THE IONIZATION BEHAVIOR OF AMIDES IN CONCENTRATED SULFURIC ACIDS: II. APPLICATIONS OF THE HA FUNCTION TO RATES AND EQUILIBRIA

Abstract

The newly determined HA, scale of acidity has been tested against ionization ratio data for 33 amides. Twenty-nine of these compounds give log I vs. HA slopes of 0.9–1.1 and most are within 0.95–1.05. The average slope for these is 1.001 ± 0.051. The HA function is thus considered to be generally applicable to the ionization of this type of base, and the significance of previously reported amide pK values is discussed in the light of these results. Previously reported basicity – substituent constant relations have been reexamined using thermodynamically significant pK data and earlier conclusions confirmed. Appropriate equations are derived in an attempt to explain the rate–acidity dependence of amide hydrolysis directly in terms of the water activity of the reaction medium. The picture of the hydrolysis transition state which results is in accord with that obtained using methods described by other workers.