排序方式: 共有19条查询结果,搜索用时 55 毫秒
1.
Jayadevan Jayashankaran 《Tetrahedron》2005,61(23):5595-5598
The 1,3-dipolar cycloaddition of an azomethine ylide, generated from isatin and benzylamine by a 1,5-prototopic shift route with various p-substituted 2,6-bis(arylmethylidene)cyclohexanones under different conditions, proceeded regioselectively to give novel dispiroheterocycles. The product on subsequent annulation with hydrazine hydrate afforded 4-aryl-5-phenyl(spiro[2.3″]oxindole)3′-aryl-3′,3a′,4′,5′,6′,7′-hexahydro-2H-indazolospiro[7′.3]pyrrolidines in good yield. 相似文献
2.
A. M. George N. C. Mishra M. S. Nagar N. C. Jayadevan 《Journal of Thermal Analysis and Calorimetry》1996,47(6):1701-1708
Thermal decomposition of the amorphous coprecipitate of yttrium and aluminium hydroxides forming yttrium aluminium garnet has been investigated employing thermal analyses, X-ray diffraction and IR spectroscopy. On heating, the coprecipitate progressively loses water forming a stable but highly disordered hydroxy garnet which crystallizes at 1180 K and decomposes to YAG at 1290 K. Nucleation of the crystalline phase appears to begin at 800 K.The authors thank Dr. P. V. Ravindran of the Analytical Chemistry and Shri N. K. Kulkarni of the Fuel Chemistry Divisions of BARC for their assistance in the thermoanalytical experiments. 相似文献
3.
K. D. Singh Mudher K. Krishnan N. C. Jayadevan 《Journal of Radioanalytical and Nuclear Chemistry》1993,176(2):175-184
Chemical characterization of rubidium uranium(IV) trisulfate, Rb2U(SO4)3, a new chemical assay standard for uranium requires accurate analysis of rubidium. A gravimetric and an X-ray fluorescence method (XRF) for the determination of rubidium in this compound are described. In the gravimetric method, rubidium is determined as Rb2Na[Co(NO2)6].H2O without separating uranium with a precision of the order of ±0.5%. In the XRF method, the concentration ratio of rubidium to uranium, CRb/CU, is determined in the solid samples by the binary ratio method using calibration between intensity ratios (IRb/IU) and concentration ratios (CRb/CU). The concentration of rubidium is derived using the uranium value which is known with a precision better than ±0.05%. The XRF method has a precision better than ±0.8% for rubidium determination. 相似文献
4.
S. Sampath N. K. Kulkarni N. C. Jayadevan 《Journal of Thermal Analysis and Calorimetry》1989,35(4):1089-1095
Thermal decomposition of metal uranyl acetates is one of the best ways of preparation of uranates in crystalline form at low temperatures. Acetates of the type M(UO2)2(OAc)6·7H2O (M=Zn(II), Mg(II) and Ni(II) were prepared and characterised. Their X-ray powder diffraction analysis showed that they all belong to the orthorhombic crystal class.The thermal decomposition of acetates in air goes through the reduction of uranium(VI) to uranium(IV) during acetate decomposition followed by reoxidation by oxygen. Zinc uranylacetate gave on thermal decomposition ZnU3O10, the nickel salt gave NiU3O10 and the magnesium salt gave a mixture of MgUO4 and MgU3O10. The thermal decomposition of acetates in helium led to reduction of uranium(VI) to uranium(IV) with the formation of UO2. No lower valent uranates could be identified.
The authors thank Dr. D. D. Sood, Head, Fuel Chemistry Division, for his encouragement during the course of this work. 相似文献
Zusammenfassung Thermische Zersetzung von Metalluranylazetaten ist eine der geeignetsten Methoden zur Darstellung kristalliner Uranate bei niedrigen Temperaturen. Azetate des Types M(UO2)2(OAc)6·7H2O mitM=Zn(II), Mg(II) und Ni(II) wurden hergestellt und beschrieben. Eine Pulverdiffraktionsanalyse zeigte, daß alle der orthorhombischen Kristallklasse angehören. Der thermische Zerfall der Azetate in Luft vollzieht sich während des Azetatzerfalls über die Reduktion von Uran(VI) zu Uran(IV) bis zu einer anschließenden Reoxydation durch Sauerstoff. Bei der thermischen Zersetzung liefert Zinkuranylazetat ZnU3O10, das Nickelsalz liefert NiU3O10 und das Magnesiumsalz ein Gemisch aus MgUO4 und MgU3O10. Der thermische Zerfall der Azetate in Helium führt zur Reduktion von Uran(VI) zu Uran(IV) unter Bildung von UO3. Uranate mit niedrigerer Wertigkeit konnten nicht identifiziert werden.
. M(UO2)2(OAc)6 · 7H2O, M = , . , . , . ZnU3O10, — NiU3O10, MgUO4 MgU3O10. . .
The authors thank Dr. D. D. Sood, Head, Fuel Chemistry Division, for his encouragement during the course of this work. 相似文献
5.
Subramanya Hegde Jayadevan Jayashankaran Atanu Ghosal T.S.R Prasanna Y. Shivaraj K. Mohana Raju 《Journal of heterocyclic chemistry》2013,50(2):442-449
A straightforward and general approach for the stereoselective synthesis of fused pyrrolo[1,2‐a] indoles frameworks from>intramolecular 1,3‐dipolar cycloaddition using N‐alkylated Baylis–Hillman derivatives is presented. It was found that the cycloaddition proceeded efficiently under microwave irradiation in solvent‐free condition to afford highly stereoselective cycloadducts in good yield. 相似文献
6.
A series of novel N‐methyl spiropyrrolidines have been synthesized in good yield by the cycloaddition reaction of azomethine ylides generated by a decarboxylative route from sarcosine and paraformaldehyde with conformationally locked s‐trans enone functionality present in the (E)‐3‐arylidene‐4‐chromanone as dipolarophiles. The structure of the title compound was established by spectroscopic techniques. 相似文献
7.
Jayapalan Kasthuri Jayadevan Santhanalakshmi Nagappan Rajendiran 《Transition Metal Chemistry》2008,33(7):899-905
The oxidative coupling of phenols with 4-aminoantipyrine (AmNH2) has been studied by UV–visible spectroscopy using platinum nanoparticles as catalyst. The rate of antipyrilquinoneimine
dye formation depends on the nature of substrates, temperature, pH, and the use of microheterogeneous media such as sodium
dodecylsulphate (SDS), cetyl trimethylammonium bromide (CTAB) and Triton X-100 (TX-100). The reactivity trend observed for
differently substituted phenols follows the order: 3,5-dimethylphenol > phenol > o-chlorophenol > o-nitrophenol. The rate of dye formation is greater at acid pH than at basic pH and the optimum pH is 5.4. A reaction pathway
is proposed, involving the activation of o-chlorophenol with AmNH2 by metal nanoparticles and concomitant reactions of free radicals. Transmission electron microscopy results show that the
particle size is 20 nm for the platinum nanoparticles involved in catalysis.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
8.
N. C. Jayadevan K. L. Chawla K. D. Singh Mudher N. D. Dahale D. M. Chackraburtty 《Journal of Radioanalytical and Nuclear Chemistry》1984,82(1):125-134
An X-ray fluorescence binary ratio method to measure non-destructively the relative percentage of PuO2 in (U, Pu)O2 samples is described. Calibration lines for pellet and microsphere samples are established and evaluated. Independent X-ray measurement of the major component after dissolution leads to the determination of individual concentrations within ±0.5% rel. of the chemical values. 相似文献
9.
K. D. Singh Mudher K. Krishnan R. R. Khandekar M. B. Yadav N. C. Jayadevan D. D. Sood 《Journal of Radioanalytical and Nuclear Chemistry》1999,240(1):183-191
Rubidium uranium trisulphate [Rb2U(SO4)3] was prepared as a high purity compound of uranium in different lots of 250 g each. The compound was characterised and evaluated
by chemical, atomic spectrosopic, infrared, X-ray diffraction and thermogravimetric methods for its use as a chemical assay
standard for uranium. The compound is stoichiometric, pure, homogeneous and stable in atmospheric conditions. The solubility
studies showed that Rb2U(SO4)3 is easily soluble in mineral acids. An experiment based on Randomised Block Design was carried out to assign a value to the
uranium content in Rb2U(SO4)3 from the statistically analysed chemical data. The assigned value of [34.167±0.042]% to the uranium content is in close agreement
with the theoretical value of 34.152%. Based on these studies, Rb2U(SO4)3 is recommended as a chemical assay standard for uranium. 相似文献
10.
Jayadevan Jayashankaran 《Tetrahedron letters》2006,47(13):2265-2270
The synthesis of novel polycyclic thiopyrano coumarin/chromone frameworks through intramolecular domino Knoevenagel hetero Diels-Alder reactions of 4-hydroxy coumarin and its benzo-analogous with S-prenylated aromatic aldehydes was studied. A high degree of chemoselectivity was achieved by the application of microwave irradiation and a solid support. 相似文献