I effect: halogens, amino group, hydroxyl, carbonyl, carboxyl groups.

The inductive effect also manifests itself in the case when the bonded carbon atoms differ in their state of hybridization. Thus, in a propene molecule, the methyl group exhibits a +I-effect, since the carbon atom in it is in the sp3-hybridized state, and the sp2-hybridized atom (at a double bond) acts as an electron acceptor, since it has a higher electronegativity:

When the inductive effect of a methyl group is transferred to a double bond, the mobile π bond is first influenced by it.

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

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

Classification of organic reactions

− Classification according to the type of chemical bond breaking in reacting particles. Of these, two can be distinguished large groups reactions - radical and ionic.

Radical reactions - These are processes that occur with homolytic cleavage of a covalent bond. In homolytic cleavage, the pair of electrons forming the bond is divided in such a way that each of the resulting particles receives one electron. As a result of homolytic cleavage, free radicals are formed:

A neutral atom or particle with an unpaired electron is calledfree radical.

Ionic reactions- these are processes that occur with heterolytic cleavage of covalent bonds, when both bond electrons remain with one of the previously bonded particles:

As a result of heterolytic bond cleavage, charged particles are obtained: nucleophilic and electrophilic.

A nucleophilic particle (nucleophile) is a particle that has a pair of electrons in the outer electron level. Due to a pair of electrons, a nucleophile is able to form a new covalent bond.

An electrophilic particle (electrophile) is a particle that has an unfilled outer electron level. An electrophile presents unfilled, vacant orbitals for the formation of a covalent bond due to the electrons of the particle with which it interacts.

−Classification according to the composition and structure of starting substances and reaction products. In organic chemistry, all structural changes are considered relative to the carbon atom (or atoms) involved in the reaction. The most common types of transformations are:

accession

substitution

cleavage (elimination)

polymerization

In accordance with the above, the chlorination of methane under the influence of light is classified as radical substitution, the addition of halogens to alkenes as electrophilic addition, and the hydrolysis of alkyl halides as nucleophilic substitution.

Organic chemistry is the science of organic compounds and their transformations. The term "organic chemistry" was introduced by the Swedish scientist J. Berzelius in early XIX V. Previously, substances were classified according to their source. Therefore, in the 18th century. distinguished three chemistry: “plant”, “animal” and “mineral”. At the end of the 18th century. French chemist A. Lavoisier showed that substances obtained from plant and animal organisms (hence their name “organic compounds”), unlike mineral compounds, contain only a few elements: carbon, hydrogen, oxygen, nitrogen, and sometimes phosphorus and sulfur. Since carbon is certainly present in all organic compounds, organic chemistry has been developed since the mid-19th century. often called the chemistry of carbon compounds.

The ability of carbon atoms to form long unbranched and branched chains, as well as rings and attach other elements or their groups to them is the reason for the diversity of organic compounds and the fact that they significantly exceed inorganic compounds in number. Currently, about 7 million organic compounds are known, and about 200 thousand inorganic compounds.

After the works of A. Lavoisier and until the middle of the 19th century. Chemists conducted an intensive search for new substances in natural products and developed new methods for their transformation. Particular attention was paid to determining the elemental composition of compounds, deducing their molecular formulas and establishing the dependence of the properties of compounds on their composition. It turned out that some compounds, having the same composition, differ in their properties. Such compounds were called isomers (see Isomerism). It has been observed that many compounds in chemical reactions exchange groups of elements that remain unchanged. These groups were called radicals, and the doctrine that tried to present organic compounds as consisting of such radicals was called radical theory. In the 40-50s. XIX century attempts were made to classify organic compounds according to the type of inorganic ones (for example, ethyl alcohol C2H5-O-H and diethyl ether C2H5-O-C2H5 were classified as water N-O-N). However, all these theories, as well as the determination of the elemental composition and molecular weight of organic compounds, were not yet based on a solid foundation of a sufficiently developed atomic-molecular theory. Therefore, in organic chemistry there was a discrepancy in the ways of recording the composition of substances, and even such a simple compound as acetic acid was represented by different empirical formulas: C4H4o4, C8H804, CrH402, of which only the last was correct.

Only after the Russian scientist A.M. Butlerov created the theory of chemical structure (1861) did organic chemistry receive a solid scientific foundation, which ensured its rapid development in the future. The prerequisites for its creation were the successes in the development of atomic-molecular science, ideas about valence and chemical bonds in the 50s. XIX century This theory made it possible to predict the existence of new compounds and their properties. Scientists have begun the systematic chemical synthesis of scientifically predicted organic compounds that do not occur in nature. Thus, organic chemistry became largely the chemistry of artificial compounds.

In the first half of the 19th century. Organic chemists were engaged in the synthesis and study mainly of alcohols, aldehydes, acids and some other compounds - alicyclic and benzenoid (see Aliphatic compounds; Alicyclic compounds). Derivatives of chlorine, iodine and bromine, as well as the first organometallic compounds (see Organoelement Compounds) were synthesized from substances not found in nature. Coal tar became a new source of organic compounds. Benzene, naphthalene, phenol and other benzenoid compounds, as well as heterocyclic compounds - quinoline, pyridine, were isolated from it.

In the second half of the 19th century. hydrocarbons, alcohols, acids with branched carbon chains were synthesized, the study of the structure and synthesis of compounds important in in practical terms(indigo, isoprene, sugar). The synthesis of sugars (see Carbohydrates) and many other compounds became possible after the emergence of stereochemistry, which continued the development of the theory of chemical structure. Organic chemistry of the first half of the 19th century. was closely connected with pharmacy - the science of medicinal substances.

In the second half of the 19th century. a strong alliance of organic chemistry with industry, primarily aniline dyes, emerged. Chemists were tasked with deciphering the structure of known natural dyes (alizarin, indigo, etc.), creating new dyes, and developing technically acceptable methods for their synthesis. So, in the 70s and 80s. XIX century applied organic chemistry arose.

The end of the 19th - the beginning of the 20th century. were marked by the creation of new directions in the development of organic chemistry. On an industrial scale, the richest source of organic compounds, oil, began to be used, and this was associated with the rapid development of the chemistry of alicyclic compounds and the chemistry of hydrocarbons in general (see Petrochemistry). Practically important catalytic methods for the transformation of organic compounds appeared, created by P. Sabatier in France, V. N. Ipatiev and later N. D. Zelinsky in Russia (see Catalysis). The theory of chemical structure has deepened significantly as a result of the discovery of the electron and the creation of electronic ideas about the structure of atoms and molecules. Powerful methods for physicochemical and physical studies of molecules, primarily X-ray diffraction analysis, were discovered and developed. This made it possible to clarify the structure, and therefore, understand the properties and facilitate the synthesis of a huge number of organs! ical compounds.

Since the beginning of the 30s. XX century in connection with the emergence of quantum mechanics, computational methods appeared that made it possible to draw conclusions about the structure and properties of organic compounds by calculation (see Quantum chemistry).

Among the new areas of chemical science is the chemistry of organic fluorine derivatives, which have received great attention practical significance. In the 50s XX century the chemistry of price compounds (ferrocene, etc.) arose, representing a connecting link between organic and inorganic chemistry. The use of isotopes has become firmly established in the practice of organic chemists. Back at the beginning of the 20th century. freely existing organic radicals were discovered (see Free Radicals), and subsequently the chemistry of incompletely valent organic compounds was created - carbonium ions, carbanions, radical ions, molecular ions (see Ions). In the 60s Entirely new types of organic compounds were synthesized, such as catenanes, in which individual cyclic molecules are linked to each other, much like the five intertwined Olympic rings.

Organic chemistry in the 20th century. has acquired enormous practical importance, especially for oil refining, polymer synthesis, synthesis and physiological study active substances. As a result, such areas as petrochemistry, polymer chemistry, and bioorganic chemistry emerged from organic chemistry into independent disciplines.

Modern organic chemistry has complex structure. Its core is preparative organic chemistry, which deals with the isolation from natural products and the artificial preparation of individual organic compounds, as well as the creation of new methods for their preparation. It is impossible to solve these problems without relying on analytical chemistry, which makes it possible to judge the degree of purification, homogeneity (homogeneity) and individuality of organic compounds, providing data on their composition and structure in an isolated state, as well as when they act as starting substances, intermediate and final reaction products. For this purpose, analytical chemistry uses various chemical, physicochemical and physical research methods. A conscious approach to solving problems facing preparative and analytical organic chemistry is ensured by relying on theoretical organic chemistry. The subject of this science is further development theories of structure, as well as the formulation of dependencies between the composition and structure of organic compounds and their properties, between the conditions for the occurrence of organic reactions and their speed and achievement chemical equilibrium. The objects of theoretical organic chemistry can be both non-reacting compounds and compounds during their transformations, as well as intermediate, unstable formations that arise during reactions.

This structure of organic chemistry was formed under the influence of various factors, the most important of which were and remain the needs of practice. This explains, for example, the fact that in modern organic chemistry the chemistry of heterocyclic compounds is rapidly developing, closely related to such applied areas as the chemistry of synthetic and natural medicines.

From all the variety of chemical compounds most(over four million) contains carbon. Almost all of them are organic substances. Organic compounds found in nature, such as carbohydrates, proteins, vitamins, they play important role in the life of animals and plants. Many organic matter and their mixtures (plastics, rubber, oil, natural gas and others) have great value for the development of the country's national economy.

The chemistry of carbon compounds is called organic chemistry. This is how the great Russian organic chemist A.M. defined the subject of organic chemistry. Butlerov. However, not all carbon compounds are considered organic. Such simple substances as carbon monoxide (II) CO, carbon dioxide CO2, carbonic acid H2CO3 and its salts, for example, CaCO3, K2CO3, are classified as inorganic compounds. Organic substances may contain other elements besides carbon. The most common are hydrogen, halogens, oxygen, nitrogen, sulfur and phosphorus. There are also organic substances containing other elements, including metals.

2. Structure of the carbon atom (C), structure of its electronic shell

2.1 The importance of the carbon atom (C) in the chemical structure of organic compounds

CARBON (lat. Carboneum), C, chemical element subgroup IVa of the periodic table; atomic number 6, atomic mass 12.0107, refers to non-metals. Natural carbon consists of two stable nuclides - 12C (98.892% by mass) and 13C (1.108%) and one unstable - C with a half-life of 5730 years.

Prevalence in nature. Carbon accounts for 0.48% of the mass of the earth's crust, in which it ranks 17th among other elements in content. The main carbon-containing rocks are natural carbonates (limestones and dolomites); the amount of carbon in them is about 9,610 tons.

In a free state, carbon is found in nature in the form of fossil fuels, as well as in the form of minerals - diamond and graphite. About 1013 tons of carbon are concentrated in such combustible minerals as coal and brown coal, peat, shale, bitumen, which form powerful accumulations in the bowels of the Earth, as well as in natural combustible gases. Diamonds are extremely rare. Even diamond-bearing rocks (kimberlites) contain no more than 9-10% diamonds weighing, as a rule, no more than 0.4 g. Large diamonds found are usually given a special name. The largest diamond "Cullinan" weighing 621.2 g (3106 carats) was found in South Africa(Transvaal) in 1905, and the largest Russian diamond “Orlov” weighing 37.92 g (190 carats) was in Siberia in the mid-17th century.

Black-gray, opaque, greasy to the touch with a metallic sheen, graphite is an accumulation of flat polymer molecules made of carbon atoms, loosely layered on top of each other. In this case, the atoms inside the layer are more strongly connected to each other than the atoms between the layers.

Diamond is another matter. In its colorless, transparent and highly refracting crystal, each carbon atom is linked by chemical bonds to four similar atoms located at the vertices of the tetrahedron. All ties are the same length and very strong. They form a continuous three-dimensional frame in space. The entire diamond crystal is like one giant polymer molecule that has no “weak” points, because the strength of all bonds is the same.

The density of diamond at 20°C is 3.51 g/cm3, graphite - 2.26 g/cm3. Physical properties diamond (hardness, electrical conductivity, coefficient of thermal expansion) are almost the same in all directions; it is the hardest of all substances found in nature. In graphite, these properties in different directions - perpendicular or parallel to the layers of carbon atoms - differ greatly: with small lateral forces, parallel layers of graphite shift relative to each other and it stratifies into separate flakes, leaving a mark on the paper. In terms of electrical properties, diamond is a dielectric, while graphite conducts electric current.

When heated without access to air above 1000 °C, diamond turns into graphite. Graphite, when constantly heated under the same conditions, does not change up to 3000 ° C, when it sublimes without melting. The direct transition of graphite into diamond occurs only at temperatures above 3000°C and enormous pressure - about 12 GPa.

The third allotropic modification of carbon, carbyne, was obtained artificially. It is a fine crystalline black powder; in its structure, long chains of carbon atoms are arranged parallel to each other. Each chain has the structure (-C=C) L or (=C=C=) L. The density of carbine is average between graphite and diamond - 2.68-3.30 g/cm 3 . One of the most important features carbine - its compatibility with fabrics human body, which allows it to be used, for example, in the manufacture of artificial blood vessels that are not rejected by the body (Fig. 1).

Fullerenes got their name not in honor of the chemist, but after the American architect R. Fuller, who proposed building hangars and other structures in the form of domes, the surface of which is formed by pentagons and hexagons (such a dome was built, for example, in the Moscow Sokolniki Park).

Carbon is also characterized by a state with a disordered structure - this is the so-called. amorphous carbon (soot, coke, charcoal) fig. 2. Obtaining carbon (C):

Most of the substances around us are organic compounds. These are animal and plant tissues, our food, medicines, clothing (cotton, wool and synthetic fibers), fuels (oil and natural gas), rubber and plastics, detergents. Currently, more than 10 million such substances are known, and their number increases significantly every year due to the fact that scientists isolate unknown substances from natural objects and create new compounds that do not exist in nature.

This diversity of organic compounds is associated with unique feature carbon atoms form strong covalent bonds, both among themselves and with other atoms. Carbon atoms, connecting to each other with both simple and multiple bonds, can form chains of almost any length and cycles. The wide variety of organic compounds is also associated with the existence of the phenomenon of isomerism.

Almost all organic compounds also contain hydrogen; often they contain atoms of oxygen, nitrogen, and less often - sulfur, phosphorus, and halogens. Compounds containing atoms of any element (except O, N, S and halogens) directly bonded to carbon are collectively called organoelement compounds; The main group of such compounds are organometallic compounds (Fig. 3).

The huge number of organic compounds requires their clear classification. The basis of an organic compound is the skeleton of the molecule. The skeleton can have an open (unclosed) structure, in which case the compound is called acyclic (aliphatic; aliphatic compounds are also called fatty compounds, since they were first isolated from fats), and a closed structure, in which case it is called cyclic. The skeleton can be carbon (consist only of carbon atoms) or contain other atoms other than carbon - the so-called. heteroatoms, most often oxygen, nitrogen and sulfur. Cyclic compounds are divided into carbocyclic (carbon), which can be aromatic and alicyclic (containing one or more rings), and heterocyclic.

Hydrogen and halogen atoms are not included in the skeleton, and heteroatoms are included in the skeleton only if they have at least two bonds with carbon. Thus, in ethyl alcohol CH3CH2OH the oxygen atom is not included in the skeleton of the molecule, but in dimethyl ether CH3OCH3 is included in it.

In addition, the acyclic skeleton can be unbranched (all atoms are arranged in one row) and branched. Sometimes an unbranched skeleton is called linear, but it should be remembered that the structural formulas that we most often use convey only the bond order, and not the actual arrangement of atoms. Thus, a “linear” carbon chain has a zigzag shape and can twist in space in various ways.

There are four types of carbon atoms in the molecular skeleton. It is customary to call a carbon atom primary if it forms only one bond with another carbon atom. The secondary atom is connected to two other carbon atoms, the tertiary atom is connected to three, and the quaternary atom spends all four of its bonds on forming bonds with carbon atoms.

The next classification feature is the presence of multiple bonds. Organic compounds containing only simple bonds are called saturated (limit). Compounds containing double or triple bonds are called unsaturated (unsaturated). In their molecules there are fewer hydrogen atoms per carbon atom than in the limiting ones. Cyclic unsaturated hydrocarbons of the benzene series are classified as a separate class of aromatic compounds.

The third classification feature is the presence of functional groups - groups of atoms that are characteristic of a given class of compounds and determine it chemical properties. Based on the number of functional groups, organic compounds are divided into monofunctional - they contain one functional group, polyfunctional - they contain several functional groups, for example glycerol, and heterofunctional - there are several different groups in one molecule, for example amino acids.

Depending on which carbon atom the functional group is located, the compounds are divided into primary, for example, ethyl chloride CH 3 CH 2 C1, secondary - isopropyl chloride (CH3) 2 CH 1 and tertiary - butyl chloride (CH 8) 8 CCl.