QUANTUM MODELLING OF THE TOXICITIES OF SOME POLYCHLORINATED AROMATIC COMPOUNDS
QUANTUM MODELLING OF THE TOXICITIES OF SOME POLYCHLORINATED AROMATIC COMPOUNDS
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Date
2017-02
Authors
HASSAN, SAMUEL,
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Abstract
Poly chlorinated aromatic compounds represent a large group of industrial and byproduct compounds which are resistant to chemical and biological degradation and highly toxic. QSAR analysis was performed on 74 molecules of three classes of polychlorinated aromatic compounds (polychlorinated dibenzo-p-dioxin (PCDDs), polychlorinated dibenzofuran (PCDF) and polychlorinated biphenyl (PCB)). QSAR models were also developed using each of the three series. Genetic function algorithm (GFA) approach was used to generate 5 models, for the three series all together and for each of the three series. The models with the highest statistical significance were selected as the best. For the three series all together: (Model-1: R2 = 0.9673, R2 adjusted = 0.9592, R2cv = 0.9402, R2 pred. = 0.7209, F-test = 118.48, LOF = 0.4377). For the series PCDDs: (Semi empirical- LOF = 0.5881, R2= 0.9516, R2 adj.= 0.9389, R2cv= 0.9090, F-value = 74; DFT- LOF = 0.3877, R2 = 0.9680, R2adj= 0.9596, R2cv = 0.9518, F-value = 115.07). For the series PCDFs: (LOF = 0.2955, R2 = 0.9229, R2adj. = 0.9091, R2cv = 0.8885, F-value = 67.03).For the series PCBs: (LOF = 0.4582, R2 = 0.9186, R2adj. = 0.8734, R2cv = 0.8086, F-value = 20.31). From the models generated using the three series all together, it seems that polarizability, SP-7, ETA_Epsilon_5, GRAVH_3, and MOMI-R contributed positively to the toxicity of these compounds while MaxHBint5, ETA_dApha_B, ETA_Epsinlon-2, n5Ring and GRAV_2 contribute negatively. From the comparison of the models generated using DFT and semi-empirical and based on their statistical parameters, semi-empirical (AM1) has slightly better predictive power than DFT (BLYP/6-31G*). The robustness and applicability of the models were established by internal and external validation techniques. These validated models bring important insight to aid the prediction and identification of other toxic poly chlorinated aromatic compounds.
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A DISSERTATION SUBMITTED TO THE SCHOOL OF POSTGRADUATE STUDIES, AHMADU BELLO UNIVERSITY, ZARIA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE AWARD OF MASTERS OF SCIENCE IN PHYSICAL CHEMISTRY DEPARTMENT OF CHEMISTRY FACULTY OF PHYSICAL SCIENCES AHMADU BELLO UNIVERSITY, ZARIA, NIGERIA.
Keywords
QUANTUM MODELLING,, TOXICITIES,, POLY CHLORINATED,, AROMATIC COMPOUNDS,