Mechanism of initiation in the thermal polymerization of styrene. Thermal decomposition of cis-3,6-diphenyl-3,4,5,6-tetrahydropyridazine

Abstract

Thermal decomposition of cis-3,6-diphenyl-3,4,5,6-tetrahydropyridazine, 1, (k = 5.6 × 10−4s−1 at 79.5°) results in the formation of about 60% styrene, 27% cis- and 13% trans-1,2-diphenylcyclobutane. The relative product yields vary little over the temperature range 64–133°. This indicates that 1 decomposes exclusively to the 1,4-diphenyl-1,4-butadiyl diradical, 2, and nitrogen. The diradical, 2, cannot be trapped by styrene and 1 is not an initiator of styrene polymerization. Therefore, 2 is not the radical intermediate responsible for the thermal initiation of styrene polymerization.