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  • 1
    ISSN: 1572-9001
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The microwave spectrum of gaseous 1-bromo-2-methoxyethane, BrCH2CH2OCH3, has been recorded from 18.0 to 27.0 GHz at low resolution. The Raman spectra of the gas, liquid, and solid along with the infrared spectra of the gas and solid have been recorded from 3500 to 50 cm−1. A comparison of the vibrational spectra obtained for the fluid phases with those obtained for the annealed solid indicates the presence of more than one conformer in the fluid phases. The presence of two asymmetric rotors allows for five possible conformations, a majority of which are present in the gaseous phase. It is concluded that the conformation present in the solid phase is that of the gauche/trans (GT) form, where the first term refers to the carbon-bromine bond and the second term to the carbon-oxygen bond (methoxy group). In the gas phase the major absorption in the microwave spectrum is a result of the trans/trans (TT) form although it is certain that other conformations are also present. From a variable temperature study of the Raman spectrum of the liquid, the enthalpy difference between the conformers of the—OCH3 group was found to be 850 ±115 cm−1 (2.43±0.33 kcal/mol) whereas the difference between the conformers of the—CH2Br group as found to be 510±24cm−1 (1.46±0.07 kcal/mol). The conformational energy differences, vibrational frequencies, and structural parameters have been obtained from ab initio calculations with the STO-3G* basis set, and these theoretical values are compared to the experimental values. All of these results are compared to similar data for some corresponding molecules.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Journal of Raman Spectroscopy 25 (1994), S. 795-797 
    ISSN: 0377-0486
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A colloidal silver oxide hydrosol was prepared for surface-enhanced Raman scattering (SERS). Its performance as a SERS-active substrate was tested using benzoic acid and 1,1′-diethyl-2,2′cyanine iodide as analytes. SERS and surface enhanced resonance Raman scattering were observed for the adsorbed samples. In the preparation of the sol, the relative amounts of reagents should be an important factor in affecting the surface enhancement of the substrate. The surface enhancement activity of the colloidal hydrosol might indicate that silver oxide films generated in the electrochemical oxidation of a silver electrode could enhance the Raman spectra of adsorbed molecules and/or passivated films.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Journal of Raman Spectroscopy 22 (1991), S. 191-196 
    ISSN: 0377-0486
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The silver colloid surface-enhanced Raman scattering (SERS) spectrum of phenylpropanolamine (PPA) and the surface-enhanced resonance Raman scattering (SERRS) spectrum of the PPA-ninhydrin reaction product were studied. It was found that the spectral intensity varied with time, and the rate of the variation was related to the PPA concentration. From scanning electron microscopic photographs taken at different times, the SERS intensity appeared to be correlated with the coagulation of silver particles. Temperature was found to be another factor that would change the kinetic rate of the coagulation. Addition of potassium chloride served effectively to activate the surface-enhanced effect and to reduce the time required to reach maximum intensity. The rate of activation was found to be dependent on the concentration.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0377-0486
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Because of the importance of developing an active substrate for surface-enhanced Raman (SER) spectroscopic applications, a silver-coated filter-paper substrate was prepared for surface-enhanced Raman scattering (SRS) by using a chemical reduction method at room temperature. Optimization of the silver deposition time was achieved by using p-nitrophenol (PNP) as an analyte. Its performance as an SERS-active substrate was tested using PNP, p-chlorobenzoic acid, m-chlorobenzoic acid and o-chlorobenzoic acid. To overcome the problem of low enhancement when a dipping method was adopted for sample applications, a silver-coated alumina-based substrate was prepared. The new substrate was found to exhibit strong SERS with both the solution and the dipping methods for sample applications of PNP. Using the new substrate, the limit of detection for methyl red was estimated to be 3 ng ml-1.
    Additional Material: 7 Ill.
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  • 5
    ISSN: 0377-0486
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The Raman spectra of gaseous, liquid and solid 1, 1, 1-trifluoro-2-methoxypropane, CF3(CH3)CHOCH3, and the corresponding methoxy-d3 isotope, CF3(CH3)CHOCD3, together with the infrared spectra of the gases and solids were recorded from 3500 to 30 cm-1. A comparison of the vibrational spectra obtained for the fluid phases with those obtained for the amorphous and annealed solids indicates the predominance of two conformers in the fluid phases at ambient temperature. Owing to possible steric hindrance, it is suggested that the most stable conformer is the gauche-2 form, which has the methoxy group trans with respect to the carbon-carbon bond of the perfluoromethyl group. This conformer is the one present in the solid. The other conformer in appreciable abundance in the fluid states is probably the gauche-1 form, which has the methoxy group trans to the carbon-carbon bond of the methyl group. From a temperature study of the Raman spectrum of the liquid, the enthalpy difference between these conformers was determined to be 180 ± 100 cm-1 (515 ± 286 cal mol-1). The asymmetric torsional frequencies for the gauche-2 and gauche-1 conformers are 93 and 53 cm-1, respectively, and from these data and the enthalpy difference the values for the potential constants governing the internal rotation have been estimated. The normal modes have been assigned based on group frequencies, isotopic shifts, depolarization values and infrared band contours. The barrier to internal rotation of the methyl group is calculated to be 1275 cm-1 (3.65 kcal mol-1) from the torsional frequency of 234 cm-1 of the solid.
    Additional Material: 7 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Journal of Raman Spectroscopy 22 (1991), S. 345-347 
    ISSN: 0377-0486
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The surface interaction between ZrO2 and TiO2 in physical mixtures was studies using laser Raman spectroscopy (LRS). The characteristic peaks of ZrO2 disappeared after mixing ZrO2 and TiO2 with a loading ZrO2 of less than 25 wt.% and calcination at 773 K for 12 h. Surface polyhedrally coordinated Zr on TiO2 could not be detected by LRS. Therefore, MoO3 was used as a molecular probe to detect the nature of the interactions between ZrO2 and TiO2. The results revealed that ZrO2 could disperse on the surface of TiO2 and its interaction with TiO2 is different from that of MoO3 and TiO2.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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