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991.
Summary Unsaturated hexenoic acids are important compounds due to their utilization for specific aromatic alcohol (leaf alcohols)
preparation. The influences of the reaction conditions on the sorbic acid hydrogenation to cis-hex-3-enoic acid are given.
[Cp*Ru(sorbic acid)]CF3SO3 was used as a catalyst in two-phase hydrogenation. 相似文献
992.
Summary A simple and general scheme to exploit any discrete point group symmetry in two-electron integral transformations is introduced. It has been implemented together with integral pre-screening techniques in direct two-electron integral transformations. Its application has also been extended to subsequent MO integral processing steps like MP2 or solution of the coupled-perturbed Hartree-Fock equations (CPHF). Timings for representative applications are presented. 相似文献
993.
994.
Ambident anions derived from phosphorus thioselcnoacids were glycosylated with 2,3,4,6 - tetra - O - acetyl - α - d - glucopyranosyl bromide, 2,3,4,6 - tetra - O - acetyl - α - d - galactopyranosyl bromide and 2,3,4 - tri- O - acetyl - α - d - xylopyranosyl bromide. The products were β-Se-glucosyl- and β-S-glucosylthioselenoates. The Se/S ratio of the glycosylated phosphorothioselenoates depends on the reaction conditions. At higher temperatures an equilibrium was observed. As a result of this equilibrium the Se/S ratio of the linkages formed in the glycosylated products was different from that observed under kinetic control. The structures of the glycosylated phosphorothioselenoates were confirmed by spectroscopy, independent synthesis and selective oxidation. 相似文献
995.
Vasyl Kinzhybalo Jan Janczak 《Acta Crystallographica. Section C, Structural Chemistry》2007,63(3):m105-m107
The crystals of the title compound, [Mg(C32H16N8)(H2O)]·2C3H9N, are built up from MgPc(H2O) [Pc is phthalocyaninate(2−)] and n‐propylamine molecules that interact via O—H⋯N hydrogen bonds. The MgPc(H2O) molecule is non‐planar. The central Mg atom is coordinated by the four equatorial isoindole N atoms of the Pc ring system and by the O atom of an axial water molecule. The Mg atom is displaced by 0.509 (1) Å from the N4 plane towards the water O atom. MgPc(H2O)·2(n‐propylamine) molecules related by the inversion centre are linked by N—H⋯O hydrogen bonds to form a dimeric aggregate. 相似文献
996.
Cejka C Pláteník J Guryca V Sirc J Michálek J Brůnová B Cejková J 《Photochemistry and photobiology》2007,83(3):652-657
Under normal conditions, the cornea absorbs the majority of UVB (ultraviolet B, 280-320 nm) rays, which is very important for the protection of the inner eye against their damaging effect. Our previous studies have shown that repeated irradiation of the rabbit cornea with UVB rays for 5 days (daily dose of 1.01 J cm(- 2)) caused photokeratitis accompanied by swelling (hydration) of the corneal stroma, thinning of the corneal epithelium and decrease in antioxidants. The purpose of this study was to examine the light absorption properties of such damaged rabbit cornea. Results of both spectrophotometry of the whole corneal buttons and corneal tissue dissolved in sodium hydroxide show that because of above mentioned disturbances, UVB-irradiated cornea absorbs more light throughout the whole measurable UV-VIS spectral range than the normal cornea. Increased corneal thickness (result of hydration), changes of corneal transparency (the cornea becomes grayish) and some increase in protein content all contribute to the increased light absorption of UVB irradiated corneas. We suggest that the UVB-irradiated cornea, although damaged and nearly without antioxidants, might actually through its higher UV absorbance protect the inner eye against further damage from UVB rays. 相似文献
997.
998.
We consider two classes of probability distributions for configurations of the ideal gas. They depend only on kinetic energy and they remain of the same form when degrees of freedom are integrated out. The relation with equilibrium distributions of Tsallis’ thermostatistics is discussed. 相似文献
999.
1000.
On the basis of the polarized absorption spectra, the guest order parameter as a function of temperature for five dichroic azo dyes dissolved in four members (pentyl to octyl) of the homologous series of n-alkyl-4-(4-isothiocyanatophenyl)bicyclo[2,2,2]octanes has been evaluated. Moreover, the influence of the dichroic dye addition on the nematic-isotropic phase transition temperature has been examined. The relation between the molecular geometry of the guest, its orientation efficiency in the nematic host and the clearing temperature of the azo dye-liquid crystal mixtures has been determined. The experimental results have been compared in some detail with calculations performed on the basis of the mean field theory for binary mixtures. 相似文献