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991.
Rajneesh Kumar Pankaj Sharma P. B. Barman Vineet Sharma S. C. Katyal V. S. Rangra 《Journal of Thermal Analysis and Calorimetry》2012,110(3):1053-1060
The present article deals with the differential scanning calorimetric (DSC) study of Se?CTe glasses containing Sn. DSC runs are taken at four different heating rates (10, 15, 20 and 25?K?min?1). The crystallization data are examined in terms of modified Kissinger, Matusita equations, Mahadevan method and Augis and Bennett approximation for the non-isothermal crystallization. The activation energy for crystallization (E c) is evaluated from the data obtained at different heating rates. Activation energy of glass transition is calculated by Kissinger??s relation and Moynihan theory. The glass forming tendency is also calculated for each composition. The glass transition temperature and peak crystallization temperature increases with the increase in Sn % as well as with the heating rate. 相似文献
992.
The thermal decomposition behaviours of oxovanadium(IV)hydroxamate complexes of composition [VO(Q)2?n(HL1,2)n]: [VO(C9H6ON)(C6H4(OH)(CO)NHO)] (I), [VO(C6H4(OH)(CO)NHO)2] (II), [VO(C9H6ON)(C6H4(OH)(5-Cl)(CO)NHO)] (III), and [VO(C6H4(OH)(5-Cl)(CO)NHO)2] (IV) (where Q?=?C9H6NO? 8-hydroxyquinolinate ion; HL1?=?[C6H4(OH)CONHO]? salicylhydroxamate ion; HL2?=?[C6H3(OH)(5-Cl)CONHO]? 5-chlorosalicylhydroxamate ion; n?=?1 and 2), which are synthesised by the reactions of [VO(Q)2] with predetermined molar ratios of potassium salicylhydroxamate and potassium 5-chlorosalicylhydroxamate in THF?+?MeOH solvent medium, have been studied by TG and DTA techniques. Thermograms indicate that complexes (I) and (III) undergo single-step decomposition, while complexes (II) and (IV) decompose in two steps to yield VO(HL1,2) as the likely intermediate and VO2 as the ultimate product of decomposition. The formation of VO2 has been authenticated by IR and XRD studies. From the initial decomposition temperatures, the order of thermal stabilities for the complexes has been inferred as III?>?I > II?>?IV. 相似文献
993.
In this study, we have studied the effect of elements Ag, Cd, and Sn as chemical modifiers on some thermal transport properties (thermal conductivity, diffusivity, and specific heat per unit volume) of amorphous Se. Concurrent measurements of thermal transport properties such as effective thermal conductivity (??e), thermal diffusivity (??e), and specific heat per unit volume (??C v) are used at room temperature for twin pellets of pure Se- and Se-based binary Se98M2 (M?=?Ag, Cd, and Sn) alloys using transient plane source technique. We have also determined the thermal inertia I T using the experimental values of thermal conductivity and specific heat per unit volume for present amorphous alloys. The increasing sequence of measured thermal transport properties is also discussed. 相似文献
994.
Reaction of dibutyltin dichloride, dimethyltin dichloride, and tributyltin chloride with ligands derived from thiosemicarbazone
and semicarbazone leads to the formation of a new series of organotin(IV) complexes of general formula R2SnCl2·L and R3SnCl·L (where L ligands derived from the condensation of thiosemicarbazide and semicarbazide with 4-hydroxy-3-methoxybenzaldehyde). The authenticity
of these ligands and their metal complexes have been established on the basis of elemental analysis, conductance measurements,
molecular weight determinations, infrared, 1H NMR, 13C NMR, 119Sn NMR, and UV spectral studies. These studies showed that the ligands coordinate to the metal atom in a bidentate. An octahedral
structure is proposed for the organotin(IV) complexes. The ligands and its metal complexes are screened for their antimicrobial
activities against some Gram-positive and Gram-negative bacteria, and fungus. The studies demonstrated that metalation can
increase the antimicrobial activity rather than the free ligands. 相似文献
995.
Sonali Verma Barkha Srivastava Kusum Sharma Rahul Joshi Pushpa Pardasani R. T. Pardasani 《Research on Chemical Intermediates》2012,38(3-5):723-731
[4?+?2]-Photocycloadditions of benzo[b]thiophene-2,3-dione with electron-rich and electron-deficient alkenes have been described. Olefins preferentially add at both carbonyl groups to give the head-to-head [4?+?2] cycloadducts, i.e., dioxanes only. Comprehensive molecular orbital calculations at DFT-B3LYP level have been carried out to address the mechanism as well as regiochemical course of the reaction. 相似文献
996.
Ranjan K. Bhatt Satyasheel Sharma Mahendra Nath 《Monatshefte für Chemie / Chemical Monthly》2012,54(1):309-316
Abstract
An improved synthetic procedure is developed for the regioselective nitration of a phenyl group of meso-tetraphenylporphyrin by using NaNO2 in a mixture of trichloroacetic acid and AcOH. The meso-(4-nitrophenyl)porphyrins are successfully reduced to corresponding meso-(4-aminophenyl)porphyrins by SnCl2 under acidic conditions. In addition, an efficient one-pot methodology for synthesizing a series of novel meso-substituted porphyrinic thiazolidinone conjugates is developed by reacting meso-(4-aminophenyl)porphyrins with various aromatic aldehydes and mercaptoacetic acid in refluxing toluene using La(OTf)3 as a catalyst. The products obtained are characterized on the basis of their spectral data. Preliminary photophysical properties of the newly synthesized compounds are reported. 相似文献997.
Gangavaram V.M. Sharma Post Sai Reddy Deepak Chatterjee Ajit C. Kunwar 《Tetrahedron》2012,68(23):4390-4398
The study describes the synthesis of new β2,2-peptides made from geminally disubstituted β2,2-amino acid and their folding propensities. The (R)-C-linked carbo-β2,2-amino acid [(R)-β2,2-Caa] was prepared from d-glucose and converted into the homo-oligomeric di-, tetra-, and hexapeptides. The conformational studies were carried out using NMR (in CDCl3), CD, IR, and MD calculations. These β2,2-peptides were interestingly stabilized by five-membered (mr) inter-residue H-bonds NH(i)?O(i-1) (furanoside) and a 6-mr intra-residue H-bond between amide proton (NH(i)) and the oxygen of –OMe(i) at the C3 carbon of the carbohydrate side chain. These results amply demonstrate that the ‘epimerization’ at the spiro carbon center has an effect on the conformational behavior of these peptides. Finding of these, H-bonding patterns, which are not so common to stabilize the folds in this class of β2,2-Caa derived peptides would further facilitate augmentation in the domain of foldamer. 相似文献
998.
Dharminder Sharma Sandeep Kumar Arun K. Shil Nitul Ranjan Guha Pralay Das 《Tetrahedron letters》2012,53(52):7044-7051
Solid supported palladium nano/microparticles were found to be active catalysts to perform mono- and β,β-double-Heck reactions. Different β-unsubstituted and substituted alkenes including acrylate, methacrylate, crotonate, styrene, acrylonitrile, and acrylamide were investigated successfully for mono- and β,β-double-Heck reactions with aryl iodide under milder reaction condition. One-pot β,β-double-Heck reaction of aryl iodides with α,β-unsaturated ester, amide, nitrile, and styrene derivatives were also performed under standard reaction conditions. Wide functional group tolerance, easy catalyst recovery, and recyclability up to twelve times without significant loss of catalytic activity added extra importance to the present process. 相似文献
999.
1000.
We study a generalization of K-contact and (k, μ)-contact manifolds, and show that if such manifolds of dimensions ≥ 5 are conformally flat, then they have constant curvature +1. We also show under certain conditions that such manifolds admitting a non-homothetic closed conformal vector field are isometric to a unit sphere. Finally, we show that such manifolds with parallel Ricci tensor are either Einstein, or of zero ${\xi}$ -sectional curvature. 相似文献