Basic principles of the theory of organic substances. Lesson-lecture "Theory of the chemical structure of A.M.

Chemistry is a science that gives us all the variety of materials and household items that we use every day without thinking. But to come to the discovery of such a variety of compounds that are known today, many chemists had to go through a difficult scientific path.

Enormous 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 chemist scientists who made an invaluable contribution to the development of organic chemistry, there was a Russian man Butlerov A.M. We will briefly consider his works, merits and results in this article.

Brief biography

The date of birth of the scientist is September 1828, date in different sources unequal. He was the son of Lieutenant Colonel Mikhail Butlerov; he lost his mother quite early. He lived all his childhood on his grandfather’s family estate, in the village of Podlesnaya Shentala (now a region of the Republic of Tatarstan).

He studied in different places: first at a closed private school, then at a gymnasium. Later he entered Kazan University to study 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 in place as a teacher after graduation.

1851 - the time of defense of the scientist’s first dissertation on the topic “Oxidation of Organic Compounds.” After his brilliant performance, he was given the opportunity to manage all chemistry at his university.

The scientist died in 1886 where he spent his childhood, on his grandfather’s family estate. 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, from its walls came such scientists who later had heavy weight in the development of all science. These are the following people:

• Markovnikov;
• Zaitsev;
• Kondakov;
• Favorsky;
• Konovalov;
• Lvov and others.

Works on organic chemistry

There are many such works that can be named. After all, almost all Butlerov free time spent 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 by 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 for a long time the works of other scientists from different countries, studied their works, including experimental ones. Only then, having generalized and systematized the acquired knowledge, did he reflect all the conclusions in the provisions of his personal theory.

Theory of the structure of organic compounds by A. M. Butlerov

The 19th century was marked by the rapid development of almost all sciences, including chemistry. In particular, extensive discoveries on carbon and its compounds continue to accumulate and amaze everyone with their diversity. However, no one dares to systematize and organize all this factual material, bring it to a common denominator and identify common patterns on which everything is built.

Butlerov A.M. was the first to do this. It was he who owned the brilliant theory chemical structure organic compounds, the provisions of which he spoke en masse at a German conference of chemists. This was the beginning of a new era in the development of science, organic chemistry entered the

The scientist himself approached this gradually. He conducted many experiments and predicted the existence of substances with given properties, discovered certain types of reactions and saw the future behind them. I studied a lot of the works of my colleagues and their discoveries. 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 one is practically the same as the periodic table in the inorganic one.

Scientist's discoveries before creating theory

What discoveries were made and theoretical justifications given to scientists before A. M. Butlerov’s theory of the structure of organic compounds appeared?

1. The domestic genius was the first to synthesize such organic substances as methenamine, formaldehyde, methylene iodide and others.
2. He synthesized a sugar-like substance (tertiary alcohol) from inorganics, thereby dealing another blow to the theory of vitalism.
3. He predicted the future of polymerization reactions, calling them the best and most promising.
4. 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 at length. However, the theory of the structure of organic compounds has become the most significant today, the provisions of which we will discuss 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 his colleagues his views on the reasons for the structure and diversity of organic compounds, expressing all this in the form of theoretical principles.

The very first point is the following: all atoms within one molecule are connected in a strict sequence, which is determined by their valency. In this case, the carbon atom exhibits a valence index of four. Oxygen has a value of this indicator equal to two, hydrogen - one.

He proposed to call such a feature chemical. Later, notations for expressing it on paper using graphical complete structural, abbreviated and molecular formulas were adopted.

This also includes the phenomenon of combining carbon particles with each other into endless chains of different structures (linear, cyclic, branched).

In general, Butlerov’s theory of the structure of organic compounds, with its first position, determined the importance of valency and a single formula for each compound, reflecting the properties and behavior of the substance during reactions.

The second position of the theory

At this point, an explanation was given for the diversity of organic compounds in the world. Based on the carbon compounds in the chain, the scientist expressed the idea that there are different 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 proposition, A. M. Butlerov’s theory of the structure of organic compounds not only explained the essence of isomers and isomerism, but the scientist himself confirmed everything through practical experience.

For example, he synthesized the isomer of butane - isobutane. Then he predicted the existence of not one, but three isomers for pentane, based on the structure of the compound. And he synthesized them all, proving he was right.

Opening the third position

The next point of the theory says that all atoms and molecules within one compound are able to influence the properties of each other. The nature of the behavior of the substance in reactions will depend on this different types, exhibited chemical and other properties.

Thus, on the basis of this provision, several functional defining groups differing in appearance and structure are distinguished.

The theory of the structure of organic compounds by A. M. Butlerov is briefly outlined in almost all textbooks in organic chemistry. After all, it is precisely this that is the basis of this section, an explanation of all the patterns on which molecules are built.

The importance of theory for modern times

Of course it is great. This theory allowed:

1. combine and systematize all the factual material accumulated by the time of its creation;
2. explain the patterns of structure and properties of various compounds;
3. give a full explanation of the reasons for such a wide variety of compounds in chemistry;
4. gave rise to numerous syntheses of new substances based on the principles of the theory;
5. allowed views to advance and atomic-molecular teaching to develop.

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 founder of its theoretical foundations.

His scientific vision of the world, genius of thinking, ability to foresee the result played a role in the final analysis. This man had enormous capacity for work, patience, and tirelessly experimented, synthesized, and trained. I made mistakes, but I always learned a lesson and made the right long-term conclusions.

Only such a set of qualities, business acumen, and perseverance made it possible to achieve the desired effect.

Studying organic chemistry at school

In the secondary education course, 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 grade (according to O. S. Gabrielyan’s program). However, this time is enough for the children 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 to master 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 subsequently to theoretical and practical confirmation of them in the study of each class of substances.

(slide 1)

Purpose: Summarize information about the structure organic matter, show the universality of the theory of chemical structure, generalize and expand students’ ideas: about isomerism using examples of organic and inorganic compounds; about the mutual influence of atoms in molecules, the interdependence of the structure and properties of substances.

A.M. Butlerov is one of the greatest Russian scientists, he is Russian both in his scientific education and in the originality of his works.

(D.I. Mendeleev) “... I love my country like a mother, and my science as a spirit that blesses, illuminates and unites all peoples for the good and peaceful development of spiritual and material wealth.”

Equipment: computer, slide presentation, interactive whiteboard.

Lesson progress

Analysis of the principles of the theory of chemical structure

1) atoms in molecules are not connected randomly, but in strict sequence according to their valence . (slide 3)

What is the valency of carbon in organic matter?

(the answer is four).

Question for the class. How are carbon atoms connected in molecules of organic compounds?

Answer. Carbon atoms, connecting with each other, form unbranched, branched chains, cycles, simple, double, and triple bonds.

Class assignment (slide 4)

Construct the structural formulas of propene, butyne-1, isopentane, cyclobutane.

Question for the class. Is this provision applicable for inorganic substances?

Construct structural formulas for sulfuric acid, calcium oxide, sodium sulfate, calcium hydroxide.

The second position of the theory of A.M. Butlerov.

2) The properties of substances depend not only on their qualitative and quantitative composition, but also on the structure of the molecules.

Question for the class. What is meant by molecular structure? ?

Answer. A) the order of connection of atoms in a molecule

B) relative position atoms and groups of atoms in space

Question for the class. What phenomenon explains this situation?

Answer. This situation explains the phenomenon – isomerism.(discussion of all types of isomerism follows)

Question for the class. What types of isomerism do you know?

Answer: Structural, spatial . (slide 5)

Structural isomerism:

1. Hydrocarbon skeleton

2. Positions: substituents, functional groups, multiple bonds, radicals (for arenes) (slide 6)

3. Interclass (slide 7)

4. Tautomerism

Spatial

1. Geometric (slide 8)

Fill out the table (independent work)

Types of isomerism of organic substances

Isomerism of inorganic substances. (slide 10)

The listed pairs of acids are tautomeric; they exist simultaneously in solutions, transforming into each other.

Interclass isomers in inorganic substances

Spatial isomerism of inorganic substances (slide 12,13,14)

1. Geometric (complex compounds)

cis isomer (orange) trans isomer(yellow)

The third position of the theory of A.M. Butlerov.

3. The properties of substances depend on the mutual influence of atoms in the molecule .

1. Compare the acidic properties of ethanol and phenol? Explain the reason for the increase in acidic properties of phenol.

2. Alcohols react with hydrogen halides, but phenols do not. Why?

3. Compare the ability of benzene and phenol to undergo electrophilic substitution reactions at the benzene ring. Explain the reason for the higher reactivity of phenol.

Question for the class. What determine the properties of inorganic substances?

Explain from a position periodic law M.I. Mendeleev, and the structure of atoms of elements in groups and periods.

Class assignments followed by discussion.

1. Compare the basic properties of ammonia and phosphine. Explain the decrease in the basic properties of phosphine

2. Compare the acidic properties of hydrogen sulfide and hydrogen chloride.

3. Compare the acidic properties of hydrochloric and hydroiodic acids.

Answer. In the main subgroups, the radii of the atoms of the elements increase from top to bottom, the atoms of non-metals attract hydrogen atoms less strongly, the strength of the compounds decreases, they easily dissociate, and therefore their acidic properties increase.

How and why do the properties of hydroxides change in period and group?

Answer. The basic properties of hydroxides decrease, and the acidic ones increase in the period from left to right, as the oxidation state of the central atom increases, therefore, the energy of its binding with the oxygen atom and its repulsion of the hydrogen atom increases.

The most important reasons for changes in chemical properties are the difference in electronegativity of elements, the presence of lone electron pairs,

Electron density shift.

Is it possible to predict the properties of a substance based on its structure?

Answer. Yes, you can.

Assignment to class followed by discussion. Guess the properties of the following substances. (confirm with equations of chemical reactions)

1. The presence of a polar bond, the ability to abstract a hydrogen cation, explains the acidic properties.
2. The ability of a substance to attach a hydrogen cation and a lone electron pair are the main properties.
3. The presence of simple bonds - substitution (exchange) reactions
4. Presence of multiple bonds – addition reactions
5. The presence of an element in the highest oxidation state has oxidative properties, in the lowest oxidation state it has reduction properties, and in the intermediate state it has redox properties.

Modern directions in the development of the theory of chemical structure are:

• stereochemistry - the study of the spatial structure of molecules
• electronic structure of matter (types of hybridization, electron density shift)

Electron density shift or electronic effects (slide 15)

Question for the class. Define the inductive effect.

Answer. Inductive – electron density shift along the length of the sigma bond

Consider the reaction of hydrogen bromide with propene-1 and the reaction of hydrogen bromide with 3,3,3-trifluoropropene-1

Question for the class. Define the mesomeric effect.

Answer. Mesomeric effect - Displacement of bond electrons or lone electron pairs in alternating simple and short bonds.

The mesomeric effect is stronger than the inductive effect.

Question for the class. What are the effects?

Answer. 1. On the reactivity of a substance

CH 4 – less reactive because all bonds are low-polar

CH 3 CI – more reactive because the bonds are more polar.

On the directions of processes.

Assignment to class followed by discussion. Consider the directions of the flow of chemical reactions. (Consider the influence of the corresponding effects on the direction of a chemical reaction)

Reaction according to Markovnikov's rule.

Interaction of propene-1 with hydrogen bromide.

Reaction against Markovnikov's rule.

Interaction of propenoic (acrylic) acid with hydrogen bromide.

Conclusion at the end of the lesson (slide 16)

The theory of structure created the prerequisites for explaining and predicting various types of isomerism of molecules of organic compounds, as well as the directions and mechanisms of chemical reactions.

Comparing the two greatest theories of chemistry - the theory of structure of A.M. Butlerov and the theory of periodicity D.I. Mendeleev, you can see that both theories have a lot in common.

Homework: paragraph 8, ex. 4.5. textbook O.S. Gabrielyan.

Alexander Mikhailovich Butlerov was born on September 3 (15), 1828 in the city of Chistopol, Kazan province, into the family of a landowner, a retired officer. He received his first education at a private boarding school, then studied at the gymnasium and the Kazan Imperial University. He taught from 1849, and in 1857 became an ordinary professor of chemistry at the same university. He was its rector twice. In 1851 he defended his master's thesis “On the oxidation of organic compounds”, and in 1854 at Moscow University - his doctoral thesis “On essential oils”. Since 1868 he was an ordinary professor of chemistry at St. Petersburg University, and since 1874 - an ordinary academician of the St. Petersburg Academy of Sciences. In addition to chemistry, Butlerov paid attention practical issues agriculture, gardening, beekeeping, and under his leadership, tea cultivation began in the Caucasus. He died in the village of Butlerovka, Kazan province, on August 5 (17), 1886.

Before Butlerov, a considerable number of attempts were made to create a doctrine of the chemical structure of organic compounds. This issue was repeatedly addressed by the most eminent chemists of that time, whose work was partially used by the Russian scientist for his theory of structure. For example, German chemist August Kekule concluded that carbon can form four bonds with other atoms. Moreover, he believed that several formulas could exist for the same compound, but he always added that depending on the chemical transformation, this formula could be different. Kekule believed that the formulas do not reflect the order in which the atoms in the molecule are connected. Another prominent German scientist, Adolf Kolbe, generally considered it fundamentally impossible to elucidate the chemical structure of molecules.

Butlerov first expressed his basic ideas about the structure of organic compounds in 1861 in a report “On the chemical structure of matter,” which he presented to the participants of the Congress of German Naturalists and Doctors in Speyer. In his theory, he incorporated ideas from Kekulé about valency (the number of bonds for a particular atom) and Scottish chemist Archibald Cooper that carbon atoms could form chains. The fundamental difference Butlerov's theory from others was a provision about the chemical (and not mechanical) structure of molecules - the way in which atoms bonded with each other, forming a molecule. In this case, each atom established a bond in accordance with the “chemical force” belonging specifically to it. In his theory, the scientist made a clear distinction between a free atom and an atom that has entered into a connection with another (it transforms into a new form, and as a result of mutual influence, the connected atoms, depending on the structural environment, have different chemical functions). The Russian chemist was convinced that formulas do not just schematically depict molecules, but also reflect their real structure. Moreover, each molecule has a specific structure, which changes only during chemical transformations. From the provisions of the theory it followed (later confirmed experimentally) that the chemical properties of an organic compound are determined by its structure. This statement is especially important, as it made it possible to explain and predict chemical transformations of substances. There is also an inverse relationship: the structural formula can be used to judge the chemical and physical properties substances. In addition, the scientist drew attention to the fact that reactivity compounds is explained by the energy with which the atoms bond.

With the help of the created theory, Butlerov was able to explain isomerism. Isomers are compounds in which the quantity and “quality” of atoms are the same, but at the same time they have different chemical properties, and therefore different structure. The theory made it possible to explain clearly known cases isomerism. Butlerov believed that it was possible to determine the spatial arrangement of atoms in a molecule. His predictions were later confirmed, which gave impetus to the development of a new branch of organic chemistry - stereochemistry. It should be noted that the scientist was the first to discover and explain the phenomenon of dynamic isomerism. Its meaning is that two or more isomers under certain conditions can easily transform into each other. Generally speaking, it was isomerism that became a serious test for the theory of chemical structure and was brilliantly explained by it.

The irrefutable provisions formulated by Butlerov very soon brought the theory universal recognition. The correctness of the ideas put forward was confirmed by experiments of the scientist and his followers. In their process, they proved the hypothesis of isomerism: Butlerov synthesized one of the four butyl alcohols predicted by the theory and deciphered its structure. In accordance with the rules of isomerism, which directly followed from the theory, the possibility of the existence of four valeric acids was also suggested. They were later received.

These are just isolated facts in a chain of discoveries: the chemical theory of the structure of organic compounds had amazing predictive ability.

For relatively short period A large number of new organic substances and their isomers were discovered, synthesized and studied. As a result, Butlerov’s theory gave impetus to the rapid development of chemical science, including synthetic organic chemistry. Thus, Butlerov’s numerous syntheses are the main products of entire industries.

The theory of chemical structure continued to develop, which brought many revolutionary ideas to organic chemistry at that time. For example, Kekule suggested the cyclic structure of benzene and the movement of its double bonds in the molecule, the special properties of compounds with conjugated bonds, and much more. Moreover, the mentioned theory made organic chemistry more visual - it became possible to draw molecular formulas.

And this, in turn, marked the beginning of the classification of organic compounds. It was the use of structural formulas that helped to determine ways of synthesizing new substances and to establish the structure of complex compounds, that is, it determined the active development of chemical science and its branches. For example, Butlerov began to conduct serious research into the polymerization process. In Russia, this initiative was continued by his students, which ultimately made it possible to open industrial method obtaining synthetic rubber.

Slide 1>

Lecture objectives:

• Educational:
  • to form concepts about the essence of the theory of the chemical structure of organic substances, relying on students’ knowledge of the electronic structure of atoms of elements, their position in Periodic table DI. Mendeleev, about the degree of oxidation, the nature of the chemical bond and other major theoretical principles:
    • the sequence of arrangement 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 progress of the development of theories in organic chemistry;
  • master the concepts: isomers and isomerism;
  • explain the meaning of the structural formulas of organic substances and their advantages over molecular ones;
  • show the need and prerequisites for creating a theory of chemical structure;
  • Continue developing note-taking skills.
• Developmental:
  • develop thinking analysis techniques, comparisons, generalizations;
  • develop abstract thinking;
  • train students' attention when perceiving large amounts 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.

PROGRESS OF THE LESSON

1. Organizational part

- Greetings
– Preparing students for the lesson
– Receiving information about absentees.

2. Learning new things

Lecture outline:<Appendix 1 . Slide 2>

I. Pre-structural theories:
– vitalism;
– theory of radicals;
– theory of types.
II. Brief information on 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 significance of the theory of the chemical structure of organic substances A.M. Butlerov and its development.

3. Homework: abstract, paragraph 2.

4. Lecture

I. Knowledge about organic substances has accumulated gradually since ancient times, but organic chemistry emerged as an independent science only at the beginning of the 19th century. The establishment of independence of organizational chemistry is associated with the name of the Swedish scientist J. Berzelius<Appendix 1 . Slide 3>. In 1808-1812 he published his large manual on chemistry, in which he initially intended to consider, along with minerals, also substances of animal and plant 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 the fact that the former can be obtained in laboratories synthetically, while the latter are supposedly formed only in living organisms under the influence of a certain “vital 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 “vital force” was called vitalism. She was 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<Appendix 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<Appendix 1 . Slide 5>received triglyceride. This necessitated a change in the definition of organic chemistry.
Scientists tried, based on the composition and properties, to unravel the nature of the molecules of organic substances, they sought to create a system that would make it possible to connect together the disparate facts that had accumulated over time. early XIX 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<Appendix 1 . Slide 6>. This was an attempt to consider from a single point of view quite large group organic 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 contained in this theory - the approach to an organic substance as consisting of 2 parts - subsequently formed the basis of a broader theory of radicals (J. Berzelius, J. Liebig, F. Wöhler). This theory is based on the idea of ​​the “dualistic structure” of substances. J. Berzelius wrote: “every organic substance consists of 2 components, carrying an opposite electric charge." J. Berzelius considered oxygen to be one of these components, namely the electronegative part, while the rest, actually organic, should have been an electropositive radical.

Basic provisions of the theory of radicals:<Appendix 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 from one molecule to another without changes;
– radicals can exist in free form.

Gradually, science accumulated facts that contradicted the theory of the radicals. This is how J. Dumas replaced hydrogen with chlorine in hydrocarbon radicals. It seemed incredible to scientists who were adherents of the radical theory that chlorine, charged negatively, could play the role of hydrogen, charged positively, in compounds. In 1834, J. Dumas received the task of investigating an unpleasant incident during a ball in the palace of the French king: candles emitted choking smoke when burning. J. Dumas established that the wax from which the candles were made was treated with chlorine by the manufacturer for bleaching. In this case, 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). Subsequently, J. Dumas obtained trichloroacetic acid from acetic acid.
Thus, the electropositive hydrogen was replaced by the extremely electronegative element chlorine, and 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 single whole.

The radical theory was gradually rejected, but it left a deep mark on organic chemistry:<Appendix 1 . Slide 8>
– the concept of “radical” has become firmly established in chemistry;
– the statement about the possibility of the existence of radicals in free form, about the transition to a huge number reactions of certain groups of atoms from one compound to another.

In the 40s XIX century The study of homology was initiated, which made it possible to clarify some of the relationships between the composition and properties of compounds. Homologous series and homologous differences were identified, which made it possible to classify organic substances. Classification of organic substances based on homology led to the emergence of the theory of types (40-50s of the 19th century, C. Gerard, A. Kekule, etc.)<Appendix 1 . Slide 9>

The essence of type theory<Appendix 1 . Slide 10>

– the theory is based on an analogy in the reactions between organic and some inorganic substances, accepted as types (types: hydrogen, water, ammonia, hydrogen chloride, etc.). By replacing hydrogen atoms in the type of substance with other groups of atoms, scientists predicted various derivatives. For example, replacing a hydrogen atom in a water molecule with a methyl radical results in the formation of an alcohol molecule. Substitution of two hydrogen atoms results in the appearance of an ether molecule<Appendix 1 . Slide 11>

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

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

<Appendix 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 influenced 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 substance undergoes. For each substance, you can write as many rational formulas as there are different types of transformations the substance can undergo. The theory of types allowed for a multiplicity of “rational formulas” for substances, depending on what reactions they wanted to express with these formulas.

Type theory played a major role in the development of organic chemistry <Appendix 1 . Slide 14>

– made it possible to predict and discover a number of substances;
- provided positive influence on the development of the doctrine of valency;
– paid 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 the predicted compounds;
- created a systematization of organic compounds that was perfect for that time.

We should not forget that in reality theories arose and replaced each other not sequentially, but existed simultaneously. Chemists often did not understand each other well. F. Wöhler said in 1835 that “organic chemistry today can drive anyone crazy. It seems to me like a dense forest full of wonderful things, a huge thicket with no exit, no end, where you don’t dare to penetrate...”

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

A new theory was needed that would take a materialist position. This theory was theory of chemical structure A.M. Butlerov <Appendix 1 . Slides 15, 16>, which was created in 1861. Everything rational and valuable that was in the theories of radicals and types was later assimilated by the theory of chemical structure.

The need for a theory was dictated by:<Appendix 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 methods of processing agricultural products.
In connection with these problems, new methods for the synthesis of organic substances began to be developed. However, scientists have had serious difficulties in scientifically substantiating these syntheses. 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 valence only in CH4 methane. In ethane C 2 H 6, if we follow our ideas, carbon should be. 3-valent, and in propane C 3 H 8 - fractional valence. (And we know that valence must be expressed only in whole numbers).
What is the valence 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 - the molecular formula of glucose, but the same formula for fructose (a sugary substance - a component of honey).

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

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

A scientifically based 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 prepared the ground for the emergence of the theory of chemical structure were<Appendix 1 . Slide 18>

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

An important discovery for organic chemistry was the hypothesis about 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. XIX century There were no generally accepted criteria for defining the concepts: “atom”, “molecule”, “ atomic mass", "molecular weight". Only at the international congress of chemists in Karlsruhe (1860) were these concepts clearly defined, which predetermined the development of the theory of valency and the emergence of the theory of chemical structure.

Basic principles 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 principles that can be divided into 4 groups.<Appendix 1 . Slide 19>

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

<Appendix 1 . Slides 19, 20>

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

Such a schematic representation of the structure of molecules is called structural formulas and 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:<Appendix 1 . Slide 20>

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

2. The properties of a substance depend not only on what atoms and how many of them are included in the molecules, but also on the order of connection of atoms in the molecules (i.e. properties depend on the structure) <Appendix 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 connected 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.<Appendix 1 . Slide 21>

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

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

Different relative positions of carbon atoms in carbon dioxide molecules appear 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. <Appendix 1 . Slide 19>

From the course inorganic chemistry, it is known that the properties of inorganic substances depend on the structure crystal lattices. The 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 molecules of substances mutually influence each other.

<Appendix 1 . Slide 19>

As we already know, the properties of inorganic compounds containing hydroxo groups depend on which atoms they are connected to - metal or non-metal atoms. For example, both bases and acids contain a hydroxo group:<Appendix 1 . Slide 23>

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

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

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

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

The question of the mutual influence of directly non-bonded atoms was the main theoretical core of the works of V.V. Morkovnikova.

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

Theory of chemical structure A.M. Butlerova:<Appendix 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 predict the existence of unknown substances and 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 from all countries use it in their work. Latest achievements sciences supplement this theory, clarify it and find new confirmation 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:<Appendix 1 . Slide 25>

– law of transition of quantitative changes into qualitative ones can be seen using the example of alkanes:<Appendix 1 . Slide 25>.

Only the number of carbon atoms changes.

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

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

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

Isomers coexisting deny each other by their existence.

Having developed the theory, A.M. Butlerov did not consider it absolute and unchangeable. He argued that it must develop. The TCS of organic compounds has not remained unchanged. Its further development proceeded mainly in two interrelated directions:<Appendix 1 . Slide 28>

Stereochemistry is the study of the spatial structure of molecules.

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

The behavior of particles in compounds depends on many factors. The theory of the structures of organic compounds studies the behavior of molecules in compounds, the nature of atoms, valence, order and character chemical bonds. This article briefly formulates the main provisions of this theory.

Structure of organic compounds

The variety of organic compounds is explained by the peculiarities of their chemical structure. The atoms in a molecule are arranged in in a certain order according to their valence. This sequence is the chemical structure.

Substances that have the same qualitative and quantitative composition (molecular formula), but different structures, are called isomers, and their very existence is called isomerism. The famous Russian chemist A.M. Butlerov proved that new substances can be obtained using controlled reactions.

Rice. 1. Isomerism definition.

Also important is the concept that atoms and groups of atoms in a molecule mutually influence each other.

Theory of the structures of organic substances

The theory of the structure of organic compounds was formulated by the Russian chemist A. M. Butlerov in 1861. The main conclusion of this scientific work became the statement that each substance corresponds to only one formula. This work shows the behavior of atoms inside molecules.

Rice. 2. A. M. Butlerov.

The main provisions and consequences of Butlerov’s theory of structure can be formulated as follows:

• In molecules, atoms are not randomly arranged, but have a definite structure.

A schematic representation of the structure of a molecule is called a structural formula

Rice. 3. Structural formula of the molecule.

Based on the position of the valence of the carbon atom, equal to four, and its ability to form chains and cycles, structural formulas of organic substances are built.

• The chemical properties of a substance depend on the composition and arrangement of atoms and molecules.
• Different structures with the same composition and molecular weight of a substance cause the phenomenon of isomerism. Absolutely different chemical elements can have the same composition and molecular weight, it all depends on the location tiny particles and connections between them.
• By the properties of a substance you can determine the structure of a molecule, and by its structure you can predict the properties
• Since during individual reactions not all, but only some parts of the molecules change, then by studying the products of chemical transformations of a compound, its structure can be established.
• The reactivity of the atoms in a molecule varies depending on which atoms they are bonded to in the molecule. Atoms connected to each other influence each other with greater strength than unrelated ones.

What have we learned?

The significance of Butlerov's theory of chemical structures of organic compounds is great. His theory not only explains the structure of the molecules of all known organic substances and their properties, but also makes it possible to theoretically foresee the existence of unknown and new substances, as well as find a way to obtain and synthesize them.