摘要:

Abstract1J(15N13C) values obtained from FT13C NMR spectra were measured for a number of15N‐enriched aniline derivatives and are found to exhibit varying degrees of dependence on the nature of the ring substituent. Theoretical calculations of1J(15N13C) values for representative members of the systems examined were made using INDO parameters and a ‘sum‐over‐states’ perturbation approach. The calculated coupling constants are generally in fair agreement with experimental values when the integral productsSN2(o)SC2(o) and (r−3)N(r−3)Chave values of 34.437 au−6and 2.770 au

ISSN:0030-4921    

DOI:10.1002/mrc.1270120102

出版商:John Wiley&Sons Limited    

年代:1979

数据来源: WILEY

摘要:

AbstractLes configurations d'une série de bicyclo[4.2.0]octanols sont déterminées par résonance magnétique nucléaire du proton en présence d'un réactif lanthanidique [Eu(dpm)3]. La détermination des paramètres intrinsèques des adduits formés entre les réactifs et ces substrats a permis de dégager un certain nombre de critères d'attribution des stéréochimies. De plus, cette étude met en évidence, contrairement à ce qui est généralement admis, que la constante de couplage vicinaletransentre les protons cyclobutaniques peut ětre supérieure à celle entre protonscis.Les attributions des configurations sont confirmées par une étude en13C. En se basant sur les résultats précédents, il est possible d'établir sans ambiguïté les configurations de tricyclo[6.4.0.02,7]dodécanols

ISSN:0030-4921    

DOI:10.1002/mrc.1270120103

出版商:John Wiley&Sons Limited    

年代:1979

数据来源: WILEY

摘要:

AbstractA series of variously substituted aminosilanes was investigated by15N NMR spectroscopy to obtain further information on the controversial problem of pπ‐dπ interaction in these systems. The15N NMR data are consistent with the13C and29Si results and suggest that the (p‐d)π backbonding is not negligible in these systems. The values of the15N chemical shifts and the13C parameters [δ13C andJ(13CH)] are discussed in terms of nitrogen lone‐pair delocalization and provide a good basis for explaining the variations of the29Si chemical shifts with the nature of the nitrogen atom sub

ISSN:0030-4921    

DOI:10.1002/mrc.1270120104

出版商:John Wiley&Sons Limited    

年代:1979

数据来源: WILEY

摘要:

AbstractThe complete1H NMR spectral analyses of quinoline and two of its derivatives (4,7‐dichloroquinoline and 8‐nitroquinoline) have been performed. All the long‐range coupling constants were determined both in magnitude and sign. In determining the signs the INDOR technique was very useful and successful, allowing the resolution of transitions as close as a few hundredths of a Hz. The signs of the inter‐ring coupling constants alternate with the number of intervening bonds, according to McConnell's rule, except the all‐trans6Jcouplings. A linear relationship has been found between the1H−1H and19F−19F inter‐ring coupling constants for which the spin polarization is transmitted almost exclusively via the π

ISSN:0030-4921    

DOI:10.1002/mrc.1270120105

出版商:John Wiley&Sons Limited    

年代:1979

数据来源: WILEY

摘要:

AbstractL'influence de l'autoassociation en phase liquide de 15 cétones sur la constante d'écran en RMN du carbone du carbonyle est déterminée. On montre que le terme de constante d'écran correspondant ne dépend que du moment dipolaire et du volume molaire de la cétone, que celle‐ci soit aliphatique ou alicyclique. La distance moyenne séparant les deux carbonyles dans le modèle d'association bimoléculaire où les deux dipǒles sont antiparallèles est évaluée. Cette distance croǐt avec l'encombrement des substituants de 3,1 Å pour l'acétone à 4,75 Å pour la cétone encombrée C(Et)3COC(Me2tBu) pour laquelle l'effet de l'autoasssociation est encore important. Les cyclanones s'inscrivent dans ce modèle mais présentent un effet d'autoassociation plus marqué que les cétones aliphatiques ayant

ISSN:0030-4921    

DOI:10.1002/mrc.1270120106

出版商:John Wiley&Sons Limited    

年代:1979

数据来源: WILEY

摘要:

AbstractFor the investigation of the barrier to rotation about the C(sp2)—C(aryl) bond in non‐planar pivalophenones five derivatives were prepared and their1H and13C NMR spectra assigned. Methyl and bromine groups in the 3‐position have opposite substituent effects on the chemical shifts of the1H and13C signals of Me2and Me4. The ΔG c≠values were determined from the coalescence temperatures of the signal splittings generated by the addition of optically active shift reagents. The accuracy of this method was estimated by using different signals of 3‐bromo‐2,4,6‐trimethylpivalophenone and by computer simulation of the line shape. A buttressing effect of substituents in the aromatic ring was observed. A change of the twist angle by the substitution of methyl by bromine in thetert‐butyl group was suggested in order to explain the changes in ΔG c≠

ISSN:0030-4921    

DOI:10.1002/mrc.1270120107

出版商:John Wiley&Sons Limited    

年代:1979

数据来源: WILEY

摘要:

AbstractCarbon‐13 NMR spectra of a variety of mono‐ and bicyclic β‐lactams have been measured and the chemical shifts of the ring carbon atoms have been assigned unambiguously. Effects of substituents on the chemical shifts of these carbons are also dis

ISSN:0030-4921    

DOI:10.1002/mrc.1270120108

出版商:John Wiley&Sons Limited    

年代:1979

数据来源: WILEY

摘要:

AbstractLa conformation des deux sulfoxydes du diaza‐8,10 dibenzyl‐8,10 thia‐4 bicyclo[5.3.0]décanone‐9 est étudiée par RMN. L'examen des constantes de couplage permet de conclure que ces deux sulfoxydes existent sous des conformations chaises à liaison

ISSN:0030-4921    

DOI:10.1002/mrc.1270120109

出版商:John Wiley&Sons Limited    

年代:1979

数据来源: WILEY

摘要:

AbstractCarbon‐13, carbon‐13 coupling constants and carbon‐13 chemical shifts have been measured in a series of phenyl substituted ethylenes and aromatics all doubly labelled with13C at the olefinic positions (α,β‐) or at neighbouring aromatic positions, tetraphenylcyclopentadienone labelled at the 3,4‐positions, and dichlorodiphenylmethane labelled at the α‐carbon. Signs of coupling constants were determined by the symmetrical double labelling (SDL) method. Coupling constants over as many as five bonds are reported. Two‐bond couplings between carbons in the aromatic skeleton belong to different classes according to the nature of the coupling path. The magnitudes of three‐bond coupling constants between such carbons correlate linearly with π‐bond orders and a separation of the δ‐ and π‐contributions is evident. The three‐bond couplings between the 2‐position in a phenyl substituent and the olefinic β‐position or a corresponding aromatic position depend on the out‐of‐plane twist of the phenyl ring and may lead to information about the twist angle. Contrary to findings with aromatic carbonyl compounds two‐ and three‐bond couplings to the α‐carbon in the present compounds are fairly constant. The reported data suggest that the signs of coupling constants over more than two bonds alternate in aromatic systems. Carbon‐13, carbon‐13 coupling constants in naphth

ISSN:0030-4921    

DOI:10.1002/mrc.1270120110

出版商:John Wiley&Sons Limited    

年代:1979

数据来源: WILEY

摘要:

AbstractCarbon‐13, carbon‐13 one‐bound and long‐range coupling constants are determined for anthracene and 9,10‐dihydroanthracene labelled in the 9,10‐positions, and for thiophthalic anhydride and phthalimide, labelled in both carbonyl groups. Relative signs are determined by the SDL method. Signs in naphthalene, anthracene and pyrene derivatives are discussed. The general trends observed in many aromatic compounds,3J|>|2J|>|4J| and2Jpositive,3Jpositive,4Jnegative are mostly confirmed. However, evidence suggests that two‐bond couplings between carbon atoms in the same ring in aromatic hydrocarbons

ISSN:0030-4921    

DOI:10.1002/mrc.1270120111

出版商:John Wiley&Sons Limited    

年代:1979

数据来源: WILEY