Dimethyl Sulphoxide Water Mixtures Research Articles

Molecular dynamics simulations of sodium chloride solutions in water–dimethyl sulphoxide mixtures: Potentials of mean force and solvation structures

Five solutions of sodium chloride in mixtures of water and dimethyl sulphoxide (DMSO) have been simulated using the conventional molecular dynamics technique. The potentials of mean force (PMFs) of the sodium chloride ion pair in the presence of the five water–DMSO mixtures with DMSO mole fractions (xDMSO) of 0.10, 0.21, 0.35, 0.48 and 0.91 have been computed. The derived PMFs have been confirmed by the long time dynamical ion-pair trajectories. The solvation structures of the ions in the presence of these mixtures have been analyzed using the ion-solvent radial distribution functions and the corresponding integration numbers. It has been found that the Na+ ion is always preferentially solvated by the water molecules in all the water–DMSO solvent mixtures. The Cl− ion is slightly preferred by the DMSO molecules in these mixed solvents.

Bifunctional etherification of a bead cellulose for ligand attachment with allyl bromide and allyl glycidyl ether

Efficient carboxymethylation of a bead cellulose was achieved with dimethyl sulphoxide–water mixtures but low activation levels were found with epoxidation reagents. The highest activation levels were obtained with allyl bromide and allyl glycidyl ether. This was attributed to the relative inertness of the allyl group towards water and cellulose, limiting hydrolysis and crosslinking. Advantages over epoxidation chemistry for bead cellulose were efficient reagent use, reproducible activation up to high levels and specificity of matrix modification. Predictable activation was obtained and facile titration methods were developed. Efficient activations of agarose and methacrylate matrices were also obtained with the allyl reagents.

Transient electric birefringence study of agarose aggregates in water‐dimethyl sulphoxide mixtures

AbstractThe dynamical behavior of agarose aggregates in a mixture of water and dimethyl sulphoxide (DMSO) has been investigated using a Transient Electric Birefringence (TEB) set up. Different agarose concentrations for different water/DMSO proportions were considered. The relaxation of the birefringence curves can be fitted with a stretched exponential of the form Δn(t) = Δn0 exp(‐(Dt)0.5). The exponent 0.5 suggests a high polydispersity of the aggregates. The rotational diffusion coefficient, D, depends strongly on the water/DMSO proportion. For small values of the applied electric field it presents a maximum for a water volume fraction equal to 0.5. A strong dependence of D on the applied electric field is also observed. However, the same kind of behavior as for weak fields is recovered when a subtle representation of the data is used. Differential Scanning Calorimetry (DSC) results also show a maximum in the temperature of fusion of the aggregates for a water volume fraction of 0.5. This set of results suggest strongly that « complexes » of water/DMSO/agarose are formed in the mixture and that the process of aggregate formation is more « efficient » for a water/DMSO mixture of same proportions.

Heat effects and water sorption by human serum albumin on its suspension in water-dimethyl sulphoxide mixtures

The heat effects on suspending solid human serum albumin (HSA) in various water-dimethyl sulphoxide (DMSO) mixtures were measured calorimetrically at 298 K. The isotherm of the water sorption for HSA suspended in the water-DMSO mixtures was also measured. The recording of the calorimetric heat effects exhibits endothermic and exothermic peaks. The endothermic heat effects were estimated graphically from the calorimetric curves. These values are shown to obey the Langmuir isotherm of the water sorption. The quasi-thermodynamic constant of water adsorption (1.2 ± 0.3 M −1) and the monolayer formation energy (−20.1 ± 1.0 J g −1) were estimated from the calorimetric data with the Langmuir model. The adsorption constant (0.16 ± 0.08 M −1) was evaluated from fitting the water sorption isotherm by the Langmuir model also. There is a divergence between the latter constant and the adsorption constant obtained from the calorimetric data. It appears that the processes accompanying the exothermic heat evolution influence the HSA's ability to bind water. The surface area of the water monolayer was also calculated from the fitting of the water sorption isotherm. It essentially exceeds the recognised values for proteins estimated from the data for water vapour sorption. The aqueous solubility of the protein after the exposure of the HSA preparation in the water-DMSO mixtures is also essentially decreased. Hence, changes in the protein-protein interactions of a diverse nature might accompany the exothermic heat evolution on suspending HSA in water-DMSO mixtures.

A neutron diffraction study of dimethyl sulphoxide–water mixtures

Neutron diffraction with hydrogen/deuterium isotope substitution is used to investigate the structure of water in concentrated dimethyl sulphoxide (DMSO) aqueous solutions. Partial structure factors and pair correlation functions involving the hydrogen atom on the water molecule are determined. Water structure is not found to be strongly affected by the presence of DMSO. However, the percentage of water molecules which hydrogen bond to themselves is substantially reduced compared to pure water, with a large proportion of the hydrogens available for bonding associated with the lone pairs on the DMSO. These experimental findings are in good agreement with the assumptions made in the simple mean-field type model for hydrogen-bonded mixtures, developed by Luzar [J. Chem. Phys. 91, 3603 (1989)]. A general scheme for analyzing experimental data on the HH and OH pair correlation functions in terms of coordination numbers is presented. The hydrogen–hydrogen correlation in the solvent (water) is also used to discuss the interparticle correlations between solute (DMSO) particles.

Picosecond reorientational dynamics of polar dye probes in binary aqueous mixtures

Picosecond time dependent fluorescence method has been used to measure the rotational reorientation times (τr) of three kinds of dye probes—oxazine 720 (a monocation), nile red (neutral but polar), and resorufin (a monoanion)—in a series of binary mixtures of water–amides, water–dipolar aprotics, and water–alcohols at 298 K. Most of the binary mixtures are characterized by the fact that at a particular composition (between 25% to 40% of the organic solvent in water), the viscosity (η) of the solution reaches a maximum value that is higher than the viscosities of the two solvents. As a consequence, the viscosity profile of the solution as a function of the organic solvent exhibits a bivaluedness, the extent of which is more, if the liquids are nearly isoviscous. The dielectric properties of the solution also change across the composition range. All the dyes show a near linear behavior of τr vs η in formamide–water, N-methylformamide–water, and methanol–water mixtures. A dual-valued profile for τr vs η is obtained for the cation oxazine 720 in the three dipolar aprotic mixtures (N, N-dimethylformamide–water, N, N-dimethylacetamide–water, and dimethylsulphoxide–water), with the rotational reorientation times being higher in the organic solvent-rich zone, compared to the corresponding isoviscous point in the water-rich zone. However, the anion resorufin shows a bivalued profile of τr vs η only in dimethylsulphoxide–water mixtures, while the neutral nile red shows a linear behavior in all the dipolar–aprotic water mixtures. A hook-type profile of τr vs η is seen for the anion resorufin in ethanol–, 1-propanol–, and 2-propanol–water mixtures and for the cation oxazine 720 in 1-propanol– and 2-propanol–water mixtures; but nile red shows no departure from linear behavior even in alcohol–water mixtures. The rotational dynamics of the cation oxazine 720 in dipolar aprotic–water mixtures is explained in terms of solvation since the dielectric friction is minimal in these solutions. While the concept of dielectric friction model seems to be adequate to understand the nonhydrodynamic behavior of the oxazine 720, the additional contribution due to solvation effects has to be necessarily taken into account to explain the rotational dynamics of the anion resorufin in alcohol–water mixtures.

Titration of proteins in dimethyl sulphoxide–water mixtures

The acid–base behaviour of arginine, lysozyme and ovalbumin has been studied by potentiometric and catalytic thermometric titrimetry in a mixture of dimethyl sulphoxide–water, with acrylonitrile as the end-point indicator in the latter technique. It was observed that, with the exception of the SH groups, all the protonated groups, including the guanidine groups of lysozyme and ovalbumin, were titrated by catalytic thermometric titrimetry. By using potentiometric titrimetry, all the titratable groups of ovalbumin were determined, whereas the guanidine groups of lysozyme were not determined by this technique.

Electrode kinetics of the system V(III)/V(II) in aqueous dimethylsulphoxide

The rate constants for the reduction of V(III) and oxidation of V(II) were measured on a mercury electrode in water and water-dimethylsulphoxide mixtures. Their dependance on the concentration of DMSO differs from that in mixtures of water with an organic solvent of lower basicity. This can be attributed to the existence of different solvates of vanadium in solutions and to different values of the rate constant for these solvates on the electrode surface at different coverages with the organic component. The influence of DMSO both in the primary solvation sphere and in the electrode double layer on the electrode reaction rate is discussed.

Thermodynamic functions for the transfer of naphthalene from water to mixed aqueous solvents at 298.15 k

Values of free energies Δ G t XXX, enthalpies Δ H t XXX, and entropies Δ S t XXX, of transfer of naphthalene from water to urea-water, acetonitrile-water, dimethylformamide-water and dimethylsulphoxide-water mixtures at 298.15 K in the water-rich region have been determined from solubility measurements at different temperatures. The cavity term from scaled particle theory has been used to explain qualitatively the experimental transfer free energies. We have also calculated molecular-pair interaction parameters in water for the four systems studied.

Preferential solvation of copper(II) salts in water—pyridine and water—dimethyl sulphoxide mixtures

The preferential solvation of copper(II) salts, namely acetate, benzoate and iodate, has been studied in water-pyridine and water-dimethyl sulphoxide (DMSO) mixtures at 30°C by Gibbs energies of transfer and solvent transport number measurements. While the solubility of copper(II) acetate and copper(II) iodate in water-pyridine mixtures increases up to the pyridine mole fraction X py = 0.1, and then decreases, the solubility of copper(II) benzoate increases continuously with the addition of pyridine up to the pure solvent. In the case of water-DMSO mixtures, the solubilities of copper iodate and copper benzoate increase, whereas that of the acetate decreases continuously with the addition of DMSO. The Gibbs energy of transfer of the Cu 2+ ion is negative and decreases continuously with the addition of pyridine or DMSO, while that of the acetate, benzoate and iodate anions is positive and increases continuously in both the solvent mixtures. These results, along with the solvent transport number Δ of pyridine or DMSO, have been interpreted in terms of heteroselective solvation of the salts, with the Cu 2+ ion being preferentially solvated by pyridine or DMSO and the anions by water in water-pyridine and water-DMSO mixtures respectively.

Study of internal pressure and free volume of urea solutions in water-dimethyl sulphoxide mixtures from ultrasonic velocity

Mixtures of water and DMSO were prepared in a particular weight ratio (20% DMSO and 80% water) and the homogeneous system was allowed to attain room temperature. The required quantity of the non-electrolyte urea for a given molality was then dissolved and filtered. Free volume and internal pressure were evaluated using the experimentally determined ultrasonic velocity, density and velocity of the solution.

Properties of hydrogen bonds in substituted 5,8-dihydroxy-1,4-napthoquinones and 1,4-dihydroxy-9,10-anthraquinones; kinetics of the reactions of the monoanions with hydroxide ion and buffers in dimethyl sulphoxide–water mixtures

Rate coefficients and equilibrium constants for removal of the hydrogen-bonded protons from the monoanions of two 1,4-dihydroxy-9,10-anthraquinones by hydroxide ion have been measured in 50%(v/v) Me2SO–H2O. The values are compared with results from reactions in aqueous solution and with results for the reactions of the monoanions of 5,8-dihydroxy-1,4-napthoquinone and its 2-methyl derivative with buffers in 50 and 70%(v/v) Me2SO–H2O. The similarity between the rate coefficients for proton removal by buffer bases and by hydroxide ion is compatible with a mechanism involving diffusion-controlled proton removal from a low concentration of a non-hydrogen-bonded intermediate in equilibrium with the hydrogen-bonded monoanions. At high buffer concentrations the dependence of rate on buffer concentration is curvilinear, and formation of the non-hydrogen-bonded intermediate may then be rate-limiting.

Kinetic and spectral properties of the photogenerated p-nitrobenzyl carbanion in aqueous media

The p-nitrobenzyl carbanion is a photoelimination product from various p-nitrobenzyl (p-NO2C6H4CH2R, R = CO2–, PO32–, CH2OH, etc.) compounds in aqueous media. Following millisecond flash photolysis of N2-saturated p-nitrophenylacetate (pH > 6) solutions, we have shown that the carbanion decays via mixed first-(solvent protonation) and second-(dimerisation) order processes. Rate constants k1= 1.3 ± 0.1 × 10–2 s–1 and 2k2= 1.7 ± 0.3 × 103 dm3 mol–1 s–1, respectively, are determined. Reactions of the anion with O2, H+, and an efficient one-electron oxidant, IrCl62–, are also examined. Studies in dimethyl sulphoxide–water mixtures indicate that the anion exists as a hydrated form (λmax 356 nm) in water and an ‘unspecifically’ solvated species in dimethyl sulphoxide (λmaxca. 440 nm). A reaction mechanism is developed which accounts for transformation of the carbanion to p,p′-dinitrobibenzyl and p-nitrotoluene, the major isolable nitro products from these systems.

Statistical study of the influence of the hydroxyl groups in positions 3 and 4 on the ionization process of 3,4-dihydroxybenzoic acid

The contributions of each of the two hydroxyl groups to the ionization and solvation processes for 3,4-dihydroxybenzoic acid were studied by considering the enthalpy values of these processes as a linear combination of those related to the same processes for the 2,3-dihydroxy and 2,4-dihydroxy derivatives in water-dimethylsulphoxide mixtures with the mole fraction of dimethylsulphoxide ranging from 0 to 0.8. For this purpose, diparametric and monoparametric regression analyses were used. In these analyses, the total standard deviations, slope and intercept standard deviations, correlation coefficients, null hypotheses a = 0, b = 0, r = 0 (where a is the intercept, b the slope and r the regression coefficient), the Student t test and F test of the above cited values were taken into account. Particular attention was paid to the presence of the so-called collinearity between the explanatory variables. The introduction of a hydroxyl group in position 3 destabilizes the benzene ring, overcoming the stabilization effect caused by the hydroxyl in position 4.

Absolute electrode potentials in dimethyl sulphoxide-water mixtures and transfer free energies of individual ions

The standard potentials of H 2|H +, M|M + (M = Li, Na, K, Rb and Cs) and Ag¦AgX (X = Cl, Br and I) electrodes in seven aqueous solutions of dimethyl sulphoxide (DMSO), containing up to 60 wt.% DMSO, have been determined from EMF measurements of cells of the type: Ag¦AgX¦MX ( m), S¦M(Hg)¦MX ( m), W¦AgX¦Ag, or a variant of it, at 25°C by our recently reported procedure. The interest, validity and general applicability of this procedure in both aqueous protic and aprotic solvents have been demonstrated. The radii of solvated cations and their solvation extent in these media have been calculated. The standard Gibbs free energies of transfer of halogen acids and alkali metal halides as well as their constituent individual ions from water to each of the DMSO-water mixtures have been also computed. The results are interpreted and discussed.

Kinetic solvent effects on acid-catalyzed hydrolysis of sucrose in aqueous mixtures of some protic, aprotic, and dipolar aprotic solvents

Rate constants of acid-catalyzed hydrolysis of sucrose (S) to D-glucose and L-fructose have been determined at 25 °C by optical rotation measurements in aqueous mixtures of protophobic protic glycerol (GL), protophilic protic urea (UH), aprotic dioxane (D), and dipolar aprotic dimethyl sulphoxide (DMSO). Transfer free energies of the substrate sucrose, [Formula: see text] have also been determined in the solvents from solubility measurements. These values as well as those of H+, as obtained earlier by use of the widely used tetraphenylarsonium tetraphenylboron (TATB) reference electrolyte assumption, yielded transfer free energies of the transition state. The observed log (ks/kw) – composition profiles reveal that the rates increase monotonically in GL–water mixtures, that decrease more or less monotonically in UH– and DMSO–water mixtures, and decrease up to 10 mol% D in D–water mixtures, beyond which the values tend to increase. Examination of [Formula: see text]–composition profiles for the different species in each case indicates that the initial and transition state solvation get more or less compensated and the observed rates are dictated by the increased solvation of H+ in aqueous UH, DMSO, and D co-solvent systems. But in GL–water mixtures the decreased solvation of the transition state compared with the initial state is overcome by the decreased solvation of H+, thus resulting in the gradual enhancement of the rates of the reaction. The observed linearity of the correlative plots of −δ(ΔG≠) [= RT ln (ks/kw)] vs. [Formula: see text] with distinctly different slopes in the two cases also substantiates the relative importance of H+ solvation in dictating the rates of the reaction in these widely different aqueous co-solvents.

ChemInform Abstract: Systems of Salts and Mixed Solvents. Part 33. Solvation of Cations (Li+, Mg2+, A13+) in Dimethylsulphoxide‐Water Mixtures (Raman Spectroscopic Investigations into Concentrated Electrolyte Solutions)

Chemischer InformationsdienstVolume 17, Issue 29 Article ChemInform Abstract: Systems of Salts and Mixed Solvents. Part 33. Solvation of Cations (Li+, Mg2+, A13+) in Dimethylsulphoxide-Water Mixtures (Raman Spectroscopic Investigations into Concentrated Electrolyte Solutions) H.-H. EMONS, Search for more papers by this authorF. BIRKENEDER, Search for more papers by this authorK. POLLMER, Search for more papers by this author H.-H. EMONS, Search for more papers by this authorF. BIRKENEDER, Search for more papers by this authorK. POLLMER, Search for more papers by this author First published: July 22, 1986 https://doi.org/10.1002/chin.198629056AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume17, Issue29July 22, 1986 RelatedInformation

The stabilities of Meisenheimer complexes. Part 42. Kinetic studies of the reactions of methyl 3,5-dinitrobenzoate and of methyl 4-chloro-3,5-dinitrobenzoate with hydroxide ions in dimethyl sulphoxide–water mixtures. Competitive nucleophilic attack at aryl and carbonyl carbon atoms

Kinetic and equilibrium data, obtained by stopped-flow spectrophotometry, are reported for the reactions of methyl 3,5-dinitrobenzoate (1) and methyl 4-chloro-3,5-dinitrobenzoate (5) with hydroxide ions in dimethyl sulphoxide–water mixtures. There is evidence for competition between attack at carbonyl and aryl carbon atoms, the latter becoming relatively favoured as the proportion of dimethyl sulphoxide in the solvent is increased. It is shown that the major pathway in the formation of 4-hydroxy-3,5-dinitrobenzoate from (5) involves hydroxide attack at the carbonyl function followed by slow attack at the ring carbon atom carrying chlorine.

The solvent effect on the α-effect

The reaction of p-nitrophenyl acetate with butane-2,3-dione monoximate anion as the α-nucleophile, compared with p-chlorophenoxide ion as the normal nucleophile, exhibits a maximum in rate enhancement (‘α-effect’) in dimethyl sulphoxide–water mixtures as the medium composition is varied.

The stabilities of Meisenheimer complexes. Part 41. Kinetic studies of adduct formation and nucleophilic substitution in the reactions of hydroxide ions with 1-X-3,5-dinitrobenzenes and with 1-X-4-chloro-3,5-dinitrobenzenes (X = H, CF3, CO2–) in water–dimethyl sulphoxide mixtures. The effect of a chloro-substituent on the rate of nucleophilic attack

Kinetic and equilibrium measurements are compared for the reactions of (1) and (4)(X = CF3, CO2–, H) with hydroxide ions in dimethyl sulphoxide–water mixtures. The adducts (3), formed from (1), have higher thermodynamic stabilities than their isomers (2) although there is little kinetic discrimination in the rates of hydroxide attack at the three unsubstituted positions. The presence in (4) of the chlorine atom results in a general reduction in the rate of nucleophilic attack, the effect being particularly large for ipso-reaction (attack at the 4-position). Hence the reaction of (4) with base results in the initial formation of adducts (5). Contrary to a recent report the intermediates (6) on the reaction pathway to the phenols (7) are not sufficiently stable to allow spectrophotometric detection.