Gas-phase thermal decomposition reactions of 1,2-dibromopropane

Abstract

The thermal decomposition reaction of 1,2-dibromopropane (12DBP) has been studied at temperatures from 592.2 to 636.2 K over the pressure range 0.23–24.5 Torr. The main products were four different bromopropenes and hydrogen bromide. Propylene as a minor product was also observed by the concurrent heterogeneous debromination. The inhibition effect by cyclohexene and propene and the catalytic effect by HBr show that 12DBP is thermally decomposed by a dual mechanism, i.e. the unimolecular elimination and the radical-chain process. The rate constant in maximal inhibition is expressed by k₁/s^–1=(6.31 ± 2.51)× 10¹³ exp [(–50 400 ± 3000)/RT]. The pressure dependence has also been studied both in the presence and in the absence of inhibitors. The fall-off curve obtained in maximum inhibition condition is compared with the theoretical curve calculated by the RRKM formulation. The reaction mechanism is proposed to offer a satisfactory explanation for the thermal decomposition of 12DBP.