INITIAL-STAGES OF ELECTROPHILIC SUBSTITUTION STUDIED WITH QUANTUM MOLECULAR-DYNAMICS

We report molecular dynamics simulations of the initial step of electrophilic substitution in benzene. Forces are calculated at each time step using quantum mechanical methods. Comparison of the trajectories with classical calculations shows a striking difference. Whereas the classical trajectory shows a proton with no specific bonds, the quantum calculations exhibit a clear bond to one of the carbons, leading to a cyclohexadienyl cation, as expected from standard ideas derived from electrophilic substitution reactions. The simulations demonstrate that forces calculated from quantum mechanics 'on the fly' exhibit the proper chemical behavior when bonds are formed or broken.