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741.
B. Sreeramulu M. S. Prasada Rao K. V. Ramana S. R. Sagi 《Journal of Thermal Analysis and Calorimetry》1985,30(3):535-539
Sodium bis-oxalatodiaquothallate(III) monohydrate has been prepared and characterised by chemical, thermal, X-ray diffraction and infrared spectroscopic methods. Thermoanalytical studies indicated that the complex decomposes through the formation of a mixture of thallium(I) oxalate and sodium oxalate, the final product at 650° being a mixture of thallium(I) oxide, thallium(III) oxide and sodium carbonate.
Zusammenfassung Natrium-bis-oxalatodiaquothallat(III)-Monohydrat wurde hergestellt und chemisch, thermoanalytisch, röntgendiffraktometrisch und infrarotspektroskopisch charakterisiert. Thermoanalytische Untersuchungen haben ergeben, daß sich der Komplex unter Bildung eines Gemisches von Thallium(I)- und Natriumoxalat als Zwischenprodukt zersetzt. Endprodukt der Zersetzung bei 650° ist ein Gemisch von Thallium(I)-oxid, Thallium(III)-oxid und Natriumcarbonat.
, --- () . , . 650° - .相似文献
742.
Uranium–cerium mixed oxides of three different compositions (U0.2Ce0.8)O2, (U0.5Ce0.5)O2 and (U0.8Ce0.2)O2, were prepared by combustion synthesis and characterized by XRD. The compositional characterization was done by ICP-AES. Heat capacity measurements employed a heat flux type differential scanning calorimeter from 280 to 820 K. The heat capacity values of (U0.2Ce0.8)O2, (U0.5Ce0.5)O2 and (U0.8Ce0.2)O2 at 298 K are 62.8, 64.2 and 70.1 J K−1 mol−1, respectively. Enthalpy increment, entropy and Gibbs energy function were computed from the heat capacity data. 相似文献
743.
Gowravaram Sabitha E. Venkata Reddy M. Bhikshapathi J.S. Yadav 《Tetrahedron letters》2007,48(2):313-315
The total synthesis of (9S,12R,13S)-pinellic acid, a novel and potentially useful oral adjuvant, isolated from Pinelliae tuber has been accomplished. 相似文献
744.
Rao YK Damu AG Rao AJ Venkatesan S Kuo PC Rao CV Wu TS 《Chemical & pharmaceutical bulletin》2003,51(12):1374-1376
Phytochemical investigation of the whole plant of Andrographis viscosula has led to the isolation of three new 2'-oxygenated flavonoids, (2R)-5-hydroxy-7,2',3'-trimethoxyflavanone (1), 7,2',5'-trimethoxyflavone (2), 5,7,2',3'-tetramethoxyflavone (3), and eight known flavones, 5,7,2'-trimethoxyflavone (4), 5,7,2',4',5'-pentamethoxyflavone (5), echioidinin (6), 5,2',6'-trihydroxy-7-methoxyflavone (7), 5-hydroxy-7,2'-dimethoxyflavone (8), echioidin (9), echioidinin 5-O-glucoside (10), and 5,2',6'-trihydroxy-7-methoxyflavone 2'-O-glucoside (11). The structures of 1-11 were elucidated by physical and spectral methods, including extensive 2D NMR studies. The presence of 2'-oxygenated flavonoids is apparently restricted to Andrographis species in Acanthaceae. Therefore, 2'-oxygenated flavonoids are regarded as chemotaxonomic markers of Andrographis genus in the Acanthaceae family. 相似文献
745.
The reaction between thallium(III) and oxalic acid in sulphuric acid medium has been investigated. Spectrophotometric results show that thallium(III) can be quantitatively reduced to thallium(I) with oxalic acid in aqueous medium when heated to near boiling point. Conditions for the estimation of the excess of oxalic acid with cerium(IV) sulphate in the presence of thallium(I) and for the estimation of a mixture of thallium(I) and thallium(III) have been investigated. The method is simpler than many other redox methods reported for the determination of thallium(III) and is free from many interferences encountered in these titrations. The reagents are cheap and quite stable. 相似文献
746.
Ahmed Kamal B. Rajendra Prasad A. Venkata Ramana A. Hari Babu K. Srinivasa Reddy 《Tetrahedron letters》2004,45(17):3507-3509
The tetrahydroquinoline moiety is an important structural component of a number of natural products. The reaction of aryl azides with 3,4-dihydro-2H-pyran in the presence of FeCl3-NaI affords the corresponding tetrahydroquinoline derivatives in an efficient manner. Most of the cyclizations exhibited cis selectivity. 相似文献
747.
The electron-impact-induced fragmentation in 2′-nitro-4-stilbazole is triggered by the oxidation of the olefinic double bond by the ortho nitro group in the initial step, while such an interaction under the same condition is totally absent in the meta and para isomers. The important fragmentation in 2′-nitro-2-stilbazole is the formation of a cyclised ion with the elimination of the nitro group. 相似文献
748.
749.
Unexpected ortho interaction of the nitro group has been noticed during the mass spectral fragmentations of N-arylidene 2-nitrobenzenesulphenamides, where the molecular ions expel SO2 and N2 both in concerted and stepwise processes. Loss of a hydrogen or the substituent from this fragment leads to a very abundant ion in all the compounds studied. Based on chemical evidence and linked-scan studies, a 1,2-phenylenetropylium cation structure has been postulated for the [M–SO2–N2–H/substituent]+ ion. 相似文献
750.
Zeolite-confined Nano-RuO(2): A green,selective, and efficient catalyst for aerobic alcohol oxidation 总被引:3,自引:0,他引:3
Zhan BZ White MA Sham TK Pincock JA Doucet RJ Rao KV Robertson KN Cameron TS 《Journal of the American Chemical Society》2003,125(8):2195-2199
The development of green, selective, and efficient catalysts, which can aerobically oxidize a variety of alcohols to their corresponding aldehydes and ketones, is of both economic and environmental significance. We report here the synthesis of a novel aerobic oxidation catalyst, a zeolite-confined nanometer-sized RuO(2) (RuO(2)-FAU), by a one-step hydrothermal method. Using the spatial constraints of the rigid zeolitic framework, we sucessfully incorporated RuO(2) nanoparticles (1.3 +/- 0.2 nm) into the supercages of faujasite zeolite. Ru K-edge X-ray absorption fine structure results indicate that the RuO(2) nanoclusters anchored in the zeolite are structurally similar to highly hydrous RuO(2); that is, there is a two-dimensional structure of independent chains, in which RuO(6) octahedra are connected together by two shared oxygen atoms. In our preliminary catalytic studies, we find that the RuO(2) nanoclusters exhibit extraordinarily high activity and selectivity in the aerobic oxidation of alcohols under mild conditions, for example, air and ambient pressure. The physically trapped RuO(2) nanoclusters cannot diffuse out of the relatively narrow channels/pores of the zeolite during the catalytic process, making the catalyst both stable and reusable. 相似文献