Methylene electronic structure calculations

According to the relationship between three-membered rings and 7r-complexes, cyclopropane can be considered as a resonance hybrid of three equivalent methylene-ethene n-complexes Of course, such Ti-complexes do not exist but this is also true in the case of the two cyclohexatriene resonance structures normally used to present benzene. Spin-coupled valence bond calculations of Karadakov and coworkers reveal that there is a small but significant contribution of 3.7% to the electronic structure of 1 resulting from 7r-com-plex structures (see Section V. E). This indicates that the Ti-complex description of is not totally unreasonable and, although seldom used, helps to unravel some of the peculiarities of bonding in 1 ... 

For the first time quantum chemical calculation of a molecule of 1-methy-lene-4-vinylcyclohexane is executed by method MNDO with optimization of geometry on all parameters. The optimized geometrical and electronic structure of this compound is received. Acid power of l-methylen-4-vinyl-coclohexane is theoretically appreciated. It is established, than it to relate to a class of very weak H-acids (pKa = +35, where pKa-universal index of acidity). 

Geometric and electronic structures, general and electronic energies of molecule l-methylene-4-vinylcyclohexane was received by method MNDO and are shown on Fig. 2 and in Table.2. The universal factor of acidity was calculated by formula pKa = 42.11-147.18 q [4, 5] (where, a maximum positive charge on atom of the hydrogen max +0.05 (for l-methylene-4-vinylcyclohexane q J alike Table 2)). This same formula is used in references [6- 6].pKa = 35. 

Quantum-chemical calculation of molecule l-methylene-4-vinylcy-clohexane by method MNDO was executed for the first time. Optimized geometric and electronic structure of this compound was received. Acid power of molecule l-methylene-4-vinylcyclohexane was theoretically evaluated pKa 35). This compound pertains to class of very weak H-acids (pKa > 14). 

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