Theoretical study on the relationship between the molecular structure and corrosion inhibition efficiency of long alkyl side chain acetamide and isoxazolidine derivatives

Quantum mechanics calculations have been applied to three long alkyl side chain acetamides and three isoxazolidine derivatives used as corrosion inhibitors. The corresponding structures have been optimized, and the highest occupied molecular orbital energy (EHOMO), the lowest unoccupied molecular orbital energy (ELUMO), energy gap (ΔE), electronegativity (χ), hardness (η), softness (σ) and the fraction of electrons transferred from the inhibitor molecule to the metal surface (ΔN) have been calculated using the DFT/B3LYP and HF methods with the 6–31G(d, p) basis set. The electric dipole moment (μ), the mean polarizability (〈α〉) and the first order hyperpolarizability (β) values of the investigated molecules have been computed using the same methods. The calculation results also show that the molecules might have microscopic nonlinear optical (NLO) behaviour with non-zero values. Finally, the theoretical results obtained have been compared with the experimental data.