Conclusions 1. The analysis of the reaction products of the thermolyses of some substituted tetraoxanes in benzene solution and the corresponding activation parameters for these unimolecular reactions support a general homolytic stepwise mechanism, rather than a concerted process. 2. A genuine" isokinetic relationship" is observed for the unimolecular homolyses of the acetophenone, benzyl ketone, benzophenone, cyclohexanone and ...