The interactions of the one-electron oxidants, N 3 • and Br 2 •radicals, with serotonin, tryptamine and their analogues 5-methoxytryptamine, N-methyltryptamine and N(1)-methyltryptophan were studied using the technique of pulse radiolysis with spectrophotometric detection. One-electron oxidation of serotonin results in the formation of an indoloxyl radical with a pK a value ,3. With tryptamine, N-methyltryptamine and 5-methoxytryptamine, their one-electron oxidation gives indolyl radicals with pK a values of 4.2, 4.3 and 4.8, respectively. The reactions of OH radicals ( • OH) with serotonin and tryptamine lead to the formation of the respective • OH-adducts, which decay by acid catalyzed water elimination to give almost quantitatively the corresponding indoloxyl and indolyl radicals, respectively. The first-order rate constants determined for water elimination are pH dependent, suggesting that the dehydration reaction is acid and base catalyzed. The • OHadduct of serotonin reacts with oxygen in competition with the dehydration reaction to yield a peroxyl radical adduct, which is tentatively suggested to eliminate HO 2 • . On the basis of the above findings, the mechanisms for the • OH -induced formation of the indoloxyl and indolyl radicals from serotonin and tryptamine respectively are proposed.
Cs exchanged heteropolyacid catalysts functionalized with various Sn contents were prepared by wet impregnation method. These catalysts were characterized by X-ray diffraction, FT-IR, Raman spectroscopy, temperature programmed desorption of ammonia and BET surface area measurements. The catalytic properties of SnCsPW catalysts were evaluated for the synthesis of glycerol carbonate and they exhibit an unprecedented activity for the higher glycerol conversion and selectivity towards glycerol carbonate under vacuum conditions. Sn-functionalized Cs exchanged heteropolyacid catalysts (CsPW) play a significant role in the enhancement of acidity, catalytic activity and stability. The glycerol conversion and the selectivity of carbonate formation mainly depend on the Sn content and acidity of the catalysts. Different reaction parameters such as Sn molar ratio, glycerol to urea molar ratio, reaction temperature were investigated and also optimum conditions were established. The catalyst containing molar ratio of 3:1 Sn-CsPW has shown highest conversion and glycerol carbonate selectivity.
Detailed geochemical and clay mineralogical investigations were carried out on bed sediments from upper Godavari river of peninsular India. The results suggest that these sediments are mainly derived from weathering of basaltic rocks of Deccan volcanic province. Strong relationship between Fe2O3 and TiO2 is attributed to their co-occurrence in weathering resistant minerals and/or scavenging of Ti by Fe oxy-hydroxides during weathering of basalts. The concentrations of Na2O, K2O and MgO in these upper Godavari river sediments are relatively less compared to parent basalt. The abundance of minor elements like V, Cr, Cu and Zn shows significant scatter within the range of Deccan basalts. Vanadium and nickel shows significant correlation with Fe2O3 due to their association with iron minerals or their sequestration with iron oxy-hydroxides. Higher Zn concentrations at some locations of Godavari river may have been due to anthropogenic contamination. The REE pattern is greatly influenced by the degree of source rock weathering. Light rare earth elements (LREE) show greater fractionation compared to the heavy rare earth elements (HREE) during weathering and transportation. Strong positive Ce-anomaly in some sediment samples suggests oxidizing conditions of deposition. Chemical Index of Alteration (CIA) varies significantly from 37.01 to 60.16, indicating large spatial variability in the intensity of chemical weathering of Deccan basalts. Low CIA values are observed in samples that are enriched in CaO probably due to semi-arid climate which facilitates CaCO3 precipitation and restricts chemical weathering.
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