Hydrolysis of amides. IV. Dilute acid hydrolysis of amides of the type R₂CH-CONH₂ and R₃C-CONH₂

Abstract

Enthalpies and entropies of activation have been derived from rate constants measured over a range of temperature for the dilute acid hydrolysis of isobutyramide, diethylacetamide, α-methylbutyramide, cyclohexaneoarboxamide, cyclopentane-carboxamide, and trimethylacetamide.     These data, in combination with data for other amides produced earlier, show the hydrolysis rate constants to be dominated by steric influences but with a perturbing effect which is proportional to the number of α-hydrogens present in the substituent. The "α-hydrogen bonding" concept of hyperconjugation appears to offer a reasonable explanation of these perturbations.     Controlled steric changes are shown to be non-additive for this reaction and to exert their influence primarily through the enthalpy component of the observed free energy changes.