摘要:

AbstractThe effectiveness and utility of the combined use of the interactive computer program GENOA and two‐dimensional double quantum coherence13C NMR spectroscopy to solve structure elucidation problems are demonstrated with three examples. The substructural information inferred from the1H NMR and13C NMR spectra was insufficient to identify the structures of the example compounds. However, with the additional substructural information available from the two‐dimensional NMR experiment (which identifies directly bonded carbon atoms), the problems were solved in an extremely efficient man

ISSN:0030-4921    

DOI:10.1002/omr.1270210702

出版商:John Wiley&Sons Limited    

年代:1983

数据来源: WILEY

摘要:

AbstractThe hydrogen NMR spectra of 1,1‐dimethyl‐, 1,1‐dichloro‐, 1,1‐dimethoxy‐ and 1,1‐difluoro‐silacyclobutane have been analysed. A new correlation NMR instrumental technique has been used to obtain spectral parameters with very

ISSN:0030-4921    

DOI:10.1002/omr.1270210703

出版商:John Wiley&Sons Limited    

年代:1983

数据来源: WILEY

摘要:

AbstractThe1H and13C NMR spectra of a series of 1,3,2‐dioxarsolanes have been obtained at 2.1 T and some at 9.4 T. The chemical shifts and spin‐spin coupling constants have been obtained from complete spectral analyses of the1H and proton‐coupled13C spectra. The spectral data are interpreted on the basis of two rapidly interconverting half‐chair conformers with a pseudoaxial substituent at arsenic. Unique assignment ofsyn/anti or cis/transgeometries have been made from1H or13C NMR spectroscopy alone. The syn andtransisomers of the 4‐methyl‐ and 4,5‐dimethyl‐1,3,2‐dioxarsolanes, respectively, appear to be conformationally biased towards the forms with pseudoequatorial methyl groups. The general trends in the geminal and vicinal1H1H and13C1H coupling constants are interpreted in terms of stereospecific, electronegativity and lone‐pair effects of the oxygen heteroatoms and conformational factors. The NMR data on the 1,3,2‐dioxarsolanes are discussed with reference to related 1,3‐dithoxa‐ and 1,3‐dithia‐ five‐membered rings w

ISSN:0030-4921    

DOI:10.1002/omr.1270210704

出版商:John Wiley&Sons Limited    

年代:1983

数据来源: WILEY

摘要:

AbstractThe13C NMR chemical shifts in CDCI3for eight cyclic sulphites, chlorinated at C‐5, are reported. The α‐and β‐deshielding effects and the γ‐shielding effects for the chlorine substituent are compared with similar effects in the 1,3‐dioxane series and with the effects arising from methyl groups in the sulphite series. The study of two conformational equilibria shows that it is difficult to use13C NMR spectroscopy for the conformational analysis of cyclic sulphites because of the frequent participation of twist forms, with 1,4‐ and 2,5‐axes, to

ISSN:0030-4921    

DOI:10.1002/omr.1270210705

出版商:John Wiley&Sons Limited    

年代:1983

数据来源: WILEY

摘要:

AbstractThe13C and1H chemical shifts of the ferrocene moiety, as well as the carbonyl carbons and styrene moiety, of substituted 2‐benzylidene[3]ferrocenophane‐1,3‐diones have been assigned. Correlations of13C substituent chemical shifts of both carbonyl carbons with the Hammett constants have been found, and the effect of the transmission of substituent effects on these chemical shifts through the styrene moiety is discussed. An explanation is given for the different sensitivities of the carbonyl carbon chemical shifts to the electronic effect of substituents in mono‐ and dicarbonyl deri

ISSN:0030-4921    

DOI:10.1002/omr.1270210706

出版商:John Wiley&Sons Limited    

年代:1983

数据来源: WILEY

摘要:

AbstractJ‐modulation of13C spin echo signals is used to develop a strategy for the analysis of deuterated compounds. On the basis of1J(13C2H) and an experimental set‐up that allows both2H and1H decoupling,13C subspectra for various groups can be produced. The application of difference methods facilitates the analysis and, finally, leads to the identification of CD, CD2, CD3, CHD, CHD2and CH2D gro

ISSN:0030-4921    

DOI:10.1002/omr.1270210707

出版商:John Wiley&Sons Limited    

年代:1983

数据来源: WILEY

摘要:

Abstract13C NMR chemical shifts and13C31P couplings are reported for 18 phosphol‐3‐ene 1‐oxides and 18 corresponding sulfides. The effects of methyl substitution at positions 3 and 4 on the carbon shifts have been systematically explored and substituent parameters derived. One bond couplings from phosphorus to C‐2 and C‐5 have been related to the sum of the exocyclic substituent group electronegativities (covalent boundary potent

ISSN:0030-4921    

DOI:10.1002/omr.1270210708

出版商:John Wiley&Sons Limited    

年代:1983

数据来源: WILEY

摘要:

AbstractThe13C NMR signals of some mono‐ and disubstituted aryl compounds were assigned by means of empirical additive substituent parameters and information taken from fully coupled spectra. This assignment was compared with that obtained with the help of the method of automatic assignment of the signals based on the linear relationship between13C chemical shift and charge density. The results show that in the cases of XR substituents (X = O, NH and R = H, CH3, CH2CH2OH) a good correlation is observed and the automatic assignment is correct. In contrast, in the cases of CH2CH2Y substituents (Y = OH, NH2, Cl) a worsening of the correlation is observed and the automatic assignment is not correct.It is suggested that for compounds with a preliminarily known assignment, the automatic assignment can serve as an additional criterion for the reliability of the linear relationship between13C chemical shift and charge dens

ISSN:0030-4921    

DOI:10.1002/omr.1270210709

出版商:John Wiley&Sons Limited    

年代:1983

数据来源: WILEY

摘要:

AbstractPrincipal components analysis was applied to the13C and15N chemical shift data on a series of fifteen 1‐(para‐substituted‐phenyl)‐3‐acetyl‐3‐methyltriazenes. It was found that the halogen‐substituted triazenes formed a class, based on substituent effects, which was different from the remaining eleven triazenes. A one‐component model described the halogen class, whereas a two‐component model was necessary for a description of the second class. In the second class, substituents tended to cluster to form groups depending on their e

ISSN:0030-4921    

DOI:10.1002/omr.1270210710

出版商:John Wiley&Sons Limited    

年代:1983

数据来源: WILEY

摘要:

AbstractThe13C NMR chemical shifts of a series of phosphorinanes and the corresponding 4‐phosphorinanones have been evaluated using ‘double difference’ plots. Most of the compounds fit the same linear relationships for the carbons alpha and beta to the hetera group previously found for the analogous sulfur, oxygen and nitrogen six‐membered heterocycles, suggesting that these phosphorus compounds possess similar chair conformations. For the carbons gamma to the hetera group, the plots suggest that there are transannular interactions between the trivalent phosphine groups and the carbonyl group, similar to that previously observed for the sulfide group. In these 1‐hetera‐4‐cyclohexanones, transannular interactions appear whenever a lone pair of electrons on a second‐row heteroatom is present in the proper conformation for interaction with the

ISSN:0030-4921    

DOI:10.1002/omr.1270210711

出版商:John Wiley&Sons Limited    

年代:1983

数据来源: WILEY