摘要:

Calculations have been made on some dinegative ions of hydrocarbons having C3symmetry axes, namely coronene, (18)-annulene, triphenylbenzene, decacyclene and triphenylene. When configuration interaction is allowed for only decacyclene and triphenylbenzene in a twisted configuration are calculated to have triplet ground states. These calculations agree with the available experimental data.

ISSN:0026-8976    

DOI:10.1080/00268976600100911

出版商:Taylor & Francis Group    

年代:1966

数据来源: Taylor

摘要:

Wigner and Eisenbud'sR-matrix theory develops the wave function of the ‘compound molecule region’ in terms of an orthogonal set of functions. This fact suggests the use of a variational method. The method yields approximate solutions at low energies. Some results for the head-on H2+ H collision are quoted.

ISSN:0026-8976    

DOI:10.1080/00268976600100921

出版商:Taylor & Francis Group    

年代:1966

数据来源: Taylor

摘要:

The symmetry group applicable to N.M.R. problems consists of all the nuclear permutations which do not permute the N.M.R. parameters; in general, this group may be larger or smaller than the molecular symmetry group defined by Longuet-Higgins. The application of these N.M.R. symmetry groups to spin systems involving magnetic equivalence is described (i) for a single magnetically equivalent set, and (ii) for the X3AA′X3′ system. Although the group-theoretical method achieves the same degree of factorization of the spin Hamiltonian as the composite particle technique described by earlier workers, it offers no advantages in the detailed calculation of the N.M.R. spectrum, and is much more time-consuming.

ISSN:0026-8976    

DOI:10.1080/00268976600100931

出版商:Taylor & Francis Group    

年代:1966

数据来源: Taylor

摘要:

Electric field theory is used to predict the1H,13C and19F chemical shifts of a series of halogenated ethanes and the19F shifts of some cyclobutanes. The quantity 3PI/r6is used to describe the time-averaged square of the electric field at the nucleus from fluctuating point-dipoles elsewhere in the molecule. The results are compared with predictions made by an alternative method, usingP/Ir3, to define the electric fields. The calculations show that, whatever the theoretical justification or lack of it, the former quantity is often more widely applicable than the latter.

ISSN:0026-8976    

DOI:10.1080/00268976600100941

出版商:Taylor & Francis Group    

年代:1966

数据来源: Taylor

摘要:

The use of intramolecular electric field theory to describe the chemical shifts of fluorine nuclei is extended to a study of molecules containing localized double bonds. Substituted cyclopentenes are chosen for this work and it is shown that the neglect of pi-bond interactions is justified for nuclei not directly attached tosp2carbon atoms.

ISSN:0026-8976    

DOI:10.1080/00268976600100951

出版商:Taylor & Francis Group    

年代:1966

数据来源: Taylor

摘要:

The use of electric field theory to predict the chemical shifts of fluorine nuclei in molecules containing localized double bonds has been justified in a previous publication [1]. This approach is extended to a series of substituted cyclohexenes undergoing rapid conformational interconversion. No direct experimental investigation of the geometry of these molecules has been reported but the calculations have been performed for two theoretical models and a further one in which the system is completely strain-free. It is shown that whereas no real distinction may be drawn between the two theoretical models, the unstrained system is totally unrepresentative of the facts.

ISSN:0026-8976    

DOI:10.1080/00268976600100961

出版商:Taylor & Francis Group    

年代:1966

数据来源: Taylor

摘要:

The application of electric field theory to a study of fluorinated cyclohexene molecules [1] is continued with the investigation of 1,2,4-trichloroheptafluorocyclohexene. This compound is considered to exist as a fixed conformer at room temperature and the calculations have been performed with the ring chlorine atom occupying axial and equatorial positions in turn. Studies at higher temperatures have enabled the other conformer to be investigated and the results show that the ring chlorine atom probably occupies an axial position in the predominant conformer. This conclusion is the opposite of that normally proposed for cyclohexenes which have previously been assumed to follow the cyclohexane pattern.

ISSN:0026-8976    

DOI:10.1080/00268976600100971

出版商:Taylor & Francis Group    

年代:1966

数据来源: Taylor

摘要:

It is shown that MO theory predicts the butadiene molecule to be flat, and that VB theory predicts a skewed configuration of this molecule.

ISSN:0026-8976    

DOI:10.1080/00268976600100981

出版商:Taylor & Francis Group    

年代:1966

数据来源: Taylor

摘要:

The electron spin resonance spectrum of a radical formed byγ-irradiation or ultra-violet photolysis of alkali halides doped with cyanide shows a very large hyperfine coupling to one proton (AisoH=137 gauss) and one carbon atom (AisoC=74 gauss). In addition a single nitrogen atom gives a triplet having aAisoN=6·5 gauss. The radical is identified as HCN-and its electronic structure is discussed. A second radical also contaming a single strongly coupled proton has been detected and is briefly discussed.

ISSN:0026-8976    

DOI:10.1080/00268976600100991

出版商:Taylor & Francis Group    

年代:1966

数据来源: Taylor

摘要:

The molecular (molar) Kerr constantmKfor monatomic lithium and sodium vapours in the region of some of their most interesting electronic transitions is expressed in terms of transition dipole moment matrix components. Numerical values of these components allow estimates ofmKto be made for both allowed and forbidden transitions. Particular care, however, is needed in the choice of atomic wave functions if the relevant hyperpplarizabilities are to be even approximately correct. A consideration of orders of magnitude suggests that experiments to test these calculatedmKvalues should be feasible.

ISSN:0026-8976    

DOI:10.1080/00268976600101001

出版商:Taylor & Francis Group    

年代:1966

数据来源: Taylor