Electrostatic potential minimum of the aromatic ring as a measure of substituent constant

Abstract

The molecular electrostatic potential minimum (V_min) observed for the arene π system of a substituted benzene derivatives is found to correlate linearly with the substituent constant σ_p°. The use of V_min as a measure of substituent effect is further confirmed by obtaining a linear correlation between V_min and a thermodynamic measure of the substituent effect obtained from an isodesmic reaction scheme involving benzene derivatives. V_min and the recently proposed electrostatic potential value at the nucleus of the para carbon atom (V_c) show a nearly identical trend toward quantification of substituent effects. Both quantities have been compared at three different density functional theory methods, viz. B3LYP/6-311+G(2d,2p), BPW91/6-311G(d,p), and B3LYP/aug-cc-pvtz, as well as the at the MP2/6-31+G(d,p) level of theory, showing remarkable consistency among them.