摘要:

AbstractThe isomerization between Z and E isomers of benzaldoximes in different solvents were measured by TLC method. The experimental results show that acid solvents catalyze this inter‐conversion process dramatically. Solution state NMR measurements also show very different spectra for Z and E isomers of benzaldoximes in different solvents. All this suggests that the acidity of solvent is a very important factor to affect the inter‐conversion process.Theoretical investigations of Z to E inter‐conversion of benzaldoximes in different solvents were carried out by DFT calculations at B3LYP/6–3 11+G** level. The calculations show that the barrier from Z to E in the presence of acid is much lower than that without acid. This agrees with the experimental data very well. The calculated structure in the transition state is helpful for the understanding of the inter‐conversion

ISSN:0009-4536    

DOI:10.1002/jccs.200400182

出版商:WILEY‐VCH Verlag    

年代:2004

数据来源: WILEY

摘要:

AbstractIn this study glass has been used as a starting material in order to increase the resolution of the experiment and establish the kinetics of analcimes during hydrothermal synthesis. The experimental results show that the crystal growth curves represent two‐stage linear growth. The first stage is marked by rapid crystal growth whilst the second stage indicates much slower growth. The nuclei appear before the crystals start growing. The crystal growth rate is dependent on the experimental conditions. The nucleation rate increases as the glass dissolves and reaches a maximum when the glass is completely dissolved. Thereafter, the concentration decreases with the consumption of nutrients, and both nucleation and crystal growth stops when supersaturation occur

ISSN:0009-4536    

DOI:10.1002/jccs.200400183

出版商:WILEY‐VCH Verlag    

年代:2004

数据来源: WILEY

摘要:

AbstractFriedel‐Crafts cycloalkylation of biphenyl with 2,3‐dichlorobutyltrichlorosilane(Cl3Si‐CH2CHClCHClCH3) at a temperature of 100°C in the presence of anhydrous aluminum chloride catalyst gave cyclized product, 9‐methyl‐9‐(2‐trichlorosilylethyl)fluorene1a, in 33% yield. Methylation of1awith nucleophilic reagent such as methyl magnesium chloride, gave 9‐methyl‐9‐(2‐trimethylsilylethyl)fluorene2while bromination of2with excess amount of bromine in DMF resulted in 2,7‐dibromo‐9‐methyl‐9‐(2‐trichlorosilyl)fluorene3in good yield. All the compounds were structurally identified b

ISSN:0009-4536    

DOI:10.1002/jccs.200400184

出版商:WILEY‐VCH Verlag    

年代:2004

数据来源: WILEY

摘要:

AbstractThis research focuses on the UV‐Vis. absorbance spectra of the hybrid organic/inorganic complementary electro‐chromic device (ECD), comprising polyaniline‐poly(styrenesulfonic acid)[PANI‐PSSA] complexes and tungsten oxide (WO3) thin film coupled in combination with a polymer electrolyte poly(2‐acrylamido‐2‐methyl‐propane‐sulphonic acid)[PAMPSA]. PANI‐PSSA microstructure surface images have been studied by AFM. By applying a potential of ˜3.0 V across the two external ITO contacts, we are able to modulate the light absorption also in the UV‐Vis region (200–900 nm) wavelength region. For example, the absorption changes fr

ISSN:0009-4536    

DOI:10.1002/jccs.200400185

出版商:WILEY‐VCH Verlag    

年代:2004

数据来源: WILEY

摘要:

AbstractThe electrocatalytic properties of the SiC particle‐modified glassy carbon electrode (MGC) for adrenaline oxidation were studied by cyclic voltammetry (CV), double‐potential step chronocoulometry (DPSCC), and electrochemical impedance spectroscopy (EIS) techniques in McIlvaine buffer solution. It was shown that the electrode modified with SiC particles markedly displayed an electrocatalytic effect on the process of the electrochemical reaction of adrenaline, i.e., the activity and the reversibility of the MGC electrode has been significantly improved. This was attributed to the adsorption effect of the electroactive adrenaline molecules on the MGC electrode surf

ISSN:0009-4536    

DOI:10.1002/jccs.200400186

出版商:WILEY‐VCH Verlag    

年代:2004

数据来源: WILEY

摘要:

AbstractImprovement of pulse amperometric detection (PAD) method is demonstrated in determination of ethylenethiourea (imidazolidine‐2‐thione, ETU). The anodic detection of ETU will produce polymeric film on an electrode leading to an inactive electrode surface. Here, the PAD method was used to remove the polymeric film formed on the electrode surface between ETU detection. Further, the scheme was integrated with automated flow injection analysis (AFIA) for determining ETU. The operational parameters of PAD in the AFIA system were discussed thoroughly. The analytical characteristics of the system were evaluated at optimum conditions. The linear range of calibration plot was between 20 to 300 μM (the correlative coefficient, r = 0.999) and the detection limit was 0.9 μM (S/N = 3). The relative standard deviations of detection of 50 μM ETU were 0.82% with and 9.07% without PAD scheme. The results indicate the system is a very promising tool for ETU determination. Finally, the matrix effects of two water samples that were collected from a campus and a farm show good recoveries of 92% a

ISSN:0009-4536    

DOI:10.1002/jccs.200400187

出版商:WILEY‐VCH Verlag    

年代:2004

数据来源: WILEY

摘要:

AbstractThe principles of metal‐alkaloid ion‐pair formation and liquid‐liquid extraction are applied to the development of a sensitive and convenient atomic absorption spectrophotometery (AAS) method for the indirect determination of cocaine. In an aqueous medium of 5 M hydrochloric acid, cocaine is protonated and is associated with tetrachloro ferrate (III) anion prior to its extraction into 1,2‐dichloroethane. The critical experimental variables were identified and optimized. The method is simple and reproducible with a detection limit (DL) of 0.1 ng cm−3cocaine in water, a relative standard deviation of 0.07 (n = 12), and the calibration graph was linear up to 50 ng cm

ISSN:0009-4536    

DOI:10.1002/jccs.200400188

出版商:WILEY‐VCH Verlag    

年代:2004

数据来源: WILEY

摘要:

AbstractThe polystyrene‐supported α‐selenoacetic acid and α‐selenopropionic acid were prepared and used for the synthesis of 2‐alkenamides from primary and secondary amines in good yields and high

ISSN:0009-4536    

DOI:10.1002/jccs.200400189

出版商:WILEY‐VCH Verlag    

年代:2004

数据来源: WILEY

摘要:

AbstractBased on Claisen rearrangement, the double bond isomerization ofO‐allyl function together with the formation ofO‐vinyl function in one pot, and ring‐closing metathesis (RCM), various phenols were transformed into various benzofurans in good y

ISSN:0009-4536    

DOI:10.1002/jccs.200400190

出版商:WILEY‐VCH Verlag    

年代:2004

数据来源: WILEY

摘要:

AbstractThe voltammetric behaviour of four azo dyes has been compared at a glassy carbon electrode. It is shown that the azo dyes (e.g. Reactive Brilliant Red x‐3b (RBR x‐3b), Acid Red 6b (AR 6b)) with a hydroxyl group in theorthoposition with respect to the azo bridge give rise to well defined, irreversible peaks for the oxidation and reduction process within a pH range of 2–12. In the case of the non‐hydroxyl azo dye (e.g. Reactive Yellow x‐rg (RY x‐rg)), or azo dye with ametahydroxyl group (e.g. Reactive Orange x‐gn (RO x‐gn)), the oxidation was comparatively tougher, and the peak was not clear or even invisible in the accessible potential range. The mechanism of electrochemical oxidation of RBR x‐3b, as well as AR 6b is proposed. The reduction steps were only accessible when pH<8 for RY x‐rg and RO x‐gn dye compounds. For the hydroxyl‐substituted dyes, re‐oxidation peaks were obtained in the subsequent scan, owing to the oxidation of reduction products‐amin

ISSN:0009-4536    

DOI:10.1002/jccs.200400191

出版商:WILEY‐VCH Verlag    

年代:2004

数据来源: WILEY