Homogeneous gas-phase decyclization of tetralin and benzocyclobutene

Article abstract of DOI:10.1021/ja00161a001

Tetralin has been decomposed in single pulse shock tube experiments in the temperature range of 1000-1400 K. The initial unimolecular decomposition channels involve the formation of benzocyclobutene and o-allyltoluene. Benzocyclobutene decomposes to form styrene. The main products from the hydrogen atom induced decomposition of tetralin are dihydronaphthalene, styrene, indene, and naphthalene. The following rate expressions have been determined: k(tetralin → ethylene + benzocyclobutene) = 3.5 X 10¹⁵ exp(-40 003/T)s^-1,k(tetralin → o-allyltoluene) = 1.2 X 10¹⁵ exp(-40 111/T)s^-1,k(benzocyclobutene → styrene) = 1.2 X 10¹⁵ exp(-37 396/T)s^-1, k(H + tetralin → H₂ + 4-phenylbutyl radical) ≥ 0.55 X k(H + mesitylene → o-xylene + CH₃). Comparisons are made with published results from laser-powdered pyrolysis and shock tube studies, and it is concluded that in both cases initial unimolecular channels are accessed. The temperatures in the laser experiments are at least as high in the shock tube studies. The rate expressions for tetralin decomposition are compatible with a biradical mechanism and follow the general patterns for related cyclic compounds.