Just as in inorganic chemistry the fundamental theoretical basis is the Periodic law and the Periodic system of chemical elements of D. I. Mendeleev, so in organic chemistry the leading scientific basis is the theory of the structure of organic compounds of Butlerov-Kekule-Cooper.
Like any other scientific theory, the theory of the structure of organic compounds was the result of a generalization of the richest factual material accumulated by organic chemistry, which took shape as a science at the beginning of the 19th century. More and more new carbon compounds were discovered, the number of which increased like an avalanche (Table 1).
Table 1
Number of organic compounds known in different years
To explain this variety of organic compounds, scientists of the early XIX century. could not. Even more questions were raised by the phenomenon of isomerism.
For example, ethyl alcohol and dimethyl ether are isomers: these substances have the same composition C 2 H 6 O, but a different structure, that is, a different order of connection of atoms in molecules, and therefore different properties.
F. Wöhler, already known to you, in one of his letters to J. J. Berzelius, described organic chemistry as follows: “Organic chemistry can now drive anyone crazy. It seems to me a dense forest, full of amazing things, a boundless thicket from which you can’t get out, where you don’t dare to penetrate ... "
The development of chemistry was greatly influenced by the work of the English scientist E. Frankland, who, relying on the ideas of atomism, introduced the concept of valency (1853).
In the hydrogen molecule H 2, one covalent chemical bond H-H is formed, i.e., hydrogen is monovalent. The valence of a chemical element can be expressed by the number of hydrogen atoms that one atom of a chemical element attaches to itself or replaces. For example, sulfur in hydrogen sulfide and oxygen in water are divalent: H 2 S, or H-S-H, H 2 O, or H-O-H, and nitrogen in ammonia is trivalent:
In organic chemistry, the concept of "valency" is analogous to the concept of "oxidation state", which you are used to working with in the course of inorganic chemistry in elementary school. However, they are not the same. For example, in a nitrogen molecule N 2, the oxidation state of nitrogen is zero, and the valency is three:
In hydrogen peroxide H 2 O 2, the oxidation state of oxygen is -1, and the valency is two:
In the ammonium ion NH + 4, the oxidation state of nitrogen is -3, and the valency is four:
Usually, in relation to ionic compounds (sodium chloride NaCl and many other inorganic substances with an ionic bond), the term "valency" of atoms is not used, but their oxidation state is considered. Therefore, in inorganic chemistry, where most substances have a non-molecular structure, it is preferable to use the concept of "oxidation state", and in organic chemistry, where most compounds have a molecular structure, as a rule, use the concept of "valence".
The theory of chemical structure is the result of a generalization of the ideas of outstanding organic scientists from three European countries: the German F. Kekule, the Englishman A. Cooper and the Russian A. Butlerov.
In 1857, F. Kekule classified carbon as a tetravalent element, and in 1858, simultaneously with A. Cooper, he noted that carbon atoms can combine with each other in various chains: linear, branched and closed (cyclic).
The works of F. Kekule and A. Cooper served as the basis for the development of a scientific theory explaining the phenomenon of isomerism, the relationship between the composition, structure and properties of molecules of organic compounds. Such a theory was created by the Russian scientist A. M. Butlerov. It was his inquisitive mind that "dared to penetrate" the "dense forest" of organic chemistry and begin the transformation of this "boundless thicket" into a regular park filled with sunlight with a system of paths and alleys. The main ideas of this theory were first expressed by A. M. Butlerov in 1861 at the congress of German naturalists and doctors in Speyer.
Briefly formulate the main provisions and consequences of the Butlerov-Kekule-Cooper theory of the structure of organic compounds as follows.
1. The atoms in the molecules of substances are connected in a certain sequence according to their valency. Carbon in organic compounds is always tetravalent, and its atoms are able to combine with each other, forming various chains (linear, branched and cyclic).
Organic compounds can be arranged in series of substances similar in composition, structure and properties - homologous series.
- Butlerov Alexander Mikhailovich (1828-1886), Russian chemist, professor at Kazan University (1857-1868), from 1869 to 1885 - professor at St. Petersburg University. Academician of the St. Petersburg Academy of Sciences (since 1874). Creator of the theory of the chemical structure of organic compounds (1861). Predicted and studied the isomerism of many organic compounds. Synthesized many substances.
For example, methane CH 4 is the ancestor of the homologous series of saturated hydrocarbons (alkanes). Its closest homologue is ethane C 2 H 6, or CH 3 -CH 3. The next two members of the homologous series of methane are propane C 3 H 8, or CH 3 -CH 2 -CH 3, and butane C 4 H 10, or CH 3 -CH 2 -CH 2 -CH 3, etc.
It is easy to see that for homologous series one can derive a general formula for the series. So, for alkanes, this general formula is C n H 2n + 2.
2. The properties of substances depend not only on their qualitative and quantitative composition, but also on the structure of their molecules.
This position of the theory of the structure of organic compounds explains the phenomenon of isomerism. Obviously, for butane C 4 H 10, in addition to the linear structure molecule CH 3 -CH 2 -CH 2 -CH 3, a branched structure is also possible:
This is a completely new substance with its own individual properties, different from those of linear butane.
Butane, in the molecule of which the atoms are arranged in the form of a linear chain, is called normal butane (n-butane), and butane, the chain of carbon atoms of which is branched, is called isobutane.
There are two main types of isomerism - structural and spatial.
In accordance with the accepted classification, three types of structural isomerism are distinguished.
Isomerism of the carbon skeleton. Compounds differ in the order of carbon-carbon bonds, for example, n-butane and isobutane considered. It is this type of isomerism that is characteristic of alkanes.
Isomerism of the position of a multiple bond (C=C, C=C) or a functional group (i.e., a group of atoms that determine whether a compound belongs to a particular class of organic compounds), for example:
Interclass isomerism. Isomers of this type of isomerism belong to different classes of organic compounds, for example, ethyl alcohol (the class of saturated monohydric alcohols) and dimethyl ether (the class of ethers) discussed above.
There are two types of spatial isomerism: geometric and optical.
Geometric isomerism is characteristic, first of all, for compounds with a double carbon-carbon bond, since the molecule has a planar structure at the site of such a bond (Fig. 6).
Rice. 6.
Model of the ethylene molecule
For example, for butene-2, if the same groups of atoms at carbon atoms in a double bond are on one side of the C=C bond plane, then the molecule is a cisisomer, if on opposite sides it is a transisomer.
Optical isomerism is possessed, for example, by substances whose molecules have an asymmetric, or chiral, carbon atom bonded to four various deputies. Optical isomers are mirror images of each other, like two palms, and are not compatible. (Now, obviously, the second name of this type of isomerism has become clear to you: Greek chiros - hand - a sample of an asymmetric figure.) For example, in the form of two optical isomers, there is 2-hydroxypropanoic (lactic) acid containing one asymmetric carbon atom.
Isomeric pairs arise in chiral molecules, in which the isomer molecules are related to each other in their spatial organization in the same way as an object and its mirror image are related to each other. A pair of such isomers always has the same chemical and physical properties, with the exception of optical activity: if one isomer rotates the plane of polarized light clockwise, then the other necessarily counterclockwise. The first isomer is called dextrorotatory, and the second is called levorotatory.
The importance of optical isomerism in the organization of life on our planet is very great, since optical isomers can differ significantly both in their biological activity and in compatibility with other natural compounds.
3. The atoms in the molecules of substances influence each other. You will consider the mutual influence of atoms in the molecules of organic compounds in the further study of the course.
The modern theory of the structure of organic compounds is based not only on the chemical, but also on the electronic and spatial structure of substances, which is considered in detail at the profile level of the study of chemistry.
Several types of chemical formulas are widely used in organic chemistry.
The molecular formula reflects the qualitative composition of the compound, that is, it shows the number of atoms of each of the chemical elements that form the molecule of the substance. For example, the molecular formula of propane is C 3 H 8 .
The structural formula reflects the order of connection of atoms in a molecule according to valence. The structural formula of propane is:
Often there is no need to depict in detail the chemical bonds between carbon and hydrogen atoms, therefore, in most cases, abbreviated structural formulas are used. For propane, such a formula is written as follows: CH 3 -CH 2 -CH 3.
The structure of molecules of organic compounds is reflected using various models. The best known are volumetric (scale) and ball-and-stick models (Fig. 7).
Rice. 7.
Models of the ethane molecule:
1 - ball-and-stick; 2 - scale
New words and concepts
- Isomerism, isomers.
- Valence.
- Chemical structure.
- Theory of the structure of organic compounds.
- Homological series and homological difference.
- Formulas molecular and structural.
- Models of molecules: volumetric (scale) and spherical.
Questions and tasks
- What is valence? How is it different from oxidation state? Give examples of substances in which the values of the oxidation state and valence of atoms are numerically the same and different,
- Determine the valency and oxidation state of atoms in substances whose formulas are Cl 2, CO 2, C 2 H 6, C 2 H 4.
- What is isomerism; isomers?
- What is homology; homologues?
- How, using knowledge of isomerism and homology, to explain the diversity of carbon compounds?
- What is meant by the chemical structure of molecules of organic compounds? Formulate the position of the theory of structure, which explains the difference in the properties of isomers. Formulate the position of the theory of structure, which explains the variety of organic compounds.
- What contribution did each of the scientists - the founders of the theory of chemical structure - make to this theory? Why did the contribution of the Russian chemist play a leading role in the formation of this theory?
- It is possible that there are three isomers of the composition C 5 H 12. Write down their full and abbreviated structural formulas,
- According to the model of the substance molecule presented at the end of the paragraph (see Fig. 7), make up its molecular and abbreviated structural formulas.
- Calculate the mass fraction of carbon in the molecules of the first four members of the homologous series of alkanes.
Creation of the theory of structure in Russia is not an accident. The sixties of the XIX century were years of rapid growth of capitalism in Russia. This, in turn, presented a number of requirements for natural science. In shaping the worldview of the Russian naturalists of that time, D. I. Mendeleev, I. M. Sechenov, A. M. Butlerov and others, the activities of the revolutionary materialist democrats A. I. Herzen and V. G. Belinsky, N. G. Chernyshevsky and N. A. Dobrolyubov.
Butlerov took from them materialistic doctrine and a critical attitude towards all theories. For the first time, the main ideas of the theory of structure expressed by A. M. Butlerov in his report “On the chemical structure of matter”, made by him on September 19, 1861 at a conference in Speyer, and then included in his textbook, which was published in Russia in 1864-1866 ., and then translated in Germany into German in 1867-1868.
The main ideas of the theory of A. M. Butlerov can be summarized as follows:
1. All atoms, which form a molecule of organic matter, are connected in a certain sequence, and a certain proportion of chemical affinity is spent on connecting them to each other.
Quadrivalent carbon and its ability to form chains entered the theory as constituents. Chemical affinity - valence. All this led to the writing of chemical formulas, which we use at the present time, i.e. open values of carbon atoms, a chain of carbon atoms closed in a ring.
2. From the chemical structure substances depend on its chemical and physical properties. This position of the theory explained the phenomenon of isomerism.
3. Exploring properties substance allows you to determine its structure, and, consequently, its properties.
4. Chemical properties of atoms and atomic groups are immutable and change only under the influence of the atoms and atomic groups present, especially directly related to each other.
Butlerov's idea of mutual influence atoms in a molecule was subsequently brilliantly developed by his student VV Morkovnikov.
The greatest merit of A. M. Butlerov consists not only in the generalization of a huge amount of factual material and the advancement of advanced ideas, but also in the brilliant experimental proof of the theory of structure he created. Based on his theory of structure, L. M. Butlerov predicted the existence of completely unknown compounds and even classes at that time (for example, tertiary alcohols) and then was able to synthesize them.
Like D. I. Mendeleev, based on his periodic system, he predicted unknown elements, and A. M. Butlerov, based on the theory of structure, predicted the possibility of the existence of new substances and synthesized them himself.
A. M. Butlerov for the first time expressed the idea of the arrangement of atoms not on a plane, but in space, and was the founder of the idea of spatial isomerism.
He considered the chemical molecule not as something dead, but in constant motion. This idea led L. M. Butlerov to the idea of "reverse isomerism", i.e. he actually was the founder of the idea of the so-called tautomerism. More than a hundred years have passed since the theory of A. M. Butlerov was created, but even now organic chemists use it with the same success.
Later, K. Schorlemmer in 1880 determined organic chemistry as "the chemistry of hydrocarbons and their derivatives", he wanted to emphasize this:
1 The ability of carbon to form chains of C-C atoms.
2 The presence of hydrogen in most organic molecules.
WORK IN CHEMISTRY
THEORY OF THE KHIMICHK STRUCTURE
ORGANIC
COMPOUNDS A.M. BUTLEROV
COMPLETED:
Lebedev Evgeny
PLAN:
1. DEVELOPMENT OF THE INDUSTRY ASSOCIATED WITH THE PRODUCTION OF ORGANIC SUBSTANCES IN THE FIRST HALF OF THE XIX CENTURIES .LINK OF SCIENCE AND PRACTICE.
2. THE STATE OF ORGANIC CHEMISTRY IN THE MIDDLE OF THE XIX CENTURY.
3. BACKGROUND OF THE THEORY OF CHEMICAL STRUCTURE.
4. VIEWS OF A.M. BOTTLED STRUCTURE OF THE SUBSTANCE.
5. MAIN PROVISIONS OF THE THEORY.
6. THE SIGNIFICANCE OF THE THEORY OF CHEMICAL STRUCTURE AND DIRECTIONS OF ITS DEVELOPMENT.
Man has been familiar with organic substances since ancient times. . Our distant ancestors used natural dyes for dyeing fabrics, used vegetable oils, animal fats, cane sugar as food, obtained vinegar by fermenting alcoholic liquids ...
But the science of carbon compounds arose only in the first half of the 10th century. I X century.
In 1828, a student of J. Berzelius, the German scientist F. Wöhler synthesizes organic matter - urea - from inorganic substances. In 1845, the German chemist A. Kolbe artificially obtained acetic acid. In 1854, the French chemist M. Berthelot synthesized fats. Russian scientist A.M. Butlerov in 1861 for the first time obtained a sugary substance by synthesis.
It is known that developing industry and practice pose new challenges for science. As soon as a society has a technical need, it promotes
science forward more than a dozen universities.
An example can be given to confirm these words. The textile industry in the 40s of the nineteenth century could no longer
provide natural dyes - they were not enough. Science faced the task of obtaining dyes synthetically. Searches began, as a result of which various aniline dyes and alizarin, previously extracted from the roots of the madder plant, were synthesized. The resulting dyes, in turn, contributed to the rapid growth of the textile industry.
At present, many organic substances have been synthesized that are not only found in nature, but also not found in it, for example, numerous plastics, various types of rubbers, all kinds of dyes, explosives, and drugs.
More synthetically derived substances are now known than those found in nature, and their number is rapidly increasing. is growing. Syntheses of the most complex organic substances - proteins begin to be carried out .
2. State of organic chemistry in the middle of X I X century.
Meanwhile, there were pre-structural theories - the theory of radicals and the theory of types.
The theory of radicals (its creators J. Dumas, I. Berzelius) argued that the composition of organic matter stv includes radicals passing from one molecule to another: radicals are constant in composition and can exist in a free form. Later it was found that the radicals can undergo changes as a result of the substitution reaction (replacement of hydrogen atoms by chlorine atoms). Thus, trichloroacetic acid was obtained. The theory of radicals was gradually rejected, but it left a deep imprint on science: the concept of a radical has become firmly established in chemistry. The assertions about the possibility of the existence of free radicals, about the transition of certain groups from one compound to another in a huge number of reactions turned out to be true.
The most common in the 40s. XIX century was the theory of types. According to this theory, all organic substances were considered derivatives of the simplest inorganic substances - such as hydrogen, hydrogen chloride, water, ammonia, etc. For example, the type of hydrogen
According to this theory, formulas do not express the internal structure of molecules, but only the methods of formation and reaction of a substance. The creator of this theory, Sh. Gerard and his followers, believed that the structure of matter could not be known, since the molecules change during the reaction. For each substance, you can write as many formulas as there are different types of transformations that the substance can undergo.
The theory of types at one time was progressive, since it made it possible to classify organic substances, to predict and discover a number of simple substances, if it was possible to attribute them to a certain type in composition and some properties. However, not all synthesized substances fit into one or another type of compounds. The theory of types focused on the study of chemical transformations of organic compounds, which was important for understanding the properties of substances. In the future, the theory of types became a brake on the development of organic chemistry, since it was not able to explain the facts accumulated in science, to indicate ways of synthesizing new substances necessary for technology, medicine, a number of industries, etc. A new theory was needed that could not only explain the facts, observations, but also predict, indicate the ways of synthesis of new substances.
There are many facts that require explanation -
- question of valence
- isomerism
- writing formulas.
Background of the theory of chemical structure.
By the time the theory of the chemical structure of A.M. Butlerov, much was already known about the valency of elements : E. Frankland established valency for a number of metals, for organic compounds A. Kekule proposed the tetravalence of the carbon atom (1858), it was suggested that carbon-carbon bonds could be connected in a chain (1859, A.S. Cooper, A. Kekule). This idea played a big role in the development of organic chemistry.
An important event in chemistry was the International Congress of Chemists (1860, Karlsruhe), where the concepts of atom, molecule, atomic weight, molecular weight were clearly defined. Prior to this, there were no generally accepted criteria for defining these concepts, so there was confusion in writing the formulas of substances. A.M. Butlerov considered the most significant success of chemistry for the period from 1840 to 1880. the establishment of the concepts of the atom and the molecule, which gave impetus to the development of the theory of valence and made it possible to proceed to the creation of a theory of chemical structure.
Thus, the theory of chemical structure did not arise from scratch. The objective prerequisites for its appearance were : a). Introduction to chemistry of the concepts of valence and especially , about the tetravalence of the carbon atom, b). Introduction of the concept of carbon-carbon bond. in). Developing a correct understanding of atoms and molecules.
Views of A.M. Butlerov on the structure of matter.
In 1861, A.M. Butlerov on XXXU I Congress of German Physicians and Naturalists in Speyer. Meanwhile, his first speech on theoretical questions of organic chemistry took place in 1858, in Paris, at the Chemical Society. In his speech, as well as in the article about A.S. Cooper (1859) A.M. Butlerov points out that valency (chemical affinity) should play a role in creating a theory of chemical structure. Here he first used the term "structure", expressed the idea of the possibility of knowing the structure of matter, of using experimental research for these purposes.
The main ideas about the chemical structure were presented by A.M. Butlerov in 1861 in the report "On the chemical structure of substances". It noted the lag of theory behind practice, pointed out that the theory of types, despite some of its positive aspects, has major shortcomings. The report gives a clear definition of the concept of chemical structure, considers ways to establish the chemical structure (methods for the synthesis of substances, the use of various reactions).
A.M. Butlerov argued that each substance corresponds to one chemical formula : it characterizes all the chemical properties of a substance, actually reflects the order of chemical bonding of atoms in molecules. In subsequent years, A.M. Butlerov and his students carried out a number of experimental works in order to verify the correctness of the predictions made on the basis of the theory of chemical structure. Thus, isobutane, isobutylene, pentane isomers, a number of alcohols, etc. were synthesized. In terms of significance for science, these works can be compared with the discovery predicted by D.I. Mendnley elements (ekabor, ekasilicium, ekaaluminum).
In full, the theoretical views of A.M. Butlerov were reflected in his textbook "Introduction to the Complete Study of Organic Chemistry" (the first edition was published in 1864-1866), built on the basis of the theory of chemical structure. He believed that molecules are not a chaotic accumulation of atoms, that atoms in molecules are interconnected in a certain sequence and are in constant motion and mutual influence. By studying the chemical properties of a substance, it is possible to establish the sequence of compounds of atoms in molecules and express it by a formula.
A.M. Butlerov believed that with the help of chemical methods of analysis and synthesis of a substance, it is possible to establish the chemical structure of a compound and, conversely, knowing the chemical structure of a substance, one can predict its chemical properties.
The main provisions of the theory of A.M. Butlerov .
Based on the above statements by A.M. Butlerov, the essence of the theory of chemical structure can be expressed in the following provisions :
Atoms in molecules are not arranged randomly, they are connected to each other in a certain sequence according to their valency.
A) the sequence of connecting atoms in a molecule
B) carbon is tetravalent
C) structural formulas (full)
The sequence of connecting atoms in a molecule
D) abbreviated formulas
D) types of chains
Isomerism explains the diversity of organic substances. According to the theory of chemical structure, different substances correspond to a different order of interconnection of atoms with the same qualitative and quantitative composition of a molecule. If this theory is correct, there must be two butanes, differing in their structure and properties. Since only one butane was known at that time, A.M. Butlerov made an attempt to synthesize butane of a different structure. The substance he received had the same composition , but other properties, in particular a lower boiling point. AT Unlike butane, the new substance was called "isobutane" (Greek "isos" - equal).
For cooking, dyes, clothes, medicines, people have long learned to use various substances. Over time, a sufficient amount of information about the properties of certain substances has accumulated, which has made it possible to improve the methods of their production, processing, etc. And it turned out that many mineral (inorganic substances) can be obtained directly.
But some of the substances used by man were not synthesized by him, because they were obtained from living organisms or plants. These substances are called organic. Organic substances could not be synthesized in the laboratory. At the beginning of the 19th century, such a doctrine as vitalism (vita - life) actively developed, according to which organic substances arise only due to "life force" and it is impossible to create them "artificially".
But as time went on and science developed, new facts about organic substances appeared that ran counter to the existing theory of the vitalists.
In 1824, the German scientist F. Wöhler synthesized oxalic acid for the first time in the history of chemical science – organic matter from inorganic substances (cyanide and water):
(CN) 2 + 4H 2 O → COOH - COOH + 2NH 3
In 1828, Wöller heated sodium cyanate with sulfuric ammonium and synthesized urea - product of vital activity of animal organisms:
NaOCN + (NH 4) 2 SO 4 → NH 4 OCN → NH 2 OCNH 2
These discoveries played an important role in the development of science in general, and chemistry in particular. Scientists-chemists began to gradually move away from the vitalistic doctrine, and the principle of dividing substances into organic and inorganic proved to be untenable.
Currently substances still divided into organic and inorganic but the criterion for separation is already slightly different.
Substances are called organic containing carbon in their composition, they are also called carbon compounds. There are about 3 million such compounds, while the remaining compounds are about 300 thousand.
Substances that do not contain carbon are called inorganic and. But there are exceptions to the general classification: there are a number of compounds that contain carbon, but they belong to inorganic substances (carbon monoxide and dioxide, carbon disulfide, carbonic acid and its salts). All of them are similar in composition and properties to inorganic compounds.
In the course of the study of organic substances, new difficulties arose: on the basis of theories about inorganic substances, it is impossible to reveal the patterns of the structure of organic compounds, to explain the valency of carbon. Carbon in different compounds had different valencies.
In 1861, the Russian scientist A.M. Butlerov was the first to obtain a sugary substance by synthesis.
When studying hydrocarbons, A.M. Butlerov realized that they represent a very special class of chemicals. Analyzing their structure and properties, the scientist identified several patterns. They formed the basis of the theories of chemical structure.
1. The molecule of any organic substance is not disordered, the atoms in the molecules are connected to each other in a certain sequence according to their valencies. Carbon in organic compounds is always tetravalent.
2. The sequence of interatomic bonds in a molecule is called its chemical structure and is reflected by one structural formula (structure formula).
3. The chemical structure can be established by chemical methods. (Currently modern physical methods are also used).
4. The properties of substances depend not only on the composition of the molecules of the substance, but on their chemical structure (the sequence of connection of the atoms of the elements).
5. By the properties of a given substance, you can determine the structure of its molecule, and by the structure of the molecule – anticipate properties.
6. Atoms and groups of atoms in a molecule interact with each other.
This theory became the scientific foundation of organic chemistry and accelerated its development. Based on the provisions of the theory, A.M. Butlerov described and explained the phenomenon isomerism, predicted the existence of various isomers and obtained some of them for the first time.
Consider the chemical structure of ethane – C2H6. Denoting the valency of the elements with dashes, we will depict the ethane molecule in the order of the connection of atoms, that is, we will write a structural formula. According to the theory of A.M. Butlerov, it will look like this:
Hydrogen and carbon atoms are bound into one particle, hydrogen valence is equal to one, and carbon – four. Two carbon atoms are linked by a carbon bond – carbon (C – FROM). The ability of carbon to form C – The C-bond is understood from the chemical properties of carbon. On the outer electron layer, the carbon atom has four electrons, the ability to donate electrons is the same as to add the missing ones. Therefore, carbon most often forms compounds with a covalent bond, that is, due to the formation of electron pairs with other atoms, including carbon atoms with each other.
This is one of the reasons for the diversity of organic compounds.
Compounds that have the same composition but different structures are called isomers. The phenomenon of isomerism – one of the reasons for the diversity of organic compounds
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The generally accepted main provisions of Butlerov's theory are considered the foundation of modern chemistry. The scientist was the first to explain the features. He studied in detail the nature of the relationships of atoms.
Prerequisites for the appearance of the theory
Alexander Butlerov became the founder of the new theory just when a lot of questions had accumulated in science that scientists could not find answers to. For example, explanations required the phenomena of valency and isomerism. In addition, chemists continued to argue about how to write chemical formulas correctly. Butlerov clarified this issue. He proved that formulas should reflect the structure of matter.
In addition, there were several concepts that were opposite to the views expressed by Butlerov. It was the theory of the radicals. Its founder was Jens Berzelius. He argued that there are special elements in molecules - radicals that pass from one substance to another. There was also a theory of types. Its supporters believed that all complex substances are derivatives of simple inorganic substances - water, hydrogen, ammonia, etc. All these concepts contradicted each other. Science needed a theory that would put everything in its place.
Butlerov's new ideas
Alexander Mikhailovich Butlerov (1828-1886) was one of the outstanding chemists of his time. He dealt a lot with the theoretical issues of his science. In 1858, the scientist spoke at one of the meetings of the Paris Chemical Society. At the same time, for the first time, the main provisions of Butlerov's theory were heard from his lips.
The researcher used new terms in his report, which later became entrenched in international science. For example, it was he who became the author of the concept of the structure of compounds. The scientist believed that the structure of different substances allows them to be attributed to the same groups (in particular, these are methane, chloroform, methyl alcohol, etc.).
Study of the synthesis of substances
In 1861, in the published report “On the chemical structure of matter”, the main provisions of the theory of the chemical structure of A. M. Butlerov were formulated. The scientist described in detail the methods of synthesis and use of different reactions. One of the most important theses of the chemist was his assertion that one formula corresponds to each chemical substance. Its importance lies in the fact that it characterizes all properties and shows the connection of atoms within molecules.
Butlerov's theory also provided that new substances could be produced with the help of controlled reactions. In subsequent years, the famous chemist and his students conducted many experiments to prove this assumption. They managed to synthesize such new substances as isobutylene and some alcohols. For their era, these discoveries were of colossal significance, which can only be compared with the importance of the definition of other elements by Mendeleev (for example, ekabor).
Systematization of chemistry
In the 19th century, the main provisions of Butlerov's theory completely changed the idea of scientists about the elements. In particular, the researcher was the first to suggest that molecules are not a chaotic accumulation of atoms. On the contrary, they have an ordered structure. Atoms are connected to each other in a certain sequence, which also determines the nature of the entire substance.
Butlerov, developing his theory, relied on mathematical principles and laws. With the help of this science, he was able to explain most of the processes and relationships in chemicals. For contemporaries it was a real revolution. The fact was that even if scientists knew some facts about the nature of certain substances, they could not build their knowledge into a clear systematized picture. The main provisions of Butlerov's theory of structure resolved this problem. Now chemistry was not a disparate treasury of facts, but a harmonious system, where everything was subject to strict mathematical logic.
Variety of substances
Butlerov's famous theory pays much attention to isomerism - a phenomenon consisting in the existence of isomers - substances that are equal in molecular weight and atomic composition, which at the same time differ from each other in the arrangement of atoms and structure. This feature explains the variety of properties of substances in nature.
Butlerov proved his theory on the example of butane. According to the scientist's idea, two types of this substance should have existed in nature. However, at that time, science knew only one butane. Butlerov conducted many experiments and nevertheless obtained a new substance, similar in composition, but different in properties. It was named isobutane.
The influence of atoms on each other
Butlerov also discovered another important regularity. With the formation of chemical bonds, the process of transfer of electrons from one atom to another begins. At the same time, their density changes. There are electron pairs that affect the properties of the new formed substance. The scientist studied this phenomenon using the example of hydrogen chloride, where chlorine changes the electron density of hydrogen bonds.
Butlerov and the main provisions of the theory of structure were able to explain the nature of the transformation of substances. In the future, the principle discovered was studied in detail by his followers and students. Understanding the mechanism of changing substances allowed scientists to understand how to synthesize new elements. A special surge of these discoveries began at the end of the 19th century. Then European and American scientists in new laboratories, using the methods proposed by Butlerov, were able to produce new substances.
chemical bonds
Butlerov believed that the structure of substances can be studied by chemical methods. This position was confirmed thanks to many successful experiments of the scientist. Also, the researcher was a supporter of the idea that formulas can be correct only if they begin to reflect the order of chemical bonds of different atoms. Butlerov has been analyzing this assumption for many years.
He identified three types of bonds - simple, double and triple. The scientist was right, but the further development of science showed that there are other chemical bonds. In particular, now specialists can also characterize them with the help of physical parameters.
Development of Butler's theory
The new theory of the structure of chemical compounds by A. M. Butlerov was materialistic in nature. The scientist was the first to boldly declare that researchers can study the properties of atoms, from which all elements are built. At the same time, Butlerov himself treated his theory as temporary. He believed that his successors should develop it, since it did not fully explain some of the facts of chemical science.
The scientist was right. Butlerov's theory further developed in two directions. The first was that science was able to determine not only the order of connection, but also the spatial arrangement of atoms in a molecule. This is how stereochemistry was born. This discipline began to be studied in detail Butlerov himself spoke about this new direction, although he did not have time to study this theoretical issue during his lifetime.
The second direction in the development of the theory of the scientist was the emergence of a doctrine devoted to the electronic structure of atoms. This is not only a chemical, but also a physical discipline. The essence of the mutual influence of atoms was studied in more detail and the reasons for the manifestation of different properties were explained. It was the main provisions of Butlerov's theory that allowed scientists to achieve such success.
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