The Rate Constant of Ethane Formation from Methyl Radicals

The rotating sector technique has been applied to a determination of the rate constant of methyl radical recombination in the photo-decompositions of acetone and mercury dimethyl, using the small but accurately measurable rate of methane formation as a measure of methyl steady-state concentration. The resulting value of the recombination rate constant is 4.5×1013 (moles/cc)−1 sec−1, with an activation energy of E=0±700 cal regardless of radical source. The determination of this constant permits the evaluation of the rate constants for several other reactions of methyl radicals. It is found that hydrogen abstractions have steric factors of the order of 10−4.