GAS-PHASE PYROLYTIC REACTIONS .6. BEHAVIOR OF ETHYL (HETERO)ARYLCARBOXYLATE ESTERS IN THERMAL ELIMINATION-REACTIONS

Rates, Arrhenius parameters, and Hammett substituent constants are obt ained for the gas-phase thermal elimination of ethyl benzoate (1) and ethyl 2 - thienyl - (2), 3 - thienyl - (3), 2 - furyl - (4), 3 - furyl - (5), 4 - pyridyl - (6), 3 - pyridyl - (7), and 2 - pyridylcarboxyla te (8) esters. The log A/s(-1) and the E(a)/kJ mol(-1) values of these esters averaged 13.60 and 216.3, respectively. The present results ar e compared with data previously reported for the corresponding isoprop yl and t-butyl analogues, and the findings are rationalized in terms o f a plausible transition state for the elimination pathway. (C) 1997 J ohn Wiley & Sons, Inc.