EXPERIMENTAL AND COMPUTATIONAL CHEMISTRY SIMULATION STUDIES ON THE CORROSION INHIBITION POTENTIALS OF SOME AMINO ACIDS
EXPERIMENTAL AND COMPUTATIONAL CHEMISTRY SIMULATION STUDIES ON THE CORROSION INHIBITION POTENTIALS OF SOME AMINO ACIDS
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Date
2011-01
Authors
AWE, FEMI EMMANUEL
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Abstract
Inhibition and adsorption potentials of cysteine, glycine, leucine and alanine have been
investigated using experimental and quantum chemical approaches. The experimental
study was carried out using gravimetric, gasometric, thermometric and FTIR methods of
monitoring corrosion while the quantum chemical study was carried out using semiempirical
and ab-initio methods. The results obtained reveal that various concentrations
of the amino acids inhibited the corrosion of mild steel in solutions of HCl through the
mechanism of physiosorption with activation energy less than 80kJmol-1. The inhibition
potentials of the inhibitors decreased in the order, cysteine >leucine> alanine > glycine
and their adsorption was found to be exothermic, spontaneous and fitted the Langmuir
adsorption model. Computational chemistry results obtained revealed excellent
correlations between quantum chemical parameters (calculated for gas and aqueous
phases PM6, PM3, AM1, RM1 and MNDO Hamiltonians) and experimental inhibition
efficiencies. Correlations between the experimental and theoretical inhibition efficiencies
were also excellent. Application of condensed Fukui and softness functions as well as
relative nucleophilicity/electrophilicity (calculated for B3LYP(6-31G) and MP2(STO5G)
paturbations) showed that the sites for electrophilic attack are on the amine bonds
(N2-C3) of the amino acids while the sites for nucleophilic attack are on the C-3 atoms of
the amino acids. The HOMO and LUMO diagrams of the amino acids as well as the
electron density diagrams have also been used to support the information obtained from
condensed Fukui function.
Description
THESIS SUBMITTED TO THE POSTGRADUATE SCHOOL,
AHMADU BELLO UNIVERSITY, ZARIA
NIGERIA
IN PARTIAL FULFILMENT FOR THE AWARD OF MASTER OF
SCIENCE IN PHYSICAL CHEMISTRY
DEPARMENT OF CHEMISTRY
AHMADU BELLO UNIVERSITY, ZARIA
NIGERIA
Keywords
EXPERIMENTAL,, COMPUTATIONAL,, CHEMISTRY SIMULATION,, CORROSION,, INHIBITION POTENTIALS,, AMINO ACIDS