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