PYROLYSIS OF BETA-HYDROXYKETONES AND ALPHA-KETOESTERS - GAS-PHASE ELIMINATION KINETICS OF 3-HYDROXY-3-METHYL-2-BUTANONE AND METHYL BENZOYLFORMATE

The rates of gas-phase elimination reactions of methyl benzoylformate (I) and 3-hydroxy-3-methyl-2-butanone (2) were obtained at T = 600 K. The two substrates undergo unimolecular first-order elimination for wh ich the Arrhenius equations are, respectively, log k = 13.2 - 53270/(4 .574 x 600) for (I) and log k = 12.4 - 53060/(4.574 x 600) for (2). Th e products of pyrolysis of (I) are benzaldehyde, formaldehyde and CO, while those of (2) are acetaldehyde and acetone. The kinetics of the e limination reactions show benzoylformic acid to be 10(6)-fold more rea ctive than (1), and pyruvic acid ca. 10(5)-fold more reactive relative to (2); an indication of the rate-controlling part played by the acid ity of the hydrogen atom involved in the elimination process of the pr esent compounds in this particular type of reaction. (C) 1997 John Wil ey & Sons, Inc.