摘要:

AbstractAnalysis of the proton NMR spectra of Pr1PCINMe2indicates magnetic non‐equivalence of the methyl groups due to the adjacent asymmetric phosphorus atom. High temperatures, or the addition of chloride ion, induce an exchange reaction with inversion of configuration at phosphorus. The corresponding fluoride is configurationally stable at high temperatures. The compounds CICH2PXNR2(X = Cl, F; R = Me, Et) have non‐equivalent protons in the chloromethyl group. The two HCP coupling constants in the chlorides of this series are of opposite sign, whereas in the fluorides they are of the same s

ISSN:0030-4921    

DOI:10.1002/mrc.1270020202

出版商:John Wiley&Sons Limited    

年代:1970

数据来源: WILEY

摘要:

AbstractL'inversion de l'azote pyramidal d'une amine peut ětre ralentie, de manière calculable, par une protonation presque totale dans un milieu d'acidité variable. Un traitement théorique complet permet de calculer sa vitesse à partir de la durée de vie moyenne du sel d'ammonium déterminée par résonance magnétique nucléaire. On peut ainsi fixer les conditions de validité de la formule approchée de Saunders et Yamada: la vitesse de protonation de l'amine doit ětre largement supérieure à la vitesse d'inversion; la vitesse de déprotonation du sel d'ammonium peut, par contre, ětre quelconque. Au cas où l'in version se produit entre deux molécules isomères différentes, ce traitement fournit également le rapport, à l'équilibre, des concentrations des sels

ISSN:0030-4921    

DOI:10.1002/mrc.1270020203

出版商:John Wiley&Sons Limited    

年代:1970

数据来源: WILEY

摘要:

AbstractCarbon‐13 spectra of 59 α,β‐unsaturated carboxylic acids have been measured. Large differential shieldings of ethylenic carbons in thecisandtransisomers of acrylic acid derivatives were found (altogether 15 isomericZ‐ andE‐pairs of acids were investigated). The origin of differential shieldings is complex and both molecular ground states as well as changes in excited states appear to be involved. All measured13C chemical shifts can be described by additive parameters that provide a straightforward new technique by which structural assignments can be made for a wide variety of isomeric mono‐, di‐ and tri‐ substituted α,β

ISSN:0030-4921    

DOI:10.1002/mrc.1270020204

出版商:John Wiley&Sons Limited    

年代:1970

数据来源: WILEY

摘要:

AbstractThe PMR spectrum of trisformamidomethane in dimethyl sulphoxide‐d6and hexamethyl‐phosphortriamide has been explained by postulating four major structures in solution: two rotamers and two structural isomers, all of which are stabilized by intramolecular hydrogen bonding to form six membered rings. The spectrum in trifluoroacetic acid is also descri

ISSN:0030-4921    

DOI:10.1002/mrc.1270020205

出版商:John Wiley&Sons Limited    

年代:1970

数据来源: WILEY

摘要:

AbstractDipeptides of different amino acids have been studied by NMR in aqueous solutions at different pH values. The results obtained are discussed in terms of the different contributions to the chemical shift of the α‐CH proto

ISSN:0030-4921    

DOI:10.1002/mrc.1270020206

出版商:John Wiley&Sons Limited    

年代:1970

数据来源: WILEY

摘要:

AbstractDans les phosphinates d'alcoyle RPH(O)OR′, la présence de l'atome de phosphore asymétrique induit des inéquivalences magnétiques au niveau de protons ou groupes méthyles géminés. Si le reste alcoxy OR' comporte lui aussi un atome de carbone asymétrique, la résonance magnétique de31P et de1H, permet de mettre en évidence la formation des deux diastéréoisoméres attendus, en proportions égales.Par ailleurs, la résonance magnétique de31P révèle le caractère de centre de pseudo‐asymétrie de l'atome de phosphore dans les esters phosphoneux de l'a

ISSN:0030-4921    

DOI:10.1002/mrc.1270020207

出版商:John Wiley&Sons Limited    

年代:1970

数据来源: WILEY

摘要:

AbstractPMR spectral parameters are reported for the isomeric trithienyl carbonium ions. The low field shifts, relative to the corresponding carbinols, are discussed in relation to the delocalization of the positive charge into the thiophene ring bonded in position 2 or 3. A linear correlation is found between chemical shifts and π‐charge densities and the proportionality constant is higher than that previously found for benzene derivatives. Vicinal coupling constants in these systems are satisfactorily in agreement with the corresponding calculated π‐bond

ISSN:0030-4921    

DOI:10.1002/mrc.1270020208

出版商:John Wiley&Sons Limited    

年代:1970

数据来源: WILEY

摘要:

AbstractProton magnetic resonance spectra of a series of alkyl(oxinato)tin(IV) complexes, alkyl(oxinato)thallium(III), dimethylbis(oxinato)lead(IV), 8‐methoxyquinoline, 2‐methyl‐8‐hydroxyquinoline and 8‐hydroxyquinoline were studied. The indirect spin‐spin coupling constantsJ23,J34andJ24of the oxinato ligand in the alkyl(oxinato)tin(IV) complexes and of 8‐methoxyquinoline were found to be 4.4 ± 0.2, 8.3 ± 0.2 and 1.7 ± 0.2 Hz, respectively. When the interaction between tin and nitrogen in the oxinato ligand is not strong as in trialkyl(oxinato)tin(IV), the resonance of the 2‐proton of the ligand shifts to high magnetic field relative to that of 8‐methoxyquinoline, but in the case of the strong interaction, as in dimethyl(oxinato)halogenotin(IV), the resonance is shifted to low magnetic field. The 4‐proton signals, however, shift monotonously to low magnetic field with increasing interaction. The behaviour of the 2‐proton signals was explained by a paramagnetic anisotropic effect of a nitrogen lone pair of the oxinato ligand and an intramolecular electric field effect and that of the 4‐proton by the latter effect. By comparing the change of the δ‐values of the 2‐, 3‐ and 4‐protons of the alkyl(oxinato)tin(IV) complexes and those of 8‐hydroxyquinoline by altering the solvents, from methylene chloride to benzene, it was found that the electron density around the 2‐carbon is reduced in the complexes c

ISSN:0030-4921    

DOI:10.1002/mrc.1270020209

出版商:John Wiley&Sons Limited    

年代:1970

数据来源: WILEY

摘要:

AbstractThe1H magnetic resonance spectrum of the title compound has been completely analysed, using 60, 100 and 220 MHz spectrometers. The values of the chemical shifts and coupling constants obtained confirm the proposed structure and also provide information on the conformation. The molecule is slightly boat‐shape

ISSN:0030-4921    

DOI:10.1002/mrc.1270020210

出版商:John Wiley&Sons Limited    

年代:1970

数据来源: WILEY

摘要:

AbstractEn étudiant par RMN cinq anilides de formule généraleen milieu acide, les auteurs ont mis en évidence la protonation de l'atome d'azote de l'ion amidonium fo

ISSN:0030-4921    

DOI:10.1002/mrc.1270020211

出版商:John Wiley&Sons Limited    

年代:1970

数据来源: WILEY