GAS-PHASE KINETICS OF N-SUBSTITUTED DIACETAMIDE

Gas-phase elimination reactions of number of N-substituted diacetamide s have been studied. The rates of N-phenyl, 4-methoxyphenyl, 4-nitroph enyl, and benzyl diacetamide have been measured between 643 - 683, 642 -693, 673-725, and 555-610 K, respectively. They undergo unimolecular first-order elimination reactions, for which log A = 12.8,12.9,12.8, a nd 11.0 s-1 and E(a) = 185.7,191.4,193.4, and 143.6 kJ mol-1, respecti vely. The reactivity of these compounds has been compared with the uns ubstituted diacetamide at 600 K, The kinetic data reveals that each of the N-aryldiacetamides is less reactive than the parent molecule. We attribute this observation to the resonance of the lone pair of electr ons on the nitrogen with either the two carbonyl oxygen atoms or with the 6pi electrons in the aromatic ring which will result in the stabil ization of the N-aryldiacetamides related to the parent molecules. (C) 1994 John Wiley & Sons, Inc.