Femtosecond elementary dynamics of transition states and asymmetric α-cleavage in Norrish reactions

In this Letter, we report studies of the femtosecond dynamics of transition states and asymmetric α-cleavage in Norrish type-I reactions. Systematically, we consider the dynamics of dissociation along two reaction coordinates in methyl ethyl ketone and diethyl ketone, and compare these results with those of dimethyl ketone and methyl chloro ketone. The concept of concertedness as the system moves away from the transition-state region is examined and the primary and secondary processes involved in the α-cleavage are resolved. We compare experimental results with theoretical predictions of impulsive and statistical models.