摘要:

AbstractCarbon chemical shifts of cyclic dimethylene compounds were determined and interpreted. It is suggested that steric compression leads to additional shielding of theexo‐methylene group, the chemical shifts of this group being a useful measure of the amount of steric hindranc

ISSN:0030-4921    

DOI:10.1002/mrc.1270090302

出版商:John Wiley&Sons Limited    

年代:1977

数据来源: WILEY

摘要:

AbstractUne étude par spectroscopie13C d'une série de thiourées est réalisée. Des informations sont obtenues sur l'équilibre conformationnel. Une rotation empěchée des groupestert‐butyle est mise en évidence. Les effets de substituant son

ISSN:0030-4921    

DOI:10.1002/mrc.1270090303

出版商:John Wiley&Sons Limited    

年代:1977

数据来源: WILEY

摘要:

AbstractIt is found that the basic form of the 3,3‐dimethyl‐3‐sila‐1‐heterocyclohexane family (heteroatom X = O, NMe, S, Se, Te, SiMe2, SiCl2) is the chair, having ring torsion angles in the aliphatic region tending to be somewhat more puckered (up to 7°) than in cyclohexane, except next to Si when the other heteroatom is relatively small. The 5‐tertiarybutyl‐, 6‐methyl‐ and 2‐phenyl derivatives are all anancomeric, except for the latter two derivatives when X = NMe. A 5‐tertiarybutyl group causes an additional deformation, e.g. an increased puckering of the aliphatic C‐4C‐5C‐6 region (buttressing effect). Other1H n.m.r. features are discussed in detail, and the behaviour of the 3‐sila‐1‐heterocyclohexanes is compar

ISSN:0030-4921    

DOI:10.1002/mrc.1270090304

出版商:John Wiley&Sons Limited    

年代:1977

数据来源: WILEY

摘要:

AbstractDurch Cyclisierung von 3‐Dibenzofurylthioharnstoff unter Bedingungen der Hungershoff‐Reaktion entsteht ein Isomers, das die lineare Struktur1besitzt. Zur Entscheidung dienten die1H‐NMR‐ und13C‐NMR‐Spektren der zwei isomeren Aminobenzofurobenzothiazole (1und3), aufgenommen bei 220 MHz, 60 MHz und 22,62 MHz. Die magnetischen Parameter ergaben sich teils durch Spektreninterpretation nach den der der Regeln ersten Ordnung, teils durch Spektrensimulation mit Hilfe von LAOCOON 3; eine Zuordnung der Resonanzen gelang durch den Vergleich der chemischen Verschiebungen und Kopplungskonstanten mit denen der Stammkörper Dibenzofuran (4a) und 2‐Aminobenzthiazol (5c). Soweit die Zuordnungen der Stammkörper selbst unbekannt waren oder allein durch Analogieschluß erfolgten, sind sie durch experimentelle Kriterien bestimmt worden, wie durch Deuterium‐Substitution oder durch Untersuchung der Veränderungen der chemischen Verschiebungen

ISSN:0030-4921    

DOI:10.1002/mrc.1270090305

出版商:John Wiley&Sons Limited    

年代:1977

数据来源: WILEY

摘要:

AbstractThe13C spectra of several conjugated diynols and symmetrical diynediols, represented by the parent compounds 2,4‐pentadiyn‐1‐ol and 2,4‐hexadiyne 1,6‐diol, respectively, have been determined and individual resonances assigned. The data show close similarities to those observed with related 2‐yn‐1‐ols. Mutual shielding interactions between the conjugated triple bonds result in upfield shifts of both the α‐ and β‐sp‐hybridized carbon nuclei byc.4.5 ppm, relative to the ethynyl prototype. The deshielding γ OHπeffect induced by the hydroxyl group at the interior sp‐hy

ISSN:0030-4921    

DOI:10.1002/mrc.1270090306

出版商:John Wiley&Sons Limited    

年代:1977

数据来源: WILEY

摘要:

AbstractDivers calculs, dont celui utilisant la méthode des perturbations finies avec des fonctions d'onde INDO, ont été effectués pour calculer la valeur du couplage3J(1HNN1H) dans les hydrazides en fonction de l'angle dièdre. Les résultats expérimentaux (1H,13C,15N) sont examinés à la lumière de ces calculs. Le premier exemple d'un couplage2J(1H

ISSN:0030-4921    

DOI:10.1002/mrc.1270090307

出版商:John Wiley&Sons Limited    

年代:1977

数据来源: WILEY

摘要:

AbstractProton distance ratios for pyridine, benzonitrile and 4‐cyanopyridine have been obtained in a potassium laurate lyotropic mesophase and compare favorably with values for different thermotropic solvents. Order matrices indicate a preference for theC2vsymmetry axis of the molecules to be aligned along the optical axis of the mesophas

ISSN:0030-4921    

DOI:10.1002/mrc.1270090308

出版商:John Wiley&Sons Limited    

年代:1977

数据来源: WILEY

摘要:

AbstractThe geminal anisochronism (Δδ) of the isopropyl methyl groups in the1H n.m.r. spectrum ofN‐[2‐methyl‐1‐(1‐naphthyl)propylidene]benzylamine showed unusually pronounced temperature and solvent effects. It is noteworthy that both accidental and dynamic equivalences were encountered. Slow rotation around the naphthyl–imino bond is responsible for the diastereotopic nature of the geminal methyl groups, and possible reasons for the temperature and solvent effects are considered. Surprisingly, the temperature effect was not reflected in the13C anisochronism of the methyl carbon nuclei. These observations underline the need for caution in drawing firm conclusions from variable temperature studies on geminal no

ISSN:0030-4921    

DOI:10.1002/mrc.1270090309

出版商:John Wiley&Sons Limited    

年代:1977

数据来源: WILEY

摘要:

AbstractSubstituent effects upon3J(FF) are demonstrated to be additive, and a previous analysis of4J(FF) and5J(FF) in polysubstituted fluorobenzenes is updated.

ISSN:0030-4921    

DOI:10.1002/mrc.1270090310

出版商:John Wiley&Sons Limited    

年代:1977

数据来源: WILEY

摘要:

AbstractProton and deuterium n.m.r. measurements in acetylacetone and 3,3‐d2‐acetylacetone are reported. Deuterium‐isotope effects on chemical shifts and keto–enol equilibria as a function of concentration in the two solvents triethylamine and pyrrole are determined. A strong solvent concentration dependence ford‐isotope effects is observed in triethylamine; in pyrrole no dependence is obtained. The results are interpreted in terms of an equilibrium between the symmetrical (C2v) and asymmetrical (Cs) enolic forms in acetylacetone. The usefulness of2H n.m.r. for the study of exchange processes is dem

ISSN:0030-4921    

DOI:10.1002/mrc.1270090311

出版商:John Wiley&Sons Limited    

年代:1977

数据来源: WILEY