The value of the theory of the structure of organic substances. Butlerov Alexander Mikhailovich

Lesson content: Theories of the structure of organic compounds: prerequisites for creation, basic provisions. Chemical structure as the order of connection and mutual influence of atoms in molecules. Homology, isomerism. The dependence of the properties of substances on the chemical structure. The main directions of development of the theory of chemical structure. The dependence of the appearance of toxicity in organic compounds on the composition and structure of their molecules (the length of the carbon chain and the degree of its branching, the presence of multiple bonds, the formation of cycles and peroxide bridges, the presence of halogen atoms), as well as on the solubility and volatility of the compound.

Lesson Objectives:

• Organize the activities of students to familiarize and consolidate the primary provisions of the theory of chemical structure.
• Show students the universal nature of the theory of chemical structure using the example of inorganic isomers and the mutual influence of atoms in inorganic substances.

During the classes:

1. Organizational moment.

2. Actualization of students' knowledge.

1) What does organic chemistry study?

2) What substances are called isomers?

3) What substances are called homologues?

4) Name the theories known to you that arose in organic chemistry at the beginning of the 19th century.

5) What were the disadvantages of the theory of radicals?

6) What were the shortcomings of type theory?

3. Setting goals and objectives of the lesson.

The concept of valency formed an important part of the theory of the chemical structure of A.M. Butlerov in 1861

The periodic law formulated by D.I. Mendeleev in 1869, revealed the dependence of the valency of an element on its position in the periodic system.

It remained unclear the wide variety of organic substances that have the same qualitative and quantitative composition, but different properties. For example, about 80 different substances were known that corresponded to the composition C 6 H 12 O 2 . Jens Jakob Berzelius suggested calling these substances isomers.

Scientists from many countries have paved the way for the creation of a theory explaining the structure and properties of organic substances.

At the congress of German naturalists and doctors in the city of Speyer, a report was read, called "Something in the chemical structure of bodies." The author of the report was Professor of Kazan University Alexander Mikhailovich Butlerov. It was this very “something” that constituted the theory of chemical structure, which formed the basis of our modern ideas about chemical compounds.

Organic chemistry received a solid scientific basis, which ensured its rapid development in the next century up to the present day. This theory made it possible to predict the existence of new compounds and their properties. The concept of the chemical structure made it possible to explain such a mysterious phenomenon as isomerism.

The main provisions of the theory of chemical structure are as follows:
1. Atoms in the molecules of organic substances are connected in a certain sequence according to their valency.

2. The properties of substances are determined by the qualitative, quantitative composition, the order of connection and the mutual influence of atoms and groups of atoms in a molecule.

3. The structure of molecules can be established on the basis of studying their properties.

Let's consider these provisions in more detail. Molecules of organic substances contain carbon atoms (valence IV), hydrogen (valence I), oxygen (valence II), nitrogen (valency III). Each carbon atom in the molecules of organic substances forms four chemical bonds with other atoms, while carbon atoms can be combined into chains and rings. Based on the first position of the theory of chemical structure, we will draw up the structural formulas of organic substances. For example, methane has been found to have the composition CH 4 . Given the valencies of carbon and hydrogen atoms, only one structural formula of methane can be proposed:

The chemical structure of other organic substances can be described by the following formulas:

ethanol

The second position of the theory of chemical structure describes the relationship known to us: composition - structure - properties. Let's look at the manifestation of this regularity on the example of organic substances.

Ethane and ethyl alcohol have different qualitative composition. An alcohol molecule, unlike ethane, contains an oxygen atom. How will this affect properties?

The introduction of an oxygen atom into a molecule dramatically changes the physical properties of the substance. This confirms the dependence of properties on the qualitative composition.

Let's compare the composition and structure of methane, ethane, propane and butane hydrocarbons.

Methane, ethane, propane and butane have the same qualitative composition, but different quantitative composition (the number of atoms of each element). According to the second position of the theory of chemical structure, they must have different properties.

As can be seen from the table, with an increase in the number of carbon atoms in a molecule, an increase in the boiling and melting points occurs, which confirms the dependence of the properties on the quantitative composition of the molecules.

The molecular formula C 4 H 10 corresponds not only to butane, but also to its isomer isobutane:

Isomers have the same qualitative (carbon and hydrogen atoms) and quantitative (4 carbon atoms and ten hydrogen atoms) composition, but differ from each other in the order of connection of atoms (chemical structure). Let's see how the difference in the structure of isomers will affect their properties.

A branched hydrocarbon (isobutane) has higher boiling and melting points than a normal hydrocarbon (butane). This can be explained by the closer arrangement of molecules to each other in butane, which increases the forces of intermolecular attraction and, therefore, requires more energy to separate them.

The third position of the theory of chemical structure shows the feedback of the composition, structure and properties of substances: composition - structure - properties. Consider this using the example of compounds of the composition C 2 H 6 O.

Imagine that we have samples of two substances with the same molecular formula C 2 H 6 O, which was determined in the course of a qualitative and quantitative analysis. But how to find out the chemical structure of these substances? To answer this question will help the study of their physical and chemical properties. When the first substance interacts with metallic sodium, the reaction does not proceed, and the second actively interacts with it with the release of hydrogen. Let us determine the quantitative ratio of substances in the reaction. To do this, we add a certain mass of sodium to the known mass of the second substance. Let's measure the volume of hydrogen. Let's calculate the amount of substances. In this case, it turns out that out of two moles of the substance under study, one mole of hydrogen is released. Therefore, each molecule of this substance is a source of one hydrogen atom. What conclusion can be drawn? Only one hydrogen atom differs in properties and, therefore, in structure (with which atoms it is associated) from all the others. Given the valency of carbon, hydrogen and oxygen atoms, only one formula can be proposed for a given substance:

For the first substance, a formula can be proposed in which all hydrogen atoms have the same structure and properties:

A similar result can be obtained by studying the physical properties of these substances.

Thus, based on the study of the properties of substances, one can draw a conclusion about its chemical structure.

The importance of the theory of chemical structure can hardly be overestimated. It provided chemists with a scientific basis for studying the structure and properties of organic substances. The Periodic Law, formulated by D.I. Mendeleev. The theory of structure generalized all the scientific views prevailing in chemistry of that time. Scientists were able to explain the behavior of organic substances during chemical reactions. Based on the theory of A.M. Butlerov predicted the existence of isomers of certain substances, which were later obtained. Like the Periodic Law, the theory of chemical structure was further developed after the formation of the theory of the structure of the atom, chemical bonding and stereochemistry.

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Lecture objectives:

• Educational:
  • to form concepts about the essence of the theory of the chemical structure of organic substances, based on the knowledge of students about the electronic structure of atoms of elements, their position in the Periodic system of D.I. Mendeleev, on the degree of oxidation, the nature of the chemical bond, and other major theoretical provisions:
    • the sequence of carbon atoms in the chain,
    • mutual influence of atoms in a molecule,
    • dependence of the properties of organic substances on the structure of molecules;
  • form an idea of ​​the development of theories in organic chemistry;
  • learn the concepts: isomers and isomerism;
  • explain the meaning of the structural formulas of organic substances and their advantages over molecular ones;
  • show the necessity and prerequisites for the creation of a theory of chemical structure;
  • Continue developing your writing skills.
• Educational:
  • develop mental techniques of analysis, comparison, generalization;
  • develop abstract thinking;
  • to train the attention of students in the perception of a large amount of material;
  • develop the ability to analyze information and highlight the most important material.
• Educational:
  • for the purpose of patriotic and international education, provide students with historical information about the life and work of scientists.

DURING THE CLASSES

1. Organizational part

- Greetings
- Preparing students for the lesson
- Obtaining information about absentees.

2. Learning new things

Lecture plan:<Annex 1 . Slide 2>

I. Prestructural theories:
- vitalism;
– the theory of radicals;
- type theory.
II. Brief information about the state of chemical science by the 60s of the XIX century. Conditions for creating a theory of the chemical structure of substances:
- the need to create a theory;
- prerequisites for the theory of chemical structure.
III. The essence of the theory of the chemical structure of organic substances A.M. Butlerov. The concept of isomerism and isomers.
IV. The value of the theory of the chemical structure of organic substances A.M. Butlerov and its development.

3. Homework: synopsis, p. 2.

4. Lecture

I. Knowledge about organic substances has been accumulating gradually since ancient times, but as an independent science, organic chemistry arose only at the beginning of the 19th century. Registration of independence of org.chemistry is associated with the name of the Swedish scientist J. Berzelius<Annex 1 . Slide 3>. In 1808-1812. he published his large manual on chemistry, in which he originally intended to consider, along with mineral substances, also substances of animal and vegetable origin. But the part of the textbook devoted to organic substances appeared only in 1827.
J. Berzelius saw the most significant difference between inorganic and organic substances in that the former can be obtained synthetically in laboratories, while the latter are allegedly formed only in living organisms under the influence of a certain “life force” - a chemical synonym for “soul”, "spirit", "divine origin" of living organisms and their constituent organic substances.
The theory that explained the formation of organic compounds by the intervention of "life force" was called vitalism. She has been popular for some time. In the laboratory, it was possible to synthesize only the simplest carbon-containing substances, such as carbon dioxide - CO 2, calcium carbide - CaC 2, potassium cyanide - KCN.
Only in 1828 did the German scientist Wöhler<Annex 1 . Slide 4> managed to obtain the organic substance urea from an inorganic salt - ammonium cyanate - NH 4 CNO.
NH 4 CNO -– t –> CO (NH 2) 2
In 1854 the French scientist Berthelot<Annex 1 . Slide 5>Received triglyceride. This led to the need to change the definition of organic chemistry.
Scientists tried to unravel the nature of the molecules of organic substances based on the composition and properties, sought to create a system that would make it possible to link together the disparate facts that had accumulated by the beginning of the 19th century.
The first attempt to create a theory that sought to generalize the data available on organic substances is associated with the name of the French chemist J. Dumas<Annex 1 . Slide 6>. It was an attempt to consider from a unified point of view a fairly large group of org. compounds, which today we would call ethylene derivatives. Organic compounds turned out to be derivatives of some radical C 2 H 4 - etherine:
C 2 H 4 * HCl - ethyl chloride (etherine hydrochloride)
The idea embedded in this theory - an approach to organic matter as consisting of 2 parts - later formed the basis of a broader theory of radicals (J. Berzelius, J. Liebig, F. Wöhler). This theory is based on the notion of a "dualistic structure" of substances. J. Berzelius wrote: "Each organic substance consists of 2 components that carry the opposite electric charge." One of these components, namely the electronegative part, J. Berzelius considered oxygen, while the rest, actually organic, should have been an electropositive radical.

The main provisions of the theory of radicals:<Annex 1 . Slide 7>

- the composition of organic substances includes radicals that carry a positive charge;
- radicals are always constant, do not undergo changes, they pass without changes from one molecule to another;
- radicals can exist in free form.

Gradually science accumulated facts that contradicted the theory of radicals. So J. Dumas carried out the replacement of hydrogen with chlorine in hydrocarbon radicals. Scientists, adherents of the theory of radicals, it seemed incredible that chlorine, charged negatively, played the role of hydrogen, positively charged in compounds. In 1834, J. Dumas was given the task of investigating an unpleasant incident during a ball in the palace of the French king: candles emitted suffocating smoke when burned. J. Dumas found that the wax from which the candles were made was treated with chlorine for bleaching. At the same time, chlorine entered the wax molecule, replacing part of the hydrogen contained in it. The suffocating fumes that frightened the royal guests turned out to be hydrogen chloride (HCl). Later, J. Dumas received trichloroacetic acid from acetic acid.
Thus, the electropositive hydrogen was replaced by the extremely electronegative element chlorine, while the properties of the compound remained almost unchanged. Then J. Dumas concluded that the dualistic approach should be replaced by an approach to the organizational connection as a whole.

The radical theory was gradually abandoned, but it left a deep mark on organic chemistry:<Annex 1 . Slide 8>
- the concept of "radical" is firmly established in chemistry;
- the statement about the possibility of the existence of free radicals, about the transition in a huge number of reactions of certain groups of atoms from one compound to another, turned out to be true.

In the 40s. 19th century The doctrine of homology was initiated, which made it possible to clarify some relationships between the composition and properties of compounds. Homological series, homological difference were revealed, which made it possible to classify organic substances. The classification of organic substances on the basis of homology led to the emergence of type theory (40-50s of the XIX century, C. Gerard, A. Kekule and others)<Annex 1 . slide 9>

The Essence of Type Theory<Annex 1 . Slide 10>

- The theory is based on an analogy in the reactions between organic and some inorganic substances, taken as types (types: hydrogen, water, ammonia, hydrogen chloride, etc.). Replacing hydrogen atoms in the type of substance with other groups of atoms, scientists predicted various derivatives. For example, the replacement of a hydrogen atom in a water molecule by a methyl radical leads to the formation of an alcohol molecule. Substitution of two hydrogen atoms - to the appearance of an ether molecule<Annex 1 . slide 11>

C. Gerard directly said in this regard that the formula of a substance is only an abbreviated record of its reactions.

All org. substances were considered derivatives of the simplest inorganic substances - hydrogen, hydrogen chloride, water, ammonia<Annex 1 . slide 12>

<Annex 1 . slide 13>

- molecules of organic substances are a system consisting of atoms, the order of connection of which is unknown; the properties of compounds are affected by the totality of all atoms of the molecule;
- it is impossible to know the structure of a substance, since the molecules change during the reaction. The formula of a substance does not reflect the structure, but the reactions in which the given substance. For each substance, one can write as many rational formulas as there are different types of transformations that the substance can experience. The theory of types allowed for a plurality of "rational formulas" for substances, depending on what reactions they want to express with these formulas.

The theory of types played a big role in the development of organic chemistry <Annex 1 . slide 14>

- allowed to predict and discover a number of substances;
- had a positive impact on the development of the doctrine of valency;
- drew attention to the study of chemical transformations of organic compounds, which allowed a deeper study of the properties of substances, as well as the properties of predicted compounds;
- created a systematization of organic compounds that was perfect for that time.

It should not be forgotten that in reality theories arose and succeeded each other not sequentially, but existed simultaneously. Chemists often misunderstood each other. F. Wöhler in 1835 said that “organic chemistry can now drive anyone crazy. It seems to me a dense forest full of wonderful things, a huge thicket without an exit, without an end, where you dare not penetrate ... ".

None of these theories has become a theory of organic chemistry in the full sense of the word. The main reason for the failure of these ideas is their idealistic essence: the internal structure of molecules was considered fundamentally unknowable, and any reasoning about it was quackery.

A new theory was needed, which would stand on materialistic positions. Such a theory was theory of chemical structure A.M. Butlerov <Annex 1 . Slides 15, 16>, which was created in 1861. Everything rational and valuable that was in the theories of radicals and types was subsequently assimilated by the theory of chemical structure.

The need for the appearance of the theory was dictated by:<Annex 1 . Slide 17>

– increased industrial requirements for organic chemistry. It was necessary to provide the textile industry with dyes. In order to develop the food industry, it was necessary to improve the methods of processing agricultural products.
In connection with these problems, new methods for the synthesis of organic substances began to be developed. However, scientists had serious difficulties in the scientific substantiation of these syntheses. So, for example, it was impossible to explain the valency of carbon in compounds using the old theory.
Carbon is known to us as a 4-valent element (This has been proven experimentally). But here it seems to retain this valency only in methane CH 4. In ethane C 2 H 6, according to our ideas, carbon should be. 3-valent, and in propane C 3 H 8 - fractional valency. (And we know that valence should be expressed only in whole numbers).
What is the valency of carbon in organic compounds?

It was not clear why there are substances with the same composition, but different properties: C 6 H 12 O 6 is the molecular formula of glucose, but the same formula is also fructose (a sugary substance - an integral part of honey).

Pre-structural theories could not explain the diversity of organic substances. (Why can carbon and hydrogen, two elements, form such a large number of different compounds?).

It was necessary to systematize the existing knowledge from a unified point of view and develop a unified chemical symbolism.

A scientifically substantiated answer to these questions was given by the theory of the chemical structure of organic compounds, created by the Russian scientist A.M. Butlerov.

Basic prerequisites who paved the way for the emergence of the theory of chemical structure were<Annex 1 . Slide 18>

- the doctrine of valency. In 1853, E. Frankland introduced the concept of valency, established the valence for a number of metals, investigating organometallic compounds. Gradually, the concept of valence was extended to many elements.

An important discovery for organic chemistry was the hypothesis of the ability of carbon atoms to form chains (A. Kekule, A. Cooper).

One of the prerequisites was the development of a correct understanding of atoms and molecules. Until the 2nd half of the 50s. 19th century There were no generally accepted criteria for defining the concepts: "atom", "molecule", "atomic mass", "molecular mass". Only at the International Congress of Chemists in Karlsruhe (1860) were these concepts clearly defined, which predetermined the development of the theory of valence, the emergence of the theory of chemical structure.

The main provisions of the theory of chemical structure of A.M. Butlerov(1861)

A.M. Butlerov formulated the most important ideas of the theory of the structure of organic compounds in the form of basic provisions, which can be divided into 4 groups.<Annex 1 . Slide 19>

1. All atoms that form the molecules of organic substances are connected in a certain sequence according to their valence (i.e., the molecule has a structure).

<Annex 1 . Slides 19, 20>

In accordance with these ideas, the valency of elements is conventionally depicted by dashes, for example, in methane CH 4.<Annex 1 . Slide 20> >

Such a schematic representation of the structure of molecules is called structure formulas and structural formulas. Based on the provisions on the 4-valency of carbon and the ability of its atoms to form chains and cycles, the structural formulas of organic substances can be depicted as follows:<Annex 1 . Slide 20>

In these compounds, carbon is tetravalent. (The dash symbolizes a covalent bond, a pair of electrons).

2. The properties of a substance depend not only on which atoms and how many of them are part of the molecules, but also on the order of connection of atoms in molecules. (i.e. properties depend on the structure) <Annex 1 . Slide 19>

This position of the theory of the structure of organic substances explained, in particular, the phenomenon of isomerism. There are compounds that contain the same number of atoms of the same elements but are bound in a different order. Such compounds have different properties and are called isomers.
The phenomenon of the existence of substances with the same composition, but different structure and properties is called isomerism.<Annex 1 . Slide 21>

The existence of isomers of organic substances explains their diversity. The phenomenon of isomerism was predicted and proved (experimentally) by A.M. Butlerov on the example of butane

So, for example, the composition of C 4 H 10 corresponds to two structural formulas:<Annex 1 . Slide 22>

A different mutual arrangement of carbon atoms in the molecules of UV appears only with butane. The number of isomers increases with the number of carbon atoms of the corresponding hydrocarbon, for example, pentane has three isomers, and decane has seventy-five.

3. By the properties of a given substance, one can determine the structure of its molecule, and by the structure of the molecule, one can predict properties. <Annex 1 . Slide 19>

From the course of inorganic chemistry, it is known that the properties of inorganic substances depend on the structure of crystal lattices. Distinctive properties of atoms from ions are explained by their structure. In the future, we will see that organic substances with the same molecular formulas, but different structures, differ not only in physical, but also in chemical properties.

4. Atoms and groups of atoms in the molecules of substances mutually influence each other.

<Annex 1 . Slide 19>

As we already know, the properties of inorganic compounds containing hydroxo groups depend on whether they are bonded to atoms of metals or nonmetals. For example, both bases and acids contain a hydroxo group:<Annex 1 . Slide 23>

However, the properties of these substances are completely different. The reason for the different chemical nature of the group - OH (in aqueous solution) is due to the influence of the atoms and groups of atoms associated with it. With an increase in the non-metallic properties of the central atom, dissociation according to the type of base is weakened and dissociation according to the type of acid increases.

Organic compounds can also have different properties, which depend on which atoms or groups of atoms the hydroxyl groups are attached to.

The question of the mutual infusion of atoms A.M. Butlerov analyzed in detail on April 17, 1879 at a meeting of the Russian Physical and Chemical Society. He said that if two different elements are associated with carbon, for example, Cl and H, then “they here do not depend on each other to the same extent as on carbon: there is no dependence between them, that connection that exists in a particle of hydrochloric acid … But does it follow from this that there is no relationship between hydrogen and chlorine in the CH 2 Cl 2 compound? I answer this with a resounding denial.”

As a specific example, he further cites an increase in the mobility of chlorine during the transformation of the CH 2 Cl group into COCl and says in this regard: “It is obvious that the character of the chlorine in the particle has changed under the influence of oxygen, although this latter did not combine directly with chlorine.”<Annex 1 . Slide 23>

The question of the mutual influence of directly unbound atoms was the main theoretical core of V.V. Morkovnikov.

In the history of mankind, relatively few scientists are known whose discoveries are of worldwide significance. In the field of organic chemistry, such merits belong to A.M. Butlerov. In terms of significance, the theory of A.M. Butlerov is compared with the Periodic Law.

The theory of the chemical structure of A.M. Butlerov:<Annex 1 . Slide 24>

- made it possible to systematize organic substances;
– answered all the questions that had arisen by that time in organic chemistry (see above);
- made it possible to theoretically foresee the existence of unknown substances, to find ways of their synthesis.

Almost 140 years have passed since the TCS of organic compounds was created by A.M. Butlerov, but even now chemists of all countries use it in their work. The latest achievements of science supplement this theory, clarify and find new confirmations of the correctness of its basic ideas.

The theory of chemical structure remains the foundation of organic chemistry today.

TCS of organic compounds A.M. Butlerova made a significant contribution to the creation of a general scientific picture of the world, contributed to the dialectical - materialistic understanding of nature:<Annex 1 . Slide 25>

– the law of transition of quantitative changes into qualitative ones can be traced on the example of alkanes:<Annex 1 . Slide 25>.

Only the number of carbon atoms changes.

– law of unity and struggle of opposites traced to the phenomenon of isomerism<Annex 1 . Slide 26>

Unity - in composition (same), location in space.
The opposite is in the structure and properties (different sequence of arrangement of atoms).
These two substances coexist together.

– law of negation of negation - on isomerism.<Annex 1 . Slide 27>

Isomers coexisting negate each other by their existence.

Having developed the theory, A.M. Butlerov did not consider it absolute and unchangeable. He argued that it should develop. TCS of organic compounds did not remain unchanged. Its further development proceeded mainly in 2 interrelated directions:<Annex 1 . Slide 28>

Stereochemistry is the study of the spatial structure of molecules.

The doctrine of the electronic structure of atoms (allowed to understand the nature of the chemical bond of atoms, the essence of the mutual influence of atoms, to explain the reason for the manifestation of certain chemical properties by a substance).

The largest event in the development of organic chemistry was the creation in 1961 by the great Russian scientist A.M. Butlerov's theory of the chemical structure of organic compounds.

Before A.M. Butlerov, it was considered impossible to know the structure of the molecule, that is, the order of the chemical bond between atoms. Many scientists even denied the reality of atoms and molecules.

A.M. Butlerov refuted this opinion. He proceeded from correct materialistic and philosophical ideas about the reality of the existence of atoms and molecules, about the possibility of knowing the chemical bond of atoms in a molecule. He showed that the structure of a molecule can be established empirically by studying the chemical transformations of a substance. Conversely, knowing the structure of the molecule, one can derive the chemical properties of the compound.

The theory of chemical structure explains the diversity of organic compounds. It is due to the ability of tetravalent carbon to form carbon chains and rings, combine with atoms of other elements and the presence of isomerism in the chemical structure of organic compounds. This theory laid the scientific foundations of organic chemistry and explained its most important regularities. The basic principles of his theory A.M. Butlerov stated in the report "On the theory of chemical structure".

The main provisions of the theory of structure are as follows:

1) in molecules, atoms are connected to each other in a certain sequence in accordance with their valency. The bonding order of atoms is called chemical structure;

2) the properties of a substance depend not only on which atoms and in what quantity are part of its molecule, but also on the order in which they are interconnected, that is, on the chemical structure of the molecule;

3) atoms or groups of atoms that formed a molecule mutually influence each other.

In the theory of chemical structure, much attention is paid to the mutual influence of atoms and groups of atoms in a molecule.

Chemical formulas, which depict the order of connection of atoms in molecules, are called structural formulas or structure formulas.

The value of the theory of chemical structure of A.M. Butlerov:

1) is an essential part of the theoretical foundation of organic chemistry;

2) in importance it can be compared with the Periodic system of elements of D.I. Mendeleev;

3) it made it possible to systematize a huge amount of practical material;

4) made it possible to predict in advance the existence of new substances, as well as indicate ways to obtain them.

The theory of chemical structure serves as the guiding basis in all research in organic chemistry.

5. Isomerism. The electronic structure of atoms of elements of small periods. Chemical bond

The properties of organic substances depend not only on their composition, but also on the order of connection of atoms in a molecule.

Isomers are substances that have the same composition and the same molar mass, but different molecular structure, and therefore have different properties.

Scientific significance of the theory of chemical structure:

1) deepens ideas about the substance;

2) indicates the way to the knowledge of the internal structure of molecules;

3) makes it possible to understand the facts accumulated in chemistry; predict the existence of new substances and find ways to synthesize them.

All this theory greatly contributed to the further development of organic chemistry and the chemical industry.

The German scientist A. Kekule expressed the idea of ​​connecting carbon atoms to each other in a chain.

The doctrine of the electronic structure of atoms.

Features of the doctrine of the electronic structure of atoms: 1) made it possible to understand the nature of the chemical bond of atoms; 2) find out the essence of the mutual influence of atoms.

The state of electrons in atoms and the structure of electron shells.

Electron clouds are areas of the greatest probability of an electron being present, which differ in their shape, size, and orientation in space.

In the atom hydrogen a single electron during its movement forms a negatively charged cloud of a spherical (spherical) shape.

S-electrons are electrons that form a spherical cloud.

The hydrogen atom has one s-electron.

In the atom helium are two s-electrons.

Features of the helium atom: 1) clouds of the same spherical shape; 2) the highest density is equally removed from the core; 3) electron clouds are combined; 4) form a common two-electron cloud.

Features of the lithium atom: 1) has two electronic layers; 2) has a cloud of spherical shape, but is much larger than the inner two-electron cloud; 3) the electron of the second layer is weaker attracted to the nucleus than the first two; 4) is easily captured by other atoms in redox reactions; 5) has an s-electron.

Features of the beryllium atom: 1) the fourth electron is an s-electron; 2) the spherical cloud coincides with the cloud of the third electron; 3) there are two paired s-electrons in the inner layer and two paired s-electrons in the outer.

The more electron clouds overlap when atoms connect, the more energy is released and the stronger chemical bond.

Topic: The main provisions of the theory of the structure of organic compounds by A. M. Butlerova.

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: 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 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:

tetravalent carbon atoms can combine with each other, forming various chains:

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):

This position explains the phenomenon.

Substances that have the same composition, but different chemical or spatial structure, and therefore different properties, are called isomers.

Main types:

Structural isomerism, in which substances differ in the order of bonding of atoms in molecules: carbon skeleton

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:

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, organic chemistry widely used

empirical (molecular) and structural formulas. 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.

And fibers, products from which are used in technology, 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.

Created by A.M. Butlerov in the 60s of the XIX century, the theory of the chemical structure of organic compounds brought the necessary clarity to the reasons for the diversity of organic compounds, revealed the relationship between the structure and properties of these substances, made it possible to explain the properties of already known and predict the properties of organic compounds that have not yet been discovered.

Discoveries in the field of organic chemistry (tetravalent carbon, the ability to form long chains) allowed Butlerov in 1861 to formulate the main generations of the theory:

1) Atoms in molecules are connected according to their valency (carbon-IV, oxygen-II, hydrogen-I), the sequence of connection of atoms is reflected by structural formulas.

2) The properties of substances depend not only on the chemical composition, but also on the order of connection of atoms in a molecule (chemical structure). Exist isomers, that is, substances that have the same quantitative and qualitative composition, but a different structure, and, consequently, different properties.

C 2 H 6 O: CH 3 CH 2 OH - ethyl alcohol and CH 3 OCH 3 - dimethyl ether

C 3 H 6 - propene and cyclopropane - CH 2 \u003d CH−CH 3

3) Atoms mutually influence each other, this is a consequence of the different electronegativity of the atoms that form the molecules (O>N>C>H), and these elements have a different effect on the displacement of common electron pairs.

4) According to the structure of the molecule of organic matter, its properties can be predicted, and the structure can be determined from the properties.

TSOS received further development after the establishment of the structure of the atom, the adoption of the concept of the types of chemical bonds, the types of hybridization, the discovery of the phenomenon of spatial isomerism (stereochemistry).

Ticket number 7 (2)

Electrolysis as a redox process. Electrolysis of melts and solutions on the example of sodium chloride. Practical application of electrolysis.

Electrolysis- this is a redox process that occurs on the electrodes when a constant electric current passes through the melt or electrolyte solution

The essence of electrolysis is the implementation of chemical energy at the expense of electrical energy. Reactions - reduction at the cathode and oxidation at the anode.

The cathode(-) donates electrons to the cations, and the anode(+) accepts electrons from the anions.

NaCl melt electrolysis

NaCl-―> Na + +Cl -

K(-): Na + +1e-―>Na 0 | 2 percent recovery

A(+) :2Cl-2e-―>Cl 2 0 | 1 percent oxidation

2Na + +2Cl - -―>2Na+Cl 2

Electrolysis of an aqueous solution of NaCl

In the electrolysis of NaC| Na + and Cl - ions, as well as water molecules, participate in water. When current passes, Na + cations move towards the cathode, and Cl - anions move towards the anode. But at the cathode instead of Na ions, water molecules are reduced:

2H 2 O + 2e-―> H 2 + 2OH -

and chloride ions are oxidized at the anode:

2Cl - -2e-―>Cl 2

As a result, hydrogen is on the cathode, chlorine is on the anode, and NaOH accumulates in the solution

In ionic form: 2H 2 O+2e-―>H 2 +2OH-

2Cl - -2e-―>Cl 2

electrolysis

2H 2 O+2Cl - -―>H 2 +Cl 2 +2OH -

electrolysis

In molecular form: 2H 2 O+2NaCl-―> 2NaOH+H 2 +Cl 2

Application of electrolysis:

1) Protection of metals from corrosion

2) Obtaining active metals (sodium, potassium, alkaline earth, etc.)

3) Purification of some metals from impurities (electric refining)

Ticket number 8 (1)

Related information:

1. A) Theory of knowledge - a science that studies the forms, methods and techniques of the emergence and development of knowledge, its relation to reality, the criteria for its truth.