Additivity of substituent effects on the proton affinity and gas-phase basicity of pyridines

摘要: Abstract The change in the proton affinity (PA) and basicity (GB) of pyridine with substituents have been considered by quantum mechanical methods at B3LYP/6-311++G(d,p) level theory. PA GB values increase electron-donating decrease electron-withdrawing substituents. effects on are approximately additive. deviations changes that predicted from additivity substituent generally lower than 30% calculated changes. Linear relationships observed between substituted pyridines topological properties electron density, molecular electrostatic potentials (MEP), N–H bond lengths. In addition, well-defined relations established Hammett constants, reaction constant (ρ) has for protonation reaction. With some exceptions, effect also additive density its Laplacian BCP, MEP around N atom.