Organic compound in chemistry course. Student's Guide to Organic Chemistry. Isomerism of classes of organic substances

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

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

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

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

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

In 1828, the German chemist Wöhler, working with ammonium cyanate, accidentally obtained urea

O
II
NH2-C-NH2.

In 1854, the Frenchman Berthelot synthesized substances related to fats, and in 1861, the Russian scientist Butlerov synthesized substances related to the class of sugars. These were heavy blows to the vitalistic theory, finally shattering the belief that the synthesis of organic compounds is impossible.

These and other achievements of chemists required a theoretical explanation and generalization of possible routes for the synthesis of organic compounds and the connection of their properties with structure.

Historically, the first theory of organic chemistry was the theory of radicals (J. Dumas, J. Liebig, I. Berzelius). According to the authors, many transformations of organic compounds proceed in such a way that some groups of atoms (radicals), without changing, pass from one organic compound to another. However, it was soon discovered that in organic radicals, hydrogen atoms can be replaced even by atoms that are chemically different from hydrogen, such as chlorine atoms, and the type of chemical compound is preserved.

The theory of radicals was replaced by a more advanced theory of types that covered more experimental material (O. Laurent, C. Gerard, J. Dumas). The theory of types classified organic substances according to types of transformations. The type of hydrogen included hydrocarbons, the type of hydrogen chloride - halogen derivatives, the type of water - alcohols, esters, acids and their anhydrides, the type of ammonia - amines. However, the enormous experimental material that was accumulating no longer fit into the known types and, in addition, the theory of types could not predict the existence and ways of synthesizing new organic compounds. The development of science required the creation of a new, more progressive theory, for the birth of which some prerequisites already existed: the tetravalency of carbon was established (A. Kekule and A. Kolbe, 1857), the ability of the carbon atom to form chains of atoms was shown (A. Kekule and A. Cooper, 1857).

The decisive role in creating the theory of the structure of organic compounds belongs to the great Russian scientist Alexander Mikhailovich Butlerov. On September 19, 1861, at the 36th Congress of German Naturalists, A.M. Butlerov published it in his report “On the Chemical Structure of Matter.”

The main provisions of the theory of chemical structure of A.M. Butlerov can be reduced to the following.

1. All atoms in a molecule of an organic compound are bonded to each other in a certain sequence in accordance with their valence. Changing the sequence of atoms leads to the formation of a new substance with new properties. For example, the composition of the substance C2H6O corresponds to two different compounds: dimethyl ether (CH3-O-CH3) and ethyl alcohol (C2H5OH).

2. The properties of substances depend on their chemical structure. Chemical structure is a certain order in the alternation of atoms in a molecule, in the interaction and mutual influence of atoms on each other - both neighboring and through other atoms. As a result, each substance has its own special physical and chemical properties. For example, dimethyl ether is an odorless gas, insoluble in water, mp. = -138°C, t°boil. = 23.6°C; ethyl alcohol - liquid with odor, soluble in water, mp. = -114.5°C, t°boil. = 78.3°C.
This position of the theory of the structure of organic substances explained the phenomenon of isomerism, which is widespread in organic chemistry. The given pair of compounds - dimethyl ether and ethyl alcohol - is one of the examples illustrating the phenomenon of isomerism.

3. The study of the properties of substances allows us to determine their chemical structure, and the chemical structure of substances determines their physical and chemical properties.

4. Carbon atoms are able to connect with each other, forming carbon chains of various types. They can be both open and closed (cyclic), both direct and branched. Depending on the number of bonds the carbon atoms spend connecting to each other, the chains can be saturated (with single bonds) or unsaturated (with double and triple bonds).

5. Each organic compound has one specific structural formula or structural formula, which is built based on the provision of tetravalent carbon and the ability of its atoms to form chains and cycles. The structure of a molecule as a real object can be studied experimentally using chemical and physical methods.

A.M. Butlerov did not limit himself to theoretical explanations of his theory of the structure of organic compounds. He conducted a series of experiments, confirming the predictions of the theory by obtaining isobutane, tert. butyl alcohol, etc. This made it possible for A.M. Butlerov to declare in 1864 that the available facts allow us to vouch for the possibility of synthetically producing any organic substance.

In the further development and substantiation of the theory of the structure of organic compounds, Butlerov’s followers played a major role - V.V. Markovnikov, E.E. Wagner, N.D. Zelinsky, A.N. Nesmeyanov and others.

The modern period of development of organic chemistry in the field of theory is characterized by the increasing penetration of quantum mechanics methods into organic chemistry. With their help, questions about the causes of certain manifestations of the mutual influence of atoms in molecules are resolved. In the field of development of organic synthesis, the modern period is characterized by significant advances in the production of numerous organic compounds, which include natural substances - antibiotics, various medicinal compounds, and numerous high-molecular compounds. Organic chemistry has deeply penetrated the field of physiology. Thus, from a chemical point of view, the hormonal function of the body and the mechanism of transmission of nerve impulses have been studied. Scientists have come close to resolving the issue of protein structure and synthesis.

Organic chemistry as an independent science continues to exist and develop intensively. This is due to the following reasons:

1. The variety of organic compounds, due to the fact that carbon, unlike other elements, is able to combine with each other, giving long chains (isomers). Currently, about 6 million organic compounds are known, while inorganic compounds are only about 700 thousand.

2. The complexity of molecules of organic substances containing up to 10 thousand atoms (for example, natural biopolymers - proteins, carbohydrates).

3. The specificity of the properties of organic compounds compared to inorganic ones (instability at relatively low temperatures, low - up to 300 ° C - melting point, flammability).

4. Slow reactions between organic substances compared to reactions characteristic of inorganic substances, the formation of by-products, the specifics of the isolation of the resulting substances and technological equipment.

5. The enormous practical importance of organic compounds. They are our food and clothing, fuel, various medicines, numerous polymeric materials, etc.

Classification of organic compounds

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

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

Organic compounds

Acyclic (aliphatic)
(open circuit connections)

Cyclic
(closed circuit connections)

Saturated (ultimate)

Unsaturated (unsaturated)

Carbocyclic (the cycle consists only of carbon atoms)

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

Alicyclic (aliphatic cyclic)

Aromatic

The simplest representatives of acyclic compounds are aliphatic hydrocarbons - compounds containing only carbon and hydrogen atoms. Aliphatic hydrocarbons can be saturated (alkanes) and unsaturated (alkenes, alkadienes, alkynes).

The simplest representative of alicyclic hydrocarbons is cyclopropane, containing a ring of three carbon atoms.

The aromatic series includes aromatic hydrocarbons - benzene, naphthalene, anthracene, etc., as well as their derivatives.

Heterocyclic compounds may contain in the cycle, in addition to carbon atoms, one or more atoms of other elements - heteroatoms (oxygen, nitrogen, sulfur, etc.).

In each series presented, organic compounds are divided into classes depending on their composition and structure. The simplest class of organic compounds are hydrocarbons. When hydrogen atoms in hydrocarbons are replaced by other atoms or groups of atoms (functional groups), other classes of organic compounds of this series are formed.

A functional group is an atom or group of atoms that determines whether a compound belongs to classes of organic compounds and determines the main directions of its chemical transformations.

Compounds with one functional group are called monofunctional (methanol CH3-OH), with several identical functional groups - polyfunctional (glycerol

CH2-
I
OH CH-
I
OH CH2),
I
OH

with several different functional groups - heterofunctional (lactic acid

CH3-
CH-COOH).
I
OH

Compounds of each class form homologous series. A homologous series is an infinite series of organic compounds that have a similar structure and, therefore, similar chemical properties and differ from each other by any number of CH2 groups (homologous difference).

The main classes of organic compounds are as follows:

I. Hydrocarbons (R-H).

II. Halogen derivatives (R-Hlg).

III. Alcohols (R-OH).

O
IV. Esters and esters (R-O-R’, R-C).
\
OR'

O
V. Carbonyl compounds (aldehydes and ketones) (R-C
\
H

O
II
, R-C-R).

O
VI. Carboxylic acids R-C).
\
OH

R
I
VII. Amines (R-NH2, NH, R-N-R’).
I I
R' R''

VIII. Nitro compounds (R-NO2).

IX. Sulfonic acids (R-SO3H).

The number of known classes of organic compounds is not limited to those listed; it is large and is constantly increasing with the development of science.

All classes of organic compounds are interrelated. The transition from one class of compounds to another is carried out mainly due to transformations of functional groups without changing the carbon skeleton.

Classification of reactions of organic compounds according to the nature of chemical transformations

Organic compounds are capable of a variety of chemical transformations, which can take place both without changing the carbon skeleton and with it. Most reactions take place without changing the carbon skeleton.

I. Reactions without changing the carbon skeleton

Reactions without changing the carbon skeleton include the following:

1) substitution: RH + Br2 ® RBr + HBr,

2) addition: CH2=CH2 + Br2 ® CH2Br - CH2Br,

3) elimination (elimination): CH3-CH2-Cl ® CH2=CH2 + HCl,

4) isomerization: CH3-CH2-CєСH

------®
¬------

Substitution reactions are characteristic of all classes of organic compounds. Hydrogen atoms or atoms of any other element except carbon can be replaced.

Addition reactions are typical for compounds with multiple bonds, which can be between carbon atoms, carbon and oxygen, carbon and nitrogen, etc., as well as for compounds containing atoms with free electron pairs or vacant orbitals.

Compounds containing electronegative groups are capable of elimination reactions. Substances such as water, hydrogen halides, and ammonia are easily split off.

Unsaturated compounds and their derivatives are especially prone to isomerization reactions without changing the carbon skeleton.

II. Reactions involving changes in the carbon skeleton

This type of transformation of organic compounds includes the following reactions:

1) lengthening the chain,

2) shortening the chain,

3) chain isomerization,

4) cyclization,

5) opening the cycle,

6) compression and expansion of the cycle.

Chemical reactions occur with the formation of various intermediate products. The path along which the transition from starting substances to final products occurs is called the reaction mechanism. Depending on the reaction mechanism, they are divided into radical and ionic. Covalent bonds between atoms A and B can be broken in such a way that an electron pair is either shared between atoms A and B or transferred to one of the atoms. In the first case, particles A and B, having received one electron each, become free radicals. Homolytic cleavage occurs:

A: B ® A. + .B

In the second case, the electron pair goes to one of the particles and two opposite ions are formed. Because the resulting ions have different electronic structures, this type of bond breaking is called heterolytic cleavage:

A: B ® A+ + :B-

A positive ion in reactions will tend to attach an electron to itself, i.e. it will behave like an electrophilic particle. A negative ion - a so-called nucleophilic particle - will attack centers with excess positive charges.

The study of conditions and methods, as well as the mechanisms of reactions of organic compounds, constitutes the main content of this course in organic chemistry.

Issues of nomenclature of organic compounds, as a rule, are presented in all textbooks of organic chemistry, so we deliberately omit consideration of this material, drawing attention to the fact that in all cases of writing reaction equations, the starting and resulting compounds are provided with appropriate names. These names, with knowledge of the basics of nomenclature, will allow everyone to independently resolve issues related to the nomenclature of organic compounds.

The study of organic chemistry usually begins with the aliphatic series and the simplest class of substances - hydrocarbons.

Organic chemistry - branch of chemistry that studies carbon compounds, their structure, properties , methods of synthesis, as well as the laws of their transformations. Organic compounds are compounds of carbon with other elements (mainly H, N, O, S, P, Si, Ge, etc.).

The unique ability of carbon atoms to bond with each other, forming chains of different lengths, cyclic structures of different sizes, framework compounds, compounds with many elements, different in composition and structure, determines the diversity of organic compounds. To date, the number of known organic compounds far exceeds 10 million and increases every year by 250-300 thousand. The world around us is built mainly from organic compounds, these include: food, clothing, fuel, dyes, medicines, detergents, materials for a wide variety of branches of technology and the national economy. Organic compounds play a key role in the existence of living organisms.

At the intersection of organic chemistry with inorganic chemistry, biochemistry and medicine, the chemistry of metal- and organoelement compounds, bioorganic and medicinal chemistry, and the chemistry of high-molecular compounds arose.

The main method of organic chemistry is synthesis. Organic chemistry studies not only compounds obtained from plant and animal sources (natural substances), but mainly compounds created artificially through laboratory and industrial synthesis.

History of the development of organic chemistry

Methods for obtaining various organic substances have been known since ancient times. Thus, the Egyptians and Romans used dyes of plant origin - indigo and alizarin. Many peoples possessed the secrets of producing alcoholic beverages and vinegar from sugar- and starch-containing raw materials.

During the Middle Ages, practically nothing was added to this knowledge; some progress began only in the 16th and 17th centuries (the period of iatrochemistry), when new organic compounds were isolated through the distillation of plant products. In 1769-1785 K.V. Scheele isolated several organic acids: malic, tartaric, citric, gallic, lactic and oxalic. In 1773 G.F. Ruel isolated urea from human urine. The substances isolated from animal and plant materials had much in common with each other, but differed from inorganic compounds. This is how the term “Organic chemistry” arose - a branch of chemistry that studies substances isolated from organisms (definition J.Ya. Berzelius, 1807). At the same time, it was believed that these substances could only be obtained in living organisms thanks to the “vital force”.

It is generally accepted that organic chemistry as a science appeared in 1828, when F. Wöhler first obtained an organic substance - urea - as a result of evaporation of an aqueous solution of an inorganic substance - ammonium cyanate (NH 4 OCN). Further experimental work demonstrated undeniable arguments for the inconsistency of the “life force” theory. For example, A. Kolbe synthesized acetic acid M. Berthelot obtained methane from H 2 S and CS 2, and A.M. Butlerov synthesized sugary substances from formaldehyde.

In the middle of the 19th century. The rapid development of synthetic organic chemistry continues, the first industrial production of organic substances is being created ( A. Hoffman, W. Perkin Sr.- synthetic dyes, fuchsin, cyanine and aza dyes). Improving open N.N. Zinin(1842) method for the synthesis of aniline served as the basis for the creation of the aniline dye industry. In the laboratory A. Bayer natural dyes were synthesized - indigo, alizarin, indigoid, xanthene and anthraquinone.

An important stage in the development of theoretical organic chemistry was the development F. Kekule theory of valence in 1857, as well as the classical theory of chemical structure A.M. Butlerov in 1861, according to which atoms in molecules are connected in accordance with their valency, the chemical and physical properties of compounds are determined by the nature and number of atoms included in them, as well as the type of bonds and the mutual influence of directly unbonded atoms. In 1865 F. Kekule proposed the structural formula of benzene, which became one of the most important discoveries in organic chemistry. V.V. Markovnikov And A.M. Zaitsev formulated a number of rules that for the first time linked the direction of organic reactions with the structure of the substances entering into them. In 1875 Van't Hoff And Le Bel proposed a tetrahedral model of the carbon atom, according to which the valencies of carbon are directed to the vertices of the tetrahedron, in the center of which the carbon atom is located. Based on this model, combined with experimental studies I. Vislicenus(!873), which showed the identity of the structural formulas of (+)-lactic acid (from sour milk) and (±)-lactic acid, stereochemistry arose - the science of three-dimensional orientation of atoms in molecules, which predicted the presence of 4 different substituents at carbon atom (chiral structures) the possibility of the existence of spatially mirror isomers (antipodes or enantiomers).

In 1917 Lewis proposed to consider chemical bonding using electron pairs.

In 1931 Hückel applied quantum theory to explain the properties of non-benzenoid aromatic systems, which founded a new direction in organic chemistry - quantum chemistry. This served as an impetus for further intensive development of quantum chemical methods, in particular the method of molecular orbitals. The stage of penetration of orbital concepts into organic chemistry was discovered by the theory of resonance L. Pauling(1931-1933) and further works K. Fukui, R. Woodward And R. Hoffman about the role of frontier orbitals in determining the direction of chemical reactions.

Mid 20th century characterized by a particularly rapid development of organic synthesis. This was determined by the discovery of fundamental processes, such as the production of olefins using ylides ( G. Wittig, 1954), diene synthesis ( O. Diels And K. Alder, 1928), hydroboration of unsaturated compounds ( G. Brown, 1959), nucleotide synthesis and gene synthesis ( A. Todd, H. Koran). Advances in the chemistry of metal-organic compounds are largely due to the work of A.N. Nesmeyanova And G.A. Razuvaeva. In 1951, the synthesis of ferrocene was carried out, the “sandwich” structure of which was established R. Woodward And J. Wilkinson laid the foundation for the chemistry of metallocene compounds and the organic chemistry of transition metals in general.

In 20-30 A.E. Arbuzov creates the foundations of the chemistry of organophosphorus compounds, which subsequently led to the discovery of new types of physiologically active compounds, complexons, etc.

In 60-80 Ch. Pedersen, D. Kram And J.M. Linen are developing the chemistry of crown ethers, cryptands and other related structures capable of forming strong molecular complexes, and thereby approaching the most important problem of “molecular recognition”.

Modern organic chemistry continues its rapid development. New reagents, fundamentally new synthetic methods and techniques, new catalysts are introduced into the practice of organic synthesis, and previously unknown organic structures are synthesized. The search for organic new biologically active compounds is constantly underway. Many more problems of organic chemistry are awaiting solution, for example, a detailed establishment of the structure-property relationship (including biological activity), the establishment of the structure and stereodirectional synthesis of complex natural compounds, the development of new regio- and stereoselective synthetic methods, the search for new universal reagents and catalysts .

The interest of the world community in the development of organic chemistry was clearly demonstrated by the awarding of the Nobel Prize in Chemistry in 2010. R. Heku, A. Suzuki and E. Negishi for work on the use of palladium catalysts in organic synthesis for the formation of carbon-carbon bonds.

Classification of organic compounds

The classification is based on the structure of organic compounds. The basis for describing the structure is the structural formula.

Main classes of organic compounds

Hydrocarbons - compounds consisting only of carbon and hydrogen. They in turn are divided into:

Saturated- contain only single (σ-bonds) and do not contain multiple bonds;

Unsaturated- contain at least one double (π-bond) and/or triple bond;

Open chain(alicyclic);

Closed circuit(cyclic) - contain a cycle

These include alkanes, alkenes, alkynes, dienes, cycloalkanes, arenes

Compounds with heteroatoms in functional groups- compounds in which the carbon radical R is bonded to a functional group. Such compounds are classified according to the nature of the functional group:

Alcohol, phenols(contain hydroxyl group OH)

Ethers(contain the grouping R-O-R or R-O-R

Carbonyl compounds(contain the RR"C=O group), these include aldehydes, ketones, quinones.

Compounds containing a carboxyl group(COOH or COOR), these include carboxylic acids, esters

Element- and organometallic compounds

Heterocyclic compounds - contain heteroatoms as part of the ring. They differ in the nature of the cycle (saturated, aromatic), in the number of atoms in the cycle (three-, four-, five-, six-membered cycles, etc.), in the nature of the heteroatom, in the number of heteroatoms in the cycle. This determines the huge variety of known and annually synthesized compounds of this class. The chemistry of heterocycles represents one of the most fascinating and important areas of organic chemistry. Suffice it to say that more than 60% of drugs of synthetic and natural origin belong to various classes of heterocyclic compounds.

Natural compounds - compounds, as a rule, have a rather complex structure, often belonging to several classes of organic compounds. Among them are: amino acids, proteins, carbohydrates, alkaloids, terpenes, etc.

Polymers- substances with a very high molecular weight, consisting of periodically repeating fragments - monomers.

Structure of organic compounds

Organic molecules are mainly formed by covalent non-polar C-C bonds, or covalent polar bonds such as C-O, C-N, C-Hal. Polarity is explained by a shift in electron density towards the more electronegative atom. To describe the structure of organic compounds, chemists use the language of structural formulas of molecules, in which the bonds between individual atoms are designated using one (simple or single bond), two (double) or three (triple) valence primes. The concept of a valence prime, which has not lost its meaning to this day, was introduced into organic chemistry A. Cooper in 1858

The concept of hybridization of carbon atoms is very essential for understanding the structure of organic compounds. The carbon atom in the ground state has an electronic configuration of 1s 2 2s 2 2p 2, on the basis of which it is impossible to explain the inherent valency of 4 for carbon in its compounds and the existence of 4 identical bonds in alkanes directed to the vertices of the tetrahedron. Within the framework of the valence bond method, this contradiction is resolved by introducing the concept of hybridization. When excited, it is carried out s→p electron transition and the subsequent so-called sp- hybridization, and the energy of the hybridized orbitals is intermediate between the energies s- And p-orbitals. When bonds are formed in alkanes, three R-electrons interact with one s-electron ( sp 3-hybridization) and 4 identical orbitals arise, located at tetrahedral angles (109 about 28") to each other. The carbon atoms in alkenes are in sp 2-hybrid state: each carbon atom has three identical orbitals lying in the same plane at an angle of 120° to each other ( sp 2 orbitals), and the fourth ( R-orbital) is perpendicular to this plane. Overlapping R-orbitals of two carbon atoms form a double (π) bond. Carbon atoms bearing a triple bond are in sp- hybrid state.

Features of organic reactions

Inorganic reactions usually involve ions, and such reactions proceed quickly and to completion at room temperature. In organic reactions, covalent bonds often break and new ones are formed. Typically, these processes require special conditions: certain temperatures, reaction times, certain solvents, and often the presence of a catalyst. Usually, not one, but several reactions occur at once. Therefore, when depicting organic reactions, not equations are used, but diagrams without calculating stoichiometry. The yields of target substances in organic reactions often do not exceed 50%, and their isolation from the reaction mixture and purification require specific methods and techniques. To purify solids, recrystallization from specially selected solvents is usually used. Liquid substances are purified by distillation at atmospheric pressure or in vacuum (depending on the boiling point). To monitor the progress of reactions and separate complex reaction mixtures, various types of chromatography are used [thin-layer chromatography (TLC), preparative high-performance liquid chromatography (HPLC), etc.].

Reactions can occur very complexly and in several stages. Radicals R·, carbocations R+, carbanions R-, carbenes:СХ2, radical cations, radical anions and other active and unstable particles, usually living for a fraction of a second, can appear as intermediate compounds. A detailed description of all the transformations that occur at the molecular level during a reaction is called reaction mechanism. Based on the nature of the cleavage and formation of bonds, radical (homolytic) and ionic (heterolytic) processes are distinguished. According to the types of transformations, there are radical chain reactions, nucleophilic (aliphatic and aromatic) substitution reactions, elimination reactions, electrophilic addition, electrophilic substitution, condensation, cyclization, rearrangement processes, etc. Reactions are also classified according to the methods of their initiation (excitation ), their kinetic order (monomolecular, bimolecular, etc.).

Determination of the structure of organic compounds

Throughout the existence of organic chemistry as a science, the most important task has been to determine the structure of organic compounds. This means finding out which atoms are part of the structure, in what order and how these atoms are connected to each other and how they are located in space.

There are several methods for solving these problems.

Elemental analysis consists in the fact that a substance is decomposed into simpler molecules, by the number of which one can determine the number of atoms that make up the compound. This method does not make it possible to establish the order of bonds between atoms. Often used only to confirm the proposed structure.
Infrared spectroscopy (IR spectroscopy) and Raman spectroscopy (Raman spectroscopy). The method is based on the fact that the substance interacts with electromagnetic radiation (light) in the infrared range (absorption is observed in IR spectroscopy, and scattering of radiation is observed in Raman spectroscopy). This light, when absorbed, excites the vibrational and rotational levels of molecules. The reference data are the number, frequency and intensity of vibrations of the molecule associated with a change in the dipole moment (IR) or polarizability (PC). The method allows one to determine the presence of functional groups, and is also often used to confirm the identity of a substance with some already known substance by comparing their spectra.
Mass spectrometry. A substance under certain conditions (electron impact, chemical ionization, etc.) turns into ions without loss of atoms (molecular ions) and with loss (fragmentation, fragment ions). The method makes it possible to determine the molecular mass of a substance, its isotopic composition, and sometimes the presence of functional groups. The nature of fragmentation allows us to draw some conclusions about the structural features and reconstruct the structure of the compound under study.
Nuclear magnetic resonance (NMR) method is based on the interaction of nuclei that have their own magnetic moment (spin) and are placed in an external constant magnetic field (spin reorientation) with alternating electromagnetic radiation in the radio frequency range. NMR is one of the most important and informative methods for determining chemical structure. The method is also used to study the spatial structure and dynamics of molecules. Depending on the nuclei interacting with radiation, they distinguish, for example, the proton resonance method (PMR, 1 H NMR), which allows one to determine the position of hydrogen atoms in the molecule. The 19 F NMR method allows one to determine the presence and position of fluorine atoms. The 31 P NMR method provides information about the presence, valence state and position of phosphorus atoms in the molecule. The 13 C NMR method allows you to determine the number and types of carbon atoms; it is used to study the carbon skeleton of a molecule. Unlike the first three, the last method uses a minor isotope of the element, since the nucleus of the main isotope 12 C has zero spin and cannot be observed by NMR.
Ultraviolet spectroscopy method (UV spectroscopy) or spectroscopy of electronic transitions. The method is based on the absorption of electromagnetic radiation in the ultraviolet and visible regions of the spectrum during the transition of electrons in a molecule from the upper filled energy levels to vacant ones (excitation of the molecule). Most often used to determine the presence and characterization of conjugated π systems.
Methods of analytical chemistry make it possible to determine the presence of certain functional groups by specific chemical (qualitative) reactions, the occurrence of which can be recorded visually (for example, the appearance or change of color) or using other methods. In addition to chemical methods of analysis, instrumental analytical methods such as chromatography (thin-layer, gas, liquid) are increasingly used in organic chemistry. Chromatography-mass spectrometry occupies a place of honor among them, allowing not only to assess the degree of purity of the resulting compounds, but also to obtain mass spectral information about the components of complex mixtures.
Methods for studying the stereochemistry of organic compounds. Since the beginning of the 80s. The feasibility of developing a new direction in pharmacology and pharmacy related to the creation of enantiomerically pure drugs with an optimal balance of therapeutic efficacy and safety became obvious. Currently, approximately 15% of all synthesized pharmaceuticals are represented by pure enantiomers. This trend is reflected in the appearance in the scientific literature of recent years of the term chiral switch, which in Russian translation means “switching to chiral molecules.” In this regard, methods for establishing the absolute configuration of chiral organic molecules and determining their optical purity acquire special importance in organic chemistry. The main method for determining the absolute configuration should be X-ray diffraction analysis (XRD), and the optical purity should be chromatography on columns with a chiral stationary phase and the NMR method using special additional chiral reagents.

Relationship between organic chemistry and the chemical industry

The main method of organic chemistry - synthesis - closely links organic chemistry with the chemical industry. Based on the methods and developments of synthetic organic chemistry, small-scale (fine) organic synthesis arose, including the production of drugs, vitamins, enzymes, pheromones, liquid crystals, organic semiconductors, solar cells, etc. The development of large-scale (basic) organic synthesis is also based on the achievements of organic chemistry. The main organic synthesis includes the production of artificial fibers, plastics, processing of oil, gas and coal raw materials.

Recommended reading

G.V. Bykov, History of organic chemistry, M.: Mir, 1976 (http://gen.lib/rus.ec/get?md5=29a9a3f2bdc78b44ad0bad2d9ab87b87)
J. March, Organic chemistry: reactions, mechanisms and structure, in 4 volumes, M.: Mir, 1987
F. Carey, R. Sandberg, Advanced course in organic chemistry, in 2 volumes, M.: Chemistry, 1981
O.A. Reutov, A.L. Kurtz, K.P. Butin, Organic chemistry, in 4 parts, M.: “Binom, Laboratory of Knowledge”, 1999-2004. (http://edu.prometey.org./library/autor/7883.html)
Chemical encyclopedia, ed. Knunyantsa, M.: “Big Russian Encyclopedia”, 1992.

Organic chemistry
The concept of organic chemistry and the reasons for its separation into an independent discipline

Isomers– substances of the same qualitative and quantitative composition (i.e. having the same total formula), but different structures, therefore, different physical and chemical properties.

Phenanthrene (right) and anthracene (left) are structural isomers.

Brief outline of the development of organic chemistry

The first period of development of organic chemistry, called empirical(from the mid-17th to the end of the 18th century), covers a large period of time from man’s initial acquaintance with organic substances to the emergence of organic chemistry as a science. During this period, knowledge of organic substances, methods of their isolation and processing occurred experimentally. According to the definition of the famous Swedish chemist I. Berzelius, organic chemistry of this period was “the chemistry of plant and animal substances.” By the end of the empirical period, many organic compounds were known. Citric, oxalic, malic, gallic, and lactic acids were isolated from plants, urea was isolated from human urine, and hippuric acid was isolated from horse urine. The abundance of organic substances served as an incentive for an in-depth study of their composition and properties.
Next period analytical(end of the 18th - mid-19th centuries), associated with the emergence of methods for determining the composition of organic substances. The most important role in this was played by the law of conservation of mass discovered by M.V. Lomonosov and A. Lavoisier (1748), which formed the basis of quantitative methods of chemical analysis.
It was during this period that it was discovered that all organic compounds contain carbon. In addition to carbon, elements such as hydrogen, nitrogen, sulfur, oxygen, and phosphorus, which are currently called organogenic elements, were found in organic compounds. It became clear that organic compounds differ from inorganic ones primarily in composition. At that time, there was a special attitude towards organic compounds: they continued to be considered products of the vital activity of plant or animal organisms, which can only be obtained with the participation of an intangible “vital force”. These idealistic views were refuted by practice. In 1828, the German chemist F. Wöhler synthesized the organic compound urea from inorganic ammonium cyanate.
From the moment of F. Wöhler's historical experience, the rapid development of organic synthesis began. I. N. Zinin obtained by reducing nitrobenzene, thereby laying the foundation for the aniline dye industry (1842). A. Kolbe synthesized (1845). M, Berthelot – substances like fats (1854). A. M. Butlerov - the first sugary substance (1861). Nowadays, organic synthesis forms the basis of many industries.
Of great importance in the history of organic chemistry is structural period(second half of the 19th - beginning of the 20th century), marked by the birth of the scientific theory of the structure of organic compounds, the founder of which was the great Russian chemist A. M. Butlerov. The basic principles of the theory of structure were of great importance not only for their time, but also serve as a scientific platform for modern organic chemistry.
At the beginning of the 20th century, organic chemistry entered into modern period development. Currently, in organic chemistry, quantum mechanical concepts are used to explain a number of complex phenomena; chemical experiment is increasingly combined with the use of physical methods; The role of various calculation methods has increased. Organic chemistry has become such a vast field of knowledge that new disciplines are being separated from it - bioorganic chemistry, chemistry of organoelement compounds, etc.

Theory of the chemical structure of organic compounds by A. M. Butlerov

Basic provisions of the theory of chemical structure of A.M. Butlerov:

All atoms in a molecule of an organic compound are bonded to each other in a specific sequence according to their valence. Changing the sequence of atoms leads to the formation of a new substance with new properties. For example, the composition of the substance C2H6O corresponds to two different compounds: - see.
The properties of substances depend on their chemical structure. Chemical structure is a certain order in the alternation of atoms in a molecule, in the interaction and mutual influence of atoms on each other - both neighboring and through other atoms. As a result, each substance has its own special physical and chemical properties. For example, dimethyl ether is an odorless gas, insoluble in water, mp. = -138°C, t°boil. = 23.6°C; ethyl alcohol - liquid with odor, soluble in water, mp. = -114.5°C, t°boil. = 78.3°C.
This position of the theory of the structure of organic substances explained a phenomenon that is widespread in organic chemistry. The given pair of compounds - dimethyl ether and ethyl alcohol - is one of the examples illustrating the phenomenon of isomerism.
The study of the properties of substances allows us to determine their chemical structure, and the chemical structure of substances determines their physical and chemical properties.
Carbon atoms are able to connect with each other, forming carbon chains of various types. They can be both open and closed (cyclic), both direct and branched. Depending on the number of bonds the carbon atoms spend connecting to each other, the chains can be saturated (with single bonds) or unsaturated (with double and triple bonds).
Each organic compound has one specific structural formula or structural formula, which is built based on the provision of tetravalent carbon and the ability of its atoms to form chains and cycles. The structure of a molecule as a real object can be studied experimentally using chemical and physical methods.

Organic chemistry - is the science of carbon-containing compounds and ways of their synthesis. Since the diversity of organic substances and their transformations is unusually large, the study of this large branch of science requires a special approach.

If you are unsure about your ability to successfully master a subject, don’t worry! 🙂 Below are some tips that will help you dispel these fears and achieve success!

Generalizing schemes

Write down all the chemical transformations that you encounter when studying this or that class of organic compounds in summary diagrams. You can draw them to your liking. These diagrams, which contain basic reactions, will serve as guides to help you easily find ways to transform one substance into another. You can hang the diagrams near your workplace so that they catch your eye more often, and it’s easier to remember them. It is possible to construct one large diagram containing all classes of organic compounds. For example, like this: or this diagram:

The arrows should be numbered and examples of reactions and conditions should be given below (under the diagram). You can have several reactions, leave plenty of room in advance. The volume will be large, but it will help you a lot in solving USE 32 tasks in chemistry “Reactions confirming the relationship of organic compounds” (formerly C3).

Review cards

When studying organic chemistry, you need to learn a large number of chemical reactions, you will have to remember and understand how many transformations occur. Special cards can help you with this.

Get a pack of cards measuring approximately 8 X 12 cm. Write down the reagents on one side of the card and the reaction products on the other:

You can carry these cards with you and review them several times a day. It is more useful to refer to the cards several times for 5-10 minutes than once, but over a long period of time.

When you have a lot of such cards, you should divide them into two groups:

group No. 1 - those that you know well, you look at them once every 1-2 weeks, and

group No. 2 - those that cause difficulties, you look at them every day until they “pump over” to group No. 1.

This method can also be used to learn a foreign language: on one side of a card you write a word, on the back its translation, this way you can quickly expand your vocabulary. In some language courses, such cards are issued ready-made. So, this is a proven method!

Pivot table

This table needs to be rewritten or printed (copying is available after authorization on the site), if the reaction is not typical for this class of compound, then put a minus sign, and if it is typical, then a plus sign and a number in order, and below the table write examples corresponding to the numbering. This is also a very good way to systematize organic knowledge!

Constant repetition

Organic chemistry, like a foreign language, is a cumulative discipline. Subsequent material is based on knowledge of what was previously covered. Therefore, return periodically to the topics covered.

Molecular models

Since the shape and geometry of molecules are important in organic chemistry, it is a good idea for the student to have a set of molecular models. Such models, which can be held in your hands, will help in studying the stereochemical features of molecules.

Remember that paying attention to new words and terms is as important in organic chemistry as in other disciplines. Keep in mind that reading non-fiction is always slower than reading fiction. Don't try to cover everything quickly. To thoroughly understand the material presented, slow, thoughtful reading is necessary. You can read it twice: the first time for a quick glance, the second time for a more careful study.

Good luck! You will succeed!

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 many common features. At the same time, they were very different from inorganic compounds. Therefore, the servants of science urgently needed to separate them into a separate class, and 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.