Kinetics of reactions between methoxycarbonyl,methyl, and methoxy radicals formed in flash photolysis of dimethyl oxalate in gas phase

Flash photolysis of dimethyl oxalate produced the radicals CH₃, CH₃O, and COOCH₃. Thermally equilibrated methoxycarbonyl radicals did not decompose during radicalradical reactions in the presence of 40-torr cyclohexane in the temperature range 298–448 K. Cyclohexyl radicals were also generated during the flash photolysis of the reaction mixture. Rate coefficients of radical–radical reactions were calculated from the amounts of stable products determined by gas chromatography: CO, CO₂, CH₄, C₂H₄, C₂H₆, CH₂O, CH₃OH, CH₃OCH₃, HCOOCH₃, CH₃COOCH₃, CH₃OCOOCH₃, CH₃C₆H₁₁, and CH₃OC₆H₁₁. Calculations were performed using an iterative computer integration program. Absolute values of rate coefficients were based on the rate coefficient of the reaction between methyl radicals, k₁ = 2.7 × 10¹⁰ dm³ mol^?1 s^?1, measured with the same equipment. The rate coefficients for reactions (5)–(8) are: