Absolute reaction rate constants have been determined in the pyrolysis of 18 isopropyl alkanoates to acids and propene in a very carefully deactivated stainless steel static reactor. Trisubstitution by alkyl groups at the (Y position of the acid moiety showed a small, but readily measurable, rate of acceleration. Substitution at the B position had no effect on the rate of pyrolysis. This rate acceleration was reflected in the entropy of activation. a-Phenyl ...