Quantum chemistry study on the relationship between molecular structure and corrosion inhibition efficiency of amides

Quantum chemical calculations were performed on four typical amides compounds e.g. urea, thiourea, thioacetamide and thiosemicarbazide, using the semi-empirical method MINDO/3 within program package HyperChem 6.03. Obvious correlations were found between corrosion inhibition efficiency and some quantum chemical parameters such as highest occupied molecular obital (HOMO), lowest unoccupied molecular orbital (LUMO) energy levels, HOMO-LUMO energy gap and electronic density etc. Calculation results indicated that the great difference of inhibition efficiencies between these amides can be clearly explained in terms of frontier molecular orbital theory. The agreement with the experimental data was also found to be satisfactory. (C) 2002 Elsevier Science B.V. All rights reserved.