Water-DMSO mixtures complex

In water-DMSO mixtures in the presence of C104 and 1 anions, the electroreduction of Cd(II) ions was influenced by competitive adsorption of DM SO molecules and anions [224] and the rate of the Cd(II)/Cd process changed nonmonotonically with solvent composition. In water-rich mixtures, the electrode process was accelerated by the formation of activated complex Cd(II)-anion (ClO, —, I ). At higher DM SO concentration, the rate of the Cd(II)/Cd process was found to decrease and reach minimum at DM SO concentration equal to 9M. At cdmso > 9 M, the rate of the process increased again. 

The diffusion coefficients of ionic solutes show nonideal behavior with variation of composition of the solvent mixture in water-methanol binary mixtures. The degree of non-ideality of the solute diffusion is found to be similar to the nonideality that is observed for the diffusion of water and methanol molecules in these mixtures and is attributed to the enhanced stability of the HBs and formation of interspecies complexes in the mixtures. The diffusion coefficient of water is found to be minimum at 0-5 and that of methanol shows the minimum at = 0.7. However, the observed deviation from linear behavior with composition is found to be a bit weaker than that found in simulations of water-DMSO mixtures [11,12],... 

Two studies involving mixed DMSO-H2O solvates of Cr(III) have been reported.Continuing an investigation of the labilization of Cr(III) complexes by coordinated oxyanions, the reaction of the nitratopenta-aquochromium(III) ion in acidic water-DMSO mixtures has been reported. Up to five DMSO mol-... 

The stability of interpolymer complexes of linear and crosslinked polymers was studied in water-DMSO mixtures. It is known that DMSO is the acceptor of H-bonds and interpolymer complexes stabilized by H-bonds are usually destroyed in this solvent (3,4). Figures 3 and 4 represent the dependencies of swelling coefficients Kg and intrinsic viscosities [q] of [AA-VBE]/[CPVP] and [TMVEP-VP]/[LPAA] complexes on water-DMSO mixture. 

The composition of polyacrylic acid-crosslinked poly-Nvinylcaprolactam (PAA-CPVCL) complexes determined from the dependence of swelling coefficients of CPVCL on concentration of linear poly aery lie acid is equal to 1 1. The swelling coefficients of pure gel and gel-polymer complex in water-DMSO mixtures are compared in Figure 7. Poly-N-vinylcaprolactam gel undergoes sharp volume-phase transition in dependence of the thermodynamic quality of the solvent. In the case of gel-polymer complex at first the destruction of this complex occurs in mixtures containing up to 30 vol.% of DMSO, then the behavior of the system becomes similar to that for pure crosslinked polymer in water-DMSO mixtures. 

The cadmium electrodeposition on the cadmium electrode from water-ethanol [222, 223], water-DMSO [224], and water-acetonitrile mixtures [225-229] was studied intensively. It was found that promotion of Cd(II) electrodeposition [222] was caused by the formation of unstable solvates of Cd(II) ions with adsorbed alcohol molecules or by interaction with adsorbed perchlorate anions. In the presence of 1 anions, the formation of activated Cd(II)-I complex in adsorbed layer accelerated the electrode reaction [223]. 

The complexes cis- and /rn s-[RuCl2(dppm)2] undergo isomerization reactions induced by light, heat or oxidation to Ru111. The conversion trans - cis occurs thermally while cis -> trans occurs photochemically apparently by irradiation of the lowest lying d-d transition.1598 In water/alcohol mixtures photolysis of cis- or tranj-[RuCl2(dmpe)2] gives rro/u-[RuCl(OH2)(dmpe)2]+, while trans-[RuCl(DMSO)(dmpe)2]1 is always observed in DMSO. These results are consistent with the... 

The authors of this article have studied the properties of a series of complexes of alternating9, 52 54,66"711 and random72" 1 copolymers with nonionic polymers (Tables 4, 5) by means of the potentiometric, viscometric and conductometric methods. In some cases, when the copolymer is insoluble in water the complex formation has been studied in water-organic solvent mixtures. Thus, the water-DMSO (90 10 vol-%) mixed solvent for the PVP-MAA/St system761 and water-ethanol (70 30 wt-%) mixed solvent for the PVP (PEG) - MAA/MMA (MAA/BMA)771 systems have been used. 

The hydrophobic effect plays an important role in chemistry. It fosters the formation of micelles and reverse micelles and many other structures and gives rise to the unique solvation properties of aqueous binary mixtures (such as water-urea, water-DMSO, water-ethanol, to name just a few). The hydrophobic effect is also centrally important in biological systems. It is partly responsible for protein folding, micellar aggregation, lipid bilayer formation, cell membrane formation, the assembly of proteins into functional complexes, etc. 

Schmuck and coworkers reported a series of pyssole-functionalired guanidinium species (e.g., Compound 5) that are excellent receptors for carboxylates. In DMSO solution, the association constant for the formation of the acetate complex of receptor 5, proved too high to measure accurately (K>10 M ), By moving to a more polar solvent mixture (50% water-DMSO), however, it proved possible to determine the association constant it was found to be approximately 10 ... 

From the above and similar investigations [Mo 71, Be 73], it could be seen that, in various binary solvent mixtures containing water, acetonitrile, methanol and dimethyl sulphoxide, the solvating effects of the individual components are generally proportional to the effects displayed by the pure solvents. An exception is the H2O-DMSO mixture, in which the silver ion occurs only in the forms of its pure aquo complex and its pure DMSO complex. 

Gaizer and Gilbert [Ga 80] found that the stability constants of zinc chloride complexes in DMSO-water solvent mixtures of varying composition are higher than expected from the values measured in pure DMSO and pure water. 

NickeI(II) (rf ).— The mechanism of complex formation for some metal(ii) cations is now so well established, at least for simple ligands, that such reactions, particularly of nickel(n), are used to probe solvent and salt effects on kinetic patterns. Many of these studies are therefore dealt with in the Chapter on medium effects (Part II, Chapter 13). They include the reactions of nickel(n) and of magnes-ium(n) with chloride in aqueous alcohols, of nickel(ii) with imidazole in aqueous ethanol, with malonate in fructose-water solutions, with thiocyanate in methanol-DMSO mixtures, and with murexide or pada in various micellar media, and of several metal(n) cations with fluoride in aqueous salt solutions." In general, medium effects on observed rate constants (lit) for complex formation operate on the pre-association step (/fos) rather than on the interchange process (A i). The Eigen-Wilkins mechanism operates in all these media it has also been shown to operate for the bidentate ligand Etgdtc in DMSO, and even at the surface of a mercury electrode. ... 

However, these dependences are slightly nonlinear and have different inclination at different temperatures and concentrations of DMSO because of the formation of a variety of water-DMSO complexes, clusters, and nanodomains (Figure 7.87). The structure of the mixtures (especially small clusters at interfacial surface area S>1000 m /g) depends on C mso since more strongly... 

Variations in the formation and dissociation rate constants for nickel(ii) malonate in water-dioxan mixtures seem to be primarily due to changes in the ion-pair formation constant, which is very sensitive to the dielectric of the solvent, and reference has already been made (Table 3) to the stabilization of the outer-sphere complex noted in the reaction of Ni with a series of ligands in DMF. The low values of kt for the reaction of Ni with (1), (5), and (6) in DMSO (Table 4) are interpreted in terms of steric control. 

For CP-65 and LPVP systems the possibility of complex formation was also investigated in organic solvents such as ethanol and DMF. It was found that the composition of complex in ethanol is [CP-65]/[LPVP]=3 l, but in DMF there is no any complexation. Complexes are considerably less stable to the action of DMSO in comparison with complexes forming in water and are destroyed at 40 vol.% of DMSO in ethanol-DMSO mixtures. It is probably connected with weakening of hydrophobic interactions in these media. 

Water was used as the catalyst phase for the palladiiun complex of TPPTS and toluene or an excess of the substrate anihne served as the non-polar product phase. To determine an appropriate solvent system cloud titrations were performed at 90 °C, 60 °C, 40 °C and 25 °C. A solution of 4-chloro-nitroben-zene in aniline and water were mixed in a weight ratio of 1 1 and semi-polar solvents were added as a mediator until a homogeneous solution was formed. As the mediator the following solvents were apphed methanol, ethanol, isopropyl alcohol, n-butanol, DMF, DMSO, ethylene glycol, N-methylpyrrohdone (NMP), 1.4-dioxane and acetonitrile. The cloud titrations were repeated whereby the substrate 4-chloro-nitrobenzene was replaced with the product 4-nitrodiphenylamine. In all cases more of the semi-polar mediator is required for the product mixture at 25 °C than for the reaction mixture at 60 °C to obtain a clear solution. 

Reaction kinetics and mechanisms for oxidation of [Fe(diimine)2(CN)2], [Fe(diimine)(CN)4] (diimine = bipy or phen) (and indeed [Fe(CN)6] ) by peroxoanions such as (S20g, HSOs", P20g ) have been reviewed. Reactivity trends have been established, and initial state— transition state analyses carried out, for peroxodisulfate oxidation of [Fe(bipy)2(CN)2], [Fe(bipy)(CN)4] , and [Fe(Me2bsb)(CN)4] in DMSO—water mixtures. Whereas in base hydrolysis of iron(II)-diimine complexes reactivity trends in binary aqueous solvent mixtures are generally determined by hydroxide solvation, in these peroxodisulfate oxidations solvation changes for both partners affect the observed pattern. ... 

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