Isomerisation of deuterated cyclopropanes - The possibility for stereochemical control

The direct dynamics technique, based on an AM1 semiempirical Hamiltonian modified with specific reaction path parameters, has been employed to study the constant energy and thermal isomerisation of S,S-trans-cyclopropane-1,2-d(2) and cyclopropane-1,2,3-d(3). At a classical energy of 48.25 kcal mol(-1) above the conrotatory saddle point, the dynamics is mode specific. This raises the possibility of stereochemical control in this energy regime. The sensitivity of the reaction mechanism to the character of the excited normal mode eigenvector is also apparent under thermal conditions at 695 K. Similar product branching ratios are obtained for the d(2) and d(3) species at this temperature, when the trajectories are initialised al the conrotatory saddle point.