Kinetics and mechanism of thermal gas-phase elimination of 2-aryloxyaceticacid

Rates of thermal gas-phase elimination of eleven 2-aryloxyacetic acid have been measured over a 45 degreesC temperature range for each compound Hammet t correlation of the present kinetic data with the literature ao values of the given substituents gave a reaction rho constant of 0.69 at 600 K; this is more than that for the gas-phase elimination parameter of 2-aryloxypropa noic acid (rho = 0.26) and consistent with a transition state with some cha rge separation, suggesting a partial formation of carbocation, The implicat ions of this observation for the thermal gas-phase elimination of alpha -ar yloxycarboxylic acids are considered. (C) 2001 John Wiley & Sons, Inc.