Solvent effects on the acid catalysed hydrolysis of benzamide, N-methylbenzamide, and NN-dimethylbenzamide

Abstract

The rate of hydrolysis of benzamide has been measured over a wide range of acidities in HCl, H₂SO₄, HClO₄, and H₃PO₄, that of N-methylbenzamide in HCl and H₂SO₄, and that of NN-dimethylbenzamide in HCl, H₂SO₄, and HClO₄. The basicity constants of these three amides have been measured in HCl and HClO₄ and that of benzamide in H₂SO₄ also, and have been found to be non-thermodynamic functions. Interpretation of the rate data by use of existing rate-correlation equations has been found unsatisfactory, but the data do fit a two-term rate equation. Deuterium isotope effects and some Arrhenius parameters have been measured. Oxygen-18 exchange is absent. Measurements of the molar activity coefficient of unprotonated NN-dimethylbenzamide have shown that whereas acids salt-in the amide, salts generally salt it out.