摘要:

Heteroaromatic radical cations are obtained from the oxidaton of N-methyl substituted imidazoles by sulphate anion radical in aqueous solution. The optical absorbtion spectra of the radical cations in acidic medium are reported. In basic solution the radical cations are found to react with hydroxyl anion to produce allylic, OH-substituted radicals.

ISSN:0038-7010    

DOI:10.1080/00387019208020751

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Emission bands of the A1Π-X1Σ+transition of the Be18O between 600 and 900 nm have been observed and analysed for the first time. The vibrational analysis of the bands has been justified by the measurements of the isotope displacements between Be16O and Be18O bands. The rotational structure of the 5-0, 6-1, 4-0, 5-1, 3-0, 4-1 and 2-0 bands have been analysed and the molecular constants for the upper electronic state of Be18O have been derived.

ISSN:0038-7010    

DOI:10.1080/00387019208020752

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Spectroscopic studies of chemisorbed pyridine indicate that Na-montmorillonite which has been degassed at 200°C contains only Lewis acid sites. The reaction of Na-homoionic montmorillonite with Al polyoxycations generates pillared montmorillonite which is thermally stable up to 500°C. The pillaring process seems to enhance Lewis acid sites and generate Brönsted acid sites. Above 300°C pyridine is adsorbed mainly on Lewis centers.

ISSN:0038-7010    

DOI:10.1080/00387019208020753

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The 300 MHz1H-NMR and 75 MHz13C-NMR spectral assignments of taxol were made with the aid of APT and DEPTGL 1-D spectra and COSY, HETCOR, and NOESY 2-D spectra. In addition to being useful for spectral line assignments, the cross-peaks in the phase-sensitive NOESY spectrum were also used to estimate the distances between protons located on adjacent ring systems of taxol by measuring the volume integration of the cross-peaks. Key dihedral angles of taxol were also estimated using a Karplus-type equation that takes into account the heteroatom substitution on the adjacent carbon atoms. Using the proton-proton distances and the dihedral angles as a guide, molecular mechanics energy minimization molecular modeling was used to arrive at a structure of taxol that was consistent with the NMR data. While the X-ray data for taxol was not available, the NMR data and the molecular modeling results were compared to the X-ray data for taxotere, a close structural analog of taxol that has slightly more biological activity. The NMR and molecular modeling data indicate that the structure of taxol in solution had a general “U''-shape that was very similar to the crystal structure of taxotere, except that in solution the ends of the “U” were closer together than found in the crystal structure.

ISSN:0038-7010    

DOI:10.1080/00387019208020754

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The very different optical spectra found for the green coloured Y2BaNiO5and the substituted brown-tobacco Y2BaNi1−xZnxO5oxides have been explained taking account the different crystal structure which show these oxides. In this sense, Y2BaNiO5shows orthorhombic symmetry, space group Immm, with the nickel situated in a distorted octahedral coordination giving rise to a site of D4has local symmetry. The substituted Y2BaNi1−xZnxO5which are isostructural crystallyze with orthorhombic symmetry, space group Pnma showing as main characteristic the existence of isolated distorted square pyramidal coordination for the nickle NiO5which yeilds aproximately C4vas point symmetry.

ISSN:0038-7010    

DOI:10.1080/00387019208020755

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Extensive study of hydration of alkaline and alkaline earth cations in aqueous solutions of perchlorate salts has been performed using Raman spectral technique. The Raman lineshape and position of of thev1(A1) vibrational mode of perchlorate anion have been measured over a wide range of concentrations from highly dilute to the near saturated solutions. The structure of the first coordination sphere has been established for each studied cation using frequency shift and half-width changes of measured band. Spectral data are compared with those obtained by electrochemical measurements.

ISSN:0038-7010    

DOI:10.1080/00387019208020756

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The study of molecular parameters of a new dye Coumarin 7 has been made and evaluation of the parameters indicates the high potentiality for lasing, Lasing action was observed for the first time and laser characteristics were measured. In dye mixtures, there was an improvement in its lasing performance. The new dye was found to be more efficient compared to Coumarin 307. Acriflavine which does not lase alone with N2laser pumping was made to lase by energy transfer technique and laser characteristics measured are reported.

ISSN:0038-7010    

DOI:10.1080/00387019208020757

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Laser Raman Spectra of molybdena supported at different concentration on the surface of y-A12O3-prepared by both impregnation and physical mixtures- have been recorded. Formation of polymolybdate species, depending on Mo loading and time and temperature of calcination, has been detected in both series of samples.

ISSN:0038-7010    

DOI:10.1080/00387019208020758

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The uv spectra of four new nitroimidazopyridines are reported. These experimental results are interpreted using CNDO/S method (Complete Neglect of Differential Overlap for Spectroscopy). Calculations show that the observed transitions are W→W* type transitions.

ISSN:0038-7010    

DOI:10.1080/00387019208020759

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Infrared and Raman spectra were obtained for 5- methyl-2-hexyne and wereinterpreted with the aid of normal coordinate calculations. The spectra and molecular mechanics calculations show the compound to exist in two spectroscopically distinguishable stable conformations, with the C1conformer being only a little more stable than the Cs, conformer. Vibrational assignments were made for both conformers.

ISSN:0038-7010    

DOI:10.1080/00387019208020760

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor