Resonance theory. Organic Chemistry Resonance in Chemistry

chemical resonance

Resonance theory- the theory of the electronic structure of chemical compounds, according to which the distribution of electrons in molecules (including complex ions or radicals) is a combination (resonance) of canonical structures with different configurations of two-electron covalent bonds. The resonant wave function, which describes the electronic structure of a molecule, is a linear combination of the wave functions of the canonical structures.

In other words, the molecular structure is described not by one possible structural formula, but by a combination (resonance) of all alternative structures.

The consequence of the resonance of canonical structures is the stabilization of the ground state of the molecule, the measure of such resonance stabilization is resonance energy is the difference between the observed energy of the ground state of the molecule and the calculated energy of the ground state of the canonical structure with the minimum energy .

Resonance structures of the cyclopentadienide ion

Story

The idea of ​​resonance was introduced into quantum mechanics by Werner Heisenberg in 1926 when discussing the quantum states of the helium atom. He compared the structure of the helium atom to the classical system of a resonating harmonic oscillator.

The Heisenberg model was applied by Linus Pauling (1928) to describe the electronic structure of molecular structures. Within the framework of the method of valence schemes, Pauling successfully explained the geometry and physicochemical properties of a number of molecules through the mechanism of delocalization of the electron density of π bonds.

Similar ideas for describing the electronic structure of aromatic compounds were proposed by Christopher Ingold. In 1926-1934, Ingold laid the foundations of physical organic chemistry, developing an alternative theory of electronic displacements (the theory of mesomerism), designed to explain the structure of molecules of complex organic compounds that do not fit into the usual valence representations. The term proposed by Ingold to denote the phenomenon of electron density delocalization mesomerism"(1938), is used mainly in German and French literature, and English and Russian literature is dominated by" resonance". Ingold's ideas about the mesomeric effect became an important part of resonance theory. Thanks to the German chemist Fritz Arndt, the commonly accepted notation of mesomeric structures with the help of double-headed arrows was introduced.

In the post-war USSR, the theory of resonance became an object of persecution within the framework of ideological campaigns and was declared "idealistic", alien to dialectical materialism - and therefore unacceptable for use in science and education:

The "resonance theory", being idealistic and agnostic, opposes Butlerov's materialistic theory as incompatible and irreconcilable with it; ... the supporters of the "resonance theory" ignored it and distorted its essence.

"Theory of Resonance", being mechanistic through and through. denies the qualitative, specific features of organic matter and completely falsely tries to reduce the laws of organic chemistry to the laws of quantum mechanics ...

... The mesomeric-resonant theory in organic chemistry is the same manifestation of a general reactionary ideology, as is Weismannism-Morganism in biology, as well as modern "physical" idealism, with which it is closely connected.

Kedrov B.M. Against "physical" idealism in chemical science. Cit. By

The persecution of the theory of resonance received a negative assessment in the world scientific community. In one of the journals of the American Chemical Society, in a review on the situation in Soviet chemical science, in particular, it was noted:

see also

Notes

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In the forties there was a scientific breakthrough in the field of organic chemistry and the chemistry of macromolecular compounds. Qualitatively new materials are created. The process of formation of physics and chemistry of polymers is going on, the theory of macromolecules is being created. Scientific achievements in this area are becoming one of the foundations for qualitative transformations in the national economy. And it is no coincidence that it is precisely here that ideologists deliver a powerful preemptive blow.

The pretext was the theory of resonance, put forward in 1928 by a prominent chemist, Nobel Prize winner Linus Pauling. According to this theory, for molecules whose structure can be represented in the form of several structural formulas that differ in the way electron pairs are distributed between nuclei, the real structure does not correspond to any of the structures, but is intermediate between them. The contribution of each structure is determined by its nature and relative stability. The resonance theory (and Ingold's mesomerism theory close to it) was of significant importance as a convenient systematization of structural representations. This theory played an important role in the development of chemistry, especially organic chemistry. In fact, she developed a language that chemists spoke for several decades.

An idea of ​​the degree of rolling and argumentation of ideologues is given by excerpts from the article "Theory of Resonance" in /35/:

"Proceeding from subjective-idealistic considerations, adherents of the theory of resonance invented for the molecules of many chemical compounds sets of formulas - "states" or "structures" that do not reflect objective reality. In accordance with the theory of resonance, the true state of a molecule is supposedly the result of a quantum mechanical interaction, "resonance", "superposition" or "overlay" of these fictitious "states" or "structures".

… The theory of resonance, closely connected with the idealistic principles of N. Bohr's "complementarity" and P. Dirac's "superposition", is an extension of "physical" idealism to organic chemistry and has the same methodological Machist basis.

Another methodological defect of the resonance theory is its mechanism. In accordance with this theory, the presence of specific qualitative features is denied in an organic molecule. Its properties are reduced to a simple sum of the properties of its constituent parts; qualitative differences are reduced to purely quantitative differences. More precisely, the complex chemical processes and interactions occurring in organic matter are reduced here to one, simpler than chemical forms, physical forms of the motion of matter - to electrodynamic and quantum mechanical phenomena. Developing the idea of ​​reducing chemistry to physics, the well-known quantum physicist and "physical" idealist E. Schrödinger in his book "What is life from the point of view of physics?" gives a broad system of such a mechanistic reduction of the higher forms of the movement of mothers to the lower ones. In accordance with Weismannism-Morganism, he reduces the biological processes that are the basis of life to genes, genes to the organic molecules from which they are formed, and organic molecules to quantum mechanical phenomena.

Two points are interesting. Firstly, in addition to the standard accusations of idealism, the thesis about the specificity and qualitative features of the forms of movement plays the most important role here, which actually imposes a ban on the use of physical methods in chemistry, physical and chemical methods in biology, etc. Secondly, an attempt was made to link the theory of resonance with Weismannism-Morganism, that is, how to lay the foundation for a united front in the fight against advanced scientific trends.

The infamous "green volume" contains an article by BM Kedrov /37/ devoted to the "resonance theory". It depicts the consequences that this "terrible" theory brings with it. Here are some very revealing conclusions from this article.

1. The "resonance theory" is subjective-idealistic, for it transforms a fictitious image into an object; replaces the object with a mathematical representation that exists only in the head of its supporters; makes the object - the organic molecule - dependent on this representation; ascribes to this representation an independent existence outside our head; gives it the ability to move, interact, superpose, and resonate.

2. The "resonance theory" is agnostic, because in principle it denies the possibility of reflecting a single object (organic molecule) and its structure in the form of a single structural image, a single structural formula; it discards such a single image of a single object and replaces it with a set of fictitious "resonant structures".

3. The "resonance theory", being idealistic and agnostic, opposes the materialistic theory of Butlerov, as incompatible and irreconcilable with it; Since Butlerov's theory fundamentally contradicts all idealism and agnosticism in chemistry, the proponents of the "resonance theory" ignored it and distorted its essence.

4. "Resonance theory", being mechanistic through and through. denies the qualitative, specific features of organic matter and completely falsely tries to reduce the laws of organic chemistry to the laws of quantum mechanics; this is also connected with the denial of Butlerov's theory by supporters of the "resonance theory". because Butlerov's theory, being essentially dialectical, deeply reveals the specific regularities of organic chemistry, denied by modern mechanists.

5. In its essence, Ingold's theory of mesomerism coincides with Pauling's "resonance theory", which merged with the first into a single mesomeric-resonant theory. Just as the bourgeois ideologists gathered together all the reactionary currents in biology, so that they would not act separately, and merged them into a united front of Weismannism-Morganism, so they brought together the reactionary currents in organic chemistry, forming a united front of supporters of Pauling-Ingold. Any attempt to separate the theory of mesomerism from the "theory of resonance" on the grounds that the theory of mesomerism can be interpreted materialistically is a gross mistake that actually helps our ideological opponents.

6. The mesomeric-resonant theory in organic chemistry is the same manifestation of a general reactionary ideology, as is Weismannism-Morganism in biology, as well as modern "physical" idealism, with which it is closely connected.

7. The task of Soviet scientists is to resolutely fight against idealism and mechanism in organic chemistry, against kowtowing to fashionable bourgeois, reactionary trends, against theories hostile to Soviet science and our worldview, such as the mesomeric resonance theory ... "

A certain piquancy of the situation around the "resonance theory" was created by the obvious far-fetched nature of the accusations from a scientific point of view. It was just an approximate model approach that had nothing to do with philosophy. But a noisy discussion ensued. Here is what L. A. Blumenfeld writes about her / 38 /:

"In the course of this discussion, some physicists spoke, claiming that the theory of resonance is not only idealistic (this was the main motive of the discussion), but also illiterate, since it contradicts the foundations of quantum mechanics. In this regard, my teachers, Ya. K. Syrkin and M E. Dyatkina, against whom this discussion was mainly directed, took me with them and came to Igor Evgenievich Tamm to find out his opinion on this matter. Absolute scientific conscientiousness, complete absence of "physical snobbery", unaffected by any opportunistic considerations and natural benevolence - all this automatically made Tamm almost "the only possible arbiter. He said that the method of description proposed in resonance theory does not contradict anything in quantum mechanics, there is no idealism here, and, in his opinion, there is no subject for discussion at all. Subsequently, it became clear to everyone that he was right. However, the discussion, as you know, continued. There were people who claimed that the theory of resonance is a pseudoscience. This had a negative impact on the development of structural chemistry…"

Indeed, there is no subject for discussion, but there is a task to strike at specialists in high-molecular chemistry. And for the sake of this, B. M. Kedrov, when considering the theory of resonance, made a major step in the interpretation of V. I. Lenin /37/:

“The comrades who clung to the word “abstraction” acted like dogmatists. They compared the fact that the imaginary “structures” of the theory of mesomerism are abstractions and even the fruit of abstraction with what Lenin said about scientific abstraction, and concluded that once Because abstractions are necessary in science, it means that all sorts of abstractions are permissible, including abstract concepts about the fictitious structures of the theory of mesomerism.So literally they solved this issue, contrary to the essence of the matter, contrary to Lenin's direct indications of the harmfulness of empty and absurd abstractions, of the danger of turning abstract concepts into idealism. Precisely because the tendencies of the transformation of abstract concepts into idealism were present from the very beginning both in the theory of mesomerism and in the theory of resonance, both of these theories eventually merged together.

It is curious that idealism can also be different. So the article "Butlerov" /32/ says; that Soviet chemists rely on Butlerov's theory in their struggle against the idealistic theory of resonance. But on the other hand, it turns out that "in general philosophical questions not related to chemistry, Butlerov was an idealist, a propagandist of spiritualism." However, no contradictions play a role for ideologists. In the fight against advanced science, all means were good.

Resonance theory

The concept (or theory) of resonance was proposed by Pauling in the early 1930s. Its main idea was the following. If Ψ 0 represents some wave function of the system, then the integral (H ^ is the Hamilton operator) must be greater than or equal to the energy of the lowest state E 0 . The closer Ψ is to this eigenfunction, the smaller the difference E - E 0 will be. Let us assume that we have found a function Ψ 1 that represents the possible states of the system, for example, the state corresponding to some electronic Lewis formula. Then, when replacing Ψ with Ψ 1 in the indicated integral, one can calculate the electronic energy E 1 as a function of internuclear distances. Similarly, the function Ψ 2 corresponding to an alternative electronic formula can be used to calculate E 2 . If the E 1 level lies significantly below the E 2 level, then the function Ψ 1 will better approximate the ground state of the system than Ψ 2 , and if there are no other alternatives, then only the electronic formula corresponding to Ψ 1 can be taken into account. Generally speaking, if Ψ 1 and Ψ 2 have the same symmetry and, most importantly, the same multiplicity (i.e., the same number of unpaired electrons), then the value of E corresponding to the function aΨ 1 + bΨ 2 can be found. When E 1 and E 2 are not very different and when the terms corresponding to the interaction between the states Ψ 1 and &Ψ 2 are large, then it turns out that the function that gives the best approximation to the eigenfunction of the ground state of the system will not be Ψ 1 and not Ψ 2 , but their linear combination with the coefficients a and b being the same order of magnitude. In this case, no electronic formula by itself can be associated with a molecule. Both structures are needed, although one will probably carry more weight than the other. “A molecule,” notes Pauling, “could be considered as rapidly fluctuating between two electronic formulas, and its stability is greater than for any of these formulas due to the “resonance energy of these fluctuations.” Subsequently, the theory of resonance was developed by Pauling, Weland and other authors who applied it to a wide range of chemical compounds.

The genesis of this theory was considered in sufficient detail in the monograph by G. V. Bykov. Therefore, avoiding repetition, we will dwell in the future only on those issues that have not been adequately covered in the literature.

The concept of resonance has found the greatest distribution in organic chemistry. At the same time, its popularity was so great that it was often identified with the VS method. When the hypertrophy of the role of the resonance of electronic structures was criticized, such an identification had a negative effect on the attitude of many chemists to the HS method and led to a misunderstanding of the role and logical structure of the latter. The historical significance of the concept of resonance lies, first, in the fact that it determined one of the possible directions for the development of the VS method. Secondly, it allowed a deeper understanding of the relationship between the classical and quantum theories of the structure of chemical compounds, revealing those aspects of physical and chemical reality that could not be adequately reflected by the classical theory of structure.

In order to more clearly imagine the role of resonance in the logical structure of this method, let us try to answer the following question: is the "resonance-free" VS method possible, and if so, what will be its features. From a retrospective point of view, another possible way of developing the VS method could consist in preserving the ideal pairing approximation, but in this case one would have to generalize the concept of hybridization, i.e., use non-atomic, even hybrid (in the usual sense of the word) orbitals as basis functions, and their linear combinations, generally speaking, are not orthogonal * . The equations that govern these linear combinations are the Goddard equations. In a sense, this method, called by Goddard the "generalized VS method", is at the same time a generalization of the MO method. In other words, the concept of resonance served not only as one of the ways of expressing the VS method, which gave great flexibility to the thinking of chemists, but also was a kind of watershed separating the two most common methods of quantum chemistry, VS and MO, since the "resonant" version of the VS method is such a modification of the latter, which gives it the features of the MO method.

* (The basic AOs in the usual formulation of the VS method are also non-orthogonal.)

Let us illustrate this thesis by the example of the benzene molecule. In the VS method, to describe the π-electron system of the benzene molecule, it is necessary to take into account five independent structures characterized by diagrams I-V (see Fig. 16). These diagrams can be built using Young charts and tables.

The antisymmetric eigenfunction of the operator can be obtained from the product of the coordinate Φ and spin Χ functions by the action of the Goddard operator

(3.50)

(3.51b)

(3.51c)

where are operators of permutation of spatial coordinates; - permutation operators of spin variables; - matrix elements of the irreducible representation [λ] of the permutation group of N-electrons; f is the dimension of this representation.

The Goddard method uses a special choice of functions Φ and Χ in the form of products of one-electron functions:

The many-electron wave function of the Goddard method can be associated with a certain scheme of spin pairing, which will correspond to some generalized Rumer diagram * . Indeed, as Goddard showed, the action of the operator on the product of Φ and Χ is equivalent to the action of the Young operator on X followed by antisymmetrization:

which, with an appropriate choice of X, completely corresponds to the construction of the many-electron function of the VS method. For example, for the π-electron system of benzene, the choice

will correspond to the spin pairing scheme expressed by the following diagram:

(3.56)

* (By generalized we mean a Rumer diagram that may contain crossed strokes.)

Thus, instead of five diagrams in the generalized VS method, we have only one. This diagram coincides in appearance with the V diagram (see Fig. 16). However, while diagrams I-V characterize the pairing of atomic π-orbitals, in diagram (3.56) linear combinations of the latter (molecular orbitals) φ k should be considered paired, which are determined by equations of the form *

* (In the MO method, molecular orbitals satisfy similar equations, but with a common effective Hamiltonian for all k N, which makes them orthogonal. In Goddard's method, the orbitals are not orthogonal and in this respect resemble atomic orbitals.)

It is essential that these equations can be interpreted within the framework of the model of independent particles (IPM), i.e., a certain state characterized by the orbital φ k can be attributed to an individual electron. Following Goddard, there are three conditions that make such an interpretation possible:

1. N electrons are associated with no more than N different orbitals;
2. each orbital must be an eigenfunction of some effective Hamiltonian that determines the motion of an electron in the field of nuclei and in the averaged field of other electrons;
3. this averaged field may be non-local, but it must be self-consistent.

In contrast to the Goddard method, the VS method in its usual formulation does not satisfy conditions (2) and (3) and therefore cannot be interpreted in terms of MNPs. At the same time, it admits a generalization within the framework of the Goddard method that satisfies all three of the above conditions, due to which its interpretation in terms of MNP becomes possible.

Of course, in the early 1930s (and later), the approach formulated above could not be implemented, mainly because, due to the lack of necessary computer technology, the theory developed mainly on the basis of semi-empirical and empirical methods, as well as an intuitive generalization of methods developed for simple systems and similar ones (at least in the semantic plan) to the classical theory of structure. Of course, the lack of computer technology to overcome the mathematical difficulties of the many-electron problem, while striving for progress in understanding the electronic structure of atoms and molecules, contributed to the development of fundamental concepts that have retained their significance to this day. However, the greatest development was given to those ideas and methods that could be fruitfully used in the conditions of the existence of a large gap between the qualitative and quantitative sides of the theory.

Let us now turn to another question - about the reality of resonant structures. First, a few remarks about terminology. We believe that the term `resonant structures' can be used only if we are talking about equivalent structures of the VS method. For example, the structures of butadiene cannot be called resonant. or cyclooctatetraene .

In each of these examples, the first structure can be used as the structural formula of the compound, but the second cannot, since its weight is negligible. Indeed, the length of a single bond in such a structure turns out to be less than the length of a double bond, which contradicts the well-known empirical laws relating the multiplicity of a bond to its length. It makes sense to talk about resonance and resonant structures when the quantum-mechanical average values ​​of energy * corresponding to these structures are equal or close. However, resonance, understood in the above sense, should not be associated with any oscillations, oscillations, pulsations or fluctuations, as Pauling and other authors did. Such pseudo-classical ideas, which are of dubious value in relation to the electronic system of a molecule, are completely erroneous in relation to atomic nuclei, which at this level of consideration (the electronic problem in the adiabatic approximation) should be considered immobile. In the case of "resonance" of structures, the compound usually cannot be characterized by a classical structural formula that would not contradict its properties. For example, for benzene, neither of the two classical Kekule formulas reflects the symmetry of the molecule, its physical and chemical properties. Similarly, the formula is not quite adequate for the naphthalene molecule, since at least two more structures should be taken into account:

* (These values ​​of electronic energy are determined at a fixed and identical for all structures configuration of atomic nuclei by the methods of quantum chemistry. They have no direct physical or chemical meaning and are not measured experimentally.)

Resonance of structures in organic chemistry is usually due to conjugation single and double carbon-carbon bonds, especially in planar cyclic systems (aromatic hydrocarbons and heterocycles). Therefore, the concept of resonance underlay the theory of such compounds for some time, until it was replaced by the MO LCAO method.

Sometimes the concept of "electronic isomers" is associated with the concept of resonance structures. Moreover, they are defined as chemical compounds characterized by the same nuclear configuration, but different electron density distributions. Such a representation is certainly erroneous, since it is precisely the distribution of the electron density that determines the equilibrium nuclear configuration. Therefore, electronic isomers must inevitably correspond to different nuclear configurations, so that this concept is reduced to the usual concept of isomerism (see the work for more details).

In the light of what has been said above, the question is natural: what aspects of objective reality does the concept of resonance reflect?

The need to take into account several resonant structures is primarily due to the fact that it is not always possible to attribute a chemical bond to individual pairs of atoms, i.e., a chemical bond can be delocalized between three or more atoms. Such a delocalization corresponds to the resonance of covalent structures. At the same time, in compounds with localized two-center bonds, the latter can be (and usually are) polarized. To reflect the polarity of the bond, ion-covalent resonance should be taken into account. In some cases, without taking into account the resonance of the structures, a qualitatively incorrect description of the electronic structure of the molecule can be obtained, in particular, the correspondence between the symmetry of the molecule and the distribution of electron density in it can be violated, an example of which is the benzene molecule. The one-structure representation of a compound, accepted in the classical theory of chemical structure, is approximate from the point of view of quantum chemical theory, which describes the structure of chemical compounds (within the framework of the VS method) by several resonant structures. In other words, the concept of resonance at the approximation level determined by the VS method in a concentrated, extremely schematic form reflects the entire evolution of the theory of chemical structure - from assigning a certain classical structural formula to each individual compound to taking into account electron delocalization in quantum theory. Thus, in principle, the appearance of the concept of resonance historically was the completion of the circle of ideas underlying the VS method.

In the next section, modern concepts of electrophilic substitution reactions in the aromatic series will be considered. In this case, one cannot do without the theory of resonance, which has become part of the structural theory and allows one to visualize the distribution of electron density in a non-reacting molecule or in intermediate particles of organic reactions - ions and radicals. The fundamentals of resonance theory were developed Pauling in the 40s of the last century.

Using only a limited set of graphic tools, chemists work wonders - they convey on paper with the help of structural formulas the structure of millions of organic compounds. However, sometimes this fails. Perhaps one of the first examples of this kind was benzene, whose properties could not be conveyed by a single formula. Therefore, Kekule was forced to offer two formulas for him with non-localized double bonds. To get a clear idea of ​​the origins of resonance theory, let's look at a few more examples.

For nitrite ion NO 2- the following structural formula can be proposed

It follows from this formula that there are two different oxygens in the nitrite ion, one of which carries a negative charge, and the other is not charged. However, it is known that there are no two different oxygens in the nitrite ion. To overcome this difficulty, the structure of the ion had to be represented by two formulas

A similar situation develops in the case of the allyl cation, which we have already encountered before. For this particle, we also have to use two formulas that only together convey all the structural features of the cation

Having agreed with the need to convey the structure of some molecules or particles by several formulas, we put ourselves in front of a search for answers to many questions that arise. For example, how many formulas convey all the structural features of a particle? Do the real particles correspond to the selected formulas? What is the real distribution of electrons in a particle?

These and other questions are answered by the theory of resonance at a qualitative level. The main provisions of this theory are as follows.

1. If all the subtleties of the structure of a particle cannot be represented by one formula, then this must be done by resorting to several structures. These structures are called resonant, limiting, boundary, canonical.

2. If two or more acceptable structures can be drawn for a particle, then the actual distribution of electrons does not correspond to any of them, but is intermediate between them. A real-life particle is considered to be a hybrid of actually non-existing resonant structures. Each of the limiting structures contributes to the real electron density distribution in the particle. This contribution is the greater, the closer the canonical structures are in energy.

3. Resonance formulas are written in compliance with certain rules:

In various resonant structures, the positions of all atoms must be the same, their difference lies only in the arrangement of electrons;

The boundary formulas should not differ greatly in the position of the electrons, otherwise the contribution of such structures to the resonant hybrid will be minimal;

Boundary structures with significant contributions to the resonant hybrid should have the same and the smallest number of unpaired electrons.

4. The energy of a real particle is less than the energy of any of the limiting structures. In other words, the resonant hybrid is more stable than any of the structures participating in the resonance. This increase in stability is called resonance energy.

We will use the fruits of the qualitative and visual theory of resonance very soon - when explaining the orientation in substitution reactions in the aromatic series. In the meantime, we note that this theory has faithfully served chemistry for more than 70 years, although it has been criticized since its publication. Often the criticism is related to the confusing relationship between the real particle and the canonical structures. The resonance theory itself postulates that canonical structures are fictitious. However, quite often they are given a real meaning, which, of course, is not true. However, there is an opportunity to discuss the situation witty. So, to explain the relationship between the limiting structures and their resonant hybrid T. Weland proposed to use a biological analogy, which boils down to the following. “When we say that a mule is a hybrid of a donkey and a horse, we do not mean at all that some mules are donkeys and others are horses, or that every mule is a horse part of the time and a donkey part of the time. We simply refer to the fact that the mule is an animal related to both the horse and the donkey, and in describing it it is convenient to compare it with these familiar animals. It should be noted that Wheland's analogy is not quite correct. Indeed, unlike the ultimate structures, which do not really exist, the donkey and the horse are very concrete beings. In addition, some experts drew attention to the subjectivity of certain postulates of the resonance theory. Continuing the discussion of this theory within Wheland's biological analogy, O. A. Reutov As early as 1956, he noted that “the concept of resonance cannot predict that the mule is a hybrid of precisely a horse and a donkey. This needs to be known independently. Otherwise, you can, for example, take an elephant as one of the parents and choose the second parent in such a way that everything converges mathematically.

Resonance theory-idealistic theory in organic chemistry, created in the 30s of the XX century. by the American physicist and chemist L. G. Gauling and adopted by some bourgeois chemists. This theory merged with the theory of mesomerism that arose in the mid-1920s by the English physicist and chemist K. Ingold, which had the same methodological basis as the resonance theory. Adherents of the theory of resonance use (see) not for the development of the materialistic and dialectical theory of the chemical structure of molecules of the great Russian chemist (see) by studying interatomic distances, directed valences, mutual influences of atoms within a molecule, speeds and directions of chemical reactions, etc. They trying, by manipulating the data obtained with the help of quantum mechanics, to prove that Butlerov's theory is outdated.

Proceeding from subjective-idealistic considerations, adherents of the theory of resonance invented for the molecules of many chemical compounds sets of formulas - "states" or "structures" that do not reflect objective reality. In accordance with the theory of resonance, the true state of the molecule is supposedly the result of a quantum mechanical interaction, "resonance", "superposition" or "superimposition" of these fictitious "states" or "structures". In accordance with Ingold's theory of mesomerism, the true structure of some molecules is considered as intermediate between two "structures", each of which does not correspond to reality. Consequently, the theory of resonance agnostically denies the possibility of expressing the true structure of the molecule of many individual substances by one formula and, from the standpoint of subjective idealism, proves that it is expressed only by a set of formulas.

The authors of the theory of resonance deny the objectivity of chemical laws. One of Pauling's students, J. Weland, points out that "structures between which there is a resonance are only mental constructions", that "the idea of ​​resonance is a speculative concept to a greater extent than other physical theories. It does not reflect any intrinsic property of the molecule itself, but is a mathematical method invented by the physicist or chemist for his own convenience." Thus, Weland emphasizes the subjectivist nature of the idea of ​​resonance and at the same time argues that, despite this, the idea of ​​resonance is allegedly useful for understanding the true state of the molecules in question. In reality, however, both of these subjectivist theories (mesomerism and resonance) cannot serve any of the goals of genuine chemical science - the reflection of the relations of atoms within molecules, the mutual influence of atoms in a molecule, the physical properties of atoms and molecules, etc.

Therefore, for more than 25 years of the existence of the theory of resonance mesomerism, it has not brought any benefit to science and practice. It could not have been otherwise, since the theory of resonance, closely connected with the idealistic principles of "complementarity" by N. Bohr and "superposition" by P. Dirac, is an extension "(see) to organic chemistry and has the same methodological Machian basis. Another methodological defect of the resonance theory is its mechanism. In accordance with this theory, the presence of specific qualitative features is denied in an organic molecule. Its properties are reduced to a simple sum of the properties of its constituent parts; qualitative differences are reduced to purely quantitative differences. More precisely, the complex chemical processes and interactions occurring in organic matter are reduced here to one, simpler than chemical forms, physical forms of the motion of matter - to electrodynamic and quantum mechanical phenomena. G. Eyripgh, J. Walter and J. Campbellen in their book "Quantum Chemistry" went even further.

They argue that quantum mechanics allegedly reduces the problems of chemistry to the problems of applied mathematics, and only because of the very high complexity of mathematical calculations it is not possible to reduce in all cases. Developing the idea of ​​reducing chemistry to physics, the well-known quantum physicist and "physical" idealist E. Schrodinger in his book "What is life from the point of view of physics?" gives a broad system of such a mechanistic reduction of the higher forms of the motion of matter to the lower ones. According to (see), he reduces the biological processes that are the basis of life to genes, genes to the organic molecules from which they are formed, and organic molecules to quantum mechanical phenomena. Soviet chemists and philosophers are actively fighting against the idealistic theory of mesomoria-resonance, which hinders the development of chemistry.