Towards understanding proton affinity and gas-phase basicity with density functional reactivity theory

► A strong linear correlation MEP and basicity for 14 heterocyclic aromatic amines. ► A theoretical justification using density functional reactivity theory. ► We predict that the proton prefers to bind with the basic atom with the lowest MEP. ► The equivalence of MEP and natural atomic orbital was confirmed for these systems. ► Our results were valid with different density functionals and different basis sets.