Molecular-mechanical analysis of the structure of stressed organic molecules Communication 2. Bicyclo[n.1.0]alkanes

The method of molecular mechanics in the MM/2 parametrization is presented; it accurately describes a large set of thermochemical, structural, and electronic characteristics of highly stressed bicyclo(n.1.0)alkanes (BCA's). The reliability of the equilibrium geometry of BCA's with n=1 to 3 calculated by the MM/2 method is on the level of nonempirical calculations in an expanded basis, permitting the reliable evaluation of the structure of bicyclo(4.1.0)heptane (norcarane), which has n ot been established experimentally. The quantum-chemical characteristics of the electronic structure calculated for the equilibrium geometry of B CA's vary regularly, in parallel to the energy of the stresses in these hydrocarbons.