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991.
J. P. Shukla M. S. Nagar M. S. Subramanian 《Journal of Radioanalytical and Nuclear Chemistry》1981,62(1-2):61-72
Solvent extraction behaviour of Am(III) from dilute nitric acid media with sulfoxides (R2SO) in Solvesso-100 has been investigated over a wide range of conditions. Very poor extractability of Am necessitated the
use of salting-out agents, viz., nitrates of Al, Mg, Ca, Li and NH
4
+
. Effects of certain variables such as acidity, extractant concentration, saltingout agent, temperature etc., on metal extraction
by sulfoxides have been examined systematically. For a fixed sulfoxide concentration, extraction attains a maximum value up
to around 0.2–0.4M HNO3 and decreasing above 1M HNO3. In contrast, increasing the concentration of sulfoxide (0.8M DISO, 1.3M DBuSO) gives almost quantitative Am extraction up
to 1M HNO3. For satisfactory extraction, di-n-octyl as well as di-n-hexyl sulfoxide are the most suitable extracting agents. Extractability
of Am increases with increasing amounts of all the salting-out agents studied and their effect follows the sequence: Al3+>Mg2+>Ca2+>Li+>NH
4
+
; this is also the relative dehydrating effect of the cations. The species extracted would appear to be Am(NO3)3.3R2SO. Americium is easily stripped with 1–3M HNO3 solutions from the loaded organic phase. Extraction decreases with increasing temperature, indicating the extraction to be
exothermic. Extraction from partially non-aqueous solutions was also investigated. 相似文献
992.
Sanjeev K Shukla 《Journal of fluorine chemistry》2003,122(2):165-170
The reactions of tris(pentafluorophenyl)arsenic(III) with iodine monochloride, iodine monoazide, and dithiocyanogen yielded corresponding oxidative-addition products of the type (C6F5)3As(V)XY (X=I, Y=Cl, N3; X=Y=NCS). The elemental sulphur also added oxidatively with tris(pentafluorophenyl)arsenic(III) yielding tris(pentafluorophenyl)arsine(V) sulphide. Some displacement reactions were also carried out to synthesize mixed pseudohalide derivatives of the type (C6F5)3M(N3)NCS (M=As and Sb) and their insertion reactions were studied with phenyl isothiocyanate which yielded the corresponding 1,2-cycloaddition products, i.e. tetrazole-5-thiones. The compounds were characterized by elemental analysis, molar conductance, UV, IR and NMR spectroscopic studies. 相似文献
993.
Ram C. Maurya Dinesh C. Gupta Rajesh Shukla Raj K. Shukla Wahid U. Malik 《Transition Metal Chemistry》1987,12(3):273-275
Summary Novel mixed-ligand cyanonitrosyl complexes of chromium(I), [Cr(NO)(CN)2(L)2(H2O)], (where L=2-, 3-, or 4-benzylpyridine, 2-(4-chlorobenzyl)pyridine, 2-, 3-, or 4-benzoylpyridine, 3-(4-methylbenzoyl)pyridine, or 2-, 3-, or 4-acetylpyridine) have been prepared by the interaction of potassium pentacyanonitrosylchromate(I) monohydrate, K3[Cr(NO)(CN)5]·H2O with L. The complexes, characterized by elemental analyses, magnetic measurements, e.s.r. and i.r. spectral studies, contain chromium(I) in a low-spind
5-configuration. An octahedral structure, where CN istrans to CN, L istrans to L, and NO istrans to water is proposed for all the complexesEnemark and Feltham(1) have proposed circumventing the problem of the non-innocent nature of the nitrosyl ligand by considering nitrosyls as containing the {MNO}
n
group, wheren is the number of electrons of M, plus the number of electrons in the *-orbital of the NO (or more convenientlyn is the number of d-electrons if nitrosyl is regarded as being coordinated as NO+) 相似文献
994.
Satyendra N. Shukla Pratiksha Gaur Sangeeta Jhariya Bhaskar Chaurasia Preeti Vaidya Mohammad Azam 《Journal of Coordination Chemistry》2019,72(4):664-689
Molecular mechanism suggests that the incorporation of an antioxidant organic moiety to chromium will be a sound strategy for the synthesis of safer and more effective hypoglycemic compounds. Two Schiff base ligands were derived by condensation of isonicotinyl hydrazide with salicylaldehyde/o-hydroxyacetophenone which further yield four novel chromium(III) complexes of types [Cr(L)Cl2(H2O)] and [Cr(L)2]Cl. The ligands and complexes were characterized by analytical and spectroscopic techniques. DFT study at the basic set B3LYP and TD-SCF/6-311-G level was employed to confirm the geometry of the investigated compounds. Ligands were tested for their antioxidant activity and exhibited good antioxidant activity. Assessment of insulin-like activity of the complexes was initially performed in vitro by measuring the inhibition of α-amylase. The complex with highest in vitro activity was investigated for in vivo antidiabetic activity on the model of STZ-induced diabetic rats, which demonstrated that complex 4 significantly lowers the blood glucose level in rats. Toxicity level and antioxidant activity of the complex were also tested, which exhibit good tolerance level and antioxidant activity. Histological analysis of the pancreas of animals under investigation reveals the good condition of the pancreas treated with the complex. Ligands and complexes were also tested for antibacterial activity against Escherichia coli.
995.
Basic formulations used in the sedimentary210Pb dating technique are derived from fundamental considerations. The formulations are applicable to models that assume either a constant rate of supply (CRS) of unsupported210Pb to the sediments or a constant initial concentration (CIC) of this210Pb in the sediments. A previously proposed expression linking age discrepancy to mass sedimentation rates afforded by the two models is found to be inadequate in explaining the observed discrepancy between the CIC and CRS ages of segments of an undisturbed sediment core. It is noted that this age discrepancy is attributable to the mathematical treatment of data in the two models. A new expression, relating age discrepancy to the fluxes of unsupported210Pb obtainable by the two models, is derived and found to give more accurate and consistent results. 相似文献
996.
Several organic acids and bases that are very sparingly soluble in water have been determined by acid-base and redox titrimetry after solubilizing them in micellar suspensions of sodium dodecylsulfate or cetyltrimethylammonium bromide. Thermometric titrations are much more rapid, convenient, accurate, and precise than the corresponding potentiometric ones. Titrations in such media can effect some differentiations that cannot be made in water and are also much more economical than titrations in non-aqueous solvents. 相似文献
997.
Minaz A. Gagnani Ram S. Shukla Gadde Ramchandriah Sudhindra N. Misra 《Reaction Kinetics and Catalysis Letters》2004,82(1):57-64
Transition metal (Mo, V and Cr) incorporated montmorillonite KSF and K10, catalyzed the liquid phase benzylation of o-xylene by benzyl chloride efficiently with high selectivity towards monoalkylated product. Mo catalysts showed the highest catalytic activities. The catalysts were characterized by XRD, surface area, pore volume and acidity measurements and by temperature programmed desorption of ammonia.This revised version was published online in December 2005 with corrections to the Cover Date. 相似文献
998.
A new, sensitive, and selective method is described for the spectrophotometric determination of Ta(V). The method is based on the extraction of the Ta(V)-F-CV+ complex (CV+ = crystal violet cation) with a benzene solution of imidoyl derivatives (ID), i.e., N,N'-diphenylbenzamidine (DPBA), N-hydroxy-N,N'-diphenylbenzamidine, and N-(2,5-dimethyl)phenyl-p-tolylimidoylphenylhydrazine, from sulfuric acid solution; DPBA was selected for detailed study. The molar absorptivities of the Ta(V)-F-CV+-ID complexes in the benzene solution were in the range of (1.00-1.65) x 10(5) L/mol x cm at 600 nm. The limit of detection was 7 ng Ta/mL (which had an absorbance greater than that of the blank + 3 standard deviations). The optimization of the analytical variables, the composition of the complex, and the effect of diverse ions in the determination of Ta are discussed. The present method was applied to the determination of Ta in environmental samples, i.e., soil, sediment, minerals, and alloys. 相似文献
999.
Extraction behaviour of uranium(VI) from mixed organo-aqueous solutions containing water-miscible protic aliphatic alcohols and several aprotic solvents was investigated by using dicyclohexano-18-crown-6(DC18C6) as an extractant. The organic phase was a binary solution of DC18C6 and toluene while the polar phase was a three component solution of uranyl nitrate, polar additive and aqueous nitric acid. Methanol, ethanol, isobutanol, dioxane, acetone, propylene carbonate and acetonitrile were used as the organic components of the mixed (polar) phase. Propylene carbonate, acetone, acetonitrile and dioxane increased the extractability of U(VI), whereas alcoholic additives showed only an antagonistic effect. The relative increase in extraction was found to be more at lower nitric acid concentrations. Possible reasons for such behaviour are briefly discussed. Recovery of U(VI) from loaded organic phase was easily accomplished using dilute perchloric acid and sulphuric acid. A sample method was standardized for the separation of plutonium(IV) from uranium(VI) based on its reductive stripping. 相似文献
1000.
Alka Shukla Elizabeth M.J. Gillam Paul V. Bernhardt 《Electrochemistry communications》2006,8(12):1845-1849
The diflavo-protein NADPH cytochrome P450 reductase (CPR) is the key electron transfer partner for all drug metabolizing cytochrome P450 enzymes in humans. The protein delivers, consecutively, two electrons to the heme active site of the P450 in a carefully orchestrated process which ultimately leads to the generation of a high valent oxo-heme moiety. Despite its central role in P450 function, no direct electrochemical investigation of the purified protein has been reported. Here we report the first voltammetric study of purified human CPR where responses from both the FMN and FAD cofactors have been identified using both cyclic and square wave voltammetry. For human CPR redox responses at −2 and −278 mV (with a ratio of 1e−:3e−) vs NHE were seen at pH 7.9 while the potentials for rat CPR at pH 8.0 were −20 and −254 mV. All redox responses exhibit a pH dependence of approximately −59 mV/pH unit consistent with proton coupled electron transfer reactions of equal stoichiometry. 相似文献