Aqueous Dimethyl Sulfoxide Research Articles

Spectrophotometric determination of p-aminophenol in drugs using 5,7-dichloro-4,6-dinitrobenzofuroxan reagent in micellar medium

A new spectrophotometric method for determining p-aminophenol in micellar aqueous dimethylsulfoxide (DMSO) media with non-ionogenic surfactant Triton X-100 that makes use of 5,7-dichloro-4,6-dinitrobenzofuroxan as an indicator has been developed. Using the proposed method, it is possible to detect an admixture of p-aminophenol in paracetamol (acetaminophen) in such media on a level that is much lower than the limiting concentration. The presence of Triton X-100 in the form of micelles improves the sensitivity of spectrophotometric determination compared to that of standard techniques.

ChemInform Abstract: A Detailed Procedure for the Preparation of Butadiyne.

Abstract Butadiyne, HC≡CC≡CH, can be obtained in yields up to ∼90% by adding 1,4-dichloro-2-butyne, CICH2C≡CCH2CI at ∼70°C to a mixture of concentrated aqueous potassium hydroxide and dimethylsulfoxide.

ChemInform Abstract: Unusual Weiss-Cook Condensation of Dimethyl 2,3-Dioxobutanedioate and Dimethyl 3-Oxoglutarate.

The Weiss–Cook condensation of dimethyl 2,3-dioxobutanedioate with two equivalents of dimethyl 3-oxoglutarate in aqueous bicarbonate produces an abnormal product, pentamethyl cis-3-(carbomethoxymethyl)-3,7-dihydroxy-2-oxabicyclo-[3.3.0]oct-7-ene-1,4,5,6,8-pentacarboxylate 7, whose structure has been determined by X-ray crystallography. Rrapcho decarbomethoxylation (sodium chloride, aqueous dimethyl sulfoxide, 140 °C) of this compound produces dimethyl cis-3,7-dioxobi-cyclo[3.3.0]octane-1,5-dicarboxylate 4 in quantitative yield. These results suggest that compound 7 may be the product of a kinetically controlled reaction pathway involving 4-hydroxypent-2-en-1-one intermediate 5. Heating of 7 in dimethyl sulfoxide may have promoted thermodynamic equilibration to a Weiss–Cook product, which then decarbomethoxylated to produce 4.

PL14 Properties of real phototherapy lasers

A new imidazole-appended anthracene-based photoinduced electron transfer (PET) probe (P) was designed and synthesized. Probe P detected Zn2+ selectively in an 80% aqueous solution of dimethyl sulfoxide (DMSO) through a switch-on response at pH 7.5 without any interference from other metal ions. Probe P exhibited a moderately strong association constant (Ka) of 1.41 × 105 M−1 and associated with Zn2+ ions with 1:1 stoichiometry. The in situ-generated P•Zn2+ (1:1) ensemble detected H2PO4− and CN− ions sequentially through switch-off responses. The selective discrimination of H2PO4− and CN− ions occurred both in the absence and presence of Ca2+ ions at pH 7.5 in a N-2-hydroxyethylpiperazine-N-2-ethanesulfonic acid (HEPES) buffer. The switch-on response was driven by the selective complexation of P with Zn2+ ions, mediated by the combined effects of PET and chelation-induced enhanced fluorescence, resulting in a more structurally rigid complex. Applications of P to real water sample analysis and sequential logic gate operations were demonstrated. The lowest detection limits for Zn2+, H2PO4−, and CN− ions in 80% aqueous DMSO were determined to be 1.0 × 10−9, 1.0 × 10−9, and 8.0 × 10−9 M, respectively.

Supercooling of aqueous dimethylsulfoxide solution at normal and high pressures: Evidence for the coexistence of phase-separated aqueous dimethylsulfoxide solutions of different water structures

Supercooling behavior of aqueous dimethylsulfoxide (DMSO) solution was investigated as a function of DMSO concentration and at high pressures. A linear relationship was observed for T(H) (homogeneous ice nucleation temperature) and T(m) (melting temperature) for the supercooling of aqueous DMSO solution at normal pressure. Analysis of the DTA (differential thermal analysis) traces for homogeneous ice crystallization in the bottom region of the T(H) curve for a DMSO solution of R=20 (R: moles of water/moles of DMSO) at high pressures supported the contention that the second critical point (SCP) of liquid water should exist at P(c2)= approximately 200 MPa and at T(c2)<-100 degrees C (P(c2): pressure of SCP, T(c2): temperature of SCP). The presence of two T(H) peaks for DMSO solutions (R=15, 12, and 10) suggests that phase separation occurs in aqueous DMSO solution (R<or=15) at high pressures and low temperatures (<-90 degrees C). The pressure dependence of the two T(H) curves for DMSO solutions of R=10 and 12 indicates that the two phase-separated components in the DMSO solution of R=10 have different liquid water structures [LDL-like and HDL-like structures (LDL: low-density liquid water, HDL: high-density liquid water)] in the pressure range of 120-230 MPa.

Morphology of polysorbate 80 (Tween 80) micelles in aqueous dimethyl sulfoxide solutions

The structures of micelles of the surfactant polysorbate 80 (Tween 80) in 0-50% aqueous dimethyl sulfoxide (DMSO) solutions (pH 7.2, ionic strength 2.44 mM) were investigated by means of small-angle X-ray scattering. At DMSO concentrations of 0-20%, core-shell cylinder micelles formed, and at 30-50% DMSO, core-shell discus micelles formed, that is, changing the hydrophobicity of the DMSO solvent mixture changed the micelles from core-shell cylinder micelles to core-shell discus micelles.

Controlled precipitation and purification of hemicellulose from DMSO and DMSO/water mixtures by carbon dioxide as anti-solvent

Anti-solvent precipitation of xylans and mannans from dimethylsulfoxide (DMSO) or DMSO/water mixtures, and subsequent drying with supercritical carbon dioxide (scCO 2) were developed into a useful technique for preparing spherical hemicellulose micro-particles. Depending on the type of hemicellulose, water content of DMSO, precipitation pressure and temperature, the particle size can be adjusted within a wide range from less than 0.1 to more than 5 μm. For example, fast super-saturation which can be achieved by applying supercritical conditions results in the formation of very small particles as mass transfer between the solvent DMSO and anti-solvent scCO 2 is reduced to a minimum. Anti-solvent precipitation from aqueous DMSO (e.g., 10% water) allows for processing distinctly larger amounts of hemicelluloses compared to pure DMSO without the necessity of increasing the precipitation pressure. The formation of an additional inert aqueous phase increases the mass transfer resistance, which results in the formation of larger, stable agglomerates. Curiepoint pyrolysis GC/MS, gel permeation chromatography (GPC) and analysis of the monosaccharide composition of both the parent hemicellulosic material and the corresponding precipitates demonstrated that hemicelluloses can be purified from residual lignin by supercritical anti-solvent precipitation with carbon dioxide without altering the structure of the biopolymers.

Palladium‐Catalyzed One‐Pot Conversion of Aldehydes to Amides

AbstractThe palladium‐catalyzed one‐pot conversion of aldehydes into primary amides in the presence of hydroxylamine hydrochloride in aqueous dimethyl sulfoxide (DMSO) at moderate temperature is described. The process is selective and free from the addition of an external chelating ligand.

Glancing-angle Raman spectroscopic probe for reaction kinetics at water surfaces

We report glancing-angle Raman spectra acquired at the surface of aqueous dimethyl sulfoxide solutions and demonstrate that this technique can be used to measure the surface concentration of solutes. The presence of some solute molecules at the surface suppresses the intensity of the OH-stretching band of water there. We used this phenomenon to study the interfacial reaction of gas-phase ozone with aqueous NaX solutions (X = Br, I) by monitoring the decrease in intensity of the OH-stretching band of water over time. UV-VIS analysis of the product solutions indicates that X(3)(-), formed from X(2) evolved in the ozonation reaction, is the species most likely responsible for the decrease in OH-stretching intensity at the surface. The dependence of the rate of OH-Raman signal loss at the water surface on the bulk halide concentration is well described by a Langmuir-Hinshelwood kinetic model. The Langmuir-Hinshelwood parameters indicated that iodide has a approximately 50 times greater propensity for the surface compared to bromide.

Solvent-assisted optical modulation of FRET-induced fluorescence for efficient conjugated polymer-based DNA detection

The solvent effects were studied in fluorescence resonance energy transfer (FRET) from a cationic polyfluorene copolymer (FHQ, FPQ) to a fluorescein (Fl)-labelled oligonucleotide (ssDNA-Fl). Upon addition of dimethyl sulfoxide (DMSO), the optical properties of polymers and the probe dye were substantially modified and the FRET-induced PL signal was enhanced 3.8-37 times, relative to that in phosphate buffer solution (PBS). The hydrophobic interaction between polymers and ssDNA-Fl is expected to decrease in the presence of DMSO, which induces the weaker polymer/ssDNA-Fl complexation with longer intermolecular donor-acceptor separation and perturbs the competition between the FRET and PL quenching processes such as photo-induced charge transfer. The gradual decrease in Fl PL quenching with increasing the DMSO content was investigated by measuring the Stern-Volmer quenching constants (3.3-4.2 × 10(6) M(-1) in PBS, 0.56-1.1 × 10(6) M(-1) in 80 vol% DMSO) and PL lifetime of the excited Fl* in polymer/ssDNA-Fl (600 ps in PBS and 2120 ps in 80 vol% DMSO for FHQ/ssDNA-Fl) in PBS/DMSO mixtures. The substantially reduced PL quenching would amplify the resulting FRET Fl signal. The signal amplification in real DNA detection was also demonstrated with fluorescein-labelled PNA (probe PNA) in the presence of a complementary target DNA and noncomplementary DNA in aqueous DMSO solutions. This approach suggests a simple way of modifying the fine-structure of polymer/ssDNA-Fl and improving the detection sensitivity in conjugated polymer-based FRET bioassays.

Complexation between iron(III) and nicotinamide in aqueous dimethyl sulfoxide

The stability constants of iron(III) complexes with nicotinamide in water-DMSO mixtures (XDMSO = 0–0.75) were determined by potentiometric titration at 25.0 ± 0.1°C and an ionic strength of 0.25 (NaClO4). The contributions from the solvation of the reagents to the Gibbs energy of complexation transfer were analyzed. The stabilities of iron(III), copper(II), and silver(I) complexes with nicotinamide were compared. The observed decrease in the stability constants was attributed to the stabilization of iron(III) solvate complexes as the DMSO content increases.

Counterion mixing effects on the conformational transitions of polyelectrolytes. I. Volume phase transition and coil‐globule transition of alkali metal poly(acrylate)s

AbstractCounterion mixing effects on the volume phase transition and the coil‐globule transition of alkali metal poly(acrylate)s (PAAM) in aqueous organic solvents were investigated by observing the swelling behavior of PAAM gel and by measuring the solution viscosity and the conductivity as a function of the counterion mixing ratio. Marked transitions to the collapsed states were induced only for Li+/Cs+ system in most solvent systems; namely, PAA gel significantly collapsed in the presence of Li+ and Cs+ counterions irrespective of the solvent species employed, while only a slight deswelling was observed for Li+/K+ system in some aqueous organic solvents. Corresponding specific decrements in the solution viscosity and conductivity were also confirmed for the combination of Li+ and Cs+ in aqueous dimethyl sulfoxide (DMSO) system. A simple analysis of the conductivity decrement observed for Li+/Cs+ system in 60 vol % DMSO suggested that only Cs+ is tightly bound upon addition of Li+ while no restriction is induced for Li+ upon mixing with Cs+. A working hypothesis is proposed for the apparently intriguing behaviors of the counterions in the mixed system. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 2122–2131, 2009

Formation and isolation of nanocrystal complexes between dextrins and n-butanol

Starch dextrins of different molecular sizes (DP n 311, 142 and 39) were prepared by hydrolyzing a high amylose maize starch in acidic alcohol solutions. The dextrins were dissolved in an aqueous dimethyl sulfoxide solution (90% DMSO), and then the solution was allowed to migrate down into n-butanol separated by a membrane filter. The complex was gradually formed between the dextrin and butanol, and precipitated in the butanol layer. The dextrin–butanol complex yielded V6-I type crystals with broad reflections ( d-spacings 1.123, 0.657 and 0.429 nm) under X-ray diffractograms. Platelets of average length less than 100 nm, interspersed in amorphous matrices, were observed in complexes of DP n 311 and 142, but that of DP n 39 showed different morphology, and the formation of complexes was limited. By hydrolyzing the complex of DP n 311 with α-amylase, amorphous matrices were selectively removed, and crystallites of 23–72 nm showing a V6-I X-ray diffraction pattern were obtained. However, crystallites in complexes of DP n 142 and 39 were eroded by amylolysis, forming large aggregates.

Synthesis and heterocyclization of 3-aryl-2-methyl-2-thiocyanatopropanamides

Reactions of arenediazonium tetrafluoroborates with methacrylamide in the presence of potassium thiocyanate in aqueous acetone (1: 2.5) or aqueous dimethyl sulfoxide (1: 4) gave the corresponding 3-aryl-2-methyl-2-thiocyanatopropanamides which underwent heterocyclization in boiling acetic anhydride to produce difficultly accessible 2-(acetyl)amino-5-benzylthiazol-4(5H)-ones.

Protein–polysaccharide viscoelastic matrices: synergic effects of amylose on lysozyme physical gelation in aqueous dimethylsulfoxide

A synergic effect of amylose on rheological characteristics of lysozyme physical gels evolved out of dimethylsulfoxide–water was verified and analyzed. The dynamics of the gels were experimentally approached by oscillatory rheology. The synergic effect was characterized by a decrease in the threshold DMSO volume fraction required for lysozyme gelation, and by a significant strengthening of the gel structure at over-critical solvent and protein concentrations. Drastic changes in the relaxation and creep curve patterns for systems in the presence of amylose were verified. Complex viscosity dependence on temperature was found to conform to an Arrhenius-like equation, allowing the determination of an activation energy term (Ea, apparent) for discrimination of gel rigidity. A dilatant effect was found to be induced by temperature on the flow behavior of lysozyme dispersions in DMSO–H2O in sub-critical conditions for gelation, which was greatly intensified by the presence of amylose in the samples. That transition was interpreted as reflecting a change from a predominant colloidal flow regime, where globular components are the prevailing structural elements, to a mainly fibrillar, polymeric flow behavior.

Chitosan‐g‐polycaprolactone copolymer fibrous mesh scaffolds and their related properties

AbstractChitosan‐g‐polycaprolactone copolymers (CPCs) with desired composition proportions were synthesized by carefully controlling the weight ratio of polycaprolactone side chains changing approximately between 45 and 48 wt% so that the obtained CPCs could be further processed via different processing techniques. Aqueous acetic acid solutions and dimethyl sulfoxide were respectively employed as solvents to fabricate CPCs into fibrous mesh scaffolds that had nearly similar parameters characterized by the average porosity and pore‐size of scaffolds as well as the average diameter of filaments under optimal processing conditions. The swelling index, surface group analysis, antibacterial activity and tensile mechanical properties of these mesh scaffolds were investigated in several ways, and the scaffolds showed quite different properties due to the different processing methods employed, although the same type of CPC was used. Copyright © 2008 John Wiley &amp; Sons, Ltd.

Preparation of nano-sized starch particles by complex formation with n-butanol

High amylose corn starch was dissolved in an aqueous dimethyl sulfoxide solution and allowed to form complexes by migrating gravimetrically into n-butanol layer through a membrane filter at 70 °C. The starch–butanol complex yielded V6I-type crystals with broad reflections at d-spacings of 0.657 and 0.446 nm under an X-ray diffractogram. The amylose, the average Mw of which was 2.69 × 10 5 as determined by size-exclusion column chromatography, mostly contributed to complex formation. Platelets of an average length less than 100 nm, interspersed in amorphous matrices, were observed in the crude complex. By hydrolyzing the crude complex with α-amylase, amorphous matrices were removed and starch crystallites of 10–20 nm, showing a V6I X-ray diffraction pattern at d-spacings 1.187, 0.685, 0.448 and 0.394 nm, were obtained. The average chain length of starch residing in the crystalline complex was DP 9, indicating that single crystallite units consisted of approximately 1.5 helical turn of anhydroglucose chains.

Micellization of Cetyltributylphosphonium Bromide in some Binary Aqueous Solvents Mixtures

AbstractThe micellization behavior of cetyltributylphosphonium bromide (CTBPB) has been studied in aqueous ethylene glycol, dimethyl formamide, dimethyl sulfoxide, acetonitrile, 1-propanol, methanol, 1,4-dioxane and tetrahydrofuran mixtures (10–20% v/v) over the temperature range (300–320 K) by conductometry. The critical micelle concentration (cmc), extent of counterion binding (α) and thermodynamic parameters (ΔGom, ΔHom, ΔSom) for micellization process have been reported and discussed. The cmc values were found to increase with an increase in temperature and % of organic solvent.

Complex formation of silver(I) with glycinate ion in aqueous ethanol and dimethyl sulfoxide solutions

The complex formation reaction of silver(I) with glycinate ion in aqueous ethanol and dimethyl sulfoxide solutions of variable compositions was studied by potentiometric titration at 298 K. The stabilities of Ag(I) glycinate complexes were found to increase with the increasing content of the organic cosolvent. The contribution of ΔG° of the reagent resolvation to the change in the Gibbs energy of the complex formation reaction was estimated using the literature data. The change in the ligand solvate state was shown to give the main contribution to the stability of the title complexes in water-organic solvents.

Effect of Solvent on the Dimerization of the ansa-Molybdocene Catalyst [C2Me4Cp2Mo(OH)(OH2)][OTs

The monomer−dimer equilibrium behavior of the [ansa-C2Me4Cp2Mo(OH)(OH2)][OTs] and [ansa-C2Me4Cp2Mo(μ-OH)]2[OTs]2 complexes was explored in a variety of solvents. Only the monomer was detected spectroscopically in water, aqueous terahydrofuran, aqueous acetone, or aqueous dimethylsulfoxide, while appreciable dimerization was noted in aqueous solutions containing 50% ethanol or methanol. Several equilibrium constants (Keq) were estimated. In water, Keq ≥ 2 M at 25 °C. In ethanol at 25 °C, Keq is on the order of 10−2 M. In methanol at 25 °C, Keq ≈ 10−6 M. The strong dependence of the monomer−dimer equilibrium on the solvent medium does not correlate with solvent polarity, hydrogen-bonding ability, or solvent basicity. These findings illustrate that catalyst dimerization can be suppressed more effectively by solvent choice than by electronic or steric modification of the Cp ligands. Because only the monomer is catalytically active, the effect of the monomer−dimer equilibrium on molybdocene-catalyzed nitrile h...