Effect of Alkyl Chain Length on the Corrosion Inhibition Efficiency of New Synthesis Benzofuranone Derivatives: Insights From DFT, Molecular Dynamics and Monte Carlo Simulations

ABSTRACT In this study, novel benzofuranone (phenolphthalein) derivatives were synthesized via an O‐alkylation reaction. The resulting compounds, PHC2, PHC3, and PHC4, were purified and identified by IR spectroscopy, 1H and 13C NMR, and mass spectrometry. Electrochemical techniques were employed, including polarization curve analysis, impedance spectroscopy, and scanning electron microscopy coupled with energy‐dispersive X‐ray spectroscopy (SEM/EDX). Thermodynamic adsorption parameters suggest that these inhibitors slow cathodic and anodic processes through chemical adsorption and blockade of active corrosion sites. The adsorption of these compounds follows the Langmuir adsorption isotherm. Geometric optimization studies using DFT‐D determined the stable structures of PHC2, PHC3, and PHC4, while Monte Carlo simulations revealed strong and spontaneous adsorption, with PHC4 exhibiting the greatest stability. Molecular dynamics confirmed that adsorption stability was influenced by the formation of a protective layer, Fe–O interactions, and interactions of π‐electrons with iron orbitals. Theoretical studies confirm that PHC4 exhibits the strongest adsorption (−592,272.225 kcal/mol), making it the most effective corrosion inhibitor.