Comparison of Substituent Effects in Benzenes (XC 5 H 5 C), Pyridines (XC 5 H 4 N) and Phosphorines (XC 5 H 4 P) and their Protonated Species

Collection of interesting and stimulative data led us to construct Hammett plots for different properties like proton affinities, gas phase basicities, solvation free energies of free and protonated benzenes (I), pyridines (II) and phosphorines (III), and for pKa values of protonated pyridines and phosphorines. Trends in Hammett reaction constants () for all these processes were discussed.