A nuclear magnetic resonance study of the rates of protonation of dimethylacetamide and dimethylbenzamide in concentrated acid solutions

Abstract

The rates of protonation of dimethylacetamide and dimethylbenzamide are shown to increase very rapidly with increasing hydrochloric acid concentration and to correlate well with the H_A acidity function. Deuterium isotope effects on the protonation rates have also been measured at low acid concentrations, and the low values observed (k_H/k_D=ca. 1) indicate substantial transfer of the proton in the transition state, consistent with the observed correlation between the protonation rates and the acidity function.