Empirical valence bond study of radical reactions: hydrogen atom transfer in peroxidation of phenol

The use of free energy perturbation empirical valence bond (FEP/EVB) molecu lar dynamics technique for microscopic modeling of atom exchange reactions is examined. In particular, the analytical Morse and anti-Morse potentials for unpaired electron interactions are incorporated in the framework of mol ecular mechanics force field. Peroxidation of phenol is studied as a test c ase. The corresponding free energy profiles of hydrogen atom transfer are c alculated by the FEP/EVB method in gas phase and chloroform. The reaction p otential energy profile is also determined using DFT calculations. The FEP/ EVB simulations correctly predict linear approach of reactants, tight struc ture of the transition state, and lower activation barrier in gas phase com pared to solution. (C) 2001 Elsevier Science BN. All rights reserved.