Generation, structures, relative energies, and isomerization reactions of CH cations.

The B3LYP, MP2, and CBS-QB3 quantum chemical methods are used to study the relative energy and isomerization reactions of CH cations. Ease of generation of 14 CH isomers by ionic dissociation of halide precursors does not correlate well with carbocation stability. The reaction profiles of concerted isomerization of various CH cations to six select cations are established along with the respective transition states. The rate coefficients of these processes are estimated by using transition state theory and activation energies computed. The transition states for these six reactions are characterized with regard to position along the isomerization pathway as per Hammond's postulate. The 6 isomerization reactions are combined to yield multi-step conversions of various CH species to the lowest energy vinylcyclopropenyl cation 1. Finally, three different routes for obtaining the select cations from CHBr precursors are profiled and the most favored pathways predicted.