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排序方式: 共有1029条查询结果,搜索用时 15 毫秒
1.
Raviraj M Kulkarni Dinesh C Bilehal Sharanappa T Nandibewoor 《Analytical sciences》2004,20(4):743-747
The kinetics of oxidation of isoniazid in acidic medium was studied spectrophotometrically. The reaction between QDC and isoniazid in acid medium exhibits (4:1) stoichiometry (QDC:isoniazid). The reaction showed first order kinetics in quinolinium dichromate (QDC) concentration and an order of less than unity in isoniazid (INH) and acid concentrations. The oxidation reaction proceeds via a protonated QDC species, which forms a complex with isoniazid. The latter decomposes in a slow step to give a free radical derived from isoniazid and an intermediate chromium(V), which is followed, by subsequent fast steps to give the products. The reaction constants involved in the mechanism are evaluated. Isoniazid was analyzed by kinetic methods in pure and pharmaceutical formulations. 相似文献
2.
Milind V. Kulkarni Annamraju Kasi Viswanath R. Marimuthu Tanay Seth 《Journal of polymer science. Part A, Polymer chemistry》2004,42(8):2043-2049
Spectroscopic [UV–visible and Fourier transform IR (FTIR)] and thermal properties of chemically synthesized polyanilines are found to be affected by varying the protonation media (acetic, citric, oxalic, and tartaric acid). The optical spectra show the presence of a greater fraction of fully oxidized insulating pernigraniline phase in polyaniline doped with acetic acid. In contrast, the selectivity in the formation of the conducting phase is higher in oxalic acid as a protonic acid media. The FTIR spectra of these polymers reveal a higher ratio of the relative intensities of the quinoid to benzenoid ring modes in acetic acid doped polyaniline. Scanning electron micrographs revealed a sponge‐like structure derived from the aggregation of the small granules in acetic acid and oxalic acid doped polyaniline. A three‐step decomposition pattern is observed in all the polymers, regardless of the protonic acid used for the doping. The second step loss related to the loss of dopant is found to be higher in the oxalic acid doped polymer. In accordance with these results the conductivity is also found to be higher in oxalic acid doped material. The temperature dependent conductivity measurements show the thermal activated behavior in all the polymers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2043–2049, 2004 相似文献
3.
Neelesh A. Kulkarni 《Tetrahedron letters》2006,47(4):611-613
The nucleophilic allylation of camphor derived glyoxylic oxime ethers was carried out using allyltributyltin in the presence of Sn(OTf)2 affording the corresponding homoallylic amines in high chemical yields (up to 94%) and excellent stereoselectivities (up to >99%). 相似文献
4.
Mukund G. Kulkarni Attrimuni P. Dhondge Dnyaneshwar D. Gaikwad Ajit S. Borhade Sanjay W. Chavhan 《Tetrahedron letters》2006,47(6):1003-1005
A two-step synthetic sequence for an efficient synthesis of 3-allylindoles is described. 相似文献
5.
S. G. Charati A. Y. Houde S. S. Kulkarni M. G. Kulkarni 《Journal of Polymer Science.Polymer Physics》1991,29(8):921-931
Polymer packing density can be conveniently measured by either density-based measurements (direct or estimated free volume) or wide-angle X-ray diffraction (WAXD) spectra. Previously reported diffusivity and permeability values for various polyarylates and polyimides are examined on the basis of the packing density measured by these different techniques. It is shown that in these rigid glassy polymers, the mean intersegmental distance, the d-spacing, obtained from WAXD provides a better measure of the effect of polymer packing on diffusivity than either direct density measurements or estimated free volumes. It has been possible to correlate previously reported diffusivity and sorption data for various polyarylates and polycarbonate on the basis of the WAXD investigation, using the d-spacing and the amorphous peak width, respectively. The effect of polyarylate structure on d-spacing has been studied. A series of polyarylates have been synthesized with different substituents on the bridge carbon. In this series the d-spacing remains constant while the carbonyl group density and the glass transition temperatures are varied. However, small substituents on the aromatic ring cause significant changes in the d-spacing. These results can be used to tailor polyarylates with desired intersegmental distances and chain flexibility. 相似文献
6.
Stols Lucy Kulkarni Gopal Harris Ben G. Donnelly Mark I. 《Applied biochemistry and biotechnology》1997,63(1):153-158
Applied Biochemistry and Biotechnology - The malic enzyme gene ofAscaris suum was cloned into the vector pTRC99a in two forms encoding alternative arnino-termini. The resulting plasmids, pMEAl and... 相似文献
7.
Rao CN Kulkarni GU Thomas PJ Edwards PP 《Chemistry (Weinheim an der Bergstrasse, Germany)》2002,8(1):28-35
Properties of materials determined by their size are indeed fascinating and form the basis of the emerging area of nanoscience. In this article, we examine the size dependent electronic structure and properties of nanocrystals of semiconductors and metals to illustrate this aspect. We then discuss the chemical reactivity of metal nanocrystals which is strongly dependent on the size not only because of the large surface area but also a result of the significantly different electronic structure of the small nanocrystals. Nanoscale catalysis of gold exemplifies this feature. Size also plays a role in the assembly of nanocrystals into crystalline arrays. While we owe the beginnings of size-dependent chemistry to the early studies of colloids, recent findings have added a new dimension to the subject. 相似文献
8.
Lee JC Chang SW Liao CC Chi FC Chen CS Wen YS Wang CC Kulkarni SS Puranik R Liu YH Hung SC 《Chemistry (Weinheim an der Bergstrasse, Germany)》2004,10(2):399-415
A novel and convenient route for the synthesis of biologically potent and rare L-hexose derivatives from D-glucose is described. Conversion of diacetone-alpha-D-glucose (14) into 1,2:3,5-di-O-isopropylidene-beta-L-idofuranose (19) was efficiently carried out in two steps. Orthogonal isopropylidene rearrangement of compound 19 led to 1,2:5,6-di-O-isopropylidene-beta-L-idofuranose (27), which underwent regioselective epimerization at the C3 position to give the L-talo- and 3-functionalized L-idofuranosyl derivatives. Hydrolysis of compound 19 under acidic conditions furnished 1,6-anhydro-beta-L-idopyranose (35) in excellent yield, which was successfully transformed into the corresponding L-allo, L-altro, L-gulo, and L-ido derivatives via regioselective benzylation, benzoylation, triflation and nucleophilic substitution as the key steps. Applications of these 1,6-anhydro-beta-L-hexopyranoses as valuable building blocks to the syntheses of 4-methylcoumarin-7-yl-alpha-L-iduronic acid and the disaccharide moieties of bleomycin A(2) as well as heparan sulfate are highlighted. 相似文献
9.
Kulkarni Raviraj M. Bilehal Dinesh C. Nandibewoor Sharanappa T. 《Transition Metal Chemistry》2003,28(2):199-208
The kinetics of CrIII-catalysed oxidation of L-valine by permanganate in alkaline medium at a constant ionic strength has been studied spectrophotometrically. The reaction between permanganate and L-valine in alkaline medium exhibits 2:1 stoichiometry (KMnO4:l-valine). The reaction shows first order dependence on [permanganate] and [chromium(III)], and less than unit order dependence each in [L-valine] and alkali concentrations under the experimental conditions. However the order in [L-valine] and [alkali] changes from first order to zero order as the concentrations change from lower to higher respectively. The results suggest the formation of a complex between L-valine and the hydroxylated species of CrIII. The complex reacts further with 1 mol of alkaline permanganate species in a rate-determining step, resulting in the formation of a free radical, which again reacts with 1 mol of alkaline permanganate species in a subsequent fast step to yield the products. The reaction constants involved in the mechanism were evaluated. The activation parameters with respect to the slow step of the mechanism were obtained and discussed. The title reaction has been utilised to analyse chromium(III) in the 26.0 ng cm–3–1.0 g cm–3 range. 相似文献
10.
M. Subrahmanyam S. J. Kulkarni B. Srinivas 《Reaction Kinetics and Catalysis Letters》1993,49(2):455-459
N-(2-hydroxyethyl) ethylenediamine reaction was observed over zeolite catalysts giving rise to only dehydrocyclization and over chromite catalysts showing dehydrocyclization together with dehydrogenation. The major product changes from the cyclized compound piperazine to pyrazine when the reactant is switched from zeolite to chromite catalyst. This process stands as a model reaction for characterizing lone acid sites and adjacent acid-base sites over zeolite and chromite catalysts, respectively.IICT Communication No. 3175 相似文献