摘要:

2-monosulphohydroxybenzene is spontaneously formed as a white deposit in a 3mol/dm3solution of monohydroxybenzene in 96% sulphuric acid after nine days at 298K. The composition of this compound was determined by using Rast's method as well as AAS, IR and UV/VIS spectroscopy. Determination of acidity constants of 2-monosulphohydroxybenzene was done by using pH-metric and spectrophotometric titration.

ISSN:0038-7010    

DOI:10.1080/00387019909349988

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Considering the -CH3group as a single particle of 15.0 daltons, the infrared absorption intensities of the a1fundamentals vibrational bands of CH3NO2in CCl4have been measured at different concentrations considering two cases: band intensities with solvent substraction (wss) and without solvent substraction (wtss). In order to obtain the matrix of the normalized amplitudes, X, the vibrational problem was solved via compliance constant: KCX = XΦ, in this case the use of the minus sign of the ±(∂μ/∂Q1)2s expressions is justified. The experimental results of the intensities measurements were refined with a variance analysis. From the intensities experimental data, our results are: ∂μNO/∂rNO= 6.02 and 6.16 D/Å, μNO2= 1.29 and 1.34D and ∂NO/∂RNC= -2.62 and -2.68 D/Å for measurements without solvent substraction and with solvent substraction, respectively

ISSN:0038-7010    

DOI:10.1080/00387019909349989

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The experimentally observed lower proton acceptor ability of the tetrafluorober-rylate(2-) anion, compared to that of the sulphate(2-) and selenate(2-) anions, was explained on the basis of various quantum chemical approaches. The geometries of the above-mentioned XY42anions were fully optimised at theab initioHF SCF and MP2 levels of theory, as well as within the DFT (BLYP and B3LYP) approach, using the 6-311+G* and LANL2DZ basis sets. The 6-311++G(3df,3pd) basis set was also used within the DFT BLYP approach. The molecular charge distribution was partitioned among the atomic centers using the Mulliken as well as the natural population analysis. All levels of theory (both with and without inclusion of the electron correlation effects), regardless of the basis set employed, predict lower (by absolute value) atomic charge on the fluorine atom in the tetra-ftuoroberrylate(2-) anion than that on oxygen atoms in sulphate(2-) and selenate(2-) anions. The quantum chemical predictions are fully in line with the spec-troscopically observed order of the proton acceptor abilities in these anions.

ISSN:0038-7010    

DOI:10.1080/00387019909349990

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Photoacoustic (PA) responses from very-thin poly(methyl methacrylate) (PMMA) films were investigated at various lamination conditions. The PA signal increased when the dye-doped films were laminated up to five layers, but tended to saturate beyond five layers. When the blank films were superimposed on the dye-doped film, the signal became smaller. The signal was larger when the dye-doped film was arranged outermost in the laminated film assembly of dye-doped and blank films. The results imply the effect of film vibration on the PA response.

ISSN:0038-7010    

DOI:10.1080/00387019909349991

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The dissociation constant of l-acetyl-2-(coumariniminecarboxamide-3-yl) hydrazine (ACCH) has been determined potentiometrically in 0.1 M KC1 and 40% (v/v) ethanol-water mixture. The stepwise stability constants of the formed complexes of Mn2+, Co2+, Ni2+, Cu2+, Zn2+and UO22+with ACCH have been determined. The stability constants were found to UO22+> Cu2+> Zn2+> Ni2+< CO2+< Mn2+. The effect of temperature on the dissociation of ACCH and the stability of its formed complexes were studied. The corresponding thermodynamic functions were also determined and discussed. The spectral data of ACCH were investigated in pure organic solvents as well as in Britton Robinson buffer solutions of varying pH values. The dissociation constant pKH1of ACCH and the overall stability constants logβ of their complexes were determined in 20% (v/v) ethanol-water mixture at 298K.

ISSN:0038-7010    

DOI:10.1080/00387019909349992

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The electronic absorption spectrum of the title crystal of the clathrate compound of [Ni(en)2(NCS)2]-C6H6has been measured. The experimental results are discussed quantitatively with ligand field theory(LFT) and the radial wave function of non-free nickel(II) ion. The calculation value coincides well with the experimental results. In particularly, it provides significant correlation between the electronic absorption spectrum and the crystal structure of the compound.

ISSN:0038-7010    

DOI:10.1080/00387019909349993

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The preparation and structure investigation of six iron-chelates; trioxatoferrate(III), l,trioxalatoferrate(III)-pyrocatechol,2;trioxalatoferrate(III) -pyrogallol 3,Fe(III)-EDTA 4,Fe(III)-EDTA-pyrocatechol 5 and Fe(III)-EDTA-pyrogallol 6, are described in this paper. The prepared compounds were identified by elemental analysis and studied by using infrared spectroscopy and TG and DTA thermal analyses. The possible structures were also suggested and confirmed. The mechanisms of thermal decomposition of these chelates were discussed using the available thermal data. It was concluded that both compounds 1 and 4 had been formed as blue to violet colored thermally stable compounds with pyrocatechol and pyrogallol. Thus, both of them are strongly recommended as analytical chromophoric reagents for the spectrophotometric microdetermination of these di- and trihydric phenols in natural and biological extracts which are the subjects of another paper.

ISSN:0038-7010    

DOI:10.1080/00387019909349994

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The application of Artificial Neural Networks (ANNs) for nonlinear multivariate calibration using simulated FTIR data was demonstrated in this paper. Neural networks consisting of three layers of nodes were trained by using the back-propagation learning rule. Since parameters affect the performance of the network greatly, simulated data were used to train the network in order to get a satisfactory combination of all parameters. The mixtures of four air toxic organic compounds whose FTIR spectra are overlapped were chosen to evaluate the calibration and prediction ability of the network. The relative standard error (RSD%), the percent standard error of prediction samples (%SEP) and the percent standard error of calibration samples (%SEC) are used for evaluating the ability of the neural network.

ISSN:0038-7010    

DOI:10.1080/00387019909349995

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The application of artificial neural networks for pharmaceutical quantitative analysis is described. Real data sets from near-infrared reflectance spectra of Metronidazole powdered pharmaceuticals were used to build an artificial neural network to predict unknown samples. A new network evaluation criterion, termed the degree of approximation, was employed. The overfitting was discussed. Owing to the beneficial nonlinear multivariate calibration nature of ANN. the predicted results were reliable and precise.

ISSN:0038-7010    

DOI:10.1080/00387019909349996

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

2,5-, 3,4- and 2,3-Thienylenediacrylic (1, 4 and 7 respectively) were synthesized in one step reaction by catalytic vinylation of the corresponding dibromothiophenes in the presence of cyclohexylamine salt of acrylic acid. 2,4-Thienylenediacrylic acid 10 was prepared by catalytic vinylation of 3-(4-bromo-2-thienyl)acryilic acid.

ISSN:0038-7010    

DOI:10.1080/00387019909349997

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor