Conformation and reactivity. Part 9. Kinetics of the acid- or base-catalysed methanolysis of the methyl esters of trans-decalin- or cyclohexane-carboxylic acid and related acids. The validity of Taft's method for the separation of polar, steric, and resonance effects

Abstract

Rate coefficients have been measured for the acid- or base-catalysed methanolysis at several temperatures in CD3OD of methyl trans- and cis-4-t-butylcyclohexanecarboxylate, methyl cyclohexanecarboxylate, methyl trans-decalin-1α-, -1β-, -2α-, and -2β-carboxylate, methyl endo- and exo-norbornane-2-carboxylate, and methyl bicyclo[2.2.2]octane-1-carboxylate and its 4-bromo-derivative. The reactions of the methyl trans-decalin-2-carboxylates in mixtures of CD3OD with (CD3)2SO, C6D6, or D2O were also studied. The results are discussed in relation to the influence on reactivity of steric and polar effects in the various molecular skeletons and conformers. Further examples of the anomalous behaviour of the decalin-1α-carboxylate have been found. The bearing of the results for the decalin-2-carboxylates on Taft's assumption regarding the equality of steric effects in acid- and base-catalysed ester reactions is discussed. On balance the validity of Taft's assumption is confirmed.