摘要:

AbstractThe conformation of some 2‐σ‐1,3,2‐dioxaphospholanes (σ=OAlkyl, CI) is studied. The determination of the2J(POC) and3J(POCC) coupling constants, which are influenced by the bulk of the alkoxy group, is a means of obtaining information about the rotation around the POR bond, which is dependent on steric interactions between the phosphorus lone pair, the alkoxy group and the substituents on the ring. When σ is atert‐butoxy group, a direct ‘through‐space’ interaction is found between the phosphorus atom and one of the primary carbons of the OR group. If there is no substituent on the ring, the31P chemical shifts are little affected by changes in OR; a diamagnetic effect is observed, however, in the case of thetert‐butoxy group which is enhanced for the 4,4,5,5‐t

ISSN:0030-4921    

DOI:10.1002/mrc.1270130502

出版商:John Wiley&Sons Limited    

年代:1980

数据来源: WILEY

摘要:

AbstractAn important13C NMR shielding effect on carbons bearing a heavy chalcogen is demonstrated. This effect is parallel to that induced by iodine, but to a lesser extent. For acyclic compounds and for partially saturated heterocycles, there is an excellent linear correlation between the13C chemical shifts of carbons bearing a chalcogen and carbons bearing a halogen atom in the corresponding compound. The linearity of the relationship is less satisfactory with heteroaromatic compounds.

ISSN:0030-4921    

DOI:10.1002/mrc.1270130503

出版商:John Wiley&Sons Limited    

年代:1980

数据来源: WILEY

摘要:

AbstractThe changes in chemical shift induced by isomerization for all the ring protons of theZ‐ andE‐5,5‐dimethyl‐2‐cyclohexenylidene acetonitriles depend only on the through‐space effects of the cyano group. The configurational assignments were made taking into consideration the anisotropic and electric field effects, either separately or together. In the first case, the total effects are ΔXCNT=−14.7×10−6cm3mol−1and bμCNT=14.7×10−30cm3, respectively. The second approach allows the estimation of the values ΔXCN=−4.9 × 10−6cm3mol−1and bμCN=9.8 × 10−3cm3, reflecting the combined contributions of magnetic anisotropy and

ISSN:0030-4921    

DOI:10.1002/mrc.1270130504

出版商:John Wiley&Sons Limited    

年代:1980

数据来源: WILEY

摘要:

AbstractThe composition of the mixture from the reaction of the basic amino acids ornithine or lysine with pyridoxal‐5′‐phosphate was investigated in D2O by1H NMR and was found to be dependent on pH, α attack being favoured at acid pH and ω attack in basic so

ISSN:0030-4921    

DOI:10.1002/mrc.1270130505

出版商:John Wiley&Sons Limited    

年代:1980

数据来源: WILEY

摘要:

Abstract13C NMR spectroscopic data are reported for thes‐triazolo‐as‐triazinones of five isomeric series. Comparison of their13C chemical shifts and CH coupling constants allows the determination of the type of ring junction of the two heterocycles, as well as the predominant tautomeric form in each s

ISSN:0030-4921    

DOI:10.1002/mrc.1270130506

出版商:John Wiley&Sons Limited    

年代:1980

数据来源: WILEY

摘要:

AbstractThe natural abundance15N NMR spectra of glycylglycine and alanylalanine derivatives with various N‐ or O‐protecting groups were measured in dimethyl sulphoxide, pyridine and fornic acid. The nitrogens directly attached to the protecting group have chemical shifts relative to NO3−in the range −220 to −358 ppm. The influence of the amino end group on the next peptide nitrogen (Gly‐Gly bond) amounts to, at most, 1.7 ppm. The influence of the O‐protecting group is also weak (Δ δ⩽2 ppm), but strongly depende

ISSN:0030-4921    

DOI:10.1002/mrc.1270130507

出版商:John Wiley&Sons Limited    

年代:1980

数据来源: WILEY

摘要:

AbstractAssignment of the carbon resonances in nine derivatives ofN‐hydroxybenzotriazole has been carried out. The13C NMR method enables tautomericN‐hydroxy andN‐oxide and isomericO‐ andN‐acyl structures to be identified. In DMSO, the predominant tautomer ofN‐hydroxybenzotriazole was found to be theN‐hydroxy form. The structure of the benzoate and methyl and phenyl carbonate esters were likewise established, but for the two latter compounds, hydrolysis of the equilibratingO‐ andN‐acyl isomers imposed some limitations on the usefulness

ISSN:0030-4921    

DOI:10.1002/mrc.1270130508

出版商:John Wiley&Sons Limited    

年代:1980

数据来源: WILEY

摘要:

AbstractCarbon‐13 NMR spectra of solid polycrystalline bicyclo[3.3.1]nonan‐9‐one and adamantanone have been measured at 315K. The relatively narrow13C linewidths observed for these solids, together with measured spin‐lattice relaxation times, indicate that both these solids are orientationally disordered. Observed13C chemical shifts of solid bicyclo[3.3.1]nonan‐9‐one indicate a twin‐chair conformation for the two cycloh

ISSN:0030-4921    

DOI:10.1002/mrc.1270130509

出版商:John Wiley&Sons Limited    

年代:1980

数据来源: WILEY

摘要:

Abstract13C NMR spectra of six kawa‐pyrones (styryl α‐pyrones) have been assigned. The assignments are based on the splitting pattern in the coupled spectra, comparison of the chemical shifts with those of model compounds and by application of additivity relationships. The13C NMR of styrene was also reinvestig

ISSN:0030-4921    

DOI:10.1002/mrc.1270130510

出版商:John Wiley&Sons Limited    

年代:1980

数据来源: WILEY

摘要:

AbstractThe chemical shifts at infinite dilution and coupling constants of somemeta‐substituted nitrobenzenes (C6H4NO2X) were determined in CDCI3solutions (X = CHO, OCH3, CI, Br, NH2, NO2) and in CCI4solutions (X = OCH3, CI, Br). Substituent effects on the chemical shift of themeta‐hydrogen are analysed in terms of existing theor

ISSN:0030-4921    

DOI:10.1002/mrc.1270130511

出版商:John Wiley&Sons Limited    

年代:1980

数据来源: WILEY