Synthesis, Characterization and Quantum Mechanical Study of Some New 2-benzylidenehydrazinecarbothioamide Derivatives as Corrosion Inhibitors for Carbon/mild Steel in Acidic Medium

Abstract

In this work, some of new 2-benzylidenehydrazinecarbothioamide derivatives
have been prepared by condensation of thiosemicarbazide and different substituted
aromatic benzaldehydes in presence of glacial acetic acid to give compounds (1-6),
these compounds have characterized by its physical properties and spectroscopic
methods. This work also included theoretical study to prove the ability of these
compounds as corrosion inhibitors; The program package of Gaussian 09W with its
graphical user interface GaussView 5.0 had used for this purpose; the methods of
Density Functional Theory (DFT) with basis set of 6-311G (d,p) / hybrid function of
B3LYP and semiempirical method of PM3 have been used, the study included
theoretical simulation to simulate the reactivity of these compounds as corrosion
inhibitors for carbon steel in gas phase, aqueous medium and in acidic medium
(acidic medium is a medium contains acid that able to protonate these compounds
and change them to protonated form), some parameters have calculated in both
previous methods such EHOMO, ELUMO, ΔEL-H, Ionization Potential (I), Electron
Affinity (A), electronegativity (χ), Global Hardness (η), Atomic Charges, Dipole
Moment (μ) and Fraction of Electron Transferred from Inhibitor Molecules to the
Metallic Atoms (ΔN), the resulted parameters showed that these compounds are
behaving as inhibitors for corrosion of carbon steel.