Dimethyl Sulphoxide Water Mixtures Research Articles

Electron-transfer reactions in non-aqueous media. II. Reduction of CoF(NH3)52+, CoCl(NH3)52+ and CoBr(NH3)52+ by iron(II) in dimethyl sulphoxide-water mixtures

The kinetics of the reduction of the cobalt(111) octahedral complexes, CoF(NH3)52+, CoCl(NH3)52+ and CoBr(NH3)52+, by iron((11) in various Me2SO-H2O mixtures have been studied over a range of temperatures. The activation parameters obtained for the chloro and bromo systems are consistent with a change in the stereochemistry of the iron (11) atom in the bridged intermediate from octahedral in water to tetrahedral with increasing Me2SO concentration. The fluoro system, however, has activation parameters which are less sensitive to solvent composition and consistent with the iron(11) atom maintaining octahedral coordination.

Conductance of acids in dimethylsulphoxide—I: Conductance of hydrochloric acid in DMSO—water mixtures at 25°C

Conductance measurements at 25°C are reported for dilute solutions of hydrochloric acid in dimethylsulphoxide and in dimethylsulphoxide—water mixtures containing up to 15% by weight of water. The results are analysed in terms of full Fuoss—Hsia conductance equation. Association constants decrease as the water content is increased whereas Λ α values pass through a minimum at about 11% water.

Kinetics of the hydrolysis of acetic anhydride and the reaction of 4-nitrophenyl acetate with imidazole in aqueous-organic mixed solvents

With the general aim of elucidating the role of water structure in the kinetics of hydrolysis, a comparative study has been made of the kinetics of the hydrolysis of acetic anhydride and the reaction of 4-nitrophenyl acetate with imidazole in mixtures of water with ethanol, t-butyl alcohol, dimethyl sulphoxide and dioxan. Both rate constants were always reduced by the addition of organic solvent. Transition state activity coefficients were measured for both reactions in dimethyl sulphoxide-water mixtures and compared with the activity coefficient of phenylalanine (a model zwitterionic transition state). Activation parameters were measured for the hydrolysis of aceticanhydride in t-butyl alcohol-water and dimethyl sulphoxide-water mixtures. Semilogarithmic plots of rate constant against Winstein's Y-value were non-linear for some of the solvents and this fact, coupled with the effect of dimethyl sulphoxide on the transition state activity coefficients, leads to the conclusion that specific interactions of the solvent with the reactants and with the transition state could be of major importance in controlling the reaction rate.There was no obvious relationship between the effect of an organic solvent on the kinetics of hydrolysis of acetic anhydride and its effect on the structure of water.

Solvent effects on the kinetics of alkaline hydrolysis of dimethylacetylacetone. Part II. Influence of dipolar aprotic solvent–water mixtures

The influence of a few protic–dipolar aprotic mixtures on the kinetics of alkaline cleavage of dimethylacetylacetone has been studied. The aprotic components used are dimethyl sulphoxide, acetone, dioxan, sulpholan, dimethoxyethane, and hexamethylphosphoramide. In most of these mixtures, the behaviour of the reaction is very analogous with that of alkaline hydrolysis of esters which suggests an identical mechanism for both reactions. Moreover the determination of activation parameters in dimethyl sulphoxide–water mixtures enables one to discuss the part played by the substrate on the reaction rate. Finally, kinetic results which are similar for some media can be explained by their nearly identical basicity.

The standard potentials of silver–silver halide electrodes and ion solvation in dimethyl sulphoxide–water mixtures at 25 °C

Standard e.m.f.s of the cells H2|HX|AgX–Ag (X = Cl, Br, or I) in 10, 60, 70, and 80%(w/w) dimethyl sulphoxide–water mixtures are reported. These, together with values for mixtures of other compositions determined earlier, were used to calculate the molar free energies of transfer of the halogen acids from water to the mixed solvents. Single-ion values were derived therefrom by use of the extrathermodynamic assumptions of Feakins et al. and discussed in terms of ion solvation. It is shown that the solvophilicity of the ions is largely determined by their acid–base' interactions with the solvent molecules. The structural features of the solvents are briefly discussed.

Standard E.m.f.s of the cells H2|HX|AgX–Ag (X = Cl, Br, or I) in 20 and 40%(w/w) dimethyl sulphoxide–water mixtures at 25°C

Standard molal e.m.f.s at 25°C of the cells H2|HX|AgX–Ag (X = Cl, Br, or I) in 20 and 40%(w/w) dimethyl sulphoxide–water mixtures are reported. Lightly platinised hydrogen electrodes proved highly satisfactory and no special technique was required in their preparation.

Solution structures of ferrihaem in some dipolar aprotic solvents and their binary aqueous mixtures.

1. Conductivity and u.v. and visible spectroscopic techniques were used to investigate the solution structure of the prosthetic group of the ferric haemoproteins (ferrihaem) in dimethyl sulphoxide, NN-dimethylacetamide, NN-dimethylformamide and sulpholane, and certain of their aqueous mixtures. 2. In neutral or acid dimethyl sulphoxide, chlorohaemin is monomeric and completely dissociated into Cl(-)ion and a ferrihaem species with dimethyl sulphoxide molecules in the fifth and sixth co-ordination positions on iron. 3. In neutral NN-dimethylacetamide and NN-dimethylformamide chlorohaemin is monomeric but is largely undissociated, giving different spectra from that of chlorohaemin in dimethyl sulphoxide. On acidification, dissociation occurs and the dimethyl sulphoxide type of spectrum results. 4. Studies in a fourth solvent, sulpholane, indicate that solvent co-ordinating power (ligand strength) rather than bulk dielectric constant is responsible for dissociation of chlorohaemin. 5. In neutral dimethyl sulphoxide-water mixtures chlorohaemin remains monomeric and completely dissociated, and spectra are independent of mixture composition, except at high water concentrations, when precipitation occurs. In alkaline dimethyl sulphoxide-water mixtures, where the complete solvent mixture range is accessible, ferrihaem is polymeric (probably dimeric) and spectra are dependent on solvent composition. A quantitative analysis indicates that the spectral changes are due to replacement by water of one molecule of co-ordinated dimethyl sulphoxide per ferrihaem aggregate, and do not involve a two-molecule replacement as has been suggested for the alkaline pyridine-water system.

The Influence of the Solvent on Reaction Velocity. XLII. The Kinetics of the Decomposition of Peroxydisulphate in Dimethyl Sulphoxide-Water Mixtures.

The Influence of the Solvent on Reaction Velocity. XLII. The Kinetics of the Decomposition of Peroxydisulphate in Dimethyl Sulphoxide-Water Mixtures.

The Influence of the Solvent on Reaction Velocity. XL. The Reaction between Benzyl Chlorides and Thiosulphate Ion in Acetone-Water, Dioxane-Water, and Dimethyl Sulphoxide-Water Mixtures.

The Influence of the Solvent on Reaction Velocity. XL. The Reaction between Benzyl Chlorides and Thiosulphate Ion in Acetone-Water, Dioxane-Water, and Dimethyl Sulphoxide-Water Mixtures.

Über das sorptionsverhalten von kationenaustauschern auf polystyrolbasis in wässrigem dioxan bzw. dimethylsulfoxid

This study deals with the sorption behaviour of a number of cation exchangers in dioxan—water as well as dimethylsulphoxide—water mixtures. The lower the concentration of water in the surrounding solution, the more water will be relatively absorbed by the exchanger. Both the amount and composition of the inner solution are strongly influenced by pore structure, cross-linking and load of the exchanger. Macroreticular ion exchangers absorb great amounts of solvents over the entire concentration range. The absolute sorption of water decreases with increasing degree of cross-linking of the exchanger, while the selectivity increases. The selectivity of the counter-ions for water increases in the sequence Na + < Ca 2+ < Zr(IV) < Al 3+. A decisive factor is the charge of counter-ion; Zr(IV) acts as a cation with a charge of 2+. The polarity of the solvent phase has a large influence on the sorption. A preparative method of carefully dehydrating ion exchangers is described. According to the kind of exchanger the residue water is between 100–1000 p.p.m. The amount of water in macroreticular exchangers is about double that in the conventional type of exchanger.

Stabilité thermique du collagène acido-soluble dans des mélanges eau-solvants organiques

The acid-soluble collagen of calf-skin in aqueous medium was denatured by heating above a critical temperature T M. The helix- coil transition of collagen in water-organic solvents mixtures was measured by polarimetry. The water-methanol systems raise the T M, which is considerably decreased by water-amide, water-chlorinated alcohols or water dimethylsulphoxide mixtures. An attempt is made to correlate these results with the possible interactions between organic solvents and protein.

Kinetic medium effects. III. Solvent effects on A1 and A2 Hydrolyses in water-dimethyl sulphoxide mixtures

The relative rates of the concurrent A1 and A2 hydrolyses of t-butyl acetate have been measured as a function of solvent composition in water-dimethyl sulphoxide (DMSO) mixtures. A large difference in solvent effect is observed, which correlates well with observed solvent effects on ethyl acetate (A2) and acetal (Al) hydrolyses in the same solvent system. Activity coefficients have been measured for t-butyl acetate, ethyl acetate, and acetal in various water-DMSO mixtures.

A spectroscopic study of complex formation between aromatic nitrocompounds and sodium sulphite

The interactions of a series of trinitrobenzene derivatives with sodium sulphite in water and in water–dimethyl sulphoxide mixtures have been investigated by 1H nuclear magnetic resonance and visible spectroscopy. In water each nitro-compound studied gives a 1 : 1 adduct at low sulphite concentrations resulting from covalent addition of sulphite at a ring carbon atom carrying hydrogen, while at higher sulphite concentrations di-adducts are formed by addition of sulphite at two ring positions carrying hydrogen. The equilibrium constants for formation of these complexes have been determined and are compared with the values for addition of hydroxide ion The effects on the stabilities of the complexes of changes of the ionic strength or solvent are discussed.

The Influence of the Solvent on Reaction Velocity. XXX. The Reaction between Benzyl Chlorides and Hydroxide Ion in Acetone-Water and Dimethyl Sulphoxide-Water Mixtures.

The Influence of the Solvent on Reaction Velocity. XXX. The Reaction between Benzyl Chlorides and Hydroxide Ion in Acetone-Water and Dimethyl Sulphoxide-Water Mixtures.

The Influcence of the Solvent on Reaction Velocity. XXIII. The Alkaline Hydrolysis of Ethyl Acetate in Dimethyl Sulphoxide-Water Mixtures.

The Influcence of the Solvent on Reaction Velocity. XXIII. The Alkaline Hydrolysis of Ethyl Acetate in Dimethyl Sulphoxide-Water Mixtures.

Notes on Solvate Formation in Dimethyl Sulphoxide-Water Mixtures.

Notes on Solvate Formation in Dimethyl Sulphoxide-Water Mixtures.

The Influence of the Solvent on Reaction Velocity. XXV. Dependence of the Substituent Effect on Solvent Composition in Alkaline Hydrolysis of Benzoic Esters in Dimethyl Sulphoxide-Water Mixtures.

The Influence of the Solvent on Reaction Velocity. XXV. Dependence of the Substituent Effect on Solvent Composition in Alkaline Hydrolysis of Benzoic Esters in Dimethyl Sulphoxide-Water Mixtures.

The Influcence of the Solvent on Reaction Velocity. XXIV. The Acid Hydrolysis of Ethyl Acetate in Dimethyl Sulphoxide-Water Mixtures.

The Influcence of the Solvent on Reaction Velocity. XXIV. The Acid Hydrolysis of Ethyl Acetate in Dimethyl Sulphoxide-Water Mixtures.