How the topological analysis of the electron localization function accounts for the inductive effect

The topological analysis of the electron localization function has been used to investigate the inductive substituent effect. This effect is found to be very short ranged being essentially localized on the valence basins of the carbon linked to the substituent X. The basin populations N¯[V(C,C)] of the C-C bonds in α position with respect to X appear to be a reliable descriptor. Electron withdrawing substituents (−I effect) increase N¯[V(C,C)] and therefore the covalent character of the C-C bond whereas electron donating groups (+I) yield an opposite effect. The additivity of the inductive effect is verified on N¯[V(C,C)] and the correlation with the pKa of the carboxylic acids is discussed.