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21.
S. G. Sarkar S. V. Bandekar P. M. Dhadke 《Journal of Radioanalytical and Nuclear Chemistry》2000,243(3):803-807
Liquid-liquid extraction of Th(IV) and U(VI) has been investigated by commercial extractant PC-88A in toluene. The optimum conditions for extraction of these metals have been established by studying the various parameters like acid concentration/pH, reagent concentration, diluents and shaking time. The extraction of Th(IV) was found to be quantitative with 0.1–1.0M HNO3 acid and in the pH range 1.0–4.0 while U(VI) was completely extracted in the pH range 1.0–3.5 with 2.5·10–2M and 2.·10–2M PC-88A in toluene, respectively. The probable extracted species have been ascertained by log D-log C plot as ThR4·4HR and UO2R2·2HR, respectively. The method permits separation of Th(IV) and U(VI) from associated metals with a recovery of 99.0%. 相似文献
22.
Sushanta Saha Prodyut Kumar Sarkar Ambikesh Mahapatra 《Transition Metal Chemistry》2006,31(3):389-395
The reaction between Pd(N,N′)Cl2 [N,N′ ≡ 1-alkyl-2-(arylazo)imidazole (N,N′) and picolinic acid (picH) have been studied spectrophotometrically at λ = 463 nm in MeCN at 298 K. The product is [Pd(pic)2] which has been verified by the synthesis of the pure compound from Na2[PdCl4] and picH. The kinetics of the nucleophilic substitution reaction have been studied under pseudo-first-order conditions.
The reaction proceeds in a two-step-consecutive manner (A → B → C); each step follows first order kinetics with respect to
each complex and picH where the rate equations are: Rate 1 = {k′0 + k′2[picH]0} × [Pd(N,N′)Cl2] and Rate 2 = {k′′0 + k′′2[picH]0}[Pd(N,O)(monodentate N,N′)Cl2] such that the first step second order rate constant (k′2) is greater than the second step second order rate constant (k′′2). External addition of Cl− (as LiCl) suppresses the rate. Increase in π-acidity of the N,N′ ligand, increases the rate. The reaction has been studied
at different temperatures and the activation parameters (Δ‡H° and Δ‡S°) were calculated from the Eyring plot. 相似文献
23.
24.
Wu A Mukhopadhyay P Chakraborty A Fettinger JC Isaacs L 《Journal of the American Chemical Society》2004,126(32):10035-10043
We report the synthesis and characterization of eight C-shaped methylene-bridged glycoluril dimers (1-8) bearing hydrogen-bonding amide groups on their aromatic rings. Compounds 1-6 undergo tight dimerization in CDCl3 solution (Ks > 9 x 10(5) M(-1)); binary mixtures of 1-7 form mixtures of homodimers and heterodimers in moderately selective dimerization processes (0.23 < or = Keq < or = 768; 0.253 < or = chiAB < 0.933). The high affinity formation of 1.1-6.6 is due to the commensurate nature of the geometrical constraints imposed by the pi-pi interactions and only two hydrogen bonds. The differential response of the strengths of the pi-pi interactions and H-bonds of 2.2 to changes in solvent polarity--from C6D6 to D2O--results in the formation of a solvent-independent isostructural aggregate that exhibits high affinity dimerization across the full range of solvents. 相似文献
25.
A Sarkar N Biswas S Kapoor H S Mahal C K K Nair T Mukherjee 《Research on Chemical Intermediates》2005,31(9):857-866
The oxidation of flavonoids is of great interest because of their action as antioxidants with the ability to scavenge radicals
by means of electron-transfer processes. The redox reactions of the flavonoid derivative troxerutin, (2-[3,4-bis-(2-hydroxyethoxy)
phenyl]-3[[6-deoxy-α-L-manno-pyranosyl)-β-(D-glucopyranosyl]-oxy]-5-hydroxy-7-(2-hydroxyethoxy)-4H-1-benzo-pyran-4-one), were investigated over a wide range of conditions,
using pulse radiolysis and cyclic voltammetry. The oxidation mechanism proceeds in sequential steps. One-electron redox potentials
for troxerutin were found to be +1.196, +0.846 and −0.634 V vs. NHE. 相似文献
26.
Acid catalysed dehydration of the diols 5 , derived from the cyclohexenone 3 affords mixtures of 8 and 11 . The product ratio 8/11 , although strongly dependent on both the reaction conditions and the substituent R, is independent of the diol configuration; this indicates a cationic intermediate 6 . Conditions were found, which allow the sequence A → B → C → D (Scheme 2) to be applied to the syntheses of the enones 8, 21 and 25 in fair to good yields from the corresponding cyclohexenones 3, 18 and 22 . 相似文献
27.
Mondal A Sarkar S Chopra D Row TN Rajak KK 《Dalton transactions (Cambridge, England : 2003)》2004,(20):3244-3250
The green colored complexes of the type Re(V)O(L(SB))Cl(2), 1, have been synthesised by reacting NBu(4)[ReOCl(4)] with HL(SB) in dry ethanol. Here, L(SB)(-) are the deprotonated forms of N-(2-hydroxybenzyl)-2-picolylamine (HL(SB)(1)); N-(2-hydroxybenzyl)-N',N'-dimethylethylenediamine (HL(SB)(2)) and N-(2-hydroxybenzyl)-N',N'-diethylethylenediamine (HL(SB)(3)). Similarly, NBu(4)[ReOCl(4)] reacted with N,N-bis(2-hydroxybenzyl)-2-picolylamine (H(2)L(1)); N,N-bis(2-hydroxybenzyl)-N',N'-dimethylethylenediamine (H(2)L(2)); N,N-bis(2-hydroxybenzyl)-N',N'-diethylethylenediamine (H(2)L(3)); [N-(2-hydroxybenzyl)-N-(2-pyridylmethyl)]-2-aminoethanol (H(2)L(4)); [N-(2-hydroxybenzyl)-N-(2-pyridylmethyl)]-2-methyl-2-amino-1-propanol (H(2)L(5)); N,N-bis(1-hydroxyethyl)-2-picolylamine (H(2)L(6)), to give the monochloro complexes Re(V)O(L)Cl, 2. The X-ray structures of the complexes are reported. The molecular structures observed in the solid state are preserved in solution ((1)H NMR). In acetonitrile solution the Re(V)O(L)Cl, 2, display a one-electron couple, Re(VI)O(L)Cl(+)-Re(V)O(L)Cl, near 1.0 V vs SCE. The electrogenerated hexavalent complexes [Re(VI)O(L)Cl]ClO(4), 3, are paramagnetic and display sextet EPR spectra in solution at room temperature (A(av) approximately 417 (G), g approximately 1.914). 相似文献
28.
D. Choudhury P. J. O'Donnell U. Sarkar 《Zeitschrift fur Physik C Particles and Fields》1992,54(2):307-309
The EMC collaboration have reported a measurement of the proton structure function which has been interpreted to mean that the spin of the proton is not predominantly that of the quarks (=u+d+s=0.13±0.19). We show that the magnetic moments of the baryons are independent of this measurement and are given (within 10–20%) for a range of including the valence model value =1. The magnetic moments of the quarks can only be fixed if the quantity is determined very accurately. 相似文献
29.
30.
M. K. Das N. Ramamoorthy B. R. Sarkar R. S. Mani 《Journal of Radioanalytical and Nuclear Chemistry》1987,111(2):469-475
We have studied the feasibility of producing57Co (271.3 d) via the55Mn(, 2n)57Co reaction (55Mn–100%). The thick target yield of57Co in the 28 to 18 MeV energy region was measured as 3.87 Ci/Ah. However, the proximity and overlap of the excitation functions for (, n), (, 2n) and (, 3n) reactions on55Mn are such that the production of pure57Co in high yields free of58Co (70.8 d) and56Co (78.8 d) has not been feasible. We have also studied a new method for ancillary production of57Co via the reactions58Ni(, p)57Co and
during the course of producing62Zn by60Ni(, 2n)62Zn reaction. In this case the yield of57Co of reasonable purity has been up to 1 Ci/Ah. 相似文献