The effect of substituents on the rate of thermal decarboxylation of βγ-unsaturated acids is compared to their effect on the decarboxylation of β-keto-acids. From the close similarity observed, it is argued that the reactions have nearly identical transition states. It is demonstrated that the transition state for the olefinic acids is largely non-polar; by analogy, the keto-acids are concluded to decarboxylate through a largely non-polar mechanism. ...
