Stereoelectronic Effects and H-Bonding in the Conformational Equilibrium of Serine and Threonine Methyl Esters
Claudimar J. Duarte, Lucas C. Ducati, Kristerson R. L. Freire and Roberto Rittner
Abstract: An extensive conformational search through the rotation of the dihedral angles χ1 and χ2 of serine (Ser-OMe) and threonine (Thr-OMe) methyl esters – two molecules of relative complexity that do not present a zwitterionic form in solution – was performed. The identified energy minima were subjected to Quantum Theory of Atoms in Molecules and Natural Bond Orbital analyses. In addition, the experimental 3JHH spin–spin coupling constants obtained in several solvents were compared with the calculated values for each conformer and provided insights into the conformational changes induced by each solvent. It was found that steric and hyperconjugative effects rule the conformational equilibrium of Ser-OMe and Thr-OMe, whereas the influence of H-bonding on both systems is a secondary effect.
Keywords: Serine and threonine methyl esters; Conformational analysis; Stereoelectronic effects, Spin-spin coupling constants.
Pages: 65 – 74 | Full PDF Paper
Co-Terpolymerization of m-phenylenediamine, O-Anisidine, 2,3-Xyilidine: Synthesis and Charachterization
Omar Melad, Mohammed Hilles
Abstract: Copolymers of m-phenylenediamine and O-Anisidine were synthesized by oxidative polymerization at different monomer ratios using ammonium persulfate as as oxidant in HCl medium. The yield and the conductivity of the copolymers increase as O-Anisidine ratios increase which leading to increase the polymer chain in the same time increasing of conjugation system. The effect of introducing a third monomer to the copolymer of m-phenylenediamine and O-Anisidine were studied by the addition of 2,3-Xyilidine to obtain different molar ratios of terpolymers. The yield, intrinsic viscosity and the conductivity of the terpolymers were studied and compare with the copolymers. The Co-Terpolymerization of m-phenylenediamine, O-Anisidine and 2,3-Xyilidine were charachterized by FTIR and UV-Visible spectroscopy.The terpolymers seem dependency on polymerization yield, conductivity and intrinsic viscosity are 89% for MPD/OA/XY (70/10/20) terpolymer, 1.511 S/m for MPD/OA/XY (70/10/20) and 1.1 dl/g for MPD/OA/XY (70/25/5) compared to the yield obtained of MPD/OA copolymer which is 83% for [(MPD(75)/OA(25)] and conductivity of 1.228 S/m for [(MPD(25)/OA(75)], which may be attributed that the terpolymers chaotic super molecular structure than the copolymer leading to increase the polymer chain and then increasing the conjugation system. The FTIR and UV-Vis investigation suggest that the polymers obtain are actual copolymer of MPD/OA and terpolymer of MPD/OA/XY.
Keywords: Copolymer, terpolymer, conducting polymers, UV-Visible spectroscopy, IR spectroscopy, m-phenylenediamine.
Pages: 75 – 85 | Full PDF Paper
Giti Kashi, Nahid Hydarian
Abstract: Sulfanilamide was a sulfonamideantibacterial. It was a molecule consisting of the sulfonamide functional group attached to aniline. Sulfanilamide resulted in irritation skin, allergic respiratory, and mutagenic effects. The goal of this applied-analytical research was to investigate of sulfonamide removal from water by batch EPC reactor with using zinc oxide(ZnO) nanoparticles immobilized on zinc(Zn) sheet-copper electrode, and lamp emitting dynode (LED) ultraviolet-A(UV-A) lamp. Various operating variables were tested; these included current density, initial concentration of sulfonamide, lamp intensity, layering of ZnO nanoparticles, pH, and radiation time.To prepare the ZnO films on the Zn electrode, dry methods were used. The sample was prepared by adding 100-300 milligrams of sulfonamide per ml of deionized water. The studied variables werepH(3-11), the sulfonamide concentration (100-300 mg/L), the lamp intensity (360-600 mW/cm2), radiation time (0-45 min), layering of zinc oxide nanoparticles (1-3), and current density (6-12.5 mA/cm2). The sulfonamide concentration was measured by a high-performance liquid chromatography / mass spectrometry. The optimal removal(0) was obtained at pH 3, radiation time of 15 minutes, 2- layer of ZnO nanoparticles, lamp density 600 mw/cm2, and current density of 9 mA/cm2. The sulfonamide decay followed a first order reaction. The results of sulfonamide removal efficiency by Taguchi model indicated that the reaction time was the most important variable. The electrochemical(E) process was the least efficiency. The rate of decay decreased at higher concentrations. Thus, batch experiments showed that the EPC reactor could be considered as a promising technology for treating sulfonamide-polluted water.
Keywords: Aqueous water, Electrophotocatalytic, Sulfonamide, Taguchi model, Zinc oxide.
Pages: 86 – 98 | Full PDF Paper
Arun Kumar, Ranjit Kumar, Mohammad Samiur Rahman, Mohammad Asif Iqubal, Gautam Anand, Pintoo Kumar Niraj and Mohammad Ali
Abstract: Arsenic is present in the environment and human all over the world are exposed to small amounts, mostly through food, water, and air. In the developing countries like Bangladesh and India, the high prevalence of contamination, the isolation and poverty of the rural population and the high cost and complexity of arsenic removal systems have imposed a programmatic and policy challenge on an unprecedented scale. Although in India, Arsenic poisoning in ground water in Gangetic basin especially the districts adjoining the river Ganges right from Eastern Uttar Pradesh, Bihar to West Bengal is the major problem of concern. Due to which, major health related problems are arising in the population.To combat the present problem, a pre-clinical study was done on Charles foster rats and sodium arsenite at the dose of 8 mg Kg-1 body weight per day was administered to these rats for 60 days and upon these arsenic pretreated rats, novel plant extracts of Withania somnifera and Pteris longifolia were administered for 45 days to study the antidote effects of these plant extracts. These plants not only eliminated the toxic effects of arsenic but also reversed the normal physiological activity in the animal. Thus, the present study concludes that these novel plants possesses the best bioremedial impact against arsenic induced toxicity.
Keywords: Arsenic, Withania somnifera, Pteris longifolia, Antidote, Bioremediation, Pre-clinical study.
Pages: 99 – 109 | Full PDF Paper