The formate ester of benzoin (1) and the methyl ethers of benzoin and anisoin (2, 3) have been converted separately under thermal gas-phase conditions cleanly into 1,2-diarylethanone and have given, respectively, the following Arrhenius log A (s -1 ) and E a (kJ mol -1 ): 10.11 and 132.0, 11.29 and 173.0, and 11.85 and 151.1. A plausible mechanism is suggested to account for these transformations based on the kinetics and products of reaction.Key words: gas-phase, pyrolysis, kinetics, mechanism, synthesis.