Thermolysis of azoalkanes in a stirred-flow system

Abstract

The gas-phase thermal decomposition of azoethane, ethaneazo-1′-methylethane, and azo-2′-methylpropane have been investigated in a stirred-flow system using the toluene carrier technique. The order of the reaction for the disappearance of the azoalkanes has been found to be nearly unity in each case. The temperature dependence of the rate coefficients is given by the Arrhenius equations: azoethane, log k= 14.2 ± 0.2 –(186 ± 2 kJ mol^–1)/2.30RT; ethaneazo-1′-methylethane, log k= 16.5 ± 0.5 –(206 ± 3 kJ mol^–1)/2.30RT, and azo-2′-methylpropane, log k= 15.6 ± 0.3 –(170 ± 3 kJ mol^–1)/2.30RT. No evidence was found for hydrogen atom abstraction by alkyl radicals from the toluene carrier. An average value of 0.14 ± 0.03 was obtained for the disproportionation : combination ratio of the ethyl radicals in the temperature range 280–400 °C. For the t-butyl radicals this ratio had a value of 2.9 ± 0.2 between 210 and 260 °C.