Available evidence concerning the mechanism of acid catalysed amide hydrolysis and the roles played by intramolecular hydroxyl groups are briefly reviewed. Methods of treating kinetic and equilibrium data obtained from studies of reactions in moderately concentrated mineral acids are summarized. The rate enhancements observed upon the inclusion of a gamma or delta hydroxyl group in alkyl anilides are thought to be the result of a greater availability of a nucleophilic species at the reaction centre. The possible significance which can be given to the results of hydration parameter and linear free energy treatments of rate data from moderately concentrated acids is discussed. These parameters at least indicate that water performs another function besides that of nucleophile in acid catalysed amide hydrolysis. All kinetic parameters derived indicate that the intramolecular and intermolecular reactions proceed by similar mechanisms. A study was carried out of the acid catalysed lactonization of some bicyclic and olefinic hydroxy anilides in which the reactive groups are held in constant close proximity. Abnormal absorbance changes over normal anilide acid catalysed hydrolysis indicate that the reactions being monitored have changed in some way. It is suggested that the rate determining step in the reaction has altered. Two mechanisms for the reaction are proposed
