GAS-PHASE KINETICS OF ELIMINATION-REACTIONS OF PENTANE-2,4-DIONE DERIVATIVES

Gas-phase elimination reactions of pentane-2,4-dione, methyl acetoacet ate, ethyl acetoacetate, 3-phenylhydroazopentane-2,4-dione, and ethyl 3-oxo-2-phenyl-hydrazonobutyrate have been measured in the temperature ranges of 744-783, 662-695, 614-663, 604-664, and 503-555 K, respecti vely, using a flow-thermolysis technique. These compounds undergo unim olecular first-order elimination reactions, for which log A = 11.9, 11 .2, 11.7, 11.5, and 11.7 s(-1) and E(a) = 198.3, 167.1, 141.7, 165.6, and 141.7 kJ mol(-1), respectively. The kinetic data and product analy sis shows that the reactions are highly affected by the electronic nat ure of the substituents at the carbonyl and methylene carbon atoms of the substrates investigated. (C) 1995 John Wiley & Sons, Inc.