Chemistry is a science that gives us all the variety of materials and household items that we, without hesitation, use every day. But in order to come to the discovery of such a variety of compounds that is known today, many chemists had to go through a difficult scientific path.
Huge work, numerous successful and unsuccessful experiments, a colossal theoretical knowledge base - all this led to the formation of various areas of industrial chemistry, made it possible to synthesize and use modern materials: rubbers, plastics, plastics, resins, alloys, various glasses, silicones, and so on.
One of the most famous, honored chemists who made an invaluable contribution to the development of organic chemistry was the Russian man A. M. Butlerov. We will briefly consider his works, merits and results of work in this article.
short biography
The date of birth of the scientist is September 1828, the number varies in different sources. He was the son of Lieutenant Colonel Mikhail Butlerov, he lost his mother quite early. He lived all his childhood in his grandfather's family estate, in the village of Podlesnaya Shentala (now a district of the Republic of Tatarstan).
He studied in different places: first in a closed private school, then in a gymnasium. Later he entered Kazan University in the Department of Physics and Mathematics. However, despite this, he was most interested in chemistry. The future author of the theory of the structure of organic compounds remained on the spot after graduation as a teacher.
1851 - the time of defending the first dissertation work of a scientist on the topic "Oxidation of organic compounds". After a brilliant performance, he was given the opportunity to manage all chemistry at his university.
The scientist died in 1886 where he spent his childhood, in the family estate of his grandfather. He was buried in the local family chapel.
The scientist's contribution to the development of chemical knowledge
Butlerov's theory of the structure of organic compounds is, of course, his main work. However, not the only one. It was this scientist who first created the Russian school of chemists.
Moreover, scientists who later had great weight in the development of all science came out of its walls. These are the following people:
- Markovnikov;
- Zaitsev;
- Kondakov;
- Favorsky;
- Konovalov;
- Lvov and others.
Works in organic chemistry
There are many such works. After all, Butlerov spent almost all his free time in the laboratory of his university, carrying out various experiments, drawing conclusions and conclusions. This is how the theory of organic compounds was born.
There are several particularly capacious works of the scientist:
- he created a report for a conference on the topic "On the chemical structure of matter";
- dissertation work "About essential oils";
- first scientific work "Oxidation of organic compounds".
Before its formulation and creation, the author of the theory of the structure of organic compounds studied the works of other scientists from different countries for a long time, studied their works, including experimental ones. Only later, having generalized and systematized the knowledge gained, did he reflect all the conclusions in the provisions of his nominal theory.
Theory of the structure of organic compounds A. M. Butlerova
The 19th century is marked by the rapid development of almost all sciences, including chemistry. In particular, extensive discoveries on carbon and its compounds continue to be accumulated and amaze everyone with their diversity. However, no one dares to systematize and streamline all this factual material, bring to a common denominator and reveal common patterns on which everything is built.
Butlerov A.M. was the first to do this. It was he who owns the ingenious theory of the chemical structure of organic compounds, the provisions of which he spoke en masse at the German conference of chemists. This was the beginning of a new era in the development of science, organic chemistry rose to
The scientist himself went to this gradually. He conducted many experiments and predicted the existence of substances with given properties, discovered some types of reactions and saw the future behind them. He studied the works of his colleagues and their discoveries a lot. Only against this background, through careful and painstaking work, did he manage to create his masterpiece. And now the theory of the structure of organic compounds in this is practically the same as the periodic system in the inorganic.
Discoveries of a scientist before creating a theory
What discoveries were made and theoretical justifications given to scientists before the theory of the structure of organic compounds by A. M. Butlerov appeared?
- The domestic genius was the first to synthesize such organic substances as urotropine, formaldehyde, methylene iodide and others.
- He synthesized a sugar-like substance (tertiary alcohol) from inorganics, thereby dealing another blow to the theory of vitalism.
- He predicted the future for polymerization reactions, calling them the best and most promising.
- Isomerism was explained for the first time only by him.
Of course, these are only the main milestones of his work. In fact, many years of painstaking work of a scientist can be described for a long time. However, the theory of the structure of organic compounds has become the most significant today, the provisions of which will be discussed further.
The first position of the theory
In 1861, the great Russian scientist, at a congress of chemists in the city of Speyer, shared with colleagues his views on the causes of the structure and diversity of organic compounds, expressing all this in the form of theoretical provisions.
The very first point is as follows: all atoms within a single molecule are connected in a strict sequence, which is determined by their valency. In this case, the carbon atom exhibits a valency index of four. Oxygen has a value of this indicator equal to two, hydrogen - to one.
He proposed to call such a feature chemical. Later, the designations of expressing it on paper using graphic full structural, abbreviated and molecular formulas were adopted.
This also includes the phenomenon of the connection of carbon particles with each other in endless chains of various structures (linear, cyclic, branched).
In general, Butlerov's theory of the structure of organic compounds, with its first position, determined the significance of valence and a single formula for each compound, reflecting the properties and behavior of a substance during reactions.
The second position of the theory
In this paragraph, an explanation was given to the diversity of organic compounds in the world. Based on the carbon compounds in the chain, the scientist suggested that there are unequal compounds in the world that have different properties, but are completely identical in molecular composition. In other words, there is a phenomenon of isomerism.
With this position, the theory of the structure of organic compounds of A. M. Butlerov not only explained the essence of isomers and isomerism, but the scientist himself confirmed everything by practical experience.
So, for example, he synthesized an isomer of butane - isobutane. Then he predicted for pentane the existence of not one, but three isomers, based on the structure of the compound. And he synthesized them all, proving his case.
Disclosure of the third provision
The next point of the theory says that all atoms and molecules within the same compound are able to influence the properties of each other. The nature of the behavior of a substance in reactions of various types, the chemical and other properties exhibited, will depend on this.
Thus, on the basis of this provision, several differing in the type and structure of the functional defining group are distinguished.
The theory of the structure of organic compounds by A. M. Butlerov is summarized in almost all textbooks on organic chemistry. After all, it is she who is the basis of this section, the explanation of all the patterns on which molecules are built.
The Importance of Theory for Modernity
Certainly it is great. This theory allowed:
- combine and systematize all the factual material accumulated by the time of its creation;
- explain the patterns of structure, properties of various compounds;
- give a full explanation of the reasons for such a large variety of compounds in chemistry;
- gave rise to numerous syntheses of new substances based on the provisions of the theory;
- allowed the advancement of views, the development of atomic and molecular science.
Therefore, to say that the author of the theory of the structure of organic compounds, whose photo can be seen below, did a lot, is to say nothing. Butlerov can rightfully be considered the father of organic chemistry, the ancestor of its theoretical foundations.
His scientific vision of the world, the genius of thinking, the ability to foresee the result played a role in the final analysis. This man possessed colossal capacity for work, patience and tirelessly experimented, synthesized, and trained. I was wrong, but I always learned a lesson and made the right perspective conclusions.
Only such a set of qualities and business acumen, perseverance made it possible to achieve the desired effect.
Studying organic chemistry at school
In the course of secondary education, not much time is devoted to studying the basics of organics. Only one quarter of the 9th grade and the whole year of the 10th stage (according to the program of Gabrielyan O.S.). However, this time is enough for the guys to be able to study all the main classes of compounds, the features of their structure and nomenclature, and their practical significance.
The basis for starting the development of the course is the theory of the structure of organic compounds by A. M. Butlerov. Grade 10 is devoted to a full consideration of its provisions, and in the future - to their theoretical and practical confirmation in the study of each class of substances.
The first appeared at the beginning of the 19th century. radical theory(J. Gay-Lussac, F. Wehler, J. Liebig). Radicals were called groups of atoms that pass unchanged during chemical reactions from one compound to another. This concept of radicals has been preserved, but most of the other provisions of the theory of radicals turned out to be incorrect.
According to type theory(C. Gerard) all organic substances can be divided into types corresponding to certain inorganic substances. For example, R-OH alcohols and R-O-R ethers were considered as representatives of the H-OH type of water, in which hydrogen atoms are replaced by radicals. The theory of types created a classification of organic substances, some of the principles of which are currently applied.
The modern theory of the structure of organic compounds was created by the outstanding Russian scientist A.M. Butlerov.
The main provisions of the theory of the structure of organic compounds A.M. Butlerov
1. Atoms in a molecule are arranged in a certain sequence according to their valency. The valency of the carbon atom in organic compounds is four.
2. The properties of substances depend not only on which atoms and in what quantities are part of the molecule, but also on the order in which they are interconnected.
3. The atoms or groups of atoms that make up the molecule mutually influence each other, on which the chemical activity and reactivity of the molecules depend.
4. The study of the properties of substances allows you to determine their chemical structure.
The mutual influence of neighboring atoms in molecules is the most important property of organic compounds. This influence is transmitted either through a chain of single bonds or through a chain of conjugated (alternating) single and double bonds.
Classification of organic compounds is based on the analysis of two aspects of the structure of molecules - the structure of the carbon skeleton and the presence of functional groups.
organic compounds
Hydrocarbons Heterocyclic compounds
Limit- Nepre- Aroma-
ny efficient tic
Aliphatic Carbocyclic
Limit Unsaturated Alicyclic Aromatic
(Alkanes) (Cycloalkanes) (Arenas)
WITH P H 2 P+2 C P H 2 P WITH P H 2 P-6
End of work -
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Alkenes Alkadienes Alkynes
SpN2p SpN2p-2 SpN2p-2 Fig. 1. Classification of organic compounds by structure
The electronic structure of the carbon atom. Hybridization.
For the valence electron layer of the C atom, which is in the main subgroup of the fourth group of the second period of the Periodic Table of D. I. Mendeleev, the main quantum number n \u003d 2, side (orbitally
Related systems
There are two types of conjugate systems (and conjugations). 1. p, p-conjugation - electrons are delocalized
TOPIC 3. Chemical structure and isomerism of organic compounds
Isomerism of organic compounds. If two or more individual substances have the same quantitative composition (molecular formula), but differ from each other
Conformations of organic molecules
The rotation around the C–C s-bond is relatively easy, and the hydrocarbon chain can take different forms. Conformational forms easily pass into each other and therefore are not different compounds.
Conformations of cyclic compounds.
Cyclopentane. The five-membered ring in the planar form has bond angles of 108°, which is close to the normal value for the sp3-hybrid atom. Therefore, in planar cyclopentane, in contrast to the cycle
Configuration isomers
These are stereoisomers with a different arrangement around certain atoms of other atoms, radicals or functional groups in space relative to each other. Distinguish between the concepts of diastere
General characteristics of the reactions of organic compounds.
Acidity and basicity of organic compounds. To assess the acidity and basicity of organic compounds, two theories are of greatest importance - the Bronsted theory and the theory
Bronsted bases are neutral molecules or ions that can accept a proton (proton acceptors).
Acidity and basicity are not absolute, but relative properties of compounds: acidic properties are found only in the presence of a base; basic properties - only in the presence of ki
General characteristics of reactions of organic compounds
Most organic reactions include several successive (elementary) steps. A detailed description of the totality of these stages is called a mechanism. Reaction mechanism -
Selectivity of reactions
In many cases, several unequal reaction centers are present in an organic compound. Depending on the structure of the reaction products, one speaks of regioselectivity, chemoselectivity, and
radical reactions.
Chlorine reacts with saturated hydrocarbons only under the influence of light, heating, or in the presence of catalysts, and all hydrogen atoms are successively replaced by chlorine: CH4
Electrophilic addition reactions
Unsaturated hydrocarbons - alkenes, cycloalkenes, alkadienes and alkynes - are capable of addition reactions, as they contain double or triple bonds. More important in vivo is the double
And elimination at a saturated carbon atom
Reactions of nucleophilic substitution at the sp3-hybridized carbon atom: heterolytic reactions due to the polarization of the carbon-heteroatom s-bond (halopro
Reactions of nucleophilic substitution involving sp2-hybridized carbon atom.
Let us consider the mechanism of reactions of this type using the example of the interaction of carboxylic acids with alcohols (esterification reaction). In the carboxyl group of the acid, p, p-conjugation is realized, since the pair of elements
Reactions of nucleophilic substitution in the series of carboxylic acids.
Only from purely formal positions can the carboxyl group be considered as a combination of carbonyl and hydroxyl functions. In fact, their mutual influence on each other is such that completely and
organic compounds.
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Dicarboxylic and unsaturated carboxylic acids.
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Amino alcohols
2-Aminoethanol (ethanolamine, colamine) - a structural component of complex lipids, is formed by opening the strained three-membered cycles of ethylene oxide and ethyleneimine with ammonia or water, respectively
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Bile acids
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vitamins
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The chemical structure of a substance as the order of connection of atoms in molecules. Mutual influence of atoms and atomic groups in a molecule. In this case, the tetravalence of carbon atoms and the monovalence of hydrogen atoms are strictly observed. The properties of substances depend not only on the qualitative and quantitative composition, but also on the order of connection of atoms in a molecule, the phenomenon of isomerism.
§1.3. The main provisions of the theory of the chemical structure of organic compounds A.M. Butlerova. The chemical structure of a substance as the order of connection of atoms in molecules. The dependence of the properties of substances on the chemical structure of molecules. Mutual influence of atoms and atomic groups in a molecule.
By the sixties of the last century, organic chemistry had accumulated a huge amount of factual material that required explanation. Against the background of the continuous accumulation of experimental facts, the insufficiency of theoretical concepts of organic chemistry was especially acute. Theory lagged behind practice and experiment. This lag was painfully reflected in the course of experimental research in laboratories; chemists conducted their research to a large extent at random, blindly, often without understanding the nature of the substances they synthesized and the essence of the reactions that led to their formation. Organic chemistry, in Wöhler's apt expression, resembled a dense forest full of wonderful things, a huge thicket with no exit, no end. "Organic chemistry is like a dense forest that is easy to enter but impossible to exit." So, apparently, it was destined that it was Kazan that gave the world a compass, with which it is not scary to enter the “Dense Forest of Organic Chemistry”. And this compass, which is still used today Butlerov's theory of chemical structure. From the 60s of the century before last to the present, any textbook on organic chemistry in the world begins with the postulates of the theory of the great Russian chemist Alexander Mikhailovich Butlerov.
The main provisions of the theory of chemical structure A.M. Butlerov
1st position
Atoms in molecules are connected to each other in a certain sequence according to their valences.. The sequence of interatomic bonds in a molecule is called its chemical structure and is reflected by one structural formula (structure formula).
This provision applies to the structure of the molecules of all substances. In the molecules of saturated hydrocarbons, carbon atoms, connecting with each other, form chains. In this case, the tetravalence of carbon atoms and the monovalence of hydrogen atoms are strictly observed.
2nd position. The properties of substances depend not only on the qualitative and quantitative composition, but also on the order of connection of atoms in a molecule(the phenomenon of isomerism).
Studying the structure of hydrocarbon molecules, A. M. Butlerov came to the conclusion that these substances, starting with butane (C 4 N 10 ), a different order of connection of atoms is possible with the same composition of molecules. So, in butane, a twofold arrangement of carbon atoms is possible: in the form of a straight (unbranched) and a branched chain.
These substances have the same molecular formula, but different structural formulas and different properties (boiling point). Therefore, they are different substances. Such substances are called isomers.
And the phenomenon in which there can be several substances that have the same composition and the same molecular weight, but differ in the structure of molecules and properties, is called the phenomenon isomerism. Moreover, with an increase in the number of carbon atoms in hydrocarbon molecules, the number of isomers increases. For example, there are 75 isomers (various substances) that correspond to the formula C 10 N 22 , and 1858 isomers with formula C 14 H 30 .
For composition C 5 H 12 the following isomers may exist (there are three of them) -
3rd position. By the properties of a given substance, one can determine the structure of its molecule, and by the structure, one can predict the properties.Proof of this provision. This provision can be proved using the example of inorganic chemistry.
Example. If a given substance changes the color of purple litmus to pink, interacts with metals that are up to hydrogen, with basic oxides, bases, then we can assume that this substance belongs to the class of acids, i.e. It contains hydrogen atoms and an acidic residue. And, conversely, if a given substance belongs to the class of acids, then it exhibits the above properties. For example: N 2 S O 4 - sulfuric acid
4th position. Atoms and groups of atoms in the molecules of substances mutually influence each other.
Proof of this position
This position can be proved using the example of inorganic chemistry. For this, it is necessary to compare the properties of aqueous solutions N H 3, HC1, H 2 O (indicator action). In all three cases, substances contain hydrogen atoms, but they are connected to different atoms, which have a different effect on hydrogen atoms, so the properties of the substances are different.
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 gave an explanation for the phenomenon of isomerism, predicted the existence of various isomers, and obtained some of them for the first time.
In the autumn of 1850, Butlerov passed the exams for a master's degree in chemistry and immediately began his doctoral dissertation "On Essential Oils", which he defended at the beginning of the next year.
On February 17, 1858, Butlerov made a report at the Paris Chemical Society, where he first outlined his theoretical ideas about the structure of matter. His report aroused general interest and lively debate: “The ability of atoms to combine with each other is different. Particularly interesting in this respect is carbon, which, according to August Kekule, is tetravalent, Butlerov said in his report If we imagine valence in the form of tentacles with which atoms bind together, one cannot fail to notice that the method of communication is reflected in the properties of the corresponding connections."
No one has yet expressed such thoughts. Perhaps the time has come, Butlerov continued, when our research should become the basis of a new theory of the chemical structure of substances. This theory will be distinguished by the accuracy of mathematical laws and will make it possible to foresee the properties of organic compounds.
A few years later, during a second trip abroad, Butlerov presented the theory he had created for discussion. He made a statement at the 36th Congress of German Naturalists and Physicians in Speyer. The convention took place in September 1861. He made a presentation before the chemical section. The topic had a more than modest name - “Something about the chemical structure of bodies.” In the report, Butlerov expresses the main provisions of his theory of the structure of organic compounds.
Proceedings of A.M. Butlerov
Office of A.M. Butlerov
The theory of chemical structure made it possible to explain many of the facts accumulated in organic chemistry at the beginning of the second half of the 19th century, proved that using chemical methods (synthesis, decomposition and other reactions) it is possible to establish the order of joining atoms in molecules (this proved the possibility of knowing the structure substances);
She introduced something new into the atomic and molecular theory (the order of arrangement of atoms in molecules, the mutual influence of atoms, the dependence of properties on the structure of molecules of a substance). The theory considered the molecules of matter as an ordered system endowed with the dynamics of interacting atoms. In this regard, the atomic and molecular theory received its further development, which was of great importance for the science of chemistry;
It made it possible to foresee the properties of organic compounds based on the structure, to synthesize new substances, adhering to the plan;
Allowed to explain the variety of organic compounds;
It gave a powerful impetus to the synthesis of organic compounds, the development of the industry of organic synthesis (the synthesis of alcohols, ethers, dyes, medicinal substances, etc.).
Having developed the theory and confirmed its correctness by the synthesis of new compounds, A.M. Butlerov did not consider the theory to be absolute and immutable. He argued that it should develop, and foresaw that this development would proceed through the resolution of contradictions between theoretical knowledge and emerging new facts.
The theory of chemical structure, as A.M. Butlerov, did not remain unchanged. Its further development proceeded mainly in two interrelated directions.
The first of them was predicted by A.M. Butlerov himself
He believed that science in the future will be able to establish not only the order of connection of atoms in a molecule, but also their spatial arrangement. The doctrine of the spatial structure of molecules, called stereochemistry (Greek "stereos" - spatial), entered science in the 80s of the last century. It made it possible to explain and predict new facts that did not fit into the framework of previous theoretical concepts.
The second direction is connected with the application in organic chemistry of the doctrine of the electronic structure of atoms, developed in physics of the twentieth century. This doctrine made it possible to understand the nature of the chemical bond of atoms, to find out the essence of their mutual influence, to explain the reason for the manifestation of certain chemical properties by a substance.
Structural formulas expanded and short
Reasons for the diversity of organic compounds 
Carbon atoms form single (simple), double and triple bonds:
There are homologous series:
Isomers:
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How science took shape at the beginning of the 19th century, when the Swedish scientist J. J. Berzelius first introduced the concept of organic substances and organic chemistry. The first theory in organic chemistry is the theory of radicals. Chemists have discovered that during chemical transformations, groups of several atoms pass unchanged from a molecule of one substance to a molecule of another substance, just as atoms of elements pass from molecule to molecule. Such "immutable" groups of atoms are called radicals.
However, not all scientists agreed with the theory of radicals. Many generally rejected the idea of atomism - the idea of the complex structure of the molecule and the existence of the atom as its constituent part. What is undeniably proven in our days and does not cause the slightest doubt, in the XIX century. was the subject of fierce controversy.
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Such formulas are somewhat similar to modern ones. But supporters of the theory of types did not consider them to reflect the real structure of substances and wrote many different formulas for one compound, depending on the chemical reactions that they tried to write using these formulas. They considered the structure of molecules to be fundamentally unknowable, which harmed the development of science.
3. The introduction by J. Berzelius in 1830 of the term "isomerism" for the phenomenon of the existence of substances of the same composition with different properties.
4. Successes in the synthesis of organic compounds, as a result of which the doctrine of vitalism, that is, the "life force", under the influence of which organic substances are allegedly formed in the body of living beings, was dispelled:
In 1828, F. Wehler synthesized urea from an inorganic substance (ammonium cyanate);
In 1842, the Russian chemist N. N. Zinin received aniline;
In 1845, the German chemist A. Kolbe synthesized acetic acid;
In 1854, the French chemist M. Berthelot synthesized fats, and, finally,
In 1861, A. M. Butlerov himself synthesized a sugar-like substance.
5. In the middle of the XVIII century. chemistry becomes a more rigorous science. As a result of the work of E. Frankland and A. Kekule, the concept of the valence of atoms of chemical elements was established. Kekule developed the concept of tetravalence of carbon. Thanks to the works of Cannizzaro, the concepts of atomic and molecular masses became clearer, their meanings and methods of determination were refined.
In 1860, more than 140 leading chemists from different European countries gathered for an international congress in Karlsruhe. The congress became a very important event in the history of chemistry: the successes of science were summarized and conditions were prepared for a new stage in the development of organic chemistry - the emergence of the theory of the chemical structure of organic substances by A. M. Butlerov (1861), as well as for the fundamental discovery of D. I. Mendeleev - The Periodic Law and the System of Chemical Elements (1869).
In 1861, A. M. Butlerov spoke at the congress of doctors and naturalists in the city of Speyer with a report "On the chemical structure of bodies." In it, he outlined the foundations of his theory of the chemical structure of organic compounds. Under the chemical structure, the scientist understood the order of connection of atoms in molecules.
Personal qualities of A. M. Butlerov
A. M. Butlerov was distinguished by the encyclopedic nature of chemical knowledge, the ability to analyze and generalize facts, and to predict. He predicted the existence of an isomer of butane, and then received it, as well as the isomer of butylene - isobutylene.
Butlerov Alexander Mikhailovich (1828-1886)
Russian chemist, academician of the St. Petersburg Academy of Sciences (since 1874). Graduated from Kazan University (1849). He worked there (since 1857 - professor, in 1860 and 1863 - rector). Creator of the theory of the chemical structure of organic compounds, which underlies modern chemistry. Substantiated the idea of the mutual influence of atoms in a molecule. He predicted and explained the isomerism of many organic compounds. Wrote "Introduction to the complete study of organic chemistry" (1864) - the first manual in the history of science based on the theory of chemical structure. Chairman of the Department of Chemistry of the Russian Physical and Chemical Society (1878-1882).
A. M. Butlerov created the first school of organic chemists in Russia, from which brilliant scientists emerged: V. V. Markovnikov, D. P. Konovalov, A. E. Favorsky and others.
No wonder D. I. Mendeleev wrote: “A. M. Butlerov is one of the greatest Russian scientists, he is Russian both in terms of his scientific education and the originality of his works.”
The main provisions of the theory of the structure of chemical compounds
The theory of the chemical structure of organic compounds, put forward by A. M. Butlerov in the second half of the last century (1861), was confirmed by the work of many scientists, including Butlerov's students and himself. It turned out to be possible on its basis to explain many phenomena that until then had no interpretation: isomerism, homology, the manifestation of tetravalence by carbon atoms in organic substances. The theory also fulfilled its prognostic function: on its basis, scientists predicted the existence of still unknown compounds, described properties and discovered them.
So, in 1862-1864. A. M. Butlerov considered the isomerism of propyl, butyl and amyl alcohols, determined the number of possible isomers and derived the formulas of these substances. Their existence was later experimentally proven, and some of the isomers were synthesized by Butlerov himself.
During the XX century. the provisions of the theory of the chemical structure of chemical compounds were developed on the basis of new views that have spread in science: the theory of the structure of the atom, the theory of chemical bonding, ideas about the mechanisms of chemical reactions. At present, this theory has a universal character, that is, it is valid not only for organic substances, but also for inorganic ones.
First position. Atoms in molecules are connected in a certain order in accordance with their valency. Carbon in all organic and most inorganic compounds is tetravalent.
It is obvious that the last part of the first provision of the theory can be easily explained by the fact that carbon atoms in compounds are in an excited state: 
a) tetravalent carbon atoms can combine with each other, forming various chains:
open branched
- open unbranched
- closed
b) the order of connection of carbon atoms in molecules can be different and depends on the type of covalent chemical bond between carbon atoms - single or multiple (double and triple).
Second position. The properties of substances depend not only on their qualitative and quantitative composition, but also on the structure of their molecules.
This position explains the phenomenon of isomerism. Substances that have the same composition, but different chemical or spatial structure, and therefore different properties, are called isomers. The main types of isomerism:
Structural isomerism, in which substances differ in the order of bonding of atoms in molecules:
1) isomerism of the carbon skeleton 
3) isomerism of homologous series (interclass) 
Spatial isomerism, in which the molecules of substances differ not in the order of bonding of atoms, but in their position in space: cis-trans-isomerism (geometric).
This isomerism is typical for substances whose molecules have a planar structure: alkenes, cycloalkanes, etc.
Optical (mirror) isomerism also belongs to spatial isomerism.
The four single bonds around the carbon atom, as you already know, are arranged tetrahedrally. If a carbon atom is bonded to four different atoms or groups, then a different arrangement of these groups in space is possible, that is, two spatial isomeric forms.
Two mirror forms of the amino acid alanine (2-aminopropanoic acid) are shown in Figure 17.
Imagine that an alanine molecule is placed in front of a mirror. The -NH2 group is closer to the mirror, so it will be in front in the reflection, and the -COOH group will be in the background, etc. (see image on the right). Alanya exists in two spatial forms, which, when superimposed, do not combine with one another.
The universality of the second position of the theory of the structure of chemical compounds confirms the existence of inorganic isomers.
So, the first of the syntheses of organic substances - the synthesis of urea, carried out by Wehler (1828), showed that an inorganic substance - ammonium cyanate and an organic substance - urea are isomeric: 
If you replace the oxygen atom in urea with a sulfur atom, you get thiourea, which is isomeric to ammonium thiocyanate, a well-known reagent for Fe 3+ ions. Obviously, thiourea does not give this qualitative reaction.
Third position. The properties of substances depend on the mutual influence of atoms in molecules.
For example, in acetic acid, only one of the four hydrogen atoms reacts with alkali. Based on this, it can be assumed that only one hydrogen atom is bonded to oxygen:
On the other hand, from the structural formula of acetic acid, one can conclude that it contains one mobile hydrogen atom, that is, that it is monobasic.
To verify the universality of the position of the theory of structure on the dependence of the properties of substances on the mutual influence of atoms in molecules, which exists not only in organic, but also in inorganic compounds, we compare the properties of hydrogen atoms in hydrogen compounds of non-metals. They have a molecular structure and under normal conditions are gases or volatile liquids. Depending on the position of the non-metal in the Periodic system of D. I. Mendeleev, a pattern can be identified in the change in the properties of such compounds: 
Methane does not interact with water. The lack of basic properties of methane is explained by the saturation of the valence capabilities of the carbon atom.
Ammonia exhibits basic properties. Its molecule is capable of attaching a hydrogen ion to itself due to its attraction to the lone electron pair of the nitrogen atom (donor-acceptor bond formation mechanism).
In phosphine PH3, the basic properties are weakly expressed, which is associated with the radius of the phosphorus atom. It is much larger than the radius of the nitrogen atom, so the phosphorus atom attracts the hydrogen atom to itself more weakly.
In periods from left to right, the charges of the nuclei of atoms increase, the radii of atoms decrease, the repulsive force of the hydrogen atom with a partial positive charge G + increases, and therefore the acidic properties of hydrogen compounds of non-metals are enhanced. 
In the main subgroups, the atomic radii of elements increase from top to bottom, non-metal atoms with 5- attract hydrogen atoms with 5+ weaker, the strength of hydrogen compounds decreases, they easily dissociate, and therefore their acidic properties are enhanced.
The different ability of hydrogen compounds of non-metals to remove or add hydrogen cations in solutions is explained by the unequal effect that a non-metal atom has on hydrogen atoms.
The different influence of atoms in the molecules of hydroxides formed by elements of the same period also explains the change in their acid-base properties.
The basic properties of hydroxides decrease, while acid ones increase, as the degree of oxidation of the central atom increases, therefore, the energy of its bond with the oxygen atom (8-) and the repulsion of the hydrogen atom (8+) by it increase.
Sodium hydroxide NaOH. Since the radius of the hydrogen atom is very small, it attracts the oxygen atom to itself more strongly and the bond between hydrogen and oxygen atoms will be stronger than between sodium and oxygen atoms. Aluminum hydroxide Al(OH)3 exhibits amphoteric properties.
In perchloric acid HclO 4, the chlorine atom with a relatively large positive charge is more strongly bonded to the oxygen atom and repels the hydrogen atom with 6+ more strongly. Dissociation proceeds according to the acid type.
The main directions in the development of the theory of the structure of chemical compounds and its significance
At the time of A. M. Butlerov, empirical (molecular) and structural formulas were widely used in organic chemistry. The latter reflect the order of connection of atoms in a molecule according to their valency, which is indicated by dashes.
For ease of recording, abbreviated structural formulas are often used, in which only the bonds between carbon or carbon and oxygen atoms are indicated by dashes.
Abbreviated structural formulas
Then, with the development of knowledge about the nature of the chemical bond and the influence of the electronic structure of the molecules of organic substances on their properties, they began to use electronic formulas in which the covalent bond is conventionally denoted by two dots. In such formulas, the direction of displacement of electron pairs in a molecule is often shown.
It is the electronic structure of substances that explains the mesomeric and induction effects.
The inductive effect is the displacement of electron pairs of gamma bonds from one atom to another due to their different electronegativity. Denoted (->).
The induction effect of an atom (or a group of atoms) is negative (-/), if this atom has a high electronegativity (halogens, oxygen, nitrogen), attracts gamma bond electrons and acquires a partial negative charge. An atom (or group of atoms) has a positive inductive effect (+/) if it repels the electrons of the gamma bonds. This property is possessed by some limiting radicals C2H5). Remember Markovnikov's rule about how hydrogen and a halogen of a hydrogen halide are added to alkenes (propene) and you will understand that this rule is of a particular nature. Compare these two examples of reaction equations:
[[Theory_of_the_chemical_compounds_A._M._Butlerov| 
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In the molecules of individual substances, both induction and mesomeric effects are manifested simultaneously. In this case, they either reinforce each other (in aldehydes, carboxylic acids), or mutually weaken (in vinyl chloride).
The result of the mutual influence of atoms in molecules is the redistribution of electron density.
The idea of the spatial direction of chemical bonds was first expressed by the French chemist J. A. Le Bel and the Dutch chemist J. X. Van't Hoff in 1874. The scientists' assumptions were fully confirmed by quantum chemistry. The properties of substances are significantly affected by the spatial structure of their molecules. For example, we have already given the formulas for cis- and trans-isomers of butene-2, which differ in their properties (see Fig. 16).
The average bond energy that must be broken during the transition from one form to another is approximately 270 kJ / mol; there is not so much energy at room temperature. For the mutual transition of butene-2 forms from one to another, it is necessary to break one covalent bond and form another instead. In other words, this process is an example of a chemical reaction, and both forms of butene-2 considered are different chemical compounds.
You obviously remember that the most important problem in the synthesis of rubber was getting stereoregular rubber. It was necessary to create a polymer in which the structural units would be arranged in a strict order (natural rubber, for example, consists only of cis-units), because such an important property of rubber as its elasticity depends on this.
Modern organic chemistry distinguishes two main types of isomerism: structural (chain isomerism, isomerism of the position of multiple bonds, isomerism of homologous series, isomerism of the position of functional groups) and stereoisomerism (geometric, or cis-trans-isomerism, optical, or mirror, isomerism).
So, you were able to make sure that the second position of the theory of chemical structure, clearly formulated by A. M. Butlerov, was incomplete. From a modern standpoint, this provision requires additions:
the properties of substances depend not only on their qualitative and quantitative composition, but also on their:
Chemical,
electronic,
Spatial structure.
The creation of the theory of the structure of substances played an important role in the development of organic chemistry. From a predominantly descriptive science, it turns into a creative, synthesizing science; it became possible to judge the mutual influence of atoms in the molecules of various substances (see Table 10). The theory of structure created the prerequisites for explaining and predicting various types of isomerism of organic molecules, as well as the directions and mechanisms of chemical reactions.
On the basis of this theory, organic chemists create substances that not only replace natural ones, but significantly surpass them in their properties. So, synthetic dyes are much better and cheaper than many natural ones, for example, alizarin and indigo known in antiquity. Synthetic rubbers are produced in large quantities with a wide variety of properties. Plastics and fibers are widely used, products from which are used in engineering, everyday life, medicine, and agriculture.
The value of the theory of chemical structure of A. M. Butlerov for organic chemistry can be compared with the value of the Periodic law and the Periodic system of chemical elements of D. I. Mendeleev for inorganic chemistry. It is not for nothing that both theories have so much in common in the ways of their formation, directions of development and general scientific significance. However, in the history of any other leading scientific theory (Ch. Darwin's theory, genetics, quantum theory, etc.) one can find such common stages.
1. Establish parallels between the two leading theories of chemistry - the Periodic Law and the Periodic Table of Chemical Elements by D. I. Mendeleev and the theory of the chemical structure of organic compounds by A. M. Butlerov on the following grounds: common in prerequisites, common in the directions of their development, common in prognostic roles.
2. What role did the theory of the structure of chemical compounds play in the formation of the Periodic Law?
3. What examples from inorganic chemistry confirm the universality of each of the provisions of the theory of the structure of chemical compounds?
4. Phosphorous acid H3PO3 refers to dibasic acids. Propose its structural formula and consider the mutual influence of atoms in the molecule of this acid.
5. Write the isomers having the composition С3Н8O. Name them according to the systematic nomenclature. Determine the types of isomerism.
6. The following formulas of crystalline hydrates of chromium(III) chloride are known: [Cr(H20)6]Cl3; [Cr(H20)5Cl]Cl2 H20; [Cr(H20)4 * C12]Cl 2H2O. What would you call this phenomenon?
