摘要:

AbstractTrimethylsilylation of alcohols with hexamethyldisilazane (HMDS) catalyzed by V(HSO4)3under mild and completely heterogeneous reaction condition is reported. The method is highly chemoselective for the protection of alcohols in the presence of phenols, amines and thiols. Also, the deprotection of trimethylsilyl ethers is performed in the presence of V(HSO4)3at room temperature in good to high yields.

ISSN:0009-4536    

DOI:10.1002/jccs.200800140

出版商:WILEY‐VCH Verlag    

年代:2008

数据来源: WILEY

摘要:

AbstractA mild, eco‐friendly and efficient route for the synthesis of quinolines and polycyclic quinolines via Friedländer annulation using cyanuric chloride as a catalyst under aqueous conditions is describ

ISSN:0009-4536    

DOI:10.1002/jccs.200800141

出版商:WILEY‐VCH Verlag    

年代:2008

数据来源: WILEY

摘要:

AbstractThe removal of arsenic ions from dilute aqueous solutions using biopolymeric beads of crosslinked sodium alginate and carboxymethyl cellulose (CMC) as the adsorbent is reported in this paper. The biopolymeric alginate and carboxymethyl cellulose beads were prepared and characterized by FTIR spectra. On the surfaces of the prepared beads were performed static and dynamic adsorption studies of arsenic ions at fixed pH and ionic strength of the aqueous metal ion solutions. The adsorption data were applied to Langmuir and Freundlich isotherm equations and various static parameters were calculated. The dynamic nature of adsorption was quantified in terms of several kinetic constants such as rate constant for adsorption (k1) and Lagergreen rate constant (Kad).The influence of various experimental parameters such as solid to liquid ratio, pH, temperature, presence of salts and chemical composition of biopolymeric beads were investigated on the adsorption of arsenic ions.

ISSN:0009-4536    

DOI:10.1002/jccs.200800142

出版商:WILEY‐VCH Verlag    

年代:2008

数据来源: WILEY

摘要:

AbstractDissolution of some industrially relevant atomic and diatomic species (Ar, Ne, H, O, H2, N2and O2) in the 5 × 5 2‐D hexagonal and square helium lattices, as the model of the liquid helium cryogen, has been studied usingab initioMP2/6‐31++G computations. Structural, electronic and thermochemical properties have been calculated and analyzed for these solution lattices. Results of these calculations show that dissolution of Ar, Ne, H and H2species is more favored at higher temperatures. A reverse trend is observed for the dissolution of O, N2and O2species. A staggered orientation is preferred by all diatomic species in both lattices. Results of this study also show that breakage of the O2molecule becomes slightly easier in the 2‐D helium lattices as compared with that of the H2molecule. Effect of the cavity geometry and size, and position of the solute in the lattice have also been studied. Analysis of the results shows that the range of the interaction between the solute and solvent atoms is only one helium

ISSN:0009-4536    

DOI:10.1002/jccs.200800143

出版商:WILEY‐VCH Verlag    

年代:2008

数据来源: WILEY

摘要:

AbstractTwo simple, rapid and reliable spectrophotometric methods are described for the resolution of the three‐component mixture of amiloride hydrochloride (AMD), hydrochlorothiazide (HCT) and timolol maleate (TIM). The first method involves the use of derivative spectrophotometry with the zero‐crossing technique where AMD was easily determined using its0D and1D(Δλ = 6) amplitudes at 365 and 385 nm, respectively, while HCT and TIM were determined by measuring the3D(Δλ = 6) amplitude at 265 nm and the1D(Δλ = 8) amplitude at 315.4 nm, respectively. The second method involves the application of the ratio‐spectra zero‐crossing first and second derivative spectrophotometry where two points have been used for the quantification of each compound. For the determination of AMD, HCT was used as divisor and the1DD (Δλ = 4) and2DD (Δλ = 6) values at 299.4 and 311 nm, respectively, were plotted against AMD concentration; while — by using TIM as divisor — the2DD (Δλ = 6) amplitudes at 264.2 and 290 nm were found to be proportional to HCT concentration. TIM was assayed in the mixture using its1DD (Δλ = 6) amplitudes at 289.8 nm (Divisor was AMD) and 314.8 nm (Divisor was HCT). Synthetic mixtures of different proportions and laboratory‐made tablets were assayed by the proposed methods and the results revealed good accuracy and repeatabili

ISSN:0009-4536    

DOI:10.1002/jccs.200800144

出版商:WILEY‐VCH Verlag    

年代:2008

数据来源: WILEY

摘要:

AbstractA multi‐channel piezoelectric quartz crystal gas sensor comprising arrays coated with various organic materials and a home‐made computer interface for data processing were prepared and employed to detect six kinds of common organic pollutants from petrochemical plants including benzene, styrene, chloroform, octane, hexene and hexyne. The principal component analysis (PCA) method was employed to select six kinds of appropriate coating materials for these organic pollutants from 22 adsorbents onto piezoelectric crystals. After performing a PCA assay, six representative coating materials, namely Polyisobutylene, Poly(dimethylsiloxane) (SE30), 4‐tert‐Butylcalix[6]arene, Cholesteryl chloroformate, C60‐Polyphenyl acetylene (C60‐PPA) and Ag(I)/cryptand‐2,2/Ethylene diamine/NH3/Polyvinyl chloride were selected. Moreover, effects of coating load of adsorbents and concentration of pollutants were also investigated. Three kinds of recognition techniques including 2D PCA score map, radar plot and back‐propagation neural network (BPN) were employed for qualitative analysis of these organic pollutants, and a quantitative analysis method could be established by creating calibration curves for each organic pollutant. This homemade multi‐channel piezoelectric quartz crystal gas sensor showed a good detection limit of 0.068‐1.127 mg/L for these organic pollutants. The multi‐channel piezoelectric gas sensor exhibited good reproducibility with a relative standard deviation (RSD) of 1.1‐9.6%. Furthermore, this multi‐channel piezoelectric crystal detection system with BPN recognition technique was also utilized to successfully distinguish and identify each component of the mixture of organic gas samples. Multivariate linear regression (MLR) analysis was employed to quantitatively compute the concentration of specie

ISSN:0009-4536    

DOI:10.1002/jccs.200800145

出版商:WILEY‐VCH Verlag    

年代:2008

数据来源: WILEY

摘要:

AbstractAn electrochemiluminescence inhibition method has been developed for the determination of bisphenol A based on studying the inhibition phenomena of bisphenol A to the electrochemiluminescence of luminol. There is a linear relationship between the inhibitive intensity of electrochemiluminescence and the concentration of bisphenol A in the range of 4.4 × 10−7to 2.2 × 10−5mol/l. The method was successfully applied to the determination of bisphenol A in hot water in contact with commercially available table‐water bottle

ISSN:0009-4536    

DOI:10.1002/jccs.200800146

出版商:WILEY‐VCH Verlag    

年代:2008

数据来源: WILEY

摘要:

AbstractIn order to explore whether hydrophobicity or charge at the 71thresidue is important for chaperone‐like activity, wild type (wt) and two mutant αA‐crystallins, F71W and F71R, with an extra 11 residues including 6 histidines tagged at the N‐terminal were prepared. Chaperone‐like activity toward dithiotreitol (DTT) induced insulin aggregation showed the 11 extra residues had little effect. The activity for F71W was as active as the wild type, while F71R was much less active. For the wild type and F71W, the activity increased with the increase of molar quantity; surprisingly, for F71R it caused a drastic decline. ANS fluorescence measurements showed F71R had the highest surface hydrophobicity, suggesting positive charge at this site caused the conformational alteration leading to the increase of hydrophobicity and this hydrophobicity resulted in the formation of high molecular weight aggregates (>2000 kDa) observed from the thermal stability study. The thermal stability study revealed F71W was the most thermally stable crystallin. Chaperone‐like activity studies at various temperatures suggested the monomer and oligomer, 650 kDa, were responsible for chaperone function and surface hydrophobicity was not the prerequisite for activity. Near‐UV CD studies showed β‐sheet was the major secondary structure for all three crystallins and F71R had a higher percentage

ISSN:0009-4536    

DOI:10.1002/jccs.200800147

出版商:WILEY‐VCH Verlag    

年代:2008

数据来源: WILEY

摘要:

AbstractThree possible reaction mechanisms of methanoyl fluoride with 2H2O include a concerted and a stepwise hydrolysis of HFCO into HCOOH + HF, and a pure catalytic decomposition of HFCO into HF + CO. Among these, the two H2O molecules acting as catalyst to decompose HFCO has the lowest calculated barrier, 25.1 kcal/mol with respect to the reactant‐adduct complex, whereas the barriers for the concerted and stepwise hydrolytic reactions in which one H2O acts as a reactant and the other H2O as catalyst are similar, 30.8 kcal/mol for concerted and 29.9 kcal/mol for stepwise. The formation of transoid HCOOH in the hydrolysis of HFCO is more favorable than cisoid HCOO

ISSN:0009-4536    

DOI:10.1002/jccs.200800148

出版商:WILEY‐VCH Verlag    

年代:2008

数据来源: WILEY

摘要:

AbstractA rapid and sensitive high‐performance liquid chromatographic method was developed and validated for the simultaneous determination and quantification of atenolol, rosuvastatin, spirnolactone, glibenclamide and naproxen sodium in bulk drugs, pharmaceutical formulations and in human plasma in the presence of internal standard (flurbiprofen). Chromatograms were developed with methanol and water (80:20, v/v) solvent system on a Purospher start, C18(5 μm, 250 × 4.6 mm) column and pH was adjusted to 3.40 with ortho‐phosphoric acid. Mobile phase was pumped with a flow rate of 0.90 mL/minute with 235 nm UV detection. Standard curves were linear over the concentration range 0.25‐30 μg/mL−1. The coefficients of variation (C.V.%), were<3% and LOD and LOQ were<0.0154&0.06 for inter‐ and intra‐day, respectively. The method was applied to drug interaction studies of atenolol with rosuvastatin, spironolactone, glibenclamide and naproxen to illustrate the scope and application of the methods to manage four different therapeutic classes of drugs, as they are c

ISSN:0009-4536    

DOI:10.1002/jccs.200800149

出版商:WILEY‐VCH Verlag    

年代:2008

数据来源: WILEY