Nature of the Potential Energy Surfaces for the SN1 Reaction: A Picosecond Kinetic Study of Homolysis and Heterolysis for Diphenylmethyl Chlorides

The picosecond dynamics for the photoinduced homolysis and heterolysis of (4-methylphenyl)phenylmethyl chloride and bis(4-methylphenyl)methyl chloride in acetonitrile are examined. In less than 20 ps, both the geminate radical pair and contact ion pair are formed from the first excited singlet state. The geminate radical pair decays by either diffusional separation to free radicals or electron transfer back to the ground state surface which partitions between reactant and contact ion pair. The contact ion pair decays by diffusional separation to the solvent separated ion pair or by collapse to form the carbon−chlorine bond. The kinetics for these processes are employed in the development of the potential energy surfaces for the S N 1 reaction for diphenylmethyl chlorides in polar solvents.