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Öğe Investigation of Structure-Activity Relationship Between Chemical Structure and CCR5 Anti HIV-1 Activity in a Class of 1-[N-(Methyl)-N- (Phenylsulfonyl) Amino]-2-(Phenyl)-4-[4-(Substituted)Piperidin-1-yl]Butane Derivatives: The Electronic-Topological Approach(BENTHAM SCIENCE PUBL LTD, 2011) Saracoglu, Murat; Kandemirli, Sedat Giray; Basaran, Murat Alper; Sayiner, Hakan; Kandemirli, FatmaThe relationship between chemical structure and CCR5 anti HIV-1 activity was investigated in the series of 1-[N-(Methyl)-N-(phenylsulfonyl)amino]-2-(phenyl)-4-[4-(substituted) piperidin-1-yl]butanes derivatives including 114 molecules by using the Electron-Topological Method (ETM). In the frameworks of this approach, its input data were taken as the results of conformational and quantum-mechanical calculations. Conformational analysis and quantum-chemical calculations were carried out for each molecule. Then molecular fragments being specific for active molecules and non-active molecules were revealed by using ETM. The result of testing showed the high ability of ETM in predicting the activity and inactivity investigated series. In order to classify and to develop a model for those molecules, cluster and discriminant analyses are conducted. First, cluster analysis is implemented in order to classify similar molecules into the groups. Then, discriminant analysis is used to construct models including descriptors. By doing so, two obtained discriminant functions segregate those molecules into three different groups by using the descriptors called E-HOMO, Dipole Moment and SEZPE.Öğe Monitoring corrosion and corrosion control of iron in HCl by non-ionic surfactants of the TRITON-X series - Part II. Temperature effect, activation energies and thermodynamics of adsorption(PERGAMON-ELSEVIER SCIENCE LTD, 2011) Amin, Mohammed A.; Ahmed, M. A.; Arida, H. A.; Arslan, Taner; Saracoglu, Murat; Kandemirli, FatmaThe inhibition characteristics of non-ionic surfactants of the TRITON-X series, namely TRITON-X-100 (TX-100), TRITON-X-165 (TX-165) and TRITON-X-305 (TX-305), on the corrosion of iron was studied in 1.0 M HCl solutions as a function of inhibitor concentration (0.005-0.075 g L(-1)) and solution temperature (278-338 K). Measurements were conducted based on Tafel extrapolation method. Electrochemical frequency modulation (EFM), a non-destructive corrosion measurement technique that can directly give values of corrosion current without prior knowledge of Tafel constants, is also presented. Experimental corrosion rates determined by the Tafel extrapolation method were compared with corrosion rates obtained by the EFM technique and an independent method of chemical analysis. The chemical method of confirmation of the corrosion rates involved determination of the dissolved cation, using ICP-AES (inductively coupled plasma atomic emission spectrometry). The aim was to confirm validation of corrosion rates measured by the Tafel extrapolation method. Results obtained showed that, in all cases, the inhibition efficiency increased with increase in temperature, suggesting that chemical adsorption occurs. The adsorptive behaviour of the three surfactants followed Temkin-type isotherm. The standard free energies of adsorption decreased with temperature, reflecting better inhibition performance. These findings confirm chemisorption of the tested inhibitors. Thermodynamic activation functions of the dissolution process were also calculated as a function of each inhibitor concentration. All the results obtained from the methods employed are in reasonable agreement. (C) 2010 Elsevier Ltd. All rights reserved.Öğe Monitoring corrosion and corrosion control of iron in HCl by non-ionic surfactants of the TRITON-X series - Part III. Immersion time effects and theoretical studies(PERGAMON-ELSEVIER SCIENCE LTD, 2011) Amin, Mohammed A.; Ahmed, M. A.; Arida, H. A.; Kandemirli, Fatma; Saracoglu, Murat; Arslan, Taner; Basaran, Murat A.The inhibition performance of three selected non-ionic surfactants of the TRITON-X series, namely TRITONX-100 (TX-100), TRITON-X-165 (TX-165) and TRITON-X-305 (TX-305), on the corrosion of iron was studied in 1.0 M HCl solutions as a function of inhibitor concentration (0.01-0.20 g L(-1)) and immersion time (0.0-8 h) at 298 K. Measurements were conducted based on Tafel polarization, LPR and impedance studies. At high frequencies, the impedance spectrum showed a depressed capacitive loop in the complex impedance plane, whose diameter is a function of the immersion time and the type and concentration of the introduced surfactant. In all cases, an inductive loop was observed in the low frequency and this could be attributed to the adsorption behavior. The inhibition efficiency increased with immersion time, reached a maximum and then decreased. This was attributed to the orientation change of adsorbed surfactant molecules. TX-305 inhibited iron corrosion more effectively than TX-100 and TX-165. The frontier orbital energies, the energy gap between frontier orbitals, dipole moments (mu), charges on the C and O atoms, the polarizabilities, and the quantum chemical descriptors were calculated. The quantum chemical calculation results inferred that for the HOMO representing the condensed Fukui function for an electrophilic attack (f(k)(+)), the contributions belong to the phenyl group and the oxygen atom attached to the phenyl group for each tested surfactant. Quantitative structure-activity relationship (QSAR) approach has also been used and a correlation of the composite index having some of the quantum chemical parameters with average inhibition efficiencies (I(av.)(%)) was conducted to determine the inhibition performance of the tested surfactant molecules. The results showed that the values of I(av.)(%) of the tested inhibitor molecules were closely related to some of the quantum chemical parameters. The calculated I(av.)(%) values were found to be close to the experimental ones. Based on the values of coefficients of correlations at 0.02 level concentration. B3LYP/3-21G* method outpaced the other two methods namely B3LYP/6-31G and RHF/6-31G*. The relationship between I(av.)(%) and composite index is accounted for by B3LYP/3-21G*. (C) 2011 Elsevier Ltd. All rights reserved.Öğe Quantum Chemical Investigations on Quinoline Derivatives as Effective Corrosion Inhibitors for Mild Steel in Acidic Medium(ELECTROCHEMICAL SCIENCE GROUP, 2012) Ebenso, Eno E.; Kabanda, Mwadham M.; Arslan, Taner; Saracoglu, Murat; Kandemirli, Fatma; Murulana, Lutendo C.; Eddy, N. O.The Density Functional Theory (DFT) and ab initio (HF and MP2) calculations were performed on the quinoline molecule (QL) and its derivatives, namely quinaldine (QLD) and quinaldic acid (QLDA) to investigate their possible role as corrosion inhibitors for mild steel in acidic medium. Calculations were done for non-protonated and protonated forms in vacuo and in water. Some quantum chemical parameters were calculated and discussed in order to provide insight into the reactivity and selectivity of the molecules. The performance of the different calculation methods were also compared with available experimental data. The results show that DFT/B3LYP basis set is adequate in describing the geometry and quantum chemical parameters of the studied systems. Both experimental and theoretical results established that QLDA has the highest inhibition efficiency. A comparison in the trends of the quantum chemical parameters in water solution and in vacuo shows minimal influence of the solvent effects.Öğe Quantum chemical investigations on quinoline derivatives as effective corrosion inhibitors for mild steel in acidic medium(2012) Ebenso, Eno E.; Kabanda, Mwadham M.; Arslan, Taner; Saracoglu, Murat; Kandemirli, Fatma; Murulana, Lutendo C.; Singh, Ashish K.The Density Functional Theory (DFT) and ab initio (HF and MP2) calculations were performed on the quinoline molecule (QL) and its derivatives, namely quinaldine (QLD) and quinaldic acid (QLDA) to investigate their possible role as corrosion inhibitors for mild steel in acidic medium. Calculations were done for non-protonated and protonated forms in vacuo and in water. Some quantum chemical parameters were calculated and discussed in order to provide insight into the reactivity and selectivity of the molecules. The performance of the different calculation methods were also compared with available experimental data. The results show that DFT/B3LYP basis set is adequate in describing the geometry and quantum chemical parameters of the studied systems. Both experimental and theoretical results established that QLDA has the highest inhibition efficiency. A comparison in the trends of the quantum chemical parameters in water solution and in vacuo shows minimal influence of the solvent effects. © 2012 by ESG.
