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931.
The doublet instabilities of the restricted Hartree-Fock (RHF) solutions for the ion radicals of fulvalene systems, some of which have been known to show the lattice instabilities, are examined in the framework of the semiempirical SCF MO approximation. The RHF solutions for the anion radical of heptafulvalene and the cation radical of pentafulvalene are found to be doublet unstable at the conventional D2h nuclear arrangement. We calculate the broken-symmetry charge-density-wave (CDW) solutions lower in energy than the usual symmetry-adapted RHF solutions and examine their properties. It is shown that the energy lowerings due to the CDW solutions are very small in both the ion radicals, but their density matrix elements are remarkably different from those for the symmetry-adapted RHF solutions. It is also shown that the proton hyperfine splittings for the anion radical of heptafulvalene calculated assuming the CDW solution are in good agreement with the experimental values. Finally, we refer to the relationship between the doublet instability of the RHF solution and the lattice instability. 相似文献
932.
933.
Chuzo Iwata Yoshiji Takemoto Hitoshi Kubota Takeshi Kuroda Takeshi Imanishi 《Tetrahedron letters》1985,26(27):3231-3234
(±)-Oxylubimin (1), the highest oxidized spirovetivane-type phytoalexin, was totally synthesized with high stereoselectivity using a novel method for α′-hydroxylation of α,β-unsaturated ketones. 相似文献
934.
935.
The reaction of singlet oxygen with N-1-(2-alkenylidene)-t- butylamines (
and
) gives the unsaturated hemiperacetal derivatives (
and 4) of the hydroperoxy aldimines (
and
). Several α, β-unsaturated aldimines which are held in the s-trans conformation failed to react with singlet oxygen. 相似文献
936.
Yassin A. Aggour Ikuyoshi Tomita Takeshi Endo 《Journal of polymer science. Part A, Polymer chemistry》1994,32(10):1991-1995
Cationic crosslinking reactions of poly(allenyl ether)s having oligo(oxyethylene) moieties prepared by the radical polymerization of the corresponding allenyl ethers were carried out under some varied reaction conditions. For instance, a crosslinked polymer was obtained in 82% yield by the treatment of poly(ethylene glycol methyl allenyl ether) ( 1a ) with 1.2 mol% of BF3·OEt2 ( 2 ) under high concentration in dichloromethane (46 wt %). The gels obtained showed good swelling properties in water, alcohols, and polar organic solvents such as dichloromethane. In particular, the degrees of swelling of these gels in aqueous sodium chloride (1M) were quite similar to those in ion-free water, indicating that these gels served as nonionic hydrogels. © 1994 John Wiley & Sons, Inc. 相似文献
937.
938.
Raman spectra of the Li+, Na+, K+, NH+4, Mg2+, Ca2+, Sr2+, Ba2+, Pb2+ complexes of 12-crown-4 and also 12-crown-4 in various states are observed. The spectra of 12-crown-4 change remarkably by complex formation with cations. Normal vibration calculations of various conformations of 12-crown-4 are carried out. On the basis of the observed spectra and the results of the calculations, the conformation of 12-crown-4 in the Li+, Na+, K+, NH+4, Mg2+ complexes is found to have approximate D2d symmetry, while that in the Ca2+, Sr2+, Ba2+ complexes is found to have approximate C2V symmetry. 相似文献
939.
Katsuhiko Saido Takeshi Kuroki Tadashi Ikemura Makoto Kirisawa 《Journal of Analytical and Applied Pyrolysis》1984,6(2):171-181
A flow apparatus equipped with a spray nozzle was developed for investigating the thermal decomposition of esters with high boiling points and viscosities. The thermal decomposition of bis(2-ethylhexyl) phthalate (BEHP), which is a typical plasticizer for poly(vinyl chloride) with a high boiling point and viscosity, was carried out by the use of the flow apparatus. The thermal decomposition products were analysed by gas chromatography and the kinetic parameters were calculated. The kinetic parameter of bis(2-ethylhexyl) phthalate was kBEHP (s?1)=4.59·1011 exp(?40600/RT). From a comparison with the values for phthalic esters, it is proposed that a cis-elimination reaction takes place with a two-step mechanism in which the rate-determining step is α-carbon cleavage. 相似文献
940.
Fuminao DoiTakahisa Ogamino Takeshi SugaiShigeru Nishiyama 《Tetrahedron letters》2003,44(26):4877-4880
Heliannuol E 1, isolated from Helianthus annuus L. cv. SH-222, was successfully synthesized in both optically active forms, by novel ring-expansion reaction of the corresponding spirodienone derivatives 8 and 17, which were produced from 7 and 16 under anodic oxidation conditions. The absolute structure of the natural product was determined to have R-configuration at the benzylic position. 相似文献