摘要:

AbstractThe structure of cyclic chlorinated hydrocarbons can be elucidated by the use of combined13C nuclear magnetic resonance and35Cl nuclear quadrupole resonance. The advantages obtained and the techniques employed with respect to some new and already investigated compounds, and typical shift values aiding studies of similar derivatives, are reported.

ISSN:0030-4921    

DOI:10.1002/mrc.1270140102

出版商:John Wiley&Sons Limited    

年代:1980

数据来源: WILEY

摘要:

AbstractNatural abundance13C NMR studies have been carried out on a series of organophosphorus compounds possessing PN bonds. For the first time aone‐bondtemperature‐dependent13C—31P nuclear spin coupling was observed for theP‐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 thetransorientation 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 that1J(PC) is

ISSN:0030-4921    

DOI:10.1002/mrc.1270140103

出版商:John Wiley&Sons Limited    

年代:1980

数据来源: WILEY

摘要:

AbstractNatural abundance13C 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 constant2J(PC) allowed determination of the orientation (axial) of the phosphorus‐substituted phenyl ring. Conclusions regarding cyclic conjugation in phospholes are pres

ISSN:0030-4921    

DOI:10.1002/mrc.1270140104

出版商:John Wiley&Sons Limited    

年代:1980

数据来源: WILEY

摘要:

Abstract13C NMR chemical shifts are reported for several alkyl or aryl amines, acetamides, diacetamides and ammonium and trimethylammonium salts. Substituent effects, determined with respect to chemical shifts of amino derivatives, are rationalized in terms of γ effects, steric interactions and for benzene derivatives, in terms of competition between inductive (σ1) and resonance (σR) effects. These perturbations can be used to assign chemical shifts of complex structures and to study certain chemical process

ISSN:0030-4921    

DOI:10.1002/mrc.1270140105

出版商:John Wiley&Sons Limited    

年代:1980

数据来源: WILEY

摘要:

AbstractAn essentially algebraic model for semi‐empirical calculations of13C chemical shicts of ketene imines and ketenes is presented which utilizes geometrical and non‐geometrical aspects of symmetry. In particular, emphasizing isoelectronic substitution as a generalized symmetry principle, it is shown that approximation functions for the description of13C chemical shifts of ketene imines and ketenes can be deduced from those used for the allenes, and that the parameters which are necessary for the calculations of the carbon resonances of the heterocumulenes are simply related to those used for the allenes. A comparison between calculated and experimental13C chemical shifts of complex ketene imines and ketenes demonstrates the relevance of the suggested mo

ISSN:0030-4921    

DOI:10.1002/mrc.1270140106

出版商:John Wiley&Sons Limited    

年代:1980

数据来源: WILEY

摘要:

AbstractThe NMR spectra of acetone, adamantanone and 1‐adamantanecarbonitrile have been studied in the presence of Eu(fod)3in various solvents. A substantial solvent dependence is found for the association constants between shift reagent and substrate. The magnitude of the association constants is correlated with solvent polarity, and a tenfold decrease inK1is observed upon changing from carbon tetrachloride to the more polar dichloromethane. Only a very small solvent dependence is observed for the bound shifts. The relative bound shifts (and therefore the structures of the LS complexes) are found to be solvent independent. The small solvent dependence of the absolute magnitude of the bound shifts for the LS complexes is suggested to result from experimental error

ISSN:0030-4921    

DOI:10.1002/mrc.1270140107

出版商:John Wiley&Sons Limited    

年代:1980

数据来源: WILEY

摘要:

Abstract‘Unexpected’ second‐order effects encountered in proton‐coupled13C NMR spectra where relative proton shifts are large compared to proton‐proton coupling constants are illustrated. The observed phenomenon is explained, with reference to the ABX spin system as a model, as being due to the near equality of the relative proton shift, in frequency units, to the difference between one‐bond and long‐range13CH couplings. The effect may be removed by a change in operating field strength or addition of a

ISSN:0030-4921    

DOI:10.1002/mrc.1270140108

出版商:John Wiley&Sons Limited    

年代:1980

数据来源: WILEY

摘要:

AbstractLanthanide induced shifts (LIS) were measured for four dimethylamides, RCON(CH3)2, and four monomethyl amides, RCONHCH3, R  H, CH3, CF3and CCl3, using Eu(fod)3in CCl4and benzene (C6D6) solution. Structural correlations for HCON(CH3)2and CH3CON(CH3)2in both solvents yield a preferred binding site for the Eu(fod)3on one of the lone‐pair orbitals of the oxygen atom, with a probable site of secondary importance on the other lone‐pair orbital. Thecis vs transisomers of HCONHCH3and CH3CONHCH3exhibit remarkably different chemical shift behavior upon addition of Eu(

ISSN:0030-4921    

DOI:10.1002/mrc.1270140109

出版商:John Wiley&Sons Limited    

年代:1980

数据来源: WILEY

摘要:

AbstractSchiff base formation by condensation of pyridoxal phosphate or pyridoxal with octopamine in aqueous or methanolic medium was investigated by13C NMR. Enolimine forms are favoured in methanolic solution, whereas in aqueous solution the predominant ketoenamine forms show a hydrogen bond between the iminium proton and the C‐3‐O−phenolate anion of the pyridoxal phosphate. The addition of Cu++ions is consistent with the hypothesis of chelation of Cu++by the nitrogen of the aldimine function and the phenolate function of pyridoxal phos

ISSN:0030-4921    

DOI:10.1002/mrc.1270140110

出版商:John Wiley&Sons Limited    

年代:1980

数据来源: WILEY

摘要:

AbstractLanthanide salt induced shifts in the NMR spectra of phenols are found to increase in basic media. The empirical relationships governing the interaction of phenolic hydroxyl groups, reported earlier, still apply.

ISSN:0030-4921    

DOI:10.1002/mrc.1270140111

出版商:John Wiley&Sons Limited    

年代:1980

数据来源: WILEY