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  • Analytical Chemistry and Spectroscopy  (98)
  • 1980-1984  (98)
  • 1981  (98)
  • 1
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 16 (1981), S. 123-125 
    ISSN: 0030-4921
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Two NQR lines were observed for 35Cl in 2,5-dichloro-4-nitroaniline at room temperature, using a self-quenched super-regenerative spectrometer. Analysis of the Zeeman effect on the two lines using a cylindrical single crystal reveals that the crystal belongs to the monoclinic system. The principal field gradient Z axes enclose an angle of 35° and 28° in the cases of the low and high frequency resonance lines, respectively. The b axis is parallel to 81°, 280°. The unit cell contains either two or a multiple of two molecules. The molecules in the crystal can be arranged into two sets, with the molecular planes in each set being parallel among each other. The angle subtended between the two planes is 159° and each of the planes is inclined to the b axis at an angle of 79.5°. There is an in-plane bending of the two C—Cl bonds by 5.5°. The ionic, single bond and double bond characters of the C—Cl bonds for both chlorines are almost equal, and are in the ratio 24:73:3.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 15 (1981), S. 280-284 
    ISSN: 0030-4921
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: 1H and 13C NMR spectra of 8-hydroxyquinoline (oxine) and its 5-Me, 5-F, 5-Cl, 5-Br and 5-NO2 derivatives have been studied in DMSO-d6 solution. The 1H and 13C chemical shifts and proton-proton, proton-fluorine, carbon-proton and carbon-fluorine coupling constants have been determined. The 1H and 13C chemical shifts have been correlated with the charge densities on the hydrogen and carbon atoms calculated by the CNDO/2 method. The correlation of the 1H and 13C chemical shifts with the total charge densities on the carbon atoms is approximately linear (rH2 = 0.85, rC2 = 0.84). The proton in peri position to the nitro group in 5-NO2-oxine is an exception.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 15 (1981), S. 311-316 
    ISSN: 0030-4921
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The assignment of all ring carbons of p-benzoquinones derived from perezone and from thymoquinone was completed using gated decoupled spectra. The long range proton-carbon couplings are discussed in terms of the degree of substitution of the quinone ring. The tautomeric interconversion of the two energetically equivalent forms of 2,5-dihydroxy-1,4-benzoquinones has been studied in various solvents and at several temperatures.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 15 (1981), S. 158-161 
    ISSN: 0030-4921
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Human serum albumin has been specifically acetylated using aspirin in which the methyl carbon of the acetyl group was enriched to 90% 13C. A single resonance at 23.13 ppm downfield from tetramethylsilane was observed in 13C differences spectra obtained at both 25.2 and 45.3 MHz. Chemical shift studies of several model compounds suggest that this is the resonance position to be expected for an acetamide group exposed to solvent. The line width observed for the enriched methyl resonance is consistent with free rotation of the methyl group.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 5
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 16 (1981), S. 7-10 
    ISSN: 0030-4921
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The structure of the bispyridinium oximes, toxogonin, HS-3, HS-6 and HI-6, used as antidotes in organophosphorus poisoning, is confirmed by 13C NMR spectroscopy. The 13C NMR spectra of the corresponding monopyridinium precursors substantiate the signal assignment in the bispyridinium oxime spectra. In all oximes studied the hydroxyiminomethyl group (—CH=N—OH) exists in the syn configuration. The 13C signal differences also readily allow analysis of binary mixtures of the oximes and provide an easy method for monitoring their stability.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 6
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 8 (1981), S. 170-173 
    ISSN: 1052-9306
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A method has been developed for the quantitation of the putative phenolamine neurotransmitter octopamine, and its precursor tyramine, in brain tissue. The procedure employs methane chemical ionization of the pentafluoropropionate derivatives of octopamine and tyramine together with the use of deuterated internal standards and selected ion monitoring. Deuterated analogues of octopamine and tyramine are added to brain homogenates in aqueous perchloric acid and ion exchange is used to isolate the brain amines. The method is capable of measuring 20 pg of octopamine and tyramine. The measured concentration (ng g-1 wet tissue) of octopamine and tyramine in rat brain was as follows: whole brain (less cerebellum) (0.6 and 2.2); hypothalamus (3.2 and tyramine value not statistically significant); striatum (0.5 and 11.8) and cortex (0.6 and 1.0). Administration of pargyline resulted in an increase (around ten-fold) in octopamine and tyramine concentration in all the above brain regions. In contrast α-methyltyrosine produced only a small increase (50%) in the concentration of tyramine in the striatum.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 7
    ISSN: 0935-6304
    Schlagwort(e): Gas chromatography ; Capillary, fused silica ; Split injection ; Splitless injection ; Polynuclear aromatic hydrocarbons, quantitation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 8
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 4 (1981), S. 366-384 
    ISSN: 0935-6304
    Schlagwort(e): GC/MS ; Capillary columns, fused silica ; Priority pollutants ; Quantitation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Operational characteristics have been determined for fused silica capillary column (FSCC) GC/MS as applied to “extractable” priority polutants. Chromatographic data show excellent relative retention time (RRT) intralaboratory precision and interlaboratory accuracy when multiple internal standards are empolyed. Potential chromatographic problems, such as column overload and “double peaking”, are addressed. Response factor relative standard deviations (RSD) at 50 ng for most of the extractable priority pollutants over the long term indicated precise determination (i.e. RSD generally ≤ 10%). Linearity was demonstrated over two orders of magnitude for FSCC GC/MS analysis of compounds with relatively low and high RF (response factor) values. Potential quantitative problems, such as saturation, are discussed. For certain aromatic priority pollutants interlaboratory RF agreement was observed. This was noted as perhaps the most important property of FSCC GC/MS analysis when the multiple internal standard approach is utilized. Determinations of extractable priority pollutants are directly compared for paced column GC/MS and FSCC GC/MS analysis of separate and composited extracts. For six extracts analyzed in triplicate, the latter configuration was shown to produce more consistent results. In view of the superior analysis logistics of composite extract FSCC GC/MS analysis, this approach was established as the preferred method for the analysis of priority pollutants classified as extractable.
    Zusätzliches Material: 12 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 9
    ISSN: 0030-4921
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The 15NMR chemical shifts were measured of a number of N-substituted formamides and acetamides at the natural abundance level. The ratios of the cis and trans isomers for several N-alkylformamides were also determined. Substituent effects on the 15N chemical shifts of formamides are compared with those of some other nitrogen-containing compounds. There is a consistent pattern of behavior of the one bond spin-spin coupling constants [1J(15NH)] wherein the trans isomers of N-alkylformamides are larger than those of the cis isomers.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 10
    ISSN: 0030-4921
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A useful and reliable procedure has been developed for the evaluation of the structures of organic nitriles using lanthanide shift reagents. The procedure is based on a statistical comparison of the experimental lanthanide induced shifts (LIS) with values which are predicted with the pseudocontact equation for a proposed structure. The experimental LIS are obtained by nonlinear regression analysis of the chemical shifts observed in the presence of varying amounts of the shift reagent, Eu(fod)3. The precise geometry for a proposed structure is obtained from molecular mechanics calculations. The LIS are then predicted with the pseudocontact equation using k=976.6 and a europium-nitrogen bond length of 2.50 Å. (Detailed arguments are presented in support of these values.) The carbon-nitrogen-europium array is approximately linear, although small distortions from linearity are both expected and observed.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
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