Density functional theory calculations on corrosion inhibitory action of five azlactones on mild steel

P. Udhayakala

Abstract

A theoretical study for five azlactones,i.e, 4-benzylidene-2-phenyl oxazol-5-one (AZ1), 4-(4-methoxy benzylidene)-2- phenyl oxazol-5-one (AZ2), 4-(4 hydroxy -3methoxy benzylidene)- 2-phenyl oxazol-5-one (AZ3), 4-(2-hydroxy benzylidene)-2-phenyl oxazol-5-one (AZ4) and 4-(2-Nitro benzylidene)-2-phenyl oxazol-5-one (AZ5), was investigated using density functional theory (DFT) at the B3LYP/6-31G(d,p) basis set level through the relationship between their molecular and electronic structure. The calculated quantum chemical parameters correlated to the inhibition efficiency such as EHOMO (highest occupied molecular orbital energy), ELUMO (lowest unoccupied molecular orbital energy), energy gap (ΔE), dipole moment (μ), absolute hardness (η), absolute softness (S), the absolute electronegativity (χ), the fractions of electrons transferred from the inhibitor molecule to the metallic atom(ΔN) and the electrophilicity index (ω) were calculated. The local selectivity and reactivity has been analyzed through the Fukui function and local softness indices in order to compare the possible sites for nucleophilic and electrophilic attacks. The theoretical results are in well accordance with the experimental data reported.