1. Introduction
Chemical bond has been always a basis of chemistry. Advancement of chemical science can be considered as evolution, development of concepts about chemical bond. Aromatic bond is fundamental basis of organic chemistry. Concept of three-electron bond in benzene molecule enable to explain specificity of aromatic bond. It also becomes apparent, why planar molecules with 6, 10 etc. electrons (according to Hückel rule 4n +2) must be aromatic, and planar molecules with 4, 8 etc. electrons cannot be aromatic by definition.
Description of chemical bond, that is given by quantum theory, especially in terms of method of molecular orbitals, is just a mathematical model. This model is an approximate representation of molecules and its bonds, whereas quantum-mechanical calculations of organic molecules require considerable simplifications and are extremely complicated.
Concept of three-electron bond and developed mathematical relations in this work are rather simple, illustrative and give exact results of different values (bond multiplicity, chemical bound energy, delocalization energy of benzene). One must clearly imagine, that three-electron bond is joint interaction of three electrons with relative spins, that results in new type of chemical bond (A • • • A (+ – +), A • • • B (+ – +)). This bond type, three-electron bond, makes possible to describe real molecules of organic and inorganic compounds without invoking virtual structures, which do not exist in real terms.
Using of three-electron bond before description of benzene molecule enables to determine delocalization energy of benzene in an elementary way, understand why multiplicity of С-С bond of benzene is more than 1.5 and to understand the main point of aromatic bond in general, which is appeared to be rather illustrative. Besides, for determination of delocalization energy it is not required to select reference structures. Delocalization energy follows from the concept of aromaticity of benzene and its structure on the basis of three-electron bond.
I note that the three-electron bond to describe the benzene molecule used W.O. Kermak, R. Robinson and J. J. Thomson at the beginning of the 20th century [5, 6].
Benzene molecule with three-electron bond (W.O. Kermak and R. Robinson, J. J. Thomson).
But since it is not taken into account the spin of electrons, have already started cyclooctatetraene problems and therefore the description of the benzene molecule by a three-electron proved unsuccessful. Using the three-electron bond with multiplicity of 1.5 and take account of the spin of each electron leads to very good results in the description of the benzene molecule and explain the aromaticity in general. With the help of three-electron bond with multiplicity of 1.5 can be represented by a real formula of many organic and inorganic molecules without the aid of virtual structures.