摘要:

A method of determining the relative signs ofJABandJBXin nuclear spin systems of the type AB2Xqis described and applied to the AB2X3proton spin system of 2-butyn-1-ol. Variation of the relative chemical shiftvA—vB(through changes in temperature or in the composition of the solvent) causes certain pairs of ‘labile’ transitions in the X spectrum to coalesce on one side or other of the X spectrum. The information about the relative signs of the coupling constants is obtained by noting the two different critical values ofvA-vBat which these coalescences occur. Since the method remains applicable even if the third coupling constantJAXis vanishingly small, it is particularly useful in the determination of the signs of long-range spin coupling constants where the usual double resonance methods often break down. It is concluded that the long-range couplingJ(H-C-C≡C-C-H) of 2-butyn-1-ol has a positive sign.

ISSN:0026-8976    

DOI:10.1080/00268976600101331

出版商:Taylor & Francis Group    

年代:1966

数据来源: Taylor

摘要:

The deuteron spin-lattice relaxation times,T1Q, have been measured for benzene, water and ammonia from the melting point to the liquid-vapour critical temperature and for bromobenzene over a smaller temperature range. The results are compared with previously measured proton spin-lattice relaxation times. It is shown that the deuteronT1Qvalues agree with the proton intramolecularT1values for benzene, thus confirming the separation of the dipolar and spin-rotation contributions performed by Powles and Figgins [1]. A value of the electric quadrupole coupling constant,e2qQ/th, is deduced, which agrees with the value for the molecule in the solid. For bromobenzene a value ofe2qQ/h=175±10 khz is obtained in a similar way.

ISSN:0026-8976    

DOI:10.1080/00268976600101341

出版商:Taylor & Francis Group    

年代:1966

数据来源: Taylor

摘要:

One-electron reduction of 1,8-bisdehydro-14-annulene yields the radical anion whose electron spin resonance spectrum is interpreted using molecular orbital theory.

ISSN:0026-8976    

DOI:10.1080/00268976600101351

出版商:Taylor & Francis Group    

年代:1966

数据来源: Taylor

摘要:

The method of obtaining sub-spectral transformations for N.M.R. spectra is reformulated so that the conditions and limitations of transformability become obvious. Explicit formulae forabnandabcsub-spectral transformations are given. It is proved that sub-patterns of energy levels of type (1 : 2 : 1) and (1 : 3 : 3 : 1) can always be transformed intoabandabcsub-spectra, whereas the pattern (1 : 2 : 4 : 2 : 1) does not necessarily correspond to the symmetrical part of anaa′bb′sub-spectrum. In spectra of the type AA′A′′A′′′XX′ the failure of the transformation method is shown to be due to the mixture of symmetry species products in the 4 × 4 matrix. The possibility of approximate sub-spectral transformations is discussed. An expansion of sub-spectral analysis to spectra of oriented molecules is indicated.

ISSN:0026-8976    

DOI:10.1080/00268976600101361

出版商:Taylor & Francis Group    

年代:1966

数据来源: Taylor

摘要:

The14N chemical shifts in a series of primary and secondary amides have been obtained from the proton spectra by double irradiation techniques. The14N shifts in the primary amides are affected only slightly by changes in the substituent on the carbonyl group, but a wider range is found for secondary amides. A qualitative explanation of the observed shift changes is put forward in terms of the effect that the various substituents, have upon the nitrogen lone pair of electrons.

ISSN:0026-8976    

DOI:10.1080/00268976600101371

出版商:Taylor & Francis Group    

年代:1966

数据来源: Taylor

摘要:

High temperature power series valid for general spin and including second-neighbour interactions are given for the physical susceptibility of the three cubic lattices and for the staggered susceptibility of some antiferromagnetic orderings of the body-centred and face-centred lattices. The critical ordering temperatures corresponding to these series are discussed and compared with the results of molecular field theory.

ISSN:0026-8976    

DOI:10.1080/00268976600101381

出版商:Taylor & Francis Group    

年代:1966

数据来源: Taylor

摘要:

A simple model of unimolecular reactions respecting the possibility of a restricted intramolecular energy flow is suggested. The calculated dependences of the unimolecular rate constantkunion the concentration are compared with the corresponding dependences of the Kassell and Slater theories. The existence of a restricted energy flow leads to a slower increase of thekunivalues with the concentration and in certain cases to a pseudolimited region wherekuniactually does not depend on the concentration, even before the final limiting value ofkuniis attained. Kassel's equation follows from this model as a limiting case for an unlimitedly rapid energy flow.

ISSN:0026-8976    

DOI:10.1080/00268976600101391

出版商:Taylor & Francis Group    

年代:1966

数据来源: Taylor

摘要:

The influence of hyperfine interaction on proton magnetic relaxation in dilute solutions of paramagnetic ions was investigated. Theoretical and experimental results were compared with the theory of Solomon and Bloembergen.

ISSN:0026-8976    

DOI:10.1080/00268976600101401

出版商:Taylor & Francis Group    

年代:1966

数据来源: Taylor

ISSN:0026-8976    

DOI:10.1080/00268976600101411

出版商:Taylor & Francis Group    

年代:1966

数据来源: Taylor

ISSN:0026-8976    

DOI:10.1080/00268976600101421

出版商:Taylor & Francis Group    

年代:1966

数据来源: Taylor