Mechanism of the reaction of radicals with peroxides and dimethyl sulfoxide in aqueous solution

The reactions of methyl and methylperoxyl radicals derived from dimethyl sulfoxide (DMSO) with hydrogen peroxide, peroxymonocarbonate (HCO4 (-)), and persulfate were studied. The major reaction observed for the hydroperoxides was the abstraction of the hydrogen atom by the radicals. The radicals interact with a lone pair of electrons on the peroxide to produce methanol and formaldehyde. Furthermore, the results indicate that in RO2H and RO2R', electron-withdrawing groups cause a considerable increase in the reactivity of the peroxides towards the radicals and not only towards nucleophiles. The HO2 (.)/O2 (.-) and CO3 (.-) radicals react with DMSO to produce methyl radicals. Thus, the formation of the (.)CH3 radicals in the presence of DMSO is not proof of the formation of the (.)OH radicals in the system. These reactions must be considered when radical processes, such as in biological and catalytic systems, are studied. Especially, the plausible role of HCO4 (-) ions in biological systems as a source of oxidative stress cannot be overlooked.     

Thermolysis of dimethyl sulfoxide

The thermal decomposition of dimethyl sulfoxide at small extent of reaction has been studied at temperatures of 297-350°C and pressures of 10–400 Torr. The major products CH₄, C₂H₄, and SO₂ were shown to follow first-order kinetics. The activation energies for production of each was about 48 kcal·mole^?1. A chain mechanism has been postulated in the light of the results of isotopic substitution experiments.     

The solvent dimethyl sulfoxide

The dipolar aprotic solvent dimethyl sulfoxide is liquid over a wide range of temperatures, is a strong electron donor, and has a high polarity. It is therefore an excellent and selective solvent for many organic and even polymeric compounds, and can enter into H-bonding and dipole-dipole association. The structure of dimethyl sulfoxide, with a “hard” oxygen atom and a “soft” sulfur atom, leads to good solvation of cations and poor solvation of anions. Mixtures of alkoxides with dimethyl sulfoxide are therefore among the most strongly basic systems in organic chemistry, and are excellently suited for the deprotonation of weakly acidic OH, NH, and CH bonds, for eliminations, and for the initiation of polymerizations.     

Absorption,desorption and interaction of SO2 with the binary system tetraethylene glycol + dimethyl sulfoxide

The gas-liquid equilibrium (GLE) data were determined for the mixture SO₂ + N₂ in the binary system of tetraethylene glycol (TeEG) + dimethyl sulfoxide (DMSO) at T = 298.15–313.15 K and p = 123.15 kPa with the SO₂ partial pressures of 0.4–150 Pa. From GLE data, Henry’s law constants (HLCs) were obtained. When the SO₂ concentration in the gas phase was designed at y_SO2 = 500 ppmv, the SO₂ solubility in the binary system is located in a minimum of 9.36 mol m^?3 in TeEG and a maximum of 80.34 mol m^?3 in DMSO. The SO₂ absorption process was reversible from the five absorption–desorption cycles, and the solvents could repeat utilisation without obvious loss of absorption capacity and the homologous SO₂ desorption efficiency was nearby 98.7%. Furthermore, the spectral consequences illustrated that H-bonding was formed among TeEG, DMSO and SO₂.     

Reaction of π-allylirontric arbonylhalides with dimethyl sulfoxide

Conclusions Dimethyl sulfoxide readily decomposes -allylirontricarbonylhalides with the evolution of 1,5-hexadiene and carbon monoxide and formation of sulfoxide complexes of composition [(CH₃)₂SO]₅FeX₂. In the complexes isolated coordination is through the oxygen of the sulfoxide group.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 192–194, January, 1968.We thank L. I. Denisovich for the polarographic studies.     

Preferential solvation of lysozyme by dimethyl sulfoxide in binary solutions of water and dimethyl sulfoxide

To reveal the denaturation mechanism of lysozyme by dimethyl sulfoxide (DMSO), thermal stability of lysozyme and its preferential solvation by DMSO in binary solutions of water and DMSO was studied by differential scanning calorimetry (DSC) and using densities of ternary solutions of water (1), DMSO (2) and lysozyme (3) at 298.15 K. A significant endothermic peak was observed in binary solutions of water and DMSO except for a solution with a mole fraction of DMSO (x ₂) of 0.4. As x ₂ was increased, the thermal denaturation temperature T _m decreased, but significant increases in changes in enthalpy and heat capacity for denaturation, ΔH _cal and ΔC _p, were observed at low x ₂ before decreasing. The obtained amount of preferential solvation of lysozyme by DMSO (∂g ₂/∂g ₃) was about 0.09 g g⁻¹ at low x ₂, indicating that DMSO molecules preferentially solvate lysozyme at low x ₂. In solutions with high x ₂, the amount of preferential solvation (∂g ₂/∂g ₃) decreased to negative values when lysozyme was denatured. These results indicated that DMSO molecules do not interact directly with lysozyme as denaturants such as guanidine hydrochloride and urea do. The DMSO molecules interact indirectly with lysozyme leading to denaturation, probably due to a strong interaction between water and DMSO molecules.     

Carbocation-forming reactions in dimethyl sulfoxide

Mesylate derivatives of 3-aryl-3-hydroxy-beta-lactams and thiolactams react in DMSO-d(6) by first-order processes to give alcohol products. Substituent effect studies implicate carbocation intermediates (ion-pairs) that are captured by DMSO-d(6) to give transient oxosulfonium ions. Rapid reaction of the oxosulfonium ions with trace amounts of water leads to the alcohol product and regenerates DMSO-d(6). H(2)(17)O labeling studies show that (17)O is incorporated into the DMSO. The mesylate derivatives of endo- and exo-2-hydroxy-2-phenylbicyclo[2.2.1]heptan-3-one also react in DMSO-d(6) to give the alcohol products. Ion-pair intermediates that capture DMSO giving unstable oxosulfonium ions are again proposed. Exo-2-phenyl-endo-bicyclo[2.2.1]heptyl trifluoroacetate readily eliminates trifluoroacetic acid in DMSO-d(6) via a cationic mechanism involving loss of the endo-trifluoroacetate leaving group as well as an exo-hydrogen. The O-methyl oxime derivative of alpha-chloro-alpha,alpha-diphenylacetophenone reacts in DMSO-d(6) to give 1-methoxy-2,3-diphenylindole, a product derived from cyclization of a cationic intermediate. A common ion rate suppression provides further evidence for a cationic mechanism. The triflate derivative of pivaloin reacts by a cationic mechanism in DMSO-d(6) to give rearranged products. The rate is even faster than in highly ionizing solvents such as trifluoroethanol or trifluoroacetic acid. 1-Adamantyl mesylate reacts in DMSO-d(6) by a first-order process (Y(OMs) = -4.00) to give a long-lived oxosulfonium ion, 1-Ad-OS(CD(3))(2)(+), which can be characterized spectroscopically. This oxosulfonium ion reacts only slowly with water at elevated temperatures to give 1-adamantanol. DMSO is therefore a viable solvent for k(s), k(C), and k(Delta) cationic processes.     

Sulfation of polysaccharides with sodium pyrosulfate in dimethyl sulfoxide

Sulfo esters of cellulose, dextran, starch, and amylopectin with a degree of substitution equal to 0.1–1.1 were prepared in the system constituted by sodium pyrosulfate and dimethyl sulfoxide. The intrinsic viscosity of aqueous solutions of sulfo polysaccharides was determined, and their anticoagulant activity was evaluated.     

Vinylation of pyrroles in dimethyl sulfoxide

A number of 1-vinylpyrroles were obtained in up to 97% yields by base-catalyzed addition of substituted pyrroles to acetylene in dimethyl sulfoxide at 80–100°C.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 213–214, February, 1977.     

X-ray crystallographic investigation of the adduct of decachloro-o-carborane with dimethyl sulfoxide

Conclusions The structure of the 11 adduct of decachloro-o-carborane with DMSO was determined by x-ray crystallography. It was established that the structure contains cyclic associates of two DMSO molecules and two decachloro-o-carborane molecules linked by hydrogen bonds of the C-H...O type.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2257–2261, October, 1982.     

Change in the reactivity of N-vinylsuccinimide after complexation with dimethyl sulfoxide

The influence of dimethyl sulfoxide on the copolymerization kinetics and the reactivity parameters of N-vinylsuccinimide was studied. It was shown that, owing to the complexation of monomer molecules with dimethyl sulfoxide molecules, the relative activities of monomers are changed. The electron structures of N-vinylsuccinimide and dimethyl sulfoxide molecules and the molecule geometry was considered, and a complexation mechanism was proposed. The Alfrey–Price Q-e parameters of N-vinylsuccinimide during the complexation were analyzed. The causes of the change in the reactivity of monomer were revealed.     

Temperature-dependent kinetics of the simplest Criegee intermediate reaction with dimethyl sulfoxide

Criegee intermediates are thought to play roles in atmospheric chemistry, including OH radical formation, oxidation of SO₂, NO₂, etc. CH₂OO is the simplest Criegee intermediate, of which the reactivity has been a hot topic. Here we investigated the kinetics of CH₂OO reaction with dimethyl sulfoxide (DMSO) under 278–349 K and 10–150 Torr. DMSO is an important species formed in the oxidation of dimethyl sulfide in the biogenic sulfur cycle. The concentration of CH₂OO was monitored in real-time via its mid-infrared absorption band at about 1,286 cm⁻¹ (Q branch of the ν₄ band) with a high-resolution quantum cascade laser spectrometer. The 298 K bimolecular rate coefficient was determined to be k₂₉₈ = (2.3 ± 0.3) × 10⁻¹² cm³/s at 30 Torr with an Arrhenius activation energy of −3.9 ± 0.2 kcal/mol and a weak pressure dependence for pressures higher than 30 Torr (k₂₉₈ = (2.8 ± 0.3) × 10⁻¹² cm³/s at 100 Torr). The reaction is speculated to undergo a five-membered ring intermediate, analogous to that of CH₂OO with SO₂. The negative activation energy indicates that the rate-determining transition state is submerged. The magnitude of the reaction rate coefficient lies in between those of CH₂OO reactions with (CH₃)₂CO and with SO₂.