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  • Analytical Chemistry and Spectroscopy  (5)
  • 1
    Electronic Resource
    Electronic Resource
    13C nuclear magnetic resonance of organophosphorus compounds XIFor Part X see Ref. 1. - aminophosphines (1980)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 14 (1980), S. 8-13 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Natural abundance 13C NMR studies have been carried out on a series of organophosphorus compounds possessing P—N bonds. For the first time a one-bond temperature-dependent 13C - 31P nuclear spin coupling was observed for the P-phenyl carbons in bis(N,N-dibenzylamino)phenylphosphine (0-9 Hz) and bis(N,N-diethylamino)phenylphosphine (0-2 Hz). This temperature-dependent behavior can be rationalized in terms of free rotation about the phenyl phosphorus bond with concomitant hindered rotation about the P—N bonds. A conformational preference for the nitrogen and phosphorus lone pairs to exist in the trans orientation is indicated. In the similarly substituted 5-membered heterocyclic ring compound, 1,3-dimethyl-2-phenyl-1,3-diazaphospholidine, the phenyl one-bond coupling increases to (-) 42.1 Hz and becomes temperature independent. These data suggest that 1J(PC) is very responsive to electronic effects.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270140103
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  • 2
    Electronic Resource
    Electronic Resource
    13C nuclear magnetic resonance of organophosphorus compounds XIIFor Part XI see G. A. Gray and J. H. Nelson, Org. Magn. Reson. 14, 476 (1980). - phospholes and dibenzophospholes (1980)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 14 (1980), S. 14-19 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Natural abundance 13C NMR studies have been carried out on a series of phospholes and dibenzophospholes. The systems were analyzed with respect to ring conformation and substituent orientation. Assignments of all chemical shifts have been made by investigating partially relaxed inversion-recovery spectra and by investigating the field dependence of the spectra. A nonplanar (6-membered central ring) tricyclic phosphine was also examined. Here, the value of the two bond coupling constant 2J(PC) allowed determination of the orientation (axial) of the phosphorus-substituted phenyl ring. Conclusions regarding cyclic conjugation in phospholes are presented.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270140104
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  • 3
    Electronic Resource
    Electronic Resource
    Multinuclear two-dimensional NMR: Assignments of natural abundance polypeptide 13C, 1H and 15N chemical shifts and demonstration of isomer interconversion (1983)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 21 (1983), S. 111-118 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The polypeptide carbobenzoxy-glycyl-L-prolyl-L-leucyl-L-alanyl-L-proline (0.2 M in DMSO-d6) was investigated using 13C, 1H and 15N NMR in natural abundance at 4.7 tesla. The existence of cis-trans-Gly-Pro and -Ala-Pro bonds permits up to four isomers, and all four were observed (in a 60:30:7:3 ratio). 13C shifts of the proline β-CH2 resonances are consistent only with the 60% form being trans-trans. The 30% form is either trans-cis or cis-trans (order as above) and was tentatively assigned as cis-trans on the basis of relaxation behavior. Refocused INEPT studies aided the 13C assignments. The 15N data were obtained using both NOE and INEPT excitation, with signals evident for the three major isomers. The spectra were analysed by starting from the 13C data, which were assigned based on known regularities in peptide spectra. A 13C—1H heteronuclear two-dimensional chemical shift correlation experiment allowed direct assignment of proton shifts for major and minor isomers. The NH proton shifts were assigned by running a homonuclear two-dimensional chemical shift correlation experiment and noting the correlation with the previously assigned α-CH protons. The 15N resonances were then assigned from a 15N—1H heteronuclear two-dimensional chemical shift correlation experiment, relating the 15N signals directly to the NH proton resonances. Isomer interconversion between the two major isomers was demonstrated by performing a magnetization transfer homonuclear 2D experiment. Off-diagonal intensity was noted relating the major and minor isomer alanine NH proton, as well as for the major and minor isomer leucine NH protons.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/omr.1270210207
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  • 4
    Electronic Resource
    Electronic Resource
    13C and 15N nuclear magnetic resonance studies of selected tetrazoles: Relationships with the chemistry of tetrazoles (1986)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 24 (1986), S. 984-994 
    Details
    ISSN: 0749-1581
    Keywords: 13C NMR ; 15N NMR ; Sodium tetrazolates ; tetrazoles ; bitetrazoles ; cobalt(III)tetrazole complexes ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Natural abundance 13C and 15N nuclear magnetic resonance studies have been carried out on a series of sodium tetrazolate salts, 1,5- and 2,5-disubstituted tetrazoles, bitetrazoles, and cobalt(III) tetrazolate complexes of the type (PBu3n)Co(DH)2(5-R-tetrazolate), where DH is the monoanion of dimethylglyoxime. The 15N chemical shifts have been analysed with respect to structure, substituent effects, electron density as determined by molecular orbital calculations, Brønsted acidity, Lewis basicity and nucleophilicity of the nitrogen atoms in the ambidentate tetrazoles.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260241111
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  • 5
    Electronic Resource
    Electronic Resource
    1H and 13C nuclear magnetic resonance of phenyldibenzophosphole and derivatives: Complete assignment using two-dimensional J-resolved and shift correlation methods (1987)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 25 (1987), S. 774-779 
    Details
    ISSN: 0749-1581
    Keywords: 1H and 13C NMR ; Phenyldibenzophospholes ; assignment, computer simulation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Proton and 13C NMR parameters have been determined for phenyldibenzophosphole and its oxide, sulfide, selenide and W(CO)5 complex from high-resolution one- and two-dimensional (COSY, HETCOR and 2DJ) experiments at 4.7, 7.1 and 9.4 tesla. Assignments of chemical shifts and coupling constants have been made and verified by computer simulation of the proton spectra. The data are discussed in relation to the geometry and electron density at phosphorus and the diamagnetic anisotropy of the W(CO)5 group.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260250908
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