Quantum chemical calculations using three methods, Hartree-Fock (HF), Moller-Plesset (MP) and density functional theory (DFT/B3LYP) method with SOD, 6-31G(d,p) and 6-31++G(d,p) basis sets are performed some benzaldehyde thiosemicarbazones and their thiole tautomers. The results of the quantum chemical calculations and experimental IE% which are belong to thione tautomers are subjected to correlation analysis and indicate that their inhibition effect are closely related to some quantum chemical parameters. The active sites are determined by using MEP diagrams, proton affinities and Fukui functions. The theoretically obtained results are found to be consistent with the experimental data which are reported for thione tautomers. (C) 2014 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.