Few people thought about the role of organic chemistry in the life of modern man. But it is huge, it is difficult to overestimate it. From the very morning, when a person wakes up and goes to wash, and until the very evening, when he goes to bed, he is accompanied every minute by products of organic chemistry. A toothbrush, clothes, paper, cosmetics, furniture and interior items and much more - she gives us all this. But once everything was completely different, and very little was known about organic chemistry.

Let us consider how the history of the development of organic chemistry developed in stages.

1. The period of development until the XIV century, called spontaneous.

2. XV - XVII centuries - the beginning of development or, iatrochemistry, alchemy.

3. Century XVIII - XIX - the dominance of the theory of vitalism.

4. XIX - XX centuries - intensive development, scientific stage.

The Beginning, or the Spontaneous Stage in the Formation of the Chemistry of Organic Compounds

This period implies the very origin of the concept of chemistry, the origins. And the origins go back to Ancient Rome and Egypt, in which very capable inhabitants learned to extract objects and clothes from natural raw materials - leaves and stems of plants - for coloring. These were indigo, which gives a rich blue color, and alizorin, which colors literally everything in juicy and attractive shades of orange and red. Unusually agile inhabitants of different nationalities of the same time also learned how to get vinegar, make alcoholic beverages from sugar and starch-containing substances of plant origin.

It is known that very common products in use during this historical period were animal fats, resins and vegetable oils, which were used by healers and cooks. And also various poisons were densely used, as the main weapon of internecine relations. All these substances are products of organic chemistry.

But, unfortunately, as such, the concept of "chemistry" did not exist, and the study of specific substances in order to clarify the properties and composition did not occur. Therefore, this period is called spontaneous. All discoveries were random, non-purposeful nature of everyday significance. This continued until the next century.

The iatrochemical period is a promising beginning of development

Indeed, it was in the 16th-17th centuries that direct ideas about chemistry as a science began to emerge. Thanks to the work of scientists of that time, some organic substances were obtained, the simplest devices for distillation and sublimation of substances were invented, special chemical utensils were used for grinding substances, separating natural products into ingredients.

The main direction of work of that time was medicine. The desire to obtain the necessary medicines led to the fact that essential oils and other raw materials were extracted from plants. So, Karl Scheele obtained some organic acids from plant materials:

• apple;
• lemon;
• gallic;
• dairy;
• oxalic.

It took the scientist 16 years to study plants and isolate these acids (from 1769 to 1785). This was the beginning of development, the foundations of organic chemistry were laid, which was directly defined and named as a branch of chemistry later (beginning of the 18th century).

In the same period of the Middle Ages, G. F. Ruel isolated uric acid crystals from urea. Other chemists obtained succinic acid from amber, tartaric acid. The method of dry distillation of vegetable and animal raw materials, thanks to which acetic acid, diethyl ether, and wood alcohol is obtained, is in use.

This was the beginning of the intensive development of the organic chemical industry in the future.

Vis vitalis, or "Life Force"

XVIII - XIX centuries for organic chemistry are very twofold: on the one hand, there are a number of discoveries that are of grandiose significance. On the other hand, for a long time the growth and accumulation of the necessary knowledge and correct ideas is hampered by the dominant theory of vitalism.

This theory was introduced into use and designated as the main one by Jens Jacobs Berzelius, who at the same time himself gave the definition of organic chemistry (the exact year is unknown, either 1807 or 1808). According to the provisions of this theory, organic substances can be formed only in living organisms (plants and animals, including humans), since only living beings have a special "life force" that allows these substances to be produced. While it is absolutely impossible to obtain organic substances from inorganic substances, since they are products of inanimate nature, non-combustible, without vis vitalis.

The same scientist proposed the first classification of all compounds known at that time into inorganic (non-living, all substances like water and salt) and organic (living, those like olive oil and sugar). Berzelius was also the first to specify specifically what organic chemistry is. The definition sounded like this: this is a branch of chemistry that studies substances isolated from living organisms.

During this period, scientists easily carried out the transformation of organic substances into inorganic ones, for example, during combustion. However, nothing is known about the possibility of reverse transformations.

Fate was pleased to dispose so that it was the student of Jens Berzelius, Friedrich Wehler, who contributed to the beginning of the collapse of the theory of his teacher.

A German scientist worked on cyanide compounds and in one of his experiments he managed to obtain crystals similar to uric acid. As a result of more careful research, he was convinced that he really managed to get organic matter from inorganic without any vis vitalis. No matter how skeptical Berzelius was, he was forced to admit this indisputable fact. Thus was dealt the first blow to the vitalistic views. The history of the development of organic chemistry began to gain momentum.

A series of discoveries that crushed vitalism

The success of Wöhler inspired the chemists of the 18th century, so widespread tests and experiments began in order to obtain organic substances in artificial conditions. Several such syntheses, which are of decisive and greatest importance, have been made.

1. 1845 - Adolf Kolbe, who was a student of Wöhler, managed to obtain acetic acid, which is an organic substance, from simple inorganic substances C, H 2, O 2 by a multi-stage complete synthesis.
2. 1812 Konstantin Kirchhoff synthesized glucose from starch and acid.
3. 1820 Henri Braconnot denatured the protein with acid and then treated the mixture with nitric acid and obtained the first of the 20 amino acids synthesized later - glycine.
4. 1809 Michel Chevrel studied the composition of fats, trying to break them down into their constituent components. As a result, he received fatty acids and glycerin. 1854 Jean Berthelot continued the work of Chevrel and heated glycerin with the result - a fat that exactly repeats the structure of natural compounds. In the future, he managed to obtain other fats and oils, which were somewhat different in molecular structure from their natural counterparts. That is, he proved the possibility of obtaining new organic compounds of great importance in the laboratory.
5. J. Berthelot synthesized methane from hydrogen sulfide (H 2 S) and carbon disulfide (CS 2).
6. 1842 Zinin managed to synthesize aniline, a dye from nitrobenzene. In the future, he managed to obtain a number of aniline dyes.
7. A. Bayer creates his own laboratory, in which he is actively and successfully synthesizing organic dyes similar to natural ones: alizarin, indigo, anthroquinone, xanthene.
8. 1846 synthesis of nitroglycerin by the scientist Sobrero. He also developed a theory of types, which says that substances are similar to some of the inorganic ones and can be obtained by replacing hydrogen atoms in the structure.
9. 1861 A. M. Butlerov synthesized a sugary substance from formalin. He also formulated the provisions of the theory of the chemical structure of organic compounds, which are relevant to this day.

All these discoveries determined the subject of organic chemistry - carbon and its compounds. Further discoveries were aimed at studying the mechanisms of chemical reactions in organic matter, at establishing the electronic nature of interactions, and at examining the structure of compounds.

The second half of the XIX and XX centuries - the time of global chemical discoveries

The history of the development of organic chemistry has undergone ever greater changes over time. The work of many scientists on the mechanisms of internal processes in molecules, in reactions and systems has yielded fruitful results. So, in 1857, Friedrich Kekule developed the theory of valency. He also belongs to the greatest merit - the discovery of the structure of the benzene molecule. At the same time, A. M. Butlerov formulated the provisions of the theory of the structure of compounds, in which he indicated the tetravalence of carbon and the phenomenon of the existence of isomerism and isomers.

V. V. Markovnikov and A. M. Zaitsev delve into the study of the mechanisms of reactions in organic matter and formulate a number of rules that explain and confirm these mechanisms. In 1873 - 1875. I. Wislicenus, van't Hoff and Le Bel study the spatial arrangement of atoms in molecules, discover the existence of stereo-isomers and become the founders of a whole science - stereochemistry. Many different people were involved in creating the field of organics that we have today. Therefore, scientists of organic chemistry deserve attention.

The end of the 19th and 20th centuries were the times of global discoveries in pharmaceuticals, the paint and varnish industry, and quantum chemistry. Let us consider the discoveries that ensured the maximum importance of organic chemistry.

1. 1881 M. Conrad and M. Gudzeit synthesized anesthetics, veronal and salicylic acid.
2. 1883 L. Knorr received antipyrine.
3. 1884 F. Stoll received a pyramidon.
4. 1869 The Hyatt brothers received the first artificial fiber.
5. 1884 D. Eastman synthesized celluloid photographic film.
6. 1890 L. Depassy copper-ammonia fiber was obtained.
7. 1891 Ch. Cross and his colleagues received viscose.
8. 1897 F. Miescher and Buchner founded the theory (cell-free fermentation and enzymes as biocatalysts were discovered).
9. 1897 F. Miescher discovered nucleic acids.
10. Beginning of the 20th century - new chemistry of organoelement compounds.
11. 1917 Lewis discovered the electronic nature of the chemical bond in molecules.
12. 1931 Hückel is the founder of quantum mechanisms in chemistry.
13. 1931-1933 Laimus Pauling substantiates the theory of resonance, and later his employees reveal the essence of directions in chemical reactions.
14. 1936 Nylon synthesized.
15. 1930-1940 A. E. Arbuzov gives rise to the development of organophosphorus compounds, which are the basis for the production of plastics, medicines and insecticides.
16. 1960 Academician Nesmeyanov and his students create the first synthetic food in the laboratory.
17. 1963 Du Vigne receives insulin, a huge advance in medicine.
18. 1968 Indian H. G. Korana managed to get a simple gene, which helped in deciphering the genetic code.

Thus, the importance of organic chemistry in people's lives is simply colossal. Plastics, polymers, fibers, paints and varnishes, rubbers, rubbers, PVC materials, polypropylenes and polyethylenes and many other modern substances, without which life is simply not possible today, have gone a difficult way to their discovery. Hundreds of scientists have contributed many years of painstaking work to form a common history of the development of organic chemistry.

Modern system of organic compounds

Having traveled a long and difficult path in development, organic chemistry does not stand still today. More than 10 million compounds are known, and this number is growing every year. Therefore, there is a certain systematized structure of the arrangement of substances that organic chemistry gives us. The classification of organic compounds is presented in the table.

Connection class	Structural features	General formula
Hydrocarbons (made up of only carbon and hydrogen atoms)	saturated (only sigma St.); unsaturated (sigma and pi St.); acyclic; cyclic.	Alkanes C n H 2n+2; Alkenes, cycloalkanes C n H 2n; Alkynes, alkadienes C n H 2n-2; Arenas C 6 H 2n-6.
Substances containing different heteroatoms in the main group	halogens; OH group (alcohols and phenols); grouping R-O-R
Carbonyl compounds	aldehydes; ketones; quinones.	R-C(H)=O
Compounds containing a carboxyl group	carboxylic acids; esters.
Compounds containing sulfur, nitrogen or phosphorus in the molecule	Can be cyclic or acyclic	-
Organoelement compounds	Carbon is bonded directly to another element, not hydrogen	S-E
Organometallic compounds	Carbon bonded to metal	S-Me
Heterocyclic compounds	The structure is based on a cycle with constituent heteroatoms	-
natural substances	Large polymer molecules found in natural compounds	proteins, nucleic acids, amino acids, alkaloids, etc.
Polymers	Substances with a large molecular weight, which are based on monomer units	n (-R-R-R-)

The study of the whole variety of substances and the reactions they enter into is the subject of organic chemistry today.

Types of chemical bonds in organic substances

For any compounds, electron-static interactions within molecules are characteristic, which in organics are expressed in the presence of covalent polar and covalent non-polar bonds. In organometallic compounds, the formation of a weak ionic interaction is possible.

Occur between C-C interactions in all organic molecules. Covalent polar interaction is characteristic of different non-metal atoms in a molecule. For example, C-Hal, C-H, C-O, C-N, C-P, C-S. These are all bonds in organic chemistry that exist to form compounds.

Varieties of formulas of substances in organic matter

The most common formulas expressing the quantitative composition of a compound are called empirical formulas. Such formulas exist for every inorganic substance. But when it came to compiling formulas in organics, scientists faced many problems. Firstly, the mass of many of them is in the hundreds, and even thousands. It is difficult to determine an empirical formula for such a huge substance. Therefore, over time, such a branch of organic chemistry as organic analysis appeared. The scientists Liebig, Wehler, Gay-Lussac and Berzelius are considered its founders. It was they, together with the works of A. M. Butlerov, who determined the existence of isomers - substances that have the same qualitative and quantitative composition, but differ in molecular structure and properties. That is why the structure of organic compounds is expressed today not by an empirical, but by a structural complete or structural abbreviated formula.

These structures are a characteristic and distinctive feature that organic chemistry has. Formulas are written using dashes denoting chemical bonds. for example, the abbreviated structural formula of butane would be CH 3 - CH 2 - CH 2 - CH 3 . The complete structural formula shows all the chemical bonds present in the molecule.

There is also a way to write down the molecular formulas of organic compounds. It looks the same as empirical in inorganic. For butane, for example, it will be: C 4 H 10. That is, the molecular formula gives an idea only of the qualitative and quantitative composition of the compound. Structural bonds characterize the bonds in a molecule, therefore, they can be used to predict the future properties and chemical behavior of a substance. These are the features that organic chemistry has. Formulas are written in any form, each of them is considered correct.

Types of reactions in organic chemistry

There is a certain classification of organic chemistry according to the type of reactions that occur. Moreover, there are several such classifications, according to various criteria. Let's consider the main ones.

Mechanisms of chemical reactions according to the methods of breaking and forming bonds:

• homolytic or radical;
• heterolytic or ionic.

Reactions by types of transformations:

• chain radical;
• nucleophilic aliphatic substitution;
• nucleophilic aromatic substitution;
• elimination reactions;
• electrophilic addition;
• condensation;
• cyclization;
• electrophilic substitution;
• rearrangement reactions.

According to the method of starting the reaction (initiation) and according to the kinetic order, reactions are also sometimes classified. These are the main features of the reactions that organic chemistry has. The theory describing the details of the course of each chemical reaction was discovered in the middle of the 20th century and is still being confirmed and supplemented with each new discovery and synthesis.

It should be noted that, in general, reactions in organic matter proceed under more severe conditions than in inorganic chemistry. This is due to the greater stabilization of the molecules of organic compounds due to the formation of intra and intermolecular strong bonds. Therefore, almost no reaction is complete without an increase in temperature, pressure, or the use of a catalyst.

Modern definition of organic chemistry

In general, the development of organic chemistry followed an intensive path over several centuries. A huge amount of information has been accumulated about substances, their structures and reactions in which they can enter. Millions of useful and simply necessary raw materials used in various fields of science, technology and industry have been synthesized. The concept of organic chemistry today is perceived as something grandiose and large, numerous and complex, diverse and significant.

At one time, the first definition of this great branch of chemistry was that given by Berzelius: it is a chemistry that studies substances isolated from organisms. A lot of time has passed since that moment, many discoveries have been made and a large number of mechanisms of intrachemical processes have been realized and revealed. As a result, today there is a different concept of what organic chemistry is. The definition is given to it as follows: it is the chemistry of carbon and all its compounds, as well as methods for their synthesis.

"FUNDAMENTALS OF ORGANIC CHEMISTRY"

Lecture questions:

1. Theory of the structure of organic compounds, their classification and nomenclature. Types of isomerism.

2. The relationship of chemical properties with the structure of molecules, the classification of reagents and reactions in organic chemistry.

3. polymers, oligomers. Structure, properties. synthesis

QUESTION 1.

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

Organic chemistry studies substances containing carbon in their composition, 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 one to separate 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 in the group of animal substances, since they were obtained by calcining, respectively, plant (wood) and animal (bones) materials .

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

Among scientists at that time, a vitalistic worldview dominated, according to which organic compounds are formed only in a living organism under the influence of a special, supernatural "life force". This meant that it was impossible to obtain organic substances by synthesis from inorganic ones, that there was an unbridgeable gulf 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

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 breaking the conviction that the synthesis of organic compounds was impossible.

These and other achievements of chemists required a theoretical explanation and generalization of possible routes for the synthesis of organic compounds and the relationship of their properties with the 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 established 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 perfect theory of types covering more experimental material (O.Laurent, Ch.Gerard, J.Dumas). The theory of types classified organic substances according to the types of transformations. Hydrocarbons were classified as hydrogen, halogen derivatives as hydrogen chloride, alcohols, esters, acids and their anhydrides as water, and amines as ammonia. However, the accumulated vast experimental material no longer fit into the known types, and, moreover, 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 there were already some prerequisites: the tetravalence 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 the creation of 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 the report "On the chemical structure of matter."

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

1. All atoms in the molecule of an organic compound are connected to each other in a certain sequence in accordance with their valency. A change in the sequence of arrangement 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. The 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, t0pl. = -1380C, t0bp. = 23.60C; ethyl alcohol is a liquid with an odor, soluble in water, t0pl. = -114.50C, t0bp = 78.30C.

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 you to determine their chemical structure, and the chemical structure of substances determines their physical and chemical properties.

4. Carbon atoms are able to combine with each other, forming carbon chains of various types. They can be both open and closed (cyclic), both straight and branched. Depending on the number of bonds spent by carbon atoms to connect with each other, 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 position 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 by 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 make it possible to vouch for the possibility of synthetic production of any organic substance.

In the further development and justification of the theory of the structure of organic compounds, the followers of Butlerov - V.V. Markovnikov, E.E. Wagner, N.D. Zelinsky, A.N.

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

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 only about 700 thousand are inorganic.

2. The complexity of the 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 in comparison with inorganic ones (instability at relatively low temperatures, low - up to 300 ° C - melting point, combustibility).

4. Slowly proceeding reactions between organic substances in comparison with the reactions typical for inorganic substances, the formation of by-products, the specifics of the release of the resulting substances and process equipment.

5. The enormous practical importance of organic compounds. They are our food and clothing, fuel, a variety of drugs, numerous polymeric materials, and so on.

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.

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 cycle of three carbon atoms.

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

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

In each presented series, organic compounds are divided into classes depending on the 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.

Functional group - an atom or a group of atoms that establishes the belonging of the compound to the 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

with different functional groups - heterofunctional (lactic acid

Compounds of each class constitute 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 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 interconnected. The transition from one class of compounds to another is carried out mainly due to the transformation 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 changes in the carbon skeleton, and with it. Most reactions proceed without changing the carbon skeleton.

I. Reactions without changing the carbon skeleton

Reactions without changing the carbon skeleton include the following:

1) substitutions: RH + Br2 RBr + HBr,

2) additions: CH2=CH2 + Br2 CH2Br – CH2Br,

3) elimination (elimination): CH3–CH2–Cl CH2=CH2 + HCl,C2H5ONa

4) isomerization: CH3CH2C?CH

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

Addition reactions are typical for compounds with multiple bonds, which can be between carbon, 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, ammonia are easily split off.

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

Reactions with a change in the carbon skeleton

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

1) chain extension,

2) chain shortening,

3) chain isomerization,

4) cyclization,

5) opening the cycle,

6) contraction and expansion of the cycle.

Chemical reactions take place with the formation of various intermediate products. The path along which the transition from the starting materials to the final products is carried out 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 the 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:

In the second case, the electron pair passes 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 positive ion in reactions will tend to attach an electron to itself, i.e., it will behave like an electrophilic particle. Negative ion - the so-called nucleophilic particle will attack centers with excess positive charges.

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

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Fundamentals of organic chemistry

Organic chemistry is singled out as a separate subspecies 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 connection.

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, otherwise a person would simply have 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 vegetable raw materials into separate substances;
• Purification and synthesis of various compounds;
• Revealing the structure of substances;
• Determination of the mechanics of the course of chemical reactions;
• Finding the relationship between the structure and properties of organic substances.

A bit from the history of organic chemistry

You may not believe it, but even in ancient times, the inhabitants of Rome and Egypt understood something in 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 the production of alcoholic beverages are known in every nation. Moreover, many ancient peoples knew the 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, small discoveries, begin.

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

Then it became clear to everyone that the products that could be isolated from plant or animal raw materials had many common features. At the same time, they differed greatly from inorganic compounds. Therefore, the servants of science urgently needed to separate them into a separate class, and 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 in the nomenclature in organic chemistry for teapots:

Branch of chemistry that studies substances derived 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 the chemical structure of Mr. Butlerov from 1861. Even then, scientists began to discover that carbon is tetravalent and is able to form chains.

In general, since then, science has regularly experienced upheavals and unrest due to new theories, discoveries of chains and compounds, which allowed organic chemistry to also actively develop.

Science itself appeared due to the fact that scientific and technological progress was not able to stand still. He kept on walking, demanding new solutions. And when coal tar was no longer enough in the industry, people simply had to create a new organic synthesis, which eventually grew into the discovery of an incredibly important substance, which is still more expensive than gold - oil. By the way, it was thanks to organic chemistry that her "daughter" was born - a subscience, which was called "petrochemistry".

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1.1 Theory of the structure of organic substances :

Butlerov's theory was the scientific foundation of organic chemistry and contributed to its rapid development. Based on the provisions of the theory, A.M. Butlerov explained the phenomenon isomerism, predicted the existence of various isomers and obtained some of them for the first time. So for the first time he experimentally proved the difference between butane (C 4 H 10) and isobutane (C 4 H 10), despite the common molecular formula. The main provisions of the theory of A. M. Butlerov are as follows:

1. In the molecules of compounds, there is a certain order of bonding of atoms, which is called the structure.

2. The chemical properties of a compound are determined by the composition and structure of its molecules.

To explain these provisions, we can cite the fact that a change in the sequence of arrangement of atoms leads to the formation of a new substance with new properties. For example, the composition of a substance C 2 H 6 O corresponds to two different compounds: dimethyl ether (CH 3 -O - CH 3) and ethyl alcohol (C 2 H 5 OH).

3. A different structure with the same composition and molecular weight of a substance causes the phenomenon of isomerism.

4. The chemical nature of the atoms that make up the molecule varies depending on which atoms they are associated with in this molecule.

1.2 Types of isomerism.

· isomerism- the phenomenon of the existence of compounds that have the same composition (the same molecular formula), but a different structure. Such connections are called isomers. Due to the diversity of organic substances, there are several types of isomerism. Here is some of them:

· Isomerism of the carbon skeleton (structural isomerism).

In a molecule, the carbon chain can be linear or branched.

Example: n - butane (linear)

isobutane; 2 methyl propane (branched)

The carbon atoms that make up the chain in hydrocarbon molecules and their derivatives can be primary, secondary, tertiary and quaternary.

Primary carbon atoms (I) are connected to one neighboring carbon atom, secondary atoms (II) - respectively with two, tertiary atoms (III) - with three carbon atoms and quaternary - with four. In the molecule 2 - methylbutane, the considered carbon atoms are shown.

· Isomerism of the position of a multiple bond.

butene-1 ,

· Isomerism of homologous series (interspecies).

Molecules belonging to different classes of hydrocarbons, for example, alkadienes and alkynes, have the same molecular formula, but differ in structure and, consequently, in properties.

Butadiene 1, 3

butin-1.

· Geometric isomerism (spatial).

Characteristic of compounds having one or more double bonds. If we consider the double bond as a plane, then the substituents located at the carbon atoms along the double bond have a different position with respect to the plane of the double bond.

cis– butene-2 trance– butene-2

So, in a butene-2 ​​molecule, CH 3 groups can be located either on one side of the double bond plane in cis-isomer, or on opposite sides in trance–isomer.

1.3 Classification of organic substances

The simplest organic molecules are hydrocarbons, they got their name because they consist only of carbon and hydrogen. Hydrocarbons are the ancestors of all other classes of organic compounds.

Classify organic substances by the presence and order of connection of atoms in their molecules. Depending on the order of connection of carbon atoms in this chain, substances are divided into acyclic, which do not contain closed chains of carbon atoms in molecules, and carbocyclic, containing such chains (cycles) in molecules (see diagram).

In this manual, saturated, unsaturated and aromatic hydrocarbons will be considered in detail, since the key to understanding all organic chemistry lies in the assimilation of simple things: the main classes of organic substances, the patterns of reactions occurring in them. In general terms, the properties of the considered classes of substances are proposed in Table 1.

Table 1

Summary table of classes of organic compounds (hydrocarbons) and their chemical properties.

ORGANIC CHEMISTRY

Basic concepts of organic chemistry

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

Theory of the chemical structure of 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 interconnected in a certain order by chemical bonds according to their valency;

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

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

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

Isomers– substances that have the same composition but different structure

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

Structural formula - conditional image of the structure of a substance, taking into account chemical bonds.

Classification of organic compounds.

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

carbon skeleton represents a sequence of chemically bonded carbon atoms.

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

In a heterocyclic skeleton, one or more atoms other than carbon are included in the carbon cycle. In the carbon skeletons themselves, individual carbon atoms must be classified according to the number of chemically bonded carbon atoms. 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 between themselves not only single, but also multiple (double and triple) bonds, then compounds containing only single C-C bonds are called rich, compounds with multiple bonds are called unsaturated.

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

Hydrocarbons are recognized in organic chemistry as ancestral. A variety of compounds are considered as derivatives of hydrocarbons 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 feature according to which the compounds belong to one or another class.

The most important functional groups

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

homologous series. The concept of a homologous series is useful for describing organic compounds. 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 the series of saturated hydrocarbons (alkanes). Its simplest representative is methane CH 4 . The 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 to the formula of the previous hydrocarbon homological difference.

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, such a formula will be C n H 2n+2, where n is the number of carbon atoms.

Nomenclature of organic compounds. At present, 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 built from the name of the main chain that forms the root of the word, and the names of functions used as prefixes or suffixes.

For the correct construction of 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 starts from the end of the chain, closer to which the older group is located. If there are several such possibilities, then the numbering is carried out in such a way that either a multiple bond or another substituent present in the molecule receives the smallest number.

In carbocyclic compounds, the numbering starts from the carbon atom at which the highest characteristic group is located. If in this case it is impossible to choose a unique numbering, then the cycle is numbered so that the substituents have the smallest 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.

Composing the name of an organic compound. The basis of the name of the compound is the root of the word, denoting a saturated hydrocarbon with the same number of atoms as the main chain ( meth-, et-, prop-, but-, pent: hex- etc.). Then follows a suffix characterizing the degree of saturation, -en if there are no multiple bonds in the molecule, -en in the presence of double bonds and -in for triple bonds, (eg pentane, pentene, pentene). If there are several multiple bonds in the molecule, then the number of such bonds is indicated in the suffix: - 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):

Further, the name of the oldest characteristic group in the molecule is placed in the suffix, indicating its position with a number. Other substituents are designated by prefixes. However, they are not listed in order of seniority, but alphabetically. The position of the substituent is indicated by a number before the prefix, for example: 3 -methyl; 2 -chlorine, etc. If there are several identical substituents in the molecule, then their number is indicated in front of the name of the corresponding group (for example, di methyl-, trichloro-, 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.

Limit hydrocarbon radicals:

Unsaturated hydrocarbon radicals:

Aromatic hydrocarbon radicals:

Let's take the following connection as an example:

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

2) the order of numbering provides the highest group (-OH) with the lowest number;

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

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

Trivial nomenclature is a collection of non-systematic 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 those 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 called isomers with different order of connection of atoms.

Spatial isomers have the same substituents on each carbon atom and differ only in their mutual arrangement in space.

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

1) compounds that differ 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 different 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 cycle. In such molecules, it is often possible to draw a conditional plane in such a way that 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 one speaks 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 experience mutual influence. This influence is transmitted mainly through a system of covalent bonds with the help of so-called electronic effects.

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

Atoms bound 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 an electron acceptor. Its δ-bond partner will accordingly have an equal electron density deficit, i.e., a partial positive charge δ +, and will be called an electron donor.

The displacement of the electron density along the chain of σ-bonds is called the inductive effect and is denoted by I.

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

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

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

Electron-donor substituents, i.e., an atom or a group of atoms that shift the electron density to the 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 show -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 the state of hybridization. So, in the propene molecule, the methyl group exhibits + I-effect, since the carbon atom in it is in the sp3-hybrid state, and the sp2-hybridized atom (with a double bond) acts as an electron acceptor, since it has a higher electronegativity:

When the inductive effect of the methyl group is transferred to the double bond, the mobile π-bond is affected first of all.

The effect 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 represented by 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 the 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 breaking of chemical bonds in reacting particles. Of these, two large groups of reactions can be distinguished - radical and ionic.

Radical reactions - these are processes that go with a homolytic rupture of a covalent bond. In a homolytic rupture, a pair of electrons forming a bond is divided in such a way that each of the formed particles receives one electron. As a result of homolytic rupture, 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 breaking of covalent bonds, when both bond electrons remain with one of the previously bound 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 electronic level. Due to the pair of electrons, the nucleophile is able to form a new covalent bond.

An electrophilic particle (electrophile) is a particle that has an unfilled outer electronic level. The electrophile represents 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 the initial 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 by the action of light is classified as a radical substitution, the addition of halogens to alkenes as an electrophilic addition, and the hydrolysis of alkyl halides as a nucleophilic substitution.