摘要:

AbstractFrom the study of the1H n.m.r. spectral parameters of differently functionalized 1,4‐diacetoxy‐2,3‐dialkylcyclopentanes it is shown that the magnitude of those parameters allows an easy configurational assignment within a set of four different configura

ISSN:0030-4921    

DOI:10.1002/mrc.1270090702

出版商:John Wiley&Sons Limited    

年代:1977

数据来源: WILEY

摘要:

AbstractDie Vorhersage der chemischen Verschiebung für1H,13C und19F Atome wird auf der Basis von SCF‐LCGO‐MO‐rechnungen versucht. Der 〈1/R〉 Erwartungswert als Maß für den Diamagnetismus wird exakt berechnet, der Paramagnetismus durch 〈1/R3〉 sowie Werte der Ladungsbindungsordnung angenähert. Der Einfluß der Nachbaratome wird über die Elektronendichtep(r) auf einem kugelförmigen Raster ermittelt. Die Terme ermöglichen in Form eines linear funktionalen Ansatzes die Berechnung von1H und13C Verschiebungen an Fluoracetylen, Fluoräthylen und Fluoräthan wobei die Regressionsrechnung für1H einen Standardfehler von 0,39 ppm und für13C einen Standardfehler von 1,6 ppm ergibt. Die19F Verschiebungen werden direkt durch Festlegung des σdia:σ

ISSN:0030-4921    

DOI:10.1002/mrc.1270090703

出版商:John Wiley&Sons Limited    

年代:1977

数据来源: WILEY

摘要:

AbstractThe internal and overall motions of 1,3‐ and 1,4‐diethylpyridinium bromides have been studied by13C relaxation. The enthalpies of activation for the rotation of the ethyl groups in positions 1 and 3 are deduced from the temperature dependence of theT1values of the methylene and methine carbons. The14N quadrupolar relaxation time,Tq, together with13C relaxation data provide an estimate of the14N quadrupolar coupling consta

ISSN:0030-4921    

DOI:10.1002/mrc.1270090704

出版商:John Wiley&Sons Limited    

年代:1977

数据来源: WILEY

摘要:

Abstract13C magnetic resonance spectra of several enamino ketones with secondary and tertiary amino groups were obtained for trifluoroacetic acid solutions. In both seriesO‐protonation is predominant and the chemical shifts are related to the electron density changes with respect to the parent base. The spectra of the tertiary compounds are interpreted in terms of slow rotation around the C–1C–2 and C–3N bonds discernible at room temperature.O‐protonated forms of the secondary enamino ketones undergo further reaction on C–2 yielding pyridinium salts. The mechanism of formation of the quaternary salts is interpreted and the additivity parameters of the13C n.m.r. chemical shifts in the pyridinium ions is br

ISSN:0030-4921    

DOI:10.1002/mrc.1270090705

出版商:John Wiley&Sons Limited    

年代:1977

数据来源: WILEY

摘要:

Abstract13C n.m.r. spectra are reported for 1,2‐indandione, coumarandione and thionaphthenequinone in CDCl3solution and for isatin in dimethyl sulphoxide solution. The chemical shifts are assigned and discussed in connection with the influence of the heteroatom on the dicarbonyl group and the aromatic ring. The13C shieldings have also been calculated by means of Pople's perturbation theory using CNDO/S wave function

ISSN:0030-4921    

DOI:10.1002/mrc.1270090706

出版商:John Wiley&Sons Limited    

年代:1977

数据来源: WILEY

摘要:

AbstractA series of (>90% isotopic purity)13C‐labeled aliphatic alcohols of the general structure CCC13COH were synthesized and studied by13C n.m.r. to obtain all13C13C couplings involving the labeled carbon. The2J(CC) values were small (<0.5 Hz) and contrast with the large (up to 2.7 Hz)2J(CC) values obtained in a previous study for 2‐butanols. The3J(CC) values, however, were strikingly similar in the two classes of compounds with respect both to magnitude and to conformational dependency. Thus, the effect of the hydroxyl substituent on3J(CC) va

ISSN:0030-4921    

DOI:10.1002/mrc.1270090707

出版商:John Wiley&Sons Limited    

年代:1977

数据来源: WILEY

摘要:

AbstractThe1H and13C spectra of fluorene, fluorenone, phenanthrene and their 4‐methyl and 4,5‐dimethyl derivatives have been examined. To complete the analyses for fluorenone and 4‐methylfluorenone,1H spectra were recorded at 270 MHz. The results from the1H spectra permitted unequivocal assignments for the protonated aryl carbons by selective proton decoupling. A consistent set of assignments for the quaternary carbons was obtained through consideration of the dominant relaxation processes operative at these centres. This series of compounds was examined to investigate the shielding effects produced by the close approach of methyl groups separated by five bonds for comparison with the contrasting trends found for methyl carbons separated by three and four bonds. The results indicate that the relative orientation of the methyl groups is an extremely critical factor governing their shieldings and those of neighboring ce

ISSN:0030-4921    

DOI:10.1002/mrc.1270090708

出版商:John Wiley&Sons Limited    

年代:1977

数据来源: WILEY

摘要:

AbstractDie Anwendung der1H{2H} Off‐Resonance Rauschentkopplung führt in den1H‐NMR‐Spektren nicht vollständig deuterierter Verbindungen zu einer selektiven Verbreiterung der Protonenrestsignale, sofern diese durch H/D Kopplungen aufgespalten sind. Diese Entkopplungstechnik ermöglicht den einfachen Nachweis von Signalen, die von Lösungsmittelrestsignalen verdeckt sind, wie am Beispiel von Gemischen aus Aceton und Aceton‐d6gezeigt wird. Typische Geräteparameter zur experimentellen Durchführung dieser Doppelresonanztechnik wer

ISSN:0030-4921    

DOI:10.1002/mrc.1270090709

出版商:John Wiley&Sons Limited    

年代:1977

数据来源: WILEY

摘要:

AbstractIt is shown that one of the two conjugate solutions compatible with the AB part of an ABX system can easily be eliminated, at an early stage of the analysis, by considering intensity ratios in the X region.

ISSN:0030-4921    

DOI:10.1002/mrc.1270090710

出版商:John Wiley&Sons Limited    

年代:1977

数据来源: WILEY

摘要:

AbstractIt is shown that sterically unperturbed vicinal HH coupling constants in planar 7‐membered π‐systems correlate linearly with the HMO π‐bond order:3J(HH) = 20.91Pμ,ν–3.85 (r.m.s. error 0.26 Hz, correlation coefficient =0.988). Systematic deviations from this relationship which most probably originate from valence angle changes are found for fused π‐systems containing rings of different size. Model calculations using the CNDO/2 method as well as finite perturbation theory and INDO wave functions support the experimental findings. An improvement of existing3J(HH)Pμ,νcorrelations for planar 6‐membered rings is possible if CNDO/2 π‐bond orders are used instead

ISSN:0030-4921    

DOI:10.1002/mrc.1270090711

出版商:John Wiley&Sons Limited    

年代:1977

数据来源: WILEY