http://nopr.niscair.res.in/handle/123456789/10169 Search the Channel search http://nopr.niscair.res.in/simple-search http://nopr.niscair.res.in/handle/123456789/10176 Title: CrO_X -Y₂O₃ catalysts for vapor phase fluorination of dichlorodifluoromethane <br/> <br/>Authors: Jia, Wen-Zhi; Xing, Li-Qiong; Qian, Lin; Chen, Xin; Wang, Yue-Juan; Lu, Ji-Qing; Chen, Ke-Feng; Zhang, Xue-Liang; Luo, Meng-Fei <br/> <br/>Abstract: <smarttagtype namespaceuri="urn:schemas-microsoft-com:office:smarttags" name="metricconverter"> A series of CrO_x-Y₂O₃ catalysts has been prepared using a deposition-precipitation method and tested for vapor phase fluorination of dichlorodifluoromethane (CCl₂F₂) for synthesis of tetrafluoromethane (CF₄). A comparative study using CCl₂F₂ and CClF₃ as the reactants for the fluorination reaction reveals that the conversion of CCl₂F₂ to CClF₃ is very fast, while that of CClF₃ to CF₄ is a rate-determining step. Pre-fluorinated CrO_X-Y₂O₃ catalyst calcined at 600 °C (CrYF-6) is found to be the most active for the reaction, (CF₄ yield 95%) and is stable during the testing period for the fluorination reaction. The characterization results indicate that the catalytic activity depends on the coordination of active Cr species and Lewis acid sites.</smarttagtype> <br/> <br/>Page(s): 1212-1216 Sun, 29 Aug 2010 22:58:59 GMT http://nopr.niscair.res.in/handle/123456789/10175 Title: Assessment of <img src='/image/spc_char/pi.gif' border=0>-nucleophilicity of silyl enolates using philicity index <br/> <br/>Authors: Deuri, Sanjib; Phukan, Prodeep <br/> <br/>Abstract: A study on the nucleophilic reactivity of silyl enol ethers and ketene silyl acetals has been carried out using conceptual density functional theory based reactivity descriptors. Silyl enolates having substituents of both electron releasing and electron withdrawing nature at various key positions of the molecules have been considered for the study. While intramolecular reactivity towards elctrophilic attack is studied on the basis of local philicity index, the intermolecular reactivity is assessed using group philicity. Role of β-methyl substituents are found to be crucial for nucleophilic reactivity of these systems. <br/> <br/>Page(s): 1206-1211 Sun, 29 Aug 2010 22:58:59 GMT http://nopr.niscair.res.in/handle/123456789/10174 Title: Molecular and supramolecular structures of diethyltellurium diiodide and diethyltellurium bis(carboxylates) <br/> <br/>Authors: Srivastava, Prakash C.; Singh, Vikas; Dwivedi, Shrinkhala; Butcher, Ray J <br/> <br/>Abstract: Diethyl tellurium bis(carboxylates) (C₂H₅)₂TeR¢₂ (R′ = C₆H₅OCO, 4-NO₂C₆H₄OCO, 3,5-(NO₂)₂C₆H₃OCO, C₆H₅CH=CHOCO, 4-OCH₃C₆H₄OCO) have been synthesised from the metathetical reactions of diethyl tellurium diiodide (C₂H₅)₂TeI₂ and corresponding silver salts and characterized by IR, ¹H, ¹³C and ¹²⁵Te NMR spectroscopy. The structures of (C₂H₅)₂TeI₂, (C₂H₅)₂Te(C₆H₅OCO)₂, (C₂H₅)₂Te(4-NO₂C₆H₄OCO)₂, (C₂H₅)₂Te{3,5-(NO₂)₂C₆H₃OCO}₂, (C₂H₅)₂Te(C₆H₅-CH=CHOCO)₂ and (C₂H₅)₂Te(4-OCH₃C₆H₄OCO)₂ have been established by single crystal X-ray diffraction studies. The structures of these complexes (the immediate environment about tellurium is that of distorted trigonal bipyramidal geometry with a stereochemically active electron lone pair) are described in the context of their ability to generate intermolecular Te---I and Te---O secondary bonds and C(<i style="">sp²</i>)-H---O and C(<i style="">sp³</i>)-H---O hydrogen bonds leading to the formation of zig-zag ribbons, stairs, dimeric, trimeric, tetrameric and extended supramolecular assemblies. The modification of supramolecular assembly present in the precursor (C₂H₅)₂TeI₂ by replacing the iodines with carboxylate groups is demonstrated and the cooperative participation of intermolecular C(<i style="">sp²</i>)-H---O and C(<i style="">sp³</i>)-H---O hydrogen bonds in strengthening the supramolecular assemblies is discussed. <br/> <br/>Page(s): 1197-1205 Sun, 29 Aug 2010 22:58:59 GMT http://nopr.niscair.res.in/handle/123456789/10173 Title: Synthesis, characterization and photocatalytic activity of alkaline earth metal doped titania <br/> <br/>Authors: Avasarala, Balaram Kiran; Tirukkovalluri, Siva Rao; Bojja, Sreedhar <br/> <br/>Abstract: The synthesis of beryllium doped titania (Be²⁺–TiO₂) at different percentages (0.25, 0.5, 0.75 and 1.0 wt %) by sol-gel method and its characterization by XRD, UV-visible absorption spectroscopy, XPS, SEM and FT-IR techniques are reported. Diffraction peaks of anatase crystalline phase have been observed both in synthesized TiO₂ as well as in Be²⁺–TiO₂. Presence of Be²⁺ ions in the TiO₂structure causes significant absorption shift towards the visible region. FT-IR and XPS data show the interstitial presence of Be²⁺ ion in TiO₂. The photocatalytic efficiency of the synthesized Be²⁺–TiO₂ and unsubstituted TiO₂ has been evaluated by the degradation of monocrotophos pesticide under visible light irradiation, wherein the degradation rate of MCP by Be²⁺–TiO₂ is found to be higher than by unsubstituted TiO₂.This may be attributed to the more efficient electron-hole creation in Be²⁺–TiO₂ in visible light, as compared to unsubstituted TiO₂ which can be excited only by UV irradiation. The effect of dopant concentration, <i style="">p</i>H, catalyst dosage and pollutant concentration have been studied for obtaining optimal degradation conditions. <br/> <br/>Page(s): 1189-1196 Sun, 29 Aug 2010 22:58:59 GMT