The pyrolysis of alkanethiols. Part 1. Kinetics of the pyrolysis of butane-1-thiol, butane-2-thiol, and 2-methylpropane-2-thiol

Abstract

The kinetics of the pyrolyses of the title alkanethiols into hydrogen sulphide and olefins have been studied in a static system in the temperature range 696.6–762.1 K and found, in the presence of cyclohexene, to be a homogeneous free radical process. For 2-methylpropane-2-thiol, the order of the reaction is 3/2 and the observed rate constant is expressible by the Arrhenius equation(i). For both butane-1- and -2-thiol, the order of the reaction is ^3/2k/cm mol^–½ s^–1= 10^{12.07 ± 0.04} exp(–169 800 ± 600 J mol^–1/RT)(i) 1 and the rate constants are given by (ii) and (iii), respectively. A radical mechanism consistent with the results is proposed. k/s^–1= 10^{9.84 ± 0.05} exp(–178 100 ±800 J mol^–1/RT)(ii)k/s^–1= 10^{8.68 ± 0.02} exp(–174 600 ±300 J mol^–1/RT)(iii)