Organic chemistry - it is the chemistry of hydrocarbons and their derivatives.
Hydrocarbons (HC) - these are the simplest organic substances, the molecules of which consist of atoms of only two elements: C and H. For example: CH 4, C 2 H 6, C 6 H 6, etc.
HC derivatives- these are the products of substitution of "H" atoms in hydrocarbon molecules for other or groups of atoms. For example:
The name "organic chemistry" appeared at the beginning of the 19th century, when it was established that carbon-containing substances are the basis of plant and animal organisms.
Until the 20s of the XIX century. many scientists believed that organic substances could not be obtained in the laboratory from inorganic substances, that they were formed only in living nature with the participation of a special "life force". The doctrine of "life force" is called vitalism.
A.M. Butlerov This doctrine did not last long, because already in the beginning and middle of the XIX century. many organic substances have been synthesized:
1828 - Wehler synthesizes urea CO (NH 2) 2, which is one of the products formed in the body;
1850s – Berthelot synthesizes fats;
1861 - Butlerov synthesized one of the carbohydrates.
Now more than 10 million organic substances are known; many of them do not exist in nature, but are obtained in the laboratory. The industrial synthesis of various organic substances is one of the main directions of the chemical industry.
There is no fundamental difference between organic and inorganic substances. However, typical organic substances have a number of properties that distinguish them from typical inorganic substances. This is due to the difference in the nature of the chemical bond:
The main provisions of the theory of the chemical structure of organic compounds
This theory was developed by the Russian scientist A.M. Butlerov (1858 - 1861).
I position . Atoms in the molecules of organic substances are connected to each other in a certain sequence according to their valency.
The sequence in which atoms are connected in a molecule is called chemical structure(structure).
In organic compounds, carbon atoms can join with each other to form chains (carbon skeleton). Depending on the presence of certain carbon atoms, the chains are:
A) straight (unbranched)- contain two primary atoms (extreme in the chain), the remaining atoms are secondary; For example:
b) branched– contain at least one tertiary or at least one quaternary carbon atom; For example:
V) closed (cycles)– do not contain primary carbon atoms; For example:
II position . The properties of substances depend not only on the composition, but also on the structure of their molecules.
For example, there are 2 different substances that have the same composition, expressed by the empirical formula C 2 H 6 O:
Isomers- these are substances that have the same composition, but a different molecular structure and different properties.
isomerism is the existence of isomers.
Isomers have the same empirical formula but different structural formulas. With an increase in the number of carbon atoms in a molecule, the number of isomers increases sharply; For example:
C 4 H 10 - 2 isomers,
C 10 H 22 - 75 isomers.
Types of isomerism
1. Structural isomerism
2. Spatial isomerism(geometric isomerism, cis-trans isomerism)
The order of connection of atoms in these isomers is the same, but the arrangement of atoms in space is different.
3. Interclass isomerism - isomerism of substances belonging to different classes organic compounds:
III position. In the molecules of organic substances, atoms and groups of atoms influence each other. This mutual influence determines the properties of substances.
Consider, for example, the effect of the OH group on the mobility of the “H” atoms in the benzene cycle:
One atom is substituted in the benzene nucleus.
In the presence of the -OH group, three hydrogen atoms are replaced in the benzene nucleus.
On the other hand, the hydrocarbon radical affects the mobility of the hydrogen atom in the OH group:
If the -OH group is bonded to the benzene ring, the hydrogen atom in it is mobile and can be replaced by an atom when interacting with.
If the -OH group is bonded to an alkyl radical, the mobility of the hydrogen atom in it is low, and it cannot be replaced by a metal under the action of an alkali.
homologous series. homologues
homologous series- this is a series of organic compounds in which each next member of the series differs from the previous one by the CH 2 group. Compounds with similar chemical properties that form a homologous series are called homologues. The CH 2 group is called homological difference.
For example: CH 4, C 2 H 6, C 3 H 8, C 4 H 10 ... CnH 2 n+ 2.
Composition of all members homologous series can be expressed by a general formula.
Classification of organic substances
Most organic compounds can be represented by the formula: R - X, where R is a hydrocarbon radical; X is a functional group.
Functional groups are groups of atoms that determine the most characteristic Chemical properties organic compounds. Hydrocarbon radicals are hydrocarbon residues associated with functional groups.
1. Classification of organic substances according to the structure of the hydrocarbon radical (R)
2. Classification of organic substances by functional groups (X)
Types of organic reactions
1. Addition reactions
2. Substitution reactions
3. Elimination reactions
4. Decomposition reactions
5. Isomerization reactions
6. Oxidation reactions
Organic chemistry is the science of organic compounds and their transformations. The term "organic chemistry" was introduced by the Swedish scientist J. Berzelius at the beginning of the 19th century. Prior to this, substances were classified according to the source of their production. Therefore, in the XVIII century. There were three types of chemistry: "plant", "animal" and "mineral". At the end of the XVIII century. the French chemist A. Lavoisier showed that substances obtained from plant and animal organisms (hence their name "organic compounds"), unlike mineral compounds, contain only a few elements: carbon, hydrogen, oxygen, nitrogen, and sometimes phosphorus and sulfur. Since carbon is invariably present in all organic compounds, organic chemistry has been occupied since the middle of the 19th century. often referred to as the chemistry of carbon compounds.
The ability of carbon atoms to form long unbranched and branched chains, as well as rings and attach other elements or their groups to them, is the reason for the diversity of organic compounds and the fact that they greatly outnumber inorganic compounds in number. About 7 million organic compounds are now known, and about 200 thousand inorganic compounds.
After the works of A. Lavoisier and until the middle of the XIX century. chemists conducted an intensive search for new substances in natural products and developed new methods for their transformation. Particular attention was paid to the determination of the elemental composition of compounds, the conclusion of their molecular formulas and establishing the dependence of the properties of compounds on their composition. It turned out that some compounds, having the same composition, differ in their properties. Such compounds were called isomers (see Isomerism). It has been observed that many compounds in chemical reactions groups of elements that remain unchanged are exchanged. These groups were called radicals, and the doctrine that tried to present organic compounds as consisting of such radicals was called the theory of radicals. In the 40-50s. 19th century attempts have been made to classify organic compounds according to the type of inorganic ones (for example, ethyl alcohol C2H5-O-H and diethyl ether C2H5-O-C2H5 were classified as water H-O-H). However, all these theories, as well as the determination of the elemental composition and molecular weight of organic compounds, have not yet been based on a solid foundation of a sufficiently developed atomic and molecular theory. Therefore, in organic chemistry there was discord in the ways of writing the composition of substances, and even such a simple compound as acetic acid was represented by different empirical formulas: C4H404, C8H804, CrH402, of which only the last one was correct.
Only after the Russian scientist A. M. Butlerov created the theory of chemical structure (1861) did organic chemistry gain a solid scientific basis which ensured its rapid development in the future. The prerequisites for its creation were the successes in the development of atomic and molecular theory, ideas about valency and chemical bonding in the 50s. 19th century This theory made it possible to predict the existence of new compounds and their properties. Scientists have begun the systematic chemical synthesis of organic compounds predicted by science that do not occur in nature. Thus, organic chemistry has become to a large extent the chemistry of artificial compounds.
In the first half of the XIX century. Organic chemists were mainly engaged in the synthesis and study of alcohols, aldehydes, acids, and some other alicyclic and benzoic compounds (see Aliphatic compounds; Alicyclic compounds). From substances not found in nature, derivatives of chlorine, iodine, and bromine were synthesized, as well as the first organometallic compounds (see Organoelement Compounds). Coal tar has become a new source of organic compounds. Benzene, naphthalene, phenol and other benzenoid compounds, as well as heterocyclic compounds - quinoline, pyridine, were isolated from it.
In the second half of the XIX century. hydrocarbons, alcohols, acids with a branched carbon chain were synthesized, the study of the structure and synthesis of compounds important in practical terms (indigo, isoprene, sugars) began. The synthesis of sugars (see Carbohydrates) and many other compounds became possible after the advent of stereochemistry, which continued the development of the theory of chemical structure. Organic chemistry first half of XIX V. was closely associated with pharmacy - the science of medicinal substances.
In the second half of the XIX century. there has been a strong alliance between organic chemistry and industry, primarily aniline dye. Chemists were tasked with deciphering the structure of known natural dyes (alizarin, indigo, etc.), creating new dyes, and developing technically acceptable methods for their synthesis. Yes, in the 70s and 80s. 19th century applied organic chemistry.
Late XIX - early XX century. were marked by the creation of new directions in the development of organic chemistry. On an industrial scale, the richest source of organic compounds, oil, began to be used, and the rapid development of the chemistry of alicyclic compounds and the chemistry of hydrocarbons in general (see Petrochemistry) was associated with this. Practically important catalytic methods for the transformation of organic compounds appeared, created by P. Sabatier in France, V. N. Ipatiev, and later N. D. Zelinsky in Russia (see Catalysis). The theory of chemical structure has deepened significantly as a result of the discovery of the electron and the creation of electronic ideas about the structure of atoms and molecules. Powerful methods of physicochemical and physical studies of molecules were discovered and developed, primarily X-ray diffraction analysis. This made it possible to find out the structure, and therefore, to understand the properties and facilitate the synthesis of a huge number of organs! ical connections.
From the beginning of the 30s. 20th century in connection with the emergence quantum mechanics computational methods appeared that made it possible to draw conclusions about the structure and properties of organic compounds by calculation (see Quantum Chemistry).
Among the new areas of chemical science is the chemistry of organic derivatives of fluorine, which have gained great practical importance. In the 50s. 20th century the chemistry of price compounds arose (ferrocene, etc.), which is a connecting link between organic and inorganic chemistry. The use of isotopes has firmly entered the practice of organic chemists. As early as the beginning of the 20th century. freely existing organic radicals were discovered (see Free radicals), and subsequently the chemistry of non-polyvalent organic compounds was created - carbonium ions, carbanions, radical ions, molecular ions (see Ions). In the 60s. completely new types of organic compounds were synthesized, such as catenanes, in which individual cyclic molecules are linked to each other, similar to the five intertwined Olympic rings.
Organic chemistry in the XX century. acquired great practical importance, especially for oil refining, polymer synthesis, synthesis and study of physiological active substances. As a result, such areas as petrochemistry, polymer chemistry, and bioorganic chemistry emerged from organic chemistry into independent disciplines.
Modern organic chemistry has a complex structure. Its core is preparative organic chemistry, which deals with the isolation from natural products and the artificial preparation of individual organic compounds, as well as the creation of new methods for their preparation. It is impossible to solve these problems without relying on analytical chemistry, which makes it possible to judge the degree of purification, homogeneity (homogeneity) and individuality of organic compounds, providing data on their composition and structure in an isolated state, as well as when they act as initial substances, intermediate and end products of the reaction. For this purpose analytical chemistry uses various chemical, physicochemical and physical methods research. A conscious approach to solving the problems facing preparative and analytical organic chemistry is provided by their reliance on theoretical organic chemistry. The subject of this science is the further development of the theory of structure, as well as the formulation of relationships between the composition and structure of organic compounds and their properties, between the conditions for the occurrence of organic reactions and their speed and achievement chemical equilibrium. The objects of theoretical organic chemistry can be both non-reacting compounds and compounds during their transformations, as well as intermediate, unstable formations that occur during reactions.
Such a structure of organic chemistry was formed under the influence of various factors, the most important of which were and remain the demands of practice. It is precisely this that explains, for example, the fact that in modern organic chemistry the chemistry of heterocyclic compounds is developing rapidly, closely related to such an applied direction as the chemistry of synthetic and natural drugs.
He studies the composition, structure, properties and application of organic compounds.
All organic compounds have one common property: They necessarily contain carbon atoms. In addition to carbon, the molecules of organic compounds include hydrogen, oxygen, nitrogen, less often sulfur, phosphorus, and halogens.
Currently, more than twenty million organic compounds are known. This diversity is possible due to the unique properties of carbon, whose atoms are able to form strong chemical bonds both with each other and with other atoms.
There is no sharp boundary between inorganic and organic compounds. Certain compounds of carbon, such as oxides of carbon, salts carbonic acid, according to the nature of their properties, they are classified as inorganic.
The simplest organic compounds are hydrocarbons containing only carbon and hydrogen atoms. Other organic compounds can be considered as derivatives of hydrocarbons.
This is the science that studies hydrocarbons and their derivatives.
There are organic compounds of natural origin (starch, cellulose, natural gas, oil, etc.) and synthetic (resulting from synthesis in laboratories and factories).
Organic compounds of natural origin also include substances formed in living organisms. This, for example, nucleic acids, proteins, fats, carbohydrates, enzymes, vitamins, hormones. The structure and properties of these substances, their biological functions are studied by biochemistry, molecular biology And bioorganic chemistry.
Overwhelming majority medicines are organic compounds. The chemistry of medicinal substances is engaged in the creation of drugs and the study of their effect on the body.
A large number of synthetic organic compounds are obtained from the processing of oil (figure below), natural gas, coal and wood.
1 - raw materials for the chemical industry; 2 - asphalt; 3 - oils; 4 - fuel for aircraft; 5 - lubricants; 6 - diesel fuel; 7 - gasoline
Achievements of organic chemistry are used in production building materials, in mechanical engineering and agriculture, medicine, electrical and semiconductor industries. Without synthetic fuels, synthetic detergents, polymers and plastics, dyes, etc., it is impossible to imagine modern life.
The impact of organic substances obtained by man on living organisms and other objects of nature is different. The use of some organic compounds in some cases leads to serious environmental issues. For example, the chlorine-containing insecticide DDT, previously used to control harmful insects, due to accumulation in living organisms and slow decomposition in natural conditions currently banned for use.
It is assumed that fluorochlorohydrocarbons (freons) (for example, difluoro-dichloromethane CF 2 Cl 2) contribute to the destruction of the ozone layer of the atmosphere, which protects our planet from the harsh ultraviolet radiation of the Sun. For this reason, freons are replaced by less dangerous saturated hydrocarbons.
You need JavaScript enabled to voteOrganic chemistry is the science that studies carbon compounds calledorganic substances. In this regard, organic chemistry is also called chemistry of carbon compounds.
The most important reasons for the separation of organic chemistry into a separate science are as follows.
1. Numerous organic compounds in comparison with inorganic ones.
The number of known organic compounds (about 6 million) significantly exceeds the number of compounds of all other elements periodic system Mendeleev. At present, about 700,000 inorganic compounds are known, and approximately 150,000 new organic compounds are now obtained in one year. This is explained not only by the fact that chemists are especially intensively engaged in the synthesis and study of organic compounds, but also by the special ability of the element carbon to give compounds containing an almost unlimited number of carbon atoms linked in chains and cycles.
2. Organic substances are of exceptional importance both because of their extremely diverse practical application and because they play a crucial role in the life processes of organisms.
3. There are significant differences in the properties and reactivity of organic compounds from inorganic, as a result, the need arose for the development of many specific methods for the study of organic compounds.
The subject of organic chemistry is the study of methods for the preparation, composition, structure, and applications of the most important classes of organic compounds.
2. Brief historical review of the development of organic chemistry
Organic chemistry as a science took shape at the beginning of the 19th century, but man's acquaintance with organic substances and their application for practical purposes began in ancient times. The first known acid was vinegar, or water solution acetic acid. The ancient peoples knew the fermentation of grape juice, they knew a primitive method of distillation and used it to obtain turpentine; Gauls and Germans knew how to make soap; in Egypt, Gaul and Germany they knew how to brew beer.
In India, Phoenicia and Egypt, the art of dyeing with the help of organic substances was highly developed. In addition, ancient peoples used such organic substances as oils, fats, sugar, starch, gum, resins, indigo, etc.
The period of development of chemical knowledge in the Middle Ages (approximately until the 16th century) was called the period of alchemy. However, the study of inorganic substances was much more successful than the study of organic substances. Information about the latter has remained almost as limited as in more ancient ages. Some progress has been made through the improvement of distillation methods. In this way, in particular, several essential oils were isolated and strong wine alcohol was obtained, which was considered one of the substances with which you can prepare the philosopher's stone.
End of the 18th century was marked by notable successes in the study of organic substances, and organic substances began to be studied from a purely scientific point of view. During this period, a number of the most important organic acids (oxalic, citric, malic, gallic) were isolated from plants and described, and it was found that oils and fats contain, as a common component, the “sweet beginning of oils” (glycerin), etc.
Gradually began to develop studies of organic substances - the products of vital activity of animal organisms. For example, urea and uric acid were isolated from human urine, and hippuric acid was isolated from cow and horse urine.
The accumulation of significant factual material was a strong impetus to a deeper study of organic matter.
For the first time the concept of organic matter and organic chemistry was introduced by the Swedish scientist Berzelius (1827). In a chemistry textbook that has gone through many editions, Berzelius expresses the conviction that “in living nature, the elements obey different laws than in lifeless nature” and that organic substances cannot be formed under the influence of ordinary physical and chemical forces, but require a special “life force” for their formation. ". He defined organic chemistry as "the chemistry of plant and animal substances, or substances formed under the influence of the vital force." The subsequent development of organic chemistry proved the fallacy of these views.
In 1828, Wöhler showed that an inorganic substance - ammonium cyanate - when heated, turns into a waste product of an animal organism - urea.
In 1845, Kolbe synthesized a typical organic substance - acetic acid, using charcoal, sulfur, chlorine and water as starting materials. In a relatively short period, a number of other organic acids were synthesized, which had previously been isolated only from plants.
In 1854, Berthelot succeeded in synthesizing substances belonging to the class of fats.
In 1861, A. M. Butlerov, by the action of lime water on paraformaldehyde, for the first time carried out the synthesis of methylenenitane, a substance belonging to the class of sugars, which, as is known, play an important role in the vital processes of organisms.
All these scientific discoveries led to the collapse of vitalism - the idealistic doctrine of "life force".
S. I. LEVCHENKOV
BRIEF OUTLINE OF THE HISTORY OF CHEMISTRY
Tutorial for students of the Faculty of Chemistry of the Russian State University
5.2. STRUCTURAL CHEMISTRY
The emergence of structural chemistry
In the first half of the 19th century, a fundamentally new concept of chemistry was born - structural chemistry, based on the premise that the properties of a substance are determined not only by its composition, but also by its structure, i.e. the order of connection of atoms and their spatial arrangement. The very first structural representations necessarily arise together with Dalton's atomism. Developing ideas about how to combine "simple atoms" into "complex atoms", Dalton pursued only one goal - to create a theory to explain the empirically discovered stoichiometric laws. However, the symbols chosen by Dalton chemical elements when depicting complex atoms, they assumed the choice of a certain order of connecting atoms to each other. However, the question of the order of connection of atoms was postponed for quite a long time, since chemists did not have any facts indicating the influence of the method of connection of atoms on the properties of a substance. The chemical symbolism of Berzelius made it possible to circumvent this issue, although Berzelius's electrochemical theory still considers some problems ("adhesion forces", "juxtaposition", etc.), which later became fundamental questions of structural chemistry.
The emergence of structural chemistry should apparently be associated with the discovery of the phenomenon of isomerism. In 1825, Johann Justus von Liebig discovered that the elemental composition of fulminic acid corresponds exactly to the composition of cyanic acid, which Friedrich Wöhler had obtained the year before. Repeated analyzes carried out by Wöhler and Liebig unambiguously established the existence of substances that are identical in composition but differ in properties. Continuing work with cyanic acid, Wöhler, by evaporating a solution of ammonium isocyanate, obtained in 1828 an isomeric organic substance, urea. In 1830, J. Ya. Berzelius found that grape and tartaric acids also have the same composition, but differ in properties. Berzelius proposed the term for the discovered phenomenon "isomerism"(from the Greek ισοζ μερον - equal measure). It soon became clear that this phenomenon is extremely common in organic chemistry. The composition of organic substances includes a relatively small number of elements - carbon, hydrogen, nitrogen, oxygen, sulfur and phosphorus (the so-called organogenic elements) - with a huge variety of properties. That is why, throughout almost the entire 19th century, structural concepts were in demand, primarily in organic chemistry. It should be emphasized, however, that the concepts of "structural chemistry" and "organic chemistry" should not be categorically equated.
The solution to the problem of the structure of organic substances was based on the ideas of Berzelius about radicals- polar groups of atoms (not containing oxygen) that can pass from one substance to another without change. Back in 1810-1811. Joseph Louis Gay-Lussac and Louis Jacques Tenard showed that cyanide radical CN behaves like a single atom (moreover, very similar to a chlorine or bromine atom). The concept of radicals, which is in good agreement with the electrochemical theory of Berzelius, made it possible to extend this theory to organic substances.
Creation of theories of structural chemistry
Theory of complex radicals arose and began to be actively developed by many chemists after the work of Liebig and Wöhler "On the radical of benzoic acid", published in 1832. Liebig and Wöhler showed that the grouping of atoms C 14 H 10 O 2 (the correct gross formula is C 7 H 5 O) in the chain of transformations of benzoic acid (benzaldehyde - benzoic acid - benzoyl chloride - benzoyl cyanide) behaves as a whole - like a kind of "organic atom". The theory of complex radicals quickly gained almost universal acceptance. In 1837, in the generalizing article "On the Current State of Organic Chemistry", one of the authors of which was Liebig, it was argued that the study of complex radicals is the main task of organic chemistry, since "cyan, amide, benzoyl, ammonia radicals, fats, alcohol and its derivatives form the true elements of organic nature, while the simplest constituents - carbon, hydrogen, oxygen and nitrogen - are found only when organic matter is destroyed. The number of described radicals increased rapidly. The theory of complex radicals proceeded from the assumption that radicals are capable of independent existence, although chemists have not been able to isolate them. Berzelius wrote about this: "The reason why we cannot isolate the radicals ... is not that they do not exist, but that they combine too quickly."
coordination chemistry
For quite a long time, the theory of valency was applied mainly to organic compounds. However, rather soon, structural representations were also in demand in chemistry. complex compounds. Theoretical representations of this section inorganic chemistry were formed on the basis of studying the properties of complexes obtained by the interaction of transition metal salts with ammonia. The first step towards coordination chemistry was ammonium hypothesis Thomas Graham (1840), who saw an analogy between the interaction of ammonia with acids and with metal salts; according to this hypothesis, the metal took the place of one of the hydrogen atoms in the ammonium ion. Graham's hypothesis was developed in 1851 by Hoffmann, who suggested that the hydrogen atom in the ammonium radical can be replaced by another ammonium radical.
The next step was chain theory, proposed in 1869 by Christian Wilhelm Blomstrand and improved by Sophus Mads Jørgensen. In the Blomstrand-Jørgensen theory, for some elements, a valency higher than usual was allowed, as well as the possibility of the formation of chains by atoms of nitrogen, oxygen and other elements. The experimentally established difference between the acid residues that make up the complex was explained by the different way of their binding - directly to the metal or to the end of the chain. For example, for ammonia complexes of the composition CoCl 3 6NH 3, CoCl 3 5NH 3 and CoCl 3 4NH 3, from solutions of which three, two and one equivalent of chlorine are deposited with silver nitrate, respectively, Jörgensen assumed the following structure:
However, the Blomstrand-Jörgensen theory could not explain, for example, the existence of two isomeric complexes of the composition CoCl 3 ·4NH 3 - praseosalts (green) and violeosalts (violet).
