HYDROGEN-BOND DONOR ACIDITY PARAMETERS FOR KINETICS STUDIES IN NONAQUEOUS SOLVENTS

Several multiterm linear solvation energy models which incorporate directly or indirectly hydrogen bond donor-acceptor parameters were compared experimentally. These included the Kamlet-Taft alpha(KT) scale, the Abraham alpha(2)H scale, and the acceptor (AN*) parameter of Riddle and Fowkes. An enlarged data base for a range of hydrogen bonding, hydrogen bonding-strongly associated, and weakly hydrogen bonding aprotic solvents was developed for this analysis. Although the alpha(KT) and alpha(2)H parameters are fundamentally parallel in their origins, the latter is less responsive to the differentiation of structural characteristics of the donor species. The AN* quantity is shown to be a coupled mixture of solvent properties in which hydrogen bond donor acidity appears to dominate for the strongly self-associated solvents.