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331.
The relative energies of beta Keggin heteropolytungstates, X(n+) W12O40(8-n)-, decrease as X(n+) is varied within period 3, from P5+ to Si4+ to Al3+. With heating of alpha-H5Ga3+ W12O40 at 200 degrees C in water, an equilibrated mixture of alpha (T(d); one 183W NMR signal) and beta (C(3v); three signals; 1:2:1 ratio) isomers is obtained. From deltaG(exp) = -RT ln K(beta-->alpha), in which (from 71Ga NMR spectra) K(beta-->alpha) (= [alpha]/[beta]) = 5.0, beta-GaW12O40(5-) is 0.65 kcal mol(-1) higher in energy than alpha-GaW12O40(5-). This finding is evaluated by analysis of the X-ray crystal structure alpha-K2Na3[GaW12O40] x 9.3 H2O [trigonal, space group P3(2)21, a = 18.9201(13) A, b = 18.9201(13) A, c = 12.5108(12) A, Z = 3, T = 100(2)K], comparison of the Shannon and Prewitt radii and Pauling electronegativities of Al3+ and Ga3+, and insight from density functional theory calculations, which predicted Ebeta - Ealpha = 0.32 kcal mol(-1). 相似文献
332.
Nitin Kumar Dr. Rapelly Venkatesh Prof. Sundaram Singh Prof. Jeyakumar Kandasamy 《European journal of organic chemistry》2023,26(37):e202300679
An efficient and eco-friendly method has been developed for the preparation of functionalized 3-(S)-arylthioindoles in good to excellent yields from indoles and aryl thiols in water. The coupling reaction was prompted by K2S2O8 in the presence of glucose at room temperature. Broad substrate scope, functional group tolerance, room temperature reactions and metal-free conditions are the salient features of the developed methodology. 相似文献
333.
Asmaa Ahmed Mohamed Elsakka Nabil Elminshawy Ayman Mohamed Senthilarasu Sundaram 《Chemical record (New York, N.Y.)》2023,23(12):e202300229
In recent years, floating photovoltaic (FPV) technologies have gained more importance as a key source of clean energy, particularly in the context of providing sustainable energy to buildings. The rise of land scarcity and the need to reduce carbon emissions have made FPV systems a cost-effective solution for generating electricity. This review article aims to explore the rapidly growing trend of floating PV systems, which can be a practical solution for regions with limited land areas. The article discusses the structure of the PV modules used in FPV plants and key factors that affect site suitability choice. Moreover, the article presents various techniques for cooling and cleaning FPV to keep optimal performance and discusses feasible trends and prospects for the technology. Finally, this paper proposes the potential integration of FPV systems with other technologies to enhance energy generation efficiency and discusses other research aimed at the advancement of the technology. By examining the various features of FPV systems, this review article contributes to understanding the advantages and challenges associated with using this sustainable energy technology in different regional contexts. 相似文献
334.
R. Krishna D. Velmurugan S. Shanmuga Sundara Raj H.‐K. Fun M. S. Sundaram R. Raghunathan 《Crystal Research and Technology》2001,36(11):1289-1294
The title compound (6,6‐dimethyl‐cis‐6H,6aH,7H,12bH,13H‐bis[1]benzopyrano[4,3‐b:4',3'‐d]pyran‐13‐one) crystallizes in monoclinic space group P21 /c with Z = 4. The unit cell dimensions are a = 8.6231(2) Å, b =10.0260(2) Å, c = 19.8376(2) Å, and β = 102.1(1)°, V = 1674.51(5) Å3 , Dcal = 1.326 Mg/m3. The coumarin moiety is in the planar conformation, the dioxadecalin moiety is cis fused and within the dioxadecalin moiety both the rings are in half cahir/sofa conformations. The structure has many C‐H … O type interactions. 相似文献