HYBRIDIZATION EFFECTS ON THE INTRINSIC BASICITIES OF PHOSPHORUS AND NITROGEN-CONTAINING BASES

This paper discuss the influence of hybridization changes at the basic center on the intrinsic basicities of nitrogen and phosphorus contain ing bases by use of the topological analysis of their charge distribut ions. The proton affinities of the species investigated, namely HCN, H 2CNH, H3CNH2, HCP, H2CPH and H3CPH2 were obtained in the framework of the G2 theory. We have found that within both series of compounds ther e is a good linear relationship between intrinsic basicities and charg e densities at the basic center lone pair. This relationship can be ea sily rationalized by means of the hybridization model. We have also fo und that hybridization effects on intrinsic basicities although qualit atively similar for nitrogen and phosphorus are quantitatively larger for the latter. When the hybridization of the basic center changes wit hout changing its coordination, a linear relationship between intrinsi c basicities and lone pair charge densities can only be expected if th e protonation process does not imply significant structural changes of the base.