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91.
New coumarin derivatives have been prepared that are soluble in water, a solvent with superior thermo-optical properties. The new dyes, flashlamp-pumped, lase with high effeciency between 450 and 520 nm (untuned). 相似文献
92.
J. A. Vanallan G. A. Reynolds C. C. Petropoulos 《Journal of heterocyclic chemistry》1978,15(3):365-367
The synthesis and electronic absorption spectra of some pyranylidene trimethine pyrylium salts are described. 相似文献
93.
94.
The first-order rate constants for aquation of Co(NH3)5(DMF)3+ were determined in aqueous perchlorate media. The rate constants were independent of hydrogen ion concentration and ionic strength, but decreased with increasing perchlorate ion concentration. Proton magnetic resonance studies showed that dimethylformamide was not hydrolyzed to formic acid and dimethylamine in the aquation step. Mass-spectrometer studies showed that cobalt–oxygen bond breaking occurred in 98 percent, or more, of the aquation acts. Enthalpies and entropies of activation were determined. It was concluded that aquation occurred by an Id mechanism. 相似文献
95.
96.
Warren L. Reynolds Kevin Kooda Brent Florine Nancy Johnson Kenneth Thielman 《国际化学动力学杂志》1980,12(2):97-105
Demetallation rates of α,β,γ,δ-tetrakis(p-sulfophenyl)porphiniron(III) in hydrochloric acid–ethanol–water, perchloric acid–ethanol–water, and sulfuric acid–alcohol–water media were determined. For a given acidity value H0 the order of the rates for the three acids was HCl > H2SO4 > HClO4. This is also the order for complex formation between acid anion and iron(III). Consequently ligands as well as protons are involved in the breaking of bonds between the metal and the porphyrin leading to the formation of the activated complex. The log k values for HCl and HClO4 media were not linearly related to the Hammett acidity function as they were for sulfuric acid–ethanol–water media. The average ΔH? and ΔS?values for the HCl media were 18.4 ± 1.4 kcal/mol and ? 19 ± 3 cal K mol, respectively, in very close agreement with those for H2SO4 media despite the difference in H 0 dependence. For H2SO4–alcohol–water media the order of the rates was butanol > propanol > ethanol with little difference between isomeric alcohols. 相似文献
97.
Létant SE Kane SR Hart BR Hadi MZ Cheng TC Rastogi VK Reynolds JG 《Chemical communications (Cambridge, England)》2005,(7):851-853
We report on the immobilization of an OPAA enzyme on luminescent porous silicon devices, and on the utilization of this new platform to hydrolyze p-nitrophenyl-soman. 相似文献
98.
The determination of glycerol : General introduction: volumetric determination as the copper complex
A method for the determination of glycerol by means of the copper-glycerol complex is described; the complex is filtered free of excess copper(II) hydroxide and the copper is determined iodimetrically. Earlier difficulties due to adsorption of the complex are overcome by the use of glass-fibre filter discs. The method gives accurate results in the range 40-4% glycerol in the solution (400 to 40 mg glycerol in the aliquot taken). 相似文献
99.
Reaction of 2,4,6-trichloropyrimidine with sodium dibenzylmalonate in p-dioxane gave 4,6-dichloro-2-(dibenzylmalonyl)pyrimidine, while reaction of 2,4,6-trichloropyrimidine with sodium dimethylmalonate yielded both 4,6-dichloro-2-(dimethylmalonyl)pyrimidine and 2,2-bis-(4,6-dichloropyrimidin-2-yl)dimethylmalonate. Structural studies using nmr, ir and uv spectroscopy indicate that for the former two compounds in basic solvent, an equilibrium exists between the keto forms and resonance-stabilized enolate ions. 相似文献
100.