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Constant Ionic Strength (constant + ionic_strength)
Selected AbstractsHydrolysis of diphenylmethyltin(iv) chloride in different aqueous solutions of ethanolHETEROATOM CHEMISTRY, Issue 7 2008Sima Mehdizadeh The hydrolysis of [(Ph)2MeSn(IV)]+ has been studied spectrophotometrically at 25,C and constant ionic strength of 0.1 mol dm,3 sodium perchlorate. Over a wide pH range, 1,11, the investigation has been performed in different aqueous solutions of ethanol. The species formed together with their formation constants have been determined using the computer program Squad. The hydrolysis constants at different media were analyzed in terms of Kamlet and Taft's parameters. A single-parameter correlation of the formation constants, K1-1 and K1-2, versus , (hydrogen-bond donor acidity), , (hydrogen-bond acceptor basicity), and ,* (dipolarity/polarizability) for both cases are relatively poor in all solutions, but multiparameter correlation represents significant improvement with regard to the single-parameter models. In this work, we have also used the normalized polarity parameter, E, alone and in combination with the Kamlet,Taft's parameters to find a better correlation of the formation constants in different aqueous solutions of ethanol. © 2008 Wiley Periodicals, Inc. Heteroatom Chem 19:654,660, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20484 [source] Oxidation of diclofenac sodium by diperiodatoargantate(III) in aqueous alkaline medium and its determination in urine and blood by kinetic methodsINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 6 2010P. N. Naik The kinetics and oxidation of diclofenac sodium (DFS) by diperiodatoargentate(III) (DPA) in alkaline medium at 298 K and at a constant ionic strength of 0.60 mol dm,3 were studied spectrophotometrically. The oxidation products were [2-(2,6-dicloro-phynylamino)-phenyl]-methenol and Ag(I), identified by LC-ESI-MS and IR spectral studies. The reaction between DFS and DPA in alkaline medium exhibits 1:1 stoichiometry. The reaction is first order in [DPA] and has a less than unit order dependence each in [DFS] and [alkali]. Increasing concentrations of IO,4 retard the reaction. The active species of DPA proposed to be monoperiodatoargentate(III), and a mechanism is suggested. The rate constants involved in the different steps of the mechanism were determined and are discussed. The activation parameters with respect to a rate-limiting step of the mechanism were determined. The thermodynamic quantities were also determined. Using the oxidation of DFS by DPA, DFS was analyzed by kinetic methods in urine and blood sample. The proposed method enables DFS analysis in the range from 5.0 × 10,5 to 5.0 × 10,3 mol dm,3. © 2010 Wiley Periodicals, Inc. Int J Chem Kinet 42: 336,346, 2010 [source] Kinetics and mechanism of decomposition of intermediate complex during oxidation of pectate polysaccharide by potassium permanganate in alkaline solutionsINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 2 2003Khalid S. Khairou The kinetics of decomposition of an [Pect·MnVIO42,] intermediate complex have been investigated spectrophotometrically at various temperatures of 15,30°C and a constant ionic strength of 0.1 mol dm,3. The decomposition reaction was found to be first-order in the intermediate concentration. The results showed that the rate of reaction was base-catalyzed. The kinetic parameters have been evaluated and found to be ,S, = , 190.06 ± 9.84 J mol,1 K,1, ,H, = 19.75 ± 0.57 kJ mol,1, and ,G, = 76.39 ± 3.50 kJ mol,1, respectively. A reaction mechanism consistent with the results is discussed. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 35: 67,72, 2003 [source] Monovalent cations affect the free solution mobility of DNA by perturbing the hydrogen-bonded structure of water,BIOPOLYMERS, Issue 2 2005Earle Stellwagen Abstract The free solution mobilities of single- and double-stranded DNA molecules of various molecular weights have been measured by capillary electrophoresis in solutions of constant ionic strength containing a common anion and fifteen different monovalent cations. In solutions with the same ionic composition, the mobilities of different DNA molecules can vary by up to 20%, depending on molecular weight, the number of strands, and the presence or absence of A-tracts, runs of four or more contiguous adenine residues. Importantly, the mobilities observed for the same DNA sample can vary by up to 40% in solutions containing different cations. The mobility differences observed for the same DNA in solutions containing different cations cannot be rationalized by differences in the anhydrous radii or intrinsic conductivities of the various cations, or by the sequence-dependent binding of certain cations to A-tracts. Instead, the observed mobilities are linearly correlated with the average number of water,water hydrogen bonds that are present in solutions containing different cations. The mobilities are also correlated with the viscosity B coefficients of the various cations and with the rotational correlation times frictional coefficients observed for water molecules in solutions containing different cations. Hence, monovalent cations modify the free solution mobility of DNA primarily by perturbing the hydrogen-bonded structure of water, affecting the friction experienced by the migrating DNA molecules during electrophoresis. © 2005 Wiley Periodicals, Inc. Biopolymers 78: 62,68, 2005 [source] | ||||||||||