Bulletin of the Chemical Society of Japan

Shimizu, Natsuko; Shimokoshi, Kazuo; Yasumori, Iwao

doi: 10.1246/bcsj.46.2929pmid: N/A

The state of adsorbed oxygen on metallic silver dispersed on silica gel has been studied by ESR. The spectra observed by the interaction of oxygen and the surface were found to be composed of spectra due to two different species. One of the species, which was formed separately by the contact with oxygen at −110 °C, was identified with O2− chemisorbed on metallic silver by a comparison of the observed g values and the other features with those previously reported. The other species has a doublet at g=2.036. This spectrum was reproduced by the interaction of N2O with the silver surface. Further, the γ-irradiation of the silver samples in the presence of O2 and N2O markedly enhanced the intensity of this spectrum, showing a low-field hump. On the basis of the g values and the splitting of the high-field doublet, assuming that the doublet is due to the hyperfine interaction of an unpaired electron with the silver nucleus, the species was assigned to Ag2+ in the present system. It is postulated that this species is possibly formed by the dissociative and/or charge-transfer chemisorption of O2 and N2O, suggesting the presence of non-paramagnetic oxygen species, such as O2−, as a counter ion of Ag2+.

Ishizu, Kazuhiko; Ohuchi, Muneki; Nemoto, Fujito; Suga, Masao

doi: 10.1246/bcsj.46.2932pmid: N/A

The cation radicals of some alkylbiphenyls such as 4,4′-bitolyl, 4,4′-di-t-butylbiphenyl, and 2,2′, 4,4′, 6,6′-bimesityl, were generated by SbCl5 oxidation in CH2Cl2. The ESR observation was carried out, and the Q, values of the methyl and t-butyl were estimated based on either the theoretical spin density or the experimentally-determined spin density from the 13C-hyperfine splitting. The Q, value of the methyl in the cation radical was found to be 1.5 times that for the anion radical. The t-butyl groups of the cation radical also showed a much larger Q value than that for the anion radical. The perturbation of the spin density due to the steric hindrance was investigated with reference to the prediction of the McLachlan’s MO calculations carried out for the hindered biphenyl. The experimentally-determined spin density derived from the Q value established for the para-derivative can be adequately interpreted on the assumption that the planar character of the biphenyl would be much reduced, contrary to the tendency found for the anion radicals. This effect suggests that a different delocalization of the unpaired electron may be expected between the cation and the anion radical: that is, the unpaired electron brings about a fair bonding on the central 1–1′ bond in the anion radical, but an antibonding for the cation radical, because the odd π-orbital of the cation has its node between the central 1–1′ bond.

Okumura, Akiko; Okazaki, Nobukazu

doi: 10.1246/bcsj.46.2937pmid: N/A

The rates of oxygen exchange between arsenate ions and water have been measured at 14.5 °C and 30 °C over the pH range of 6.5–12.5. The rate, R, may be expressed by the rate law:R=k_1[H_2AsO_4^-]+k_2[HAsO_4^2-]+k_3[AsO_4^3-]+k_4[H_2AsO_4^-]^2+k_5[H_2AsO_4^-][HAsO_4^2-]+k_6[HAsO_4^2-]^2.The exchange rates at 30 °C and I=0.55 have been analyzed in terms of this rate law to obtain the values of the rate constants, k1–k6. The activation energy of the over-all exchange reaction is 13.2±0.2 kcal/mol at pH 7.51 and 22.14±0.02 kcal/mol at pH 9.79. The reaction shows a negative salt effect in the region of pH 7.5, and a positive salt effect at pH 9.3.

Ohkubo, Katsutoshi; Kitagawa, Futoshi

doi: 10.1246/bcsj.46.2942pmid: N/A

An MO-simulation of the geometrical change in the bimolecular methane oxidation, CH3+O2→CH3O2, was performed using the CNDO/2 approximation. The geometry of CH3O2 was predicted to take rOO=1.19 Å and ∠COO=111° with fixed distances of rCO=1.44 Å and rCH=1.09 Å. The coupling reaction proceeds smoothly, without any appreciable activation energy, with the geometric transformation of the momentarily-living CH3--O2, with rCO=2.36∼1.44 Å, rOO=1.132∼1.19 Å, and ∠COO=90∼111°. The magnitude of the electron migration between CH3 and O2 throughout the reaction was estimated.

Kobayashi, Hayao

doi: 10.1246/bcsj.46.2945pmid: N/A

Crystals of the 1 : 1 charge-transfer complex of N-MePZT–TCNQ, are monoclinic with those lattice constants: a=10.904, b=13.321, c=7.086 Å, and β=91.06°, and with the space group C2/m. X-ray structure analysis showed that the mixed-stacks of N-MePZT and TCNQ, exist along the c axis. N-MePZT is disordered, and its apparent molecular symmetry is C2h, taking four possible conformations. The molecular geometry of TCNQ, indicates that the amount of the charge transferred from N-MePZT is very small (<0.2e).

Shinoda, Hiroyuki; Tatematsu, Hidenobu; Miyazaki, Tomoo

doi: 10.1246/bcsj.46.2950pmid: N/A

The effects of doubly-excited configurations, especially of the χk1mn type, on the results of P-P-P-CI calculations of unsaturated compounds have been discussed by comparing the results obtained by three different types of CI treatment. The calculations of the pi-electronic total energies of ground states, the electronic transition energies, the oscillator strengths, and the pi-electronic densities of sixteen molecules were performed. The core resonance integrals and electronic repulsion integrals were readjusted so that the transition energies, obtained by CI calculations considering all the singly- and doubly-excited configurations, might coincided with the experimental results. From the results of these calculations, it is found that χk1mn-type configurations play an important role in CI calculation.

Iida, Yôichi

doi: 10.1246/bcsj.46.2955pmid: N/A

The infrared spectra (400–4000 cm−1) were measured with neutral p-bromanil and its anion radical. Appreciable frequency differences between their corresponding bands were observed. The fundamental frequencies were assigned, and the simple Urey-Bradley force fields were determined for both the neutral p-bromanil and its anion radical. The differences in the molecular and electronic structures between these two molecules were discussed on the basis of these results. The half-occupied molecular orbital of the p-bromanil anion radical was found to belong to the b3g irreducible representation.

Takusagawa, Fusao; Hirotsu, Ken; Shimada, Akira

doi: 10.1246/bcsj.46.2960pmid: N/A

The crystal structure of trimellitic acid(benzene-1,2,4-tricarboxylic acid) for the pseudo-cell was determined by the method of X-ray diffraction. The crystal is monoclinic, with the space group of I2/c and with a=15.91, b=61.35, c=8.99 Å, and β=95.4°. The appearence of diffraction patterns strongly indicated the existence of the pseudo-cell with b⁄5 and with the space group of I2/c. The structure of the pseudo-cell was determined by the symbolic addition method. The final R value is 13.6%. There is no intramolecular hydrogen bond between the adjacent carboxyl groups, and one of these carboxyl groups twists greatly out of the plane of a benzene ring so that the repulsion between the oxygen atoms is reduced. Each molecule is joined, through three kinds of hydrogen bonds, with three neighboring molecules. These hydrogen bonds are formed between the carboxyl groups related by the center of symmetry and the two-fold axis. The molecular dimensions and packing obtained by the refinement for the pseudo-cell do not seem to contain unacceptable results.

Nakayama, Haruo; Tahara, Masao

doi: 10.1246/bcsj.46.2965pmid: N/A

The solid-liquid phase diagram for the water +1,4-dioxane system has been determined by the ordinary cooling curve method and with the aid of a differential scanning calorimeter (DSC). The diagram shows the existence of a hydrate which is stable in rather narrow ranges of temperature (−15.8∼−13.5 °C) and of composition (37.0∼46.5 wt% dioxane). From the phase relations and an analysis of the calorimetric data, the composition and the heat of formation (from the liquid states of both components) of the hydrate have been estimated to be C4H8O2·mH2O with m=36∼39 and ΔH1=−51.3 (for m=36)∼−55.6 (for m=39) kcal/mol respectively. This hydrate seems to be the same as that recently reported by Rosso et al., though the compositions and the temperature ranges are very different.

Kawashima, Yoshiyuki; Hirose, Chiaki

doi: 10.1246/bcsj.46.2969pmid: N/A

The J=2←1 transitions of methyl iodide in the v3, v6, 2v3, v2, v3+v6, and v5 vibrationally-excited states are observed. In v3+V6, the central component, ν360, of the J=2←1, K=1←1 transition is observed at 14.6 MHz, higher than the ν36+ of the l-type doubling. This is interpreted by the fact that the E state with K=−l=±1 is affected more strongly by the Fermi resonance through k356 than is the A state with K=l=±1. The Fermi resonance through k356 causes the Coriolis coupling between v2 and v5 through ζ25(y) to be transferred to v3+v6. As a result, the l-type doubling constant, q6, is determined to be −5.8 MHz. The Stark effect in the presence of the l-type doubling and nuclear quadrupole splitting is formulated and used in the analysis.