摘要:

A new method for isolation and spectrophotometric determination of plumbagin is presented. Plumbagin was isolated by thin layer chromatography (TLC) and column chromatography (CC) techniques, as an orange tinged yellow long crystalline substances. Plumbagin exhibits two absrop-tion maxima at 410 and 510 nm. Stability of the color, pKavalue, and the effect of pH were studied. Beer's law is obeyed over the range 0.9-45 ppm. The method is applied to the determination of plumbagin in roots, stems, and leaves of Plumbago europaea L. plant.

ISSN:0038-7010    

DOI:10.1080/00387019408007247

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The spectroscopic characteristics in methanol of tetra substituted aluminum 2,3-napthalocyanines (2,3-NcAl) derivatives have been investigated. The tetra substitution of an aluminum naphthalocyanine molecule produces a bathochromic shift of the Q and B band. The N band showed almost no effect by the presence of the functional group and remained at a constant frequency; however, multiple overlapping of bands occurred between 25000 cm−1(400 nm) and 35000 cm−1(250 nm). The degree of bathochromic shift of the Q band was affected by the electron withdrawing or electron donating property of the substituents. Changes in the absorption of the Q, B and N band will be discussed. The fluorescence, quantum yield and molar absorptivity of the Q-band due to structural modifications are reported. The molar absorptivity (ε) of the dyes was in the order of 3.5 (log ε); however, higher ε values were obtained with sulphonic groups. Solubility of these compounds in various solvents will be discussed. Possible use of the dye to determine metals and to other cations concentrations will be discussed.

ISSN:0038-7010    

DOI:10.1080/00387019408007248

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The electronic absorption and fluorescence spectra of 4-hydroxycoumarin, 7-hydroxycoumarin, 7-methoxycoumarin, 7-hydroxy-4-methylcoumarin, 7-amino-4-methylcoumarin, and 7-diethylamino-4-methylcoumarin were measured at room temperature (298K) in several solvents and their first excited singlet-state dipole moments were determined by the solvatochromic shift method. The excited singlet-state dipole moments of the coumarins were compared with the ground-state values.

ISSN:0038-7010    

DOI:10.1080/00387019408007249

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

A complete assignment of the1H and13C NMR spectra of four 6(9)-methylbenzo[b]naphthyridines in CDCl3is presented. The proton signals have been assigned from (1H-1H) coupling patterns and by the comparisons of chemical shifts with those of related heterocycles. Complete13C assignments have been made using proton detected one bond (13C-1H) 2D heteronuclear single quantum correlation, the INEPT technique, and chemical shift comparisons with related heterocycles. The proton detected long range (13C-1H) 2D heteronuclear multiple quantum correlation experiment leads to an unambiguous assignment of the two quaternary carbons in 6-methyl-benzo [b][1,5] naphthyridine.

ISSN:0038-7010    

DOI:10.1080/00387019408007250

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The concentration dependence of surface enhanced Raman scattering (SERS) of adsorbed polybenzimidazole on surfaces of silver has been investigated. It has been found that the spectral qualities are inversely proportional to the concentration of solutions applied. Excellent SERS spectral enhancement could be achieved for the sample applied from wt-0.03% solution. This phenomenon was termed as “dilution effect” on SERS spectrum of polymers. The observed phenomena are in accordance with Qian's proposal for the existence for coil shrinkage in dilute solution.

ISSN:0038-7010    

DOI:10.1080/00387019408007251

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The uv spectra of three phenylthiazoles are reported. These experimental results are interpreted using CNDO/S method (Complete Neglect of Differential Overlap for Spectroscopy). Calculations show that the observed transitions, except two, are pseudo Π→Π* type transitions.

ISSN:0038-7010    

DOI:10.1080/00387019408007252

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Kinetic and equilibrium data for 1-EtIm binding to cytcat temperature range of 303–319K have been determined at pH 7.0 by using1HNMR method. Thermodynamic values (ΔH°=39.5 kJ mol−1, ΔS° = 154 J mol−1K−1and Ea = 142 kJ mol−1) are obtained from Van't Hoff and Arrhenius's relations. Some hyperfine shifted resonances of l-EtIm cytchave been assigned for the first time using 1D saturation transfer experiments. The origin of the asymmetric spin density distribution in heme groups of 1-EtIm cytcand the reason of low affinity of cytochromecfor 1-EtIm are also discussed move toward upfield from original position. However, Te-2, 4 substituents in cytcare more electron withdrawing than the propionic acid side chains, which lead to the 5-methyl group going toward downfield.

ISSN:0038-7010    

DOI:10.1080/00387019408007253

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The conformation of the inclusion complexes between barbitone sodium and β-cyclodextrin (β-CD) has been specifically investigated by nuclear magnetic resonance (NMR) spectrometry. It appears that the presence of the nitrogen heteroatoms within the barbiturate ring and the space-regulatory role of the side-chains contribute to the relatively weak complexes formed.

ISSN:0038-7010    

DOI:10.1080/00387019408007254

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Celiprolol-hydrochloride has been determined using benzylorange and forming ion-pair. The absorbance of yellow coloured ion-pair is measured at 401 nm. Unknown concentrations of celiprolol-hydrochloride is calculated by using the calibration graph of the following calibration equation:

ISSN:0038-7010    

DOI:10.1080/00387019408007255

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

An easy sampling technique of wet-grinding has been devised to make KBr disks from insoluble crosslinked elastomers for transmission IR examinations. Satisfactory transmission IR spectra of some cured rubbers including that of high carbon black load obtained by using this method are reported. The fact that this sampling method can be applied to high resistant and tenacious rubbers suggests that transmission IR may directly be applied to most varieties of cured rubber and other tenacious polymers for their characterizations and chemical studies.

ISSN:0038-7010    

DOI:10.1080/00387019408007256

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor