Water-dimethyl Sulfoxide Mixtures Research Articles

The influence of cellulose complexite swelling on its protolytic properties in aqueous-organic mixtures

The swellability of cellulose complexite containing hydroxamic acid and amidoxime groups and its matrix (grafted copolymer of cellulose and polyacrylonitrle) in variable-composition water-methanol and water-dimethylsulfoxide mixtures was studied by pH metry, refractometry, and atomic absorption spectroscopy over the pH range 5.30–12.87 corresponding to the dissociation of the functional groups of fibers. The solvation characteristics of fibers, including specific volume, degree of sorption, and interphase distribution coefficients of mixture components, were determined experimentally. The Gibbs energies of sample swelling and the dissociation constants of complexite groups were calculated taking into account the contribution of the solvation parameter. The suggestion was made that the acid properties of the polymer were determined by the predominant influence of the specific solvation of its matrix caused by the formation of H-bonds in complexite-solvent systems.

Cyclic resolution of racemic ibuprofen via coupled efficient lipase and acid‐base catalysis

Extracellular lipase LIP prepared in our lab from the yeast Yarrowia lipolytica was used for the resolution of racemic ibuprofen. The (S)-enantiomer was preferred by lipase LIP, and the unreacted (R)-enantiomer was extracted and racemized in basic solvent-water medium to be re-resolved. Solvent, content of solvent, base concentration, and temperature have a strong effect on racemization. The (S)-ester was separated and hydrolyzed to (S)-ibuprofen in acidic dimethyl sulfoxide-water mixture containing 70% dimethyl sulfoxide. The high purity (S)-ibuprofen (ee = 0.98) was obtained using lipase LIP to catalyze hydrolysis of (S)-ester in 0.1 M phosphate buffer (pH = 8).

Study of ion–solvent interactions and activation energy of LiBr in DMSO, H2O and DMSO–H2O mixtures at various temperatures

The Jones–Dole B coefficients of the electrolyte Lithium bromide (LiBr), reference salts tetra butyl ammonium tetra phenyl borate (BU4NBPh4), tetra butyl ammonium bromide (BU4NBr), and potassium chloride (KCl) in dimethylsulfoxide (DMSO), water, and DMSO–water mixtures were obtained at different temperatures range from 25 to 45 °C For this, the relative viscosities were measured for Lithium bromide (LiBr) and reference salts in DMSO, water, and DMSO–water mixtures at above-mentioned temperatures. The B coefficients of these electrolytes were behaved as structure makers in DMSO, while in H2O and DMSO–H2O mixtures, the B-coefficient values were less positive showing the weak structure-making effect. Ionic viscosity B coefficients allow us to assess the behavior of ions in the solvent mixtures. In this study it was observed that all the values of ionic B coefficient of (Li+) were positive and small showing the weak structure-making effects. It was also observed that Br− ions maintain negative B coefficient values in all DMSO–H2O mixtures, except in 60% DMSO mole fraction. From this it can be concluded that Br− ion behaved as a structure breaker in water and in all DMSO–H2O mixtures except in 60% DMSO mole fraction mixtures. The low B ± values of alkali metal ions and Br− ions in water are due to the breakdown of the tetrahedral structural of water and the formation of strongly structured solvated ion. It is also observed that the values of the energy of activation of the flow for LiBr are greater in DMSO–water mixtures and in pure water than in DMSO. This may be due the presence of a network of hydrogen bonds which cause the hindrance in the flow of the solution of LiBr in DMSO–water mixtures and in pure water than in DMSO.

Solvent effect on PCR from a viewpoint of a change of microscopic environment of Mg 2+ in a solution

The effect of an organic solvent on PCR (polymerase chain reaction) was studied by measuring the molecular clustering of Mg 2+ and a nucleoside cytidine in an aqueous solution through a mass spectrometry. In the PCR, the addition of 5% methanol (CH 3OH) and dimethyl sulfoxide (DMSO) did not inhibit amplification of a human β-globin DNA fragment, while no amplification was observed in the presence of 5% acetonitrile (CH 3CN). The measurement of the clusters isolated from an aqueous solution including a nucleoside cytidine, Mg 2+, and an organic solvent (CH 3OH, DMSO, or CH 3CN) showed obvious differences in the structures of generated clusters; the self-aggregation of cytidine around Mg 2+ clearly occurred in water, water–methanol mixture and water–DMSO mixture, however, it was not effective in water–acetonitrile mixture. The solvation structure of Mg 2+ also showed dependent on the solvent composition, which suggested that the effective hydration of Mg 2+ seemed to promote cytidine clustering and a positive reaction in PCR. The microscopic structures in a solution depended on the coexisting organic solvent may provide a new insight to rationalize the role of the organic solvent on PCR.

Vibrational Spectroscopy and Dynamics of Azide Ion in Ionic Liquid and Dimethyl Sulfoxide Water Mixtures

Steady-state and time-resolved infrared spectroscopy of the azide (N(3)-) anion has been used to characterize aqueous mixtures both with the ionic liquid (IL) 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF(4)]) and with dimethyl sulfoxide (DMSO). In the DMSO-water mixtures, two anion vibrational bands are observed for low water mole fractions (0 > X(w) > 0.25), which indicates a heterogeneous ion solvation environment. The band at 2000 cm(-1) observed for neat DMSO does not shift but decreases in amplitude as the amount of water is increased. Another band appears at slightly higher frequency at low X(w) (=0.05). As the amount of water is increased, this band shifts to higher frequency and becomes stronger and is attributed to azide with an increasing degree of hydration. At intermediate and high X(w), a single band is observed that shifts almost linearly with water mole fraction toward the bulk water value. The heterogeneity is evident from the infrared pump-probe studies in which the decay times depend on probe frequency at low mole fraction. For the azide spectra in IL-water mixtures, a single azide band is observed for each mole fraction mixture. The azide band shifts almost linearly with mole fraction, indicating nearly ideal mixing behavior. As with the DMSO-water mixtures, the time-resolved IR decay times are probe-frequency-dependent at low mole fraction, again indicating heterogeneous solvation. In both the DMSO and IL mixtures with water, the relaxation times are slower than would be expected from ideal mixing, suggesting that vibrational relaxation of azide is more sensitive than its vibrational frequency to the solvent structure. The results are discussed in terms of preferential solvation and the degree to which the azide shift and vibrational relaxation depend on the degree of water association in the mixtures.

Interaction of water-DMSO mixtures with cellulose

The character of the interaction of cellulose with water-dimethyl sulfoxide mixtures is investigated. It is shown that, in the concentration range 0 < x D < 0.28, cellulose predominantly sorbs water; in this case, in the presence of small amounts of DMSO (x D ∼ 0.1), the sorption is higher than that for pure water. It is established that the formation of hydrogen bonds between hydroxyl groups of cellulose and oxygen atoms in DMSO molecules is most probable at x D > 0.6, where large clusters dominate over hydrophobic dimers.

2,7-Dimethyl-3,8-dinitrodipyrazolo[1,5-a:1′,5′-d]pyrazine-4,9-dione: A new labelling reagent for liquid chromatographic analysis of amino acids

The use of 2,7-dimethyl-3,8-dinitrodipyrazolo[1,5-a:1′,5′-d]pyrazine-4,9-dione as pre-column reagent for LC analysis of amino acids is proposed. The compound reacts (30 min at 68 °C in presence of 0.04 M triethylamine in a dimethylsulfoxide–water mixture) with primary and secondary amino function and the stable resulting adducts can be chromatographed under reversed-phase conditions and detected at λ = 280 nm. The derivatization conditions were optimized by a series of experiments. The effect of temperature, triethylamine concentration and reagent on the reaction was investigated. The yield of the glycine derivative was found to be quantitative at a reagent amino acid molar ratio of about 6 by comparison with an authentic specimen of synthesized glycine adduct. Application of the method to quality control of commercially available oral polyaminoacid formulations is described.

Interactions of water–DMSO mixtures with cellulose

The equilibrium in water–dimethylsulfoxide (DMSO) and cellulose–water–DMSO systems was studied in a wide range of solvent compositions by Knudsen's effusion method. It was shown that water sorption on cellulose dominates in the concentration range of 0 < x D < 0.28. At low DMSO concentrations ( x D ∼ 0.1) the water sorption on cellulose is higher than that for pure water. The hydrogen bonding between the hydroxyls of cellulose and the oxygen atom of DMSO is more favorable at x D > 0.6 when the formation of “large” DMSO clusters dominates over the formation of DMSO dimers with hydrophobic properties.

Quasi-elastic neutron scattering study of dimethyl-sulfoxide–water mixtures: Probing molecular mobility in a nonideal solution

The translational and rotational motions of water and dimethyl sulfoxide, [DMSO, (CH(3))(2)SO] have been investigated using quasi-elastic neutron scattering. Water-DMSO mixtures at five DMSO mole fractions, chi(DMSO), ranging from 0 to 0.75, were measured. Hydrogen-deuterium substitution was used to extract independently the water proton dynamics (d-DMSO-H(2)O), the DMSO methyl proton dynamics (h-DMSO-D(2)O) and to obtain background corrections (d-DMSO-D(2)O). The translational diffusion of water slows down significantly compared to bulk water at all chi(DMSO)>0. The rotational time constant for water exhibits a maximum at chi(DMSO)=0.33 that corresponds to the observed maximum of the viscosity of the mixture. Data for DMSO can be analyzed in terms of a relatively slow tumbling of the molecule about its center-of-mass in conjunction with random translational diffusion. The rotational time constant for this motion exhibits some dependence on chi(DMSO), while the translational diffusion constant shows no clear variation for chi(DMSO)>0. The results presented reinforce the idea that due to the stronger associative nature of DMSO, DMSO-water aggregates are formed over the whole composition range, disturbing the tetrahedral natural arrangement of the water molecules. As a consequence adding DMSO to water causes a drastic slowing down of the dynamics of the water molecule, and vice versa.

Potentiometric Studies on Some α-Amino Acid-Schiff Bases and Their Manganese(III) Complexes in Dimethyl Sulfoxide–Water Mixtures at 25°C

In this study the stoichiometric protonation constants were determined for some α-amino acids (glycine, L-alanine, L-methionine, L-phenylalanine, and L-threonine), the Schiff bases derived from them and 2-hydroxy-1-naphthaldehyde, along with the stoichiometric stability constants of Schiff base–Mn(III) complexes. These equilibrium constants were determined potentiometrically using a combined pH electrode system calibrated in concentration units of the hydrogen ion at 25°C, and at an ionic strength of 0.10 mol-dm−3 NaCl in 30 and 50% dimethyl sulfoxide–water mixtures. The calculations of these constants were carried out using the PKAS and the BEST computer programs. In addition, the effects of solvent composition and structures on the protonation and the complex formation constants were investigated. The mole ratio of Mn(III) to amino acid-Schiff bases was also determined and it was found that the complexes were of the MnL2 type.

Macromolecular helicity induction on a poly(phenylacetylene) with C2-symmetric chiral [60]fullerene-bisadducts.

Three chiral N-methylfulleropyrrolidine bisadducts were prepared, isolated, and completely resolved into each enantiomer using a chiral HPLC column, which were then converted to the corresponding optically active, cationic C(60)-bisadducts to investigate if they could act as a macromolecular helicity inducer in a poly(phenylacetylene) bearing an anionic monoethyl phosphonate pendant (poly-1) in aqueous solution. Upon complexation with the chiral C(60)-bisadducts, only the trans-3 bisadduct exhibited the characteristic induced circular dichroism (ICD) in the UV-visible region of the polymer backbone in dimethyl sulfoxide-water mixtures due to the predominantly one-handed helix formation of poly-1, while the trans-2 and cis-3 bisadducts induced almost no apparent CD in the same region. These results indicate that the helicity induction on poly-1 is highly sensitive to the structure and geometry of the cationic C(60)-bisadducts with a different distance between the separated charges.

Thermochemical behaviour of crown ethers in the mixtures of water with organic solvents: Part VII . Enthalpy of solution of 15-crown-5 and benzo-15-crown-5 in the mixtures of water with acetone at 298.15 K

Enthalpy of solution of crown ethers (15-crown-5 and benzo-15-crown-5) in water–acetone mixtures have been measured within the whole range of mole fraction at 298.15 K. The obtained data have been compared with those of the solution enthalpy of both crown ethers in the mixtures of water with dimethyl sulfoxide. The replacement of SO group with CO in the molecule of the organic solvent brings about an increase in the exothermic effect of the solution of 15-crown-5 and benzo-15-crown-5 ethers, especially in the mixtures with a medium water content. The observed effect is connected with the preferential solvation of the molecules of both crown ethers by acetone molecules in the water–acetone mixtures. The process of preferential solvation of 15-crown-5 and benzo-15-crown-5 ethers does not take place in the water–dimethyl sulfoxide mixture.

Phase behavior of dipalmitoylphosphatidylethanolamine in dimethylsulfoxide–water mixture

The phase behaviors of dipalmitoylphosphatidylethanolamine (DPPE) dispersed in dimethyl sulfoxide (DMSO) aqueous solutions were studied by using differential scanning calorimetry and X-ray diffraction methods. At low concentration of DMSO (mole fraction, x<0.2), phase transition between lamellar-gel and lamellar liquid-crystal phase can be observed during heating/cooling cycles at a scanning rate of 5 °C min −1. The formation of the stable lamellar-crystal phase from the metastable lamellar-gel phase needs long time incubation. At moderate concentration of DMSO (0.2< x<0.37), phase transition from lamellar-gel to crystalline phase can be detected during either cooling or heating at the same scanning rate. At high concentrations ( x>0.37), DMSO promotes remarkably the formation of lamellar-crystal phase of the lipid, resulting in phase transitions between lamellar-crystal phase and liquid-crystal phase during heating/cooling cycling. A phase diagram has been constructed over the entire concentration range of the mixed solvent. In addition, it was found that DMSO could decrease the lamellar repeat spacing of crystalline and liquid crystalline phase.

Solvent‐induced switching of the macromolecular helicity of poly[(4‐carboxyphenyl)acetylene] induced by a single chiral amino alcohol

AbstractCis–transoidal poly[(4‐carboxyphenyl)acetylene] (poly‐1) complexed with optically active amines and amino alcohols showed an induced circular dichroism (ICD) in the ultraviolet–visible region because of a predominantly one‐handed helix formation in water and in dimethyl sulfoxide (DMSO). The Cotton effect signs of the poly‐1/chiral amino alcohol complexes were inverted in the presence of water, whereas the ICD pattern of the poly‐1/chiral amine complexes showed no change, regardless of the water content. These results demonstrated that the helix sense of poly‐1 induced by optically active amino alcohols through noncovalent acid–base interactions could be switched by changes in the solvent ratio in the DMSO–water mixtures. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3625–3631, 2003

An all-atom simulation study on intermolecular interaction of DMSO–water system

An all-atom dimethyl sulfoxide (DMSO) model and a TIP5P water model have been adopted for molecular dynamics simulation. Two new qualities η rel E and η rel are introduced to describe the anomalous nonideal behaviors of DMSO–water mixtures. The simulation is compared with chemical shift and excess enthalpy of mixing, which shows good concentration dependences. In addition, our all-atom simulation also indicates that the C–H groups of DMSO may interact with the oxygen atoms of water and DMSO. The weak C–H⋯O contacts and the strong O–H⋯O hydrogen bonds represent the consistent concentration dependences, which exhibits the cooperation effect.

Tracer diffusion of ionic and hydrophobic solutes in water–dimethyl sulfoxide mixtures: Effects of varying composition

We have performed a series of molecular dynamics simulations of water–dimethyl sulfoxide (DMSO) mixtures containing either an ionic or a neutral atomic solute to investigate the effects of composition of the mixture on the diffusion of these solutes. Several different compositions of the mixtures ranging from pure DMSO to pure water are considered. Altogether, 23 different systems are simulated in the present work. The diffusion coefficients of both ionic and neutral solutes are found to show strong nonideal behavior with variation of composition of the solvent mixture. The extent of nonideality of the solute diffusion is found to be similar to the nonideality that is observed for the diffusion and orientational relaxation of water and DMSO molecules in these mixtures and is attributed to the presence of rather strong water–DMSO hydrogen bonds in these mixtures. The simulation results are compared with those of experiments wherever available.

Polarizability anisotropy relaxation in pure and aqueous dimethylsulfoxide

A molecular dynamics simulation study is presented for the relaxation of the polarizability anisotropy of liquid dimethylsulfoxide (DMSO) and DMSO–water mixtures of DMSO mole fractions xD=0.05, 0.10, 0.25, 0.50, and 0.75. The system’s collective polarizability is computed through a dipolar induction mechanism involving the intrinsic polarizability and first hyperpolarizability tensors for water and DMSO, obtained from ab initio quantum chemical calculations at the MP2/6-311++G(d,p) level. The rotational-diffusion components of the anisotropy relaxation of the pure liquids increase upon mixing to a maximum near 25% DMSO, showing consistency with other dynamical properties of these mixtures. Features of the optical Kerr effect (OKE) nuclear response of liquid water, previously ascribed to hydrogen bonding distortions, show significant enhancement upon addition of DMSO due to the formation of strong DMSO–water H-bonds. The OKE spectrum for DMSO is in close agreement with experimental measurements, but there are discrepancies for pure water in the vicinity of 60 cm−1, pointing to the existence of inaccuracies in our description of OKE sensitive polarizability fluctuations of water. The mixtures OKE spectra feature an enhancement in the high frequency water librational band.

A potentiometric study of the adsorption of a cationic surfactant onto laponite in water–methanol and water–dimethylsulfoxide mixtures

We studied the adsorption of a cationic surfactant, dodecyltrimethylammonium bromide (DTABr), onto laponite in water–methanol and water–DMSO mixtures at 298 K. Adsorption isotherms were determined by potentiometric methods using DTA + and Br −-selective electrodes. All of the isotherm shapes in the mixture were classical. Activity coefficients were determined for the transfer between water and hydroorganic mixtures. Comparison of the adsorption isotherms obtained for different surfactant chemical potentials showed that at higher concentrations of free surfactant, the aggregation state does not depend on the nature of the surrounding media. A study of the influence of the ionic strength showed that there is a common intersection point in each hydroorganic mixture. This point corresponds to the charge compensation point and depends on the nature of the surrounding medium.

Solvation dynamics of coumarin 153 in dimethylsulfoxide–water mixtures: Molecular dynamics simulations

We present results of molecular dynamics simulations of solvation dynamics of coumarin 153 in dimethylsulfoxide (DMSO)–water mixtures of different compositions (xD=0.00, 0.25, 0.32, 0.50, 0.75, and 1.00) using an all-atom model for the solute probe. Results are reported for the global solvation responses of the simulated systems, as well as for the separate contributions from each cosolvent and the individual solute–site couplings to water and DMSO. The solvation dynamics is predominantly given by DMSO’s contribution, even at low (25%) DMSO content, because of the preferential solvation of the probe. We find that the water molecules are only mildly coupled to the charge transfer in the coumarin, resulting in a small, largely diffusive, water relaxation component. Simulation results, including solvation responses, characteristic times, and Stokes shifts are compared with recent fluorescence upconversion experimental measurements showing good agreement for the relaxation but significant differences for the shifts.

Comportamento térmico da caulinita hidratada

Well-ordered kaolinite from the Brazilian Amazon Region (State of Para) was initially reacted at 60 °C with a water dimethylsulfoxide mixture. After washing and characterisation, the resulting material was washed several times with methanol and in the final step with water. The water molecules displace the previously dimethylsulfoxide intercalated molecules and two different hydrated kaolinites were obtained. An unstable phase characterized by an interplanar basal distance of 0,996 nm that after drying collapse to the stable 0,844 nm hydrated kaolinite. The dehydration of the sample to disordered kaolinite was accompanied by Powder X-ray Diffractometry, thermal analysis (simultaneous TG and DSC) and FTIR spectroscopy.