Quantum Chemical Studies on the Inhibiting Effect of Bipyrazoles on Steel Corrosion in HCl

Correlation of the efficacy of some bipyrazoles, N,N-bis(3,5-dimethyl-pyrazol-1-ylmethyl)-cyclohexylamine (Bip 1), N,N-bis(3,5-dimethylpyrazol-1-ylmethyl)-ethanolamine (Bip 2), N,N-bis(3,5-dimethylpyrazol-1-ylmethyl) allylamine (Bip 3) and N,N-bis(3-carboethoxy-5-methylpyrazol-1-ylmethyl)-cyclohexylamine (Bip 4), against the corrosion of mild steel in HCl is discussed using density functional approach B3LYP/6-31G(d) calculations. The bipyrazole inhibitors exhibited the highest inhibition efficiency. The quantum chemical parameters calculated are, the highest occupied molecular orbital (HOMO), the lowest unoccupied molecular orbital (LUMO), the gap energy (ΔE), the dipole moment (μ), the softness (σ) and the total energy (TE).