Study on initiation mechanisms of peresters using α-methylstyrene dimer (MSD) trapping technique

Abstract

The thermal decomposition of t-butyl peroxybenzoate (2a) and t-butyl peroxylaurate (2b) was carried out in 2,4-diphenyl-4-methyl-1-pentene (α-methylstyrene dimer, MSD) at 140°C. Free radicals generated from the peresters were efficiently trapped by MSD through the addition-fragmentation reaction. Benzoyloxy radicals generated from 2a underwent two competitive reactions, i.e., addition to MSD (71%) and decarboxylation (29%). On the other hand, decarboxylation was the sole reaction for lauroyloxy radicals from 2b. For t-butoxy radicals, both results from 2a and 2b were identical, the ratio of addition to MSD/β-scission being 61/39. In the case of 2b, the efficiency of free radical production was sigmficantly lowered by cage reactions.