Kinetics of reactions between methyl and acetyl radicals in gas phase produced by flash photolysis of acetic anhydride

The reaction products of photolysis of acetic anhydride in gas phase at 25°C, where He or CO2 was present as buffer gas, were analyzed by gas chromatography. The extent of photodissociation was 52% ± 5% and the extent of intramolecular hydrogen transfer reaction producing acetic acid and ketene was 48% ± 5%. The rate constants of the hydrogen exchange and radical combination reactions between methyl and acetyl radicals were calculated from the amounts of products. The value of the ratio of the rate constants of hydrogen exchange and radical combination reactions between methyl and acetyl radicals, 𝓀7/𝓀6 = 0.15, indicates that acetyl radical is a relatively poor hydrogen donor. The corresponding ratio of rate constants for the reactions between two acetyl radicals, 𝓀9/𝓀s = 0.42, indicates that acetyl radical is a better hydrogen acceptor than methyl radical.