A Computational Study of Quinoline Derivatives as Corrosion Inhibitors for Mild Steel in Acidic Medium

E.A Erazua,B.B Adeleke

doi:10.4314/jasem.v23i10.8

Abstract

The corrosion inhibition efficiency of three quinoline derivatives namely; ethyl 2-(((8-hydroxyquinolin5-yl)methyl)amino)acetate (QN1), 5-((benzylamino)methyl)quinolin-8-ol (QN2) and 5-(azidomethyl)quinolin-8-ol (QN3) on the mild steel in 1 M HCl was studied using density functional theory (DFT) calculations and quantitative structural activity relationship (QSAR) approach. The experimental inhibition efficiency were discussed in relation with molecular descriptors such as such as EHOMO (energy of the highest occupied molecular orbital), ELUMO (energy of the lowest unoccupied molecular orbital), band gap (BG), dipole moment (DM), chemical hardness (η), softness (σ), electronegativity (χ), electrophilicity (ω), global nucleophilicity (ɛ), electrons transferred from inhibitors to metal surface (ΔN), initial molecule–metal interaction energy (∆ψ), the energy change during electronic back-donation process (ΔEb-d), Molecular weight (MW), and Volume (V). The result showed that EHOMO, σ , ω, ΔN, ∆Eb-d and ∆ψ increases as the percentage inhibition efficiency (%IE) increases. ELUMO, BG, η , DM, and e decreases with increasing% IE, while χ , MW and V did not show any correlation with %IE. The QSAR model developed reproduced the observed corrosion inhibition efficiencies of these compounds well with a cross validation (CV. R2 ) value of 0.9994 and adjusted squared correlation coefficient (R2 adj) value of 0.9988. The results obtained in the study are in good agreement with experimental inhibition efficiency results reported earlier in literature.Keywords: Corrosion Inhibition, Quantum Chemical Calculation, Quinoline Derivatives, QSAR

Highlights

5-yl)methyl)amino)acetate (QN1), 5-((benzylamino)methyl)quinolin-8-ol (QN2) and 5-(azidomethyl)quinolin-8-ol (QN3) on the mild steel in 1 M HCl was studied using density functional theory (DFT) calculations and quantitative structural activity relationship (QSAR) approach
EHOMO and ELUMO are quantum chemical parameters that indicate the ability of a molecule to donate electron and the ability of a molecule to accept electron respectively
It has been shown that molecules with high value of EHOMO would donate electrons to the metal surface with empty molecular orbital, facilitate the adsorption process and lead to good inhibition performance

Summary

Introduction

5-yl)methyl)amino)acetate (QN1), 5-((benzylamino)methyl)quinolin-8-ol (QN2) and 5-(azidomethyl)quinolin-8-ol (QN3) on the mild steel in 1 M HCl was studied using density functional theory (DFT) calculations and quantitative structural activity relationship (QSAR) approach. The use of corrosion inhibitors, mostly heterocyclic compounds is one of the effective methods that can be used to avert the corrosion of metal in acidic solution (Khaled, 2008) This is because most of these heterocyclic compounds have atoms with lone pair of electrons (e.g., heteroatoms such as N, O, S and P). Computational chemist use quantum chemical calculations to predict the corrosion inhibition performances of molecules because of the high cost of experimental methods and because the study of the inhibition mechanisms of chemical compounds is time consuming (El-Lateef et al, 2017). The aim of this work is to extend the study of Lgaz et al, on the corrosion inhibition property of quinoline derivatives using DFT method to calculate molecular descriptors to gain further insight into the factors responsible for the corrosion inhibitory properties of the studied compounds. We will correlate the calculated parameters to the experimentally observed inhibition efficiencies and establish a QSAR model from the calculated descriptors that could predict the experimental inhibition efficiencies of this class of compounds

Objectives

Methods

Results