摘要:

To test further Nagakura and Tanaka's conception of intramolecular charge-transfer absorption, an improved calculation based on Longuet-Higgins and Murrell's method was carried out for the π-electron structures of formamide and acrolein. This shows that the 1717åband of formamide and 1935åband of acrolein can be regarded as intramolecular charge-transfer absorption bands in the sense that the excited state wave functions for these two bands are mainly constructed of the charge-transfer configuration, and that the transitions corresponding to these bands are accompanied by a large amount of electron transfer from electron donor towards acceptor. The 1717åband of formamide cannotbe interpreted as a shifted 1560åformaldehyde band. The latter band must shift toshorterwavelengths as the result of interaction with non-bonding electrons of the nitrogen atom. Similar blue shifts occur in acrolein for the C = C and C = O π → π* bands relative to the corresponding bands of ethylene and formaldehyde. Similar causes operate in the blue shifts of the non-charge-transfer bands of donor-acceptor molecular complexes.

ISSN:0026-8976    

DOI:10.1080/00268976000100121

出版商:Taylor & Francis Group    

年代:1960

数据来源: Taylor

摘要:

The olefinic proton resonance spectra of a number of mono- and 1, 2 di-substituted ethylenes have been analysed as AB, ABC or ABX systems to obtain the coupling constants and chemical shifts. The values ofJtrans(range observed 13·7 to 18·0 c/s in 14 compounds) were significantly larger thanJcisin similar molecules. The values ofJcis(range observed 6·5 to 12·3 c/s in 8 compounds) are abnormally large when the olefinic bond is conjugated to an aromatic ring. Coupling between adjacent protons in an olefinic methylene group (Jgem) is much smaller, and sometimes negative. The shielding of the lone vinyl proton in mono-substituted ethylenes is smaller than that of the methylene group and in two cases (the vinyl group directly bonded to an oxygen atom) the difference is so great as to give an approximation to the ABX condition, so that the methylene protons appear to be shielded to an unusually large extent.

ISSN:0026-8976    

DOI:10.1080/00268976000100131

出版商:Taylor & Francis Group    

年代:1960

数据来源: Taylor

摘要:

The magnetic properties of Co2+ions in octahedral environment are discussed in relation to the energy-level scheme. It appears that the three low-lying levels arising from the4F(Γ4) triplet as a consequence of spinorbit coupling are responsible for a temperature-dependent magnetic moment.

ISSN:0026-8976    

DOI:10.1080/00268976000100141

出版商:Taylor & Francis Group    

年代:1960

数据来源: Taylor

摘要:

The partial rate factorskifor H-D exchange inα, α- andβ, β-dimethylnaphthalenes were measured in CF3COOD-HPO2F2-CCl4mixtures. The values of logkicorrelate well with the excess of electron charge on the carbon atoms calculated on the basis of the inductive effect of the methyl group.

ISSN:0026-8976    

DOI:10.1080/00268976000100151

出版商:Taylor & Francis Group    

年代:1960

数据来源: Taylor

摘要:

This paper examines the use of second-order perturbation theory in the interpretation and prediction of the signs of the interaction constants which are appended to the simple valence force potential functions. It is shown, for the large number of molecules considered here, that complete agreement with the observed signs can be obtained by expanding the electronic Hamiltonian in terms of the normal coordinates of motion and by then assuming that the lowest of the excited electronic states makes the most important contribution to the second-order sum in the expression for the energy. A knowledge of the symmetry of the transition density between the ground and the first excited electronic states is thus sufficient to determine which of the vibrations in a molecule is energetically favoured and thus to determine the sign of the interaction constant.

ISSN:0026-8976    

DOI:10.1080/00268976000100161

出版商:Taylor & Francis Group    

年代:1960

数据来源: Taylor

摘要:

The ultra-violet absorption spectrum of nitromethane was measured under various conditions. Besides the weak band at 270 mμ, a strong band, which may be regarded as due to the longest wavelengthπ→π* transition band, was observed at 198 mμin the gaseous state. Further, the absorption spectrum of nitromethane was measured in aqueous solutions with several different phvalues, and a strong band was observed at 233 mμ. From the fact that thepKavalue evaluated on the basis of the phdependence of the absorption intensity is equal to that obtained electrometrically, it was concluded that the 233 mμband is to be ascribed to the nitromethyl anion (H2C-NO2). This band was found to shift to 238 mμin alcoholic KOH solution.

ISSN:0026-8976    

DOI:10.1080/00268976000100171

出版商:Taylor & Francis Group    

年代:1960

数据来源: Taylor

摘要:

The intensities of cobalt nuclear resonance spectra have been used to study the rate of exchange at various temperatures between ethylenediamine and the cobalt hexammine (III) ion. The variation of the relative intensities of the two lines from sodium cobaltinitrite solutions with temperature has been studied and interpreted in terms of an isomerization equilibrium. The rates of both electron and ligand exchange in solutions of cobalt complexes have been found to be slow.

ISSN:0026-8976    

DOI:10.1080/00268976000100181

出版商:Taylor & Francis Group    

年代:1960

数据来源: Taylor

摘要:

Previous studies on13CH satellite features in the hydrogen nuclear-magnetic-resonance spectra of symmetrical molecules are extended to include the complex spectrum of liquid propane (CH3CH2CH3). The exact Hamiltonian for the nuclear system A3B2A3' and its simplification using group theoretical methods are described. A precise solution of the spectrum at 40 Mc/s, aided by the satellite features, is presented; the values of the AB chemical shift and AB coupling constant which produce the best agreement between experimental and theoretical spectra at 40 Mc/s are 17·50±0·05 c/s and 7·4±0·1 c/s respectively.

ISSN:0026-8976    

DOI:10.1080/00268976000100191

出版商:Taylor & Francis Group    

年代:1960

数据来源: Taylor

摘要:

Chemical shifts of the fluorine nuclear resonance have been measured for fluoride ion in a variety of environments. The shift varies linearly with the mole-fraction of organic solvent and is dependent upon the nature and concentration of added cations and anions. In contrast, the value for the caesium resonance from solutions of caesium salts is independent of the choice of solvent. Large, linear, chemical shifts are observed when other electrolytes are added, the effect being almost entirely due to the anions.

ISSN:0026-8976    

DOI:10.1080/00268976000100201

出版商:Taylor & Francis Group    

年代:1960

数据来源: Taylor

摘要:

The influence of a strong electric fieldFon the polarization of light scattered elastically by small gaseous molecules is investigated. Two effects are found:1.(i) The field distorts the molecules, thereby changing their polarizabilities. If they are isotropically polarizable whenF= 0, and hence capable of scattering only polarized light from a parallel beam, this distortion may lead to depolarization. For inert gas atoms, this depolarization is proportional toF4, and hence normally very small, but for tetrahedral molecules it is proportional toβ2F2, whereβis the first hyperpolarizability of the molecule.2.(ii)Ftends to orientate anisotropic molecules, thereby affecting the polarization of the scattered light; this effect is related to the anisotropy in the molecular polarizability, and to the dipole moment, but is not likely to lead to information that is not obtainable by simpler means.

ISSN:0026-8976    

DOI:10.1080/00268976000100211

出版商:Taylor & Francis Group    

年代:1960

数据来源: Taylor