Some Features of the CH3NC→CH3CN Potential Surface

Nonempirical self-consistent-field calculations are reported for about 75 points on the potential surface for the CH3NC→CH3CN isomerization. Due to interest in the possible non-RRKM behavior of CH3NC, the magnitude of the barrier to rotation of the methyl group is examined as a function of the reaction coordinate. The transition state or saddle point geometry is determined by minimizing the potential energy with respect to five geometrical parameters and maximizing with respect to a sixth. The geometries of CH3NC and CH3CN are also predicted and found to agree closely with experiment. Finally, it is established that, contrary to semiempirical results, the present theoretical approach does not predict the existence of a relative minimum in the reaction coordinate.