Sharif Digital Repository

A carbon paste electrode (CPE), modified with novel hydroquinone/TiO2 nanoparticles, was designed and used for simultaneous determination of ascorbic acid (AA), uric acid (UA) and folic acid (FA). The magnitude of the peak current for modified TiO2-nanoparticle CPE (MTNCPE) increased sharply in the presence of ascorbic acid and was proportional to its concentration. A dynamic range of 1.0-1400.0 μM, with the detection limit of 6.4x10-7M for AA, was obtained using the DPV technique (pH=7.0). The prepared electrode was successfully applied for the determination of AA, UA, and FA in real samples  

A quantitative structure-mobility relationship was developed to accurately predict the electrophoretic mobility of organic acids. The absolute electrophoretic mobilities (μ0) of a diverse dataset consisting of 115 carboxylic and sulfonic acids were investigated. A set of 1195 zero- to three-dimensional descriptors representing various structural characteristics was calculated for each molecule in the dataset. Classification and regression trees were successfully used as a descriptor selection method. Four descriptors were selected and used as inputs for adaptive neuro-fuzzy inference system. The root mean square errors for the calibration and prediction sets are 1.61 and 2.27, respectively,... 

A reaction of dithiocarbamic acid salts with carbonyl compounds was investigated for the first time in the presence of BF 3•OEt 2. The reaction is temperature dependent and gives gem-bis(dithiocarbamates) at 35-45 °C as a molecule with high equivalents of dithiocarbamate groups. At lower temperatures (15-20 °C), the 2-iminium-1,3-dithietane is obtained as the only product. The structure of a 2-iminium-1,3-dithietane was accomplished by X-ray crystallographic analysis  

Benzoins are rapidly oxidised to benzils in high yields by iodic acid supported on alumina under solvent-free conditions and microwave irradiation  

Three ternary copper(II) complexes [Cu(5-bromo-salTyr)(bipy)]·1/ 2CH3OH (1), [Cu(5-bromo-salLue)(bipy)]·CH3OH (2) and [Cu(5-bromo-salTrp)(bipy)]·3CH3OH (3) (where 5-bromo-salTyr, 5-bromo-salLue and 5-bromo-salTrp are tridentate Schiff base ligands derived from the condensation of 5-bromosalicylaldehyde with tyrosine, leucine and tryptophan, respectively, and bipy is 2,2′-bipyridine) have been prepared and characterized by elemental analysis, electronic, IR spectroscopies, magnetic measurement and cyclic voltammetry. The complexes, 1 and 3 have been also structurally characterized by X-ray diffraction technique. Crystal structures of 1 and 3 complexes displayed a distorted square-pyramidal... 

The effect of new corrosion inhibitors, namely pyridine, 2-methylpyridine (2-picoline), 4-methylpyridine (4-picoline), 2,4-dimethylpyridine (2,4-lutidine), on the corrosion of Al-surface in hydrocholoric acid (HCl) and nitric acid (HNO3) was investigated at the HF and B3LYP level using the ab initio 6-3IG and LANL2DZ basis sets from the program package Gaussian 98 (A.7 Public Domain version). The physico-chemical properties of corrosion inhibitors are one of the principal criteria for the determination and selection of inhibitors. The inhibition of the Al-surface in solutions of hydrocholoric acid and nitric acid by some N-heterocyclic compounds has been studied. The calculated results... 

The pKa value for protonated forms of different benzo-substituted quinuclidines in aqueous solution has been calculated using DFT methods (MP2//B3LYP, B3LYP and M06-2X) and 6-311++G(d,p) basis set and are compared with corresponding experimental values. The results were obtained from different theoretical methods so close to the corresponding experimental values but the best agreement were achieved with B3LYP/6-311+G(d,p) level of theory. The average error was found to be less than 1.6pKa unit. Relative pKa values were computed for each protonated benzo-substituted quinuclidine using quinuclidine as a reference. Solvation was included in the calculations in all used different methods using... 

A series of bifunctional catalysts, including Cu-ZnO-ZrO 2 and H-Y zeolite catalysts, were prepared and tested for conversion of maleic anhydride (MA) to tetrahydrofuran (THF). Cu-ZnO-ZrO 2 catalyst was used as the hydrogenating component and H-Y zeolite as the dehydrating component. The appropriate ratio of Cu/ZnO in the hydrogenation catalyst was 50:45, for which the conversion of MA and selectivity of THF reached 100 and 46%, respectively, at 50 bar and 493 K. The bifunctional catalyst of Cu-ZnOZrO 2/H-Y can produce THF from MA with high activity, selectivity, and stability. This is an abstract of a paper presented at the 18th International Congress of Chemical and Process Engineering... 

Ab initio density functional theory calculations were used to investigate cohesive, electronic, and structural properties of cagelike and spherical hydrogen terminated nanoparticles of diamond. Unlike cagelike nanodiamond particles, the variation of calculated energies of spherical ones is not monotonic. The variation range of the calculated energies and bond lengths of cagelike nanoparticles is much tighter than the variation range of spherical ones. In contrast to spherical nanodiamond particles, the C-C bond lengths of all cagelike nanoclusters are very similar to the bond length of bulk diamond. The comparison of stability, electronic highest occupied molecular orbital-lowest unoccupied... 

A mini-column was made by packing α-diphenylglyoxime (DPG), a known ligand for complexation with nickel ions, loaded on activated charcoal (AC). Water samples were buffered at the pH range 8-9 and then passed through the column. After the preconcentration step, the column was eluted with 0.2 M nitric acid into the atomic absorption spectrometer (AAS). Mixed-level orthogonal array design (OAD) was used as a chemometric approach to study the effect of various factors on recovery of extraction. Factors such as pH, amount of sorbent, flow rate of sample, concentration and volume of the sample were investigated. Effects of interference ions, i.e., Co, Cu, Bi, Fe(I1), Pt and Pd was also studied.... 

The effects of selected metal ions on the gas-phase acidity of weak organic acids have been explored using the DFT and Moller-Plesset Perturbation Theory (MP2) calculations. The three organic acids selected for this study were acetic acid (aliphatic), benzoic acid (aromatic), and glycine (amino acid). The acidities of these compounds are compared with the acidity of their Li +-, Na+-, and K+ -complexed species. The results indicate that upon complexation with Li+, Na+, and K+ at 298K, the gas-phase acidity of acetic acid, for example, varies from 345.3 to 218.8, 230.2, and 240.1 kcal/mol, respectively (i.e., its dissociation becomes much less endothermic). These values indicate that a weak... 

Bio-sequence comparators are one of the most basic and significant methods for assessing biological data, and so, due to the importance of proteins, protein sequence comparators are particularly crucial. On the other hand, the complexity of the problem, the growing number of extracted protein sequences, and the growth of studies and data analysis applications addressing protein sequences have necessitated the development of a rapid and accurate approach to account for the complexities in this field. As a result, we propose a protein sequence comparison approach, called PCV, which improves comparison accuracy by producing vectors that encode sequence data as well as physicochemical properties... 

Fatty acids are among the most important components of many biological systems and have been highlighted in many research fields in recent decades. In the food industry, it is important to check the amount and types of fatty acids in edible oils, beverages and other foods products, and checking the fatty acids parameters are among the quality control parameters for those products. In medical applications, investigation of fatty acids in biological samples and comparing imbalances in them can help to diagnose some diseases. On the other hand, the development of cell factories for the production of biofuels and other valuable chemicals requires the accurate analysis of fatty acids, which serve... 

A highly efficient and simple synthesis of dithiocarbamates is possible based on the one-pot reaction of amines, CS2, and alkyl halides without using a catalyst under solvent-free conditions. The mild reaction conditions, high yields, and broad scope of the reaction illustrate the good synthetic utility of this method. The reaction is a highly atom-economic process for production of S-alkyl thiocarbamates and successfully can be used in high quantities in the pharmaceutical or agrochemical industries  

7H-benzimidazo[2,1-a]benz[de]isoquinolin-7-one compounds were prepared in a selective manner by reaction between o-phenylenediamines and appropriate 1,8-naphthalenedicarboxylic anhydrides using acidic alumina under microwave irradiation  

Free Content Selective synthesis of conjugated enynes from α-arylalkynols using LiCl-Acidic Al2O3 under solvent-free conditions  

Mordenite (MOR) nanocrystals were synthesized using the hydrothermal method. Sol–gel and deposition methods were utilized to modify the zeolite surface with TiO2 and then AgBr or AgCl particles. Photocatalysts were characterized by using X-ray diffraction, Brunauer–Emmett–Teller (BET), and scanning electron microscopy techniques. Activity was evaluated by photodegradation of Acid Blue 92 as an azo dye. The effect of silver halide deposition on the photocatalytic behavior of the prepared nanocomposites was studied under both ultraviolet (UV) and visible light, and the results were compared. The results showed that AgCl/TiO2/MOR was more active under UV, while with visible source,... 

(Equation present) Density functional theory (DFT) was used to investigate the acidity of the various silica alkyl sulfonic acids. In this regard, cluster models with various alkyl spacer lengths were selected to mimic the surface of silica gel. The effects of distance from the surface and the role of hydrogen bond (H-bond) on the ΔHacidity values of these catalysts were investigated. DFT calculations revealed that a notable gap of ΔH acidity values exists between the structures considering lateral hydrogen bonding with the surface of the silica HB structure and the structures with omitted surface interactions (non-HB structures). Natural bonding orbital (NBO) and quantum theory of atoms in... 

The purpose of this study was to investigate the natural gas hydrate promotion capabilities of the hydrotrope Toluene Sulfonic Acid (TSA) isomers as an additive. The capabilities of TSA isomers were measured with different concentrations. The optimum additive concentration for hydrate formation was determined for the given pressure, temperature, mixing condition, and cooling time. The natural gas hydrate promotability of para-TSA was found to be 20% and 35% more than meta-TSA and ortho-TSA respectively at the optimum concentration. Beyond the optimum TSA concentration, the hydrate formation declined as the ice formation reduced the overall gas-to-water volume ratio in the hydrates  

In this study, the drastic influence of the boron atom on the acidity of alcohol has been considered. The calculated ΔHacid (320.9-338.1 kcal/mol) and pKa range of boron containing alcohol (-0.1-9.4) indicate that the boronation of alcohol leads to considerable enhancement of its acidity. For instance, we have obtained the ΔHacid values 338.1, 335.2 kcal/mol and the pKa values 4.12, 2.81 for BH 2CH2OH, BF2CH2OH alcohols, respectively, which are much smaller than that of CH3OH (with ΔHacid = 374.9 kcal/mol and pKa = 15). The increase in the acidity of boronated alcohol can be related to the stabilization of alkoxy ion due to overlap of unoccupied orbital of boron atom with the electron pairs...