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901.
(R)-(+)-Seudenol (3-methylcyclohex-2-en-1-ol) and its antipode were synthesized from optically active forms of 3-iodocyclohex-2-en-1-ol by treatment with Me2CuLi. Their absolute configurations were determined by converting (+)-3-iodocyclohex-2-en-1-ol to the known (R)-(+)-cyclohex-2-en-1-ol. 相似文献
902.
At pH 5 (AcOHAcONa) protonation of the enamine of 3,6,6-trimethylnorpinane 2-one (3-methylnopinone) yields the cis immonium ion 6 (X OAc), which isomerizes to the thermodynamically more stable trans immonium ion 6′ (X OAc). Under more strongly acid conditions (aqueous hydrochloric or perchloric acids), the enamonium salts 7 (X Cl or ClO4) are formed; these isomerize, with a rate increasing with decreasing acidity to the cis immonium salts 6, stable under these conditions. Epimerization of the cis salt 6 (X Cl), occurs in ethereal hydrogen chloride, the rate increasing also with decreasing acidity. At pH 5, hydrolysis of the enamine yields 3-methylnopinone, the proportion of the less thermodynamically stable trans isomer increasing with a rise in reaction temperature. 相似文献
903.
Summary An emission-spectrometric method is described for the quantitative determination of traces of non-rare earth elements in yttrium oxide, employing addition of AgF-Ga2O3 mixed carrier. This addition effects an increase of the rate of evaporation of the analytical elements and of the number of atoms in the arc plasma. It enhances the sensitivity of the analytical elements to a larger extent than other carriers and permits the determination of microquantities of the elements (Mg, Ca, Mn, Co, Fe, Pb, Cu, Cd, Al, B, Sn, As, Bi) within limits of detection from 0.1 to 13 ppm in high-purity yttrium oxide. The coefficients of variation are less than 20%.
Emissionsspektrometrische Bestimmung von nicht zu den Seltenen Erden gehörenden Elementspuren in Yttriumoxid mit Hilfe eines AgF-Ga2O3 -Trägergemisches
Zusammenfassung Das Trägergemisch bewirkt eine Erhöhung der Verdampfungsgeschwindigkeit der zu bestimmenden Elemente und der Anzahl der Atome im Bogenplasma. Es verbessert mehr als andere Träger die Empfindlichkeit und ermöglicht die Bestimmung von Mikromengen der Elemente (Mg, Ca, Mn, Co, Fe, Pb, Cu, Cd, Al, B, Sn, As, Bi) in hochreinem Yttriumoxid mit Nachweisgrenzen von 0,1–13 ppm. Die Variationskoeffizienten liegen unter 20%.相似文献
904.
Put R Perrin C Questier F Coomans D Massart DL Vander Heyden Y 《Journal of chromatography. A》2003,988(2):261-276
905.
C. Suresh Reddy Y. Hari Babu N. Ravi Sankar C. Devendranath Reddy 《Journal of heterocyclic chemistry》2004,41(6):1027-1031
Novel 3‐(substituted)‐2,4,8,15‐tetroxa‐3‐phosphadispiro[5.2.5]hexadecane‐3‐oxides (3‐12) have been synthesized by cyclization of 1,5‐dioxaspiro[5.5]undecande‐3,3‐dimethanol (1) with various substituted aryl phosphorus dichloridates (2) in dry toluene‐THF in the presence of triethylamine at 40‐60 oC. Their molecular structures were determined by ir, nmr and mass spectral studies and were screened for antifungal activity against Curvularia lunata and Aspergillus niger, and antibacterial activity on Staphylococcus aureus and Escherichia coli. Most of them possess significant activity. 相似文献
906.
The effect of CO2 adsorption on the catalytic activity of alkaline earth metal oxides in the title reaction reveals that the number of active (basic) sites follows the order MgO>CaO>SrO>BaO, and the order of base strength is MgO
CO2 , () : MgO>CaO>SrO>BaO, : MgO相似文献
907.
Mori A Kawashima J Shimada T Suguro M Hirabayashi K Nishihara Y 《Organic letters》2000,2(19):2935-2937
Palladium-catalyzed reaction of aryl and alkenyl halides with terminal alkynes in the presence of silver(I) oxide as an activator furnishes various arylated or alkenylated alkynes in good to excellent yields. The similar coupling reaction is also found to proceed using tetrabutylammonium fluoride (TBAF) or tetrabutylammonium hydroxide (TBAOH) as an activator. 相似文献
908.
The electrochemistry of dopamine (3-hydroxytyramine) was studied by cyclic voltammetry at a glassy carbon electrode in the presence of cetyltrimethylammonium bromide (CTAB) and sodium dodecyl sulfate (SDS) micelles at different pH. The anodic peak potential (E(pa)) and peak current (I(pa)) were found to be remarkably dependent on the charge and the concentration of the surfactant. The E(pa) and I(pa) change abruptly around the critical micellar concentration (CMC) of the surfactants and reach a plateau above the CMC. The E(pa) at the plateau shifts to more positive values in the cationic CTAB micellar solution, e.g. from 180 mV vs SCE in aqueous solution at pH 6.8 to 410 mV in CTAB micelle, whilst it shifts to less positive values in the anionic SDS micellar solution, e.g. 150 mV at pH 6.8. Therefore, the overlapped anodic peaks of dopamine and ascorbic acid in the mixture of the two compounds in aqueous solutions can be separated in CTAB micelles since the micelle shifts the E(pa) of ascorbic acid to less positive values. The two peaks are separated by ca. 400 mV at pH 6.8 in CTAB micelle, hence dopamine can be determined in the presence of 100 times excess of ascorbic acid. In SDS micelle and in the presence of ascorbic acid, the I(pa) of dopamine is greatly enhanced due to the catalytic oxidation of the latter that enables quantitative determination of both compounds. 相似文献
909.
Y. Muramatsu Y. Ohmomo D. Christoffers 《Journal of Radioanalytical and Nuclear Chemistry》1984,82(2):353-361
The possibilities of reactor induced (n, p) reactions as a tool for neutron activation analysis of titanium in geological samples are discussed. The interference of calcium and scandium is experimentally evaluated. Results for Ti, Ca and Sc in GSP-1 and PCC-1 standard rocks are presented. On the basis of the experimental values, it is concluded that the47Ti(n, p)47Sc reaction is the most favourable for titanium determination. 相似文献
910.
A. I. Pyatnitskaya G. A. Komasho V. A. Zazhigalov Y. B. Gorokhovatskii 《Reaction Kinetics and Catalysis Letters》1977,6(3):341-347
The activity of vanadium-phosphorus oxide catalysts with respect to maleic anhydride formation in n-butane oxidation has been found to correlate with the concentration of V4+ ions in the catalysts. The steady catalytic activitv of the samples examined is achieved more rapidly upon prereduction.
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