Sh. A. Markaryan

Thermodynamics of liquid-gas phase equilibria in the dipropylsulfoxide-water system in the range of 303.15 to 323.15 K

The saturation vapor pressure of pure dipropylsulfoxide (DPSO) is measured in the temperature range of 303.15 to 323.15 K. The boiling point of DPSO under normal pressure (479.15 K) is determined and the molar heat of vaporization of DPSO is calculated (ΔvH○ = 61.4 ± 3.1 kJ/mol) on the basis of data obtained via graphical extrapolation. The total saturation vapor pressure of aqueous solutions of DPSO of various concentrations at 303.15 and 308.15 K is measured. Partial pressures, the activity coefficients of DPSO and H2O, and the excess Gibbs energy of mixing are calculated on the basis of the obtained results.

The thermodynamic properties of solutions of L-ascorbic acid in dimethyl sulfoxide and water-dimethyl sulfoxide mixtures

Solutions of L-ascorbic acid (AA) in dimethyl sulfoxide (DMSO) and DMSO-water mixtures were studied by the densitometry, surface tension, and calorimetry methods. The apparent and partial molar volumes of AA in solutions at 298.15 K were calculated. Surface tension insignificantly increased as the concentration of AA in DMSO grew. The enthalpies of solution of AA in the solvents and the enthalpies of transfer of AA from water into DMSO and DMSO-water mixed solvents were calculated. The results obtained were explained by the existence of H-bonds between AA and DMSO molecules.

Complexation and reactions of molecular iodine with dimethyl and diethyl sulfoxides

The complexation and reactions of molecular iodine with dimethyl sulfoxide and diethyl sulfoxide in the neat sulfoxides and in their mixtrues with water were studied by conductometry, pH-metry, argentometric titration, UV spectroscopy, and GLC analysis. According to the results obtained, molecular iodine initially forms a charge-transfer complex with the sulfoxide, which subsequently undergoes chemical transformations to hydrogen iodide and the corresponding sulfones. A possible reaction mechanism was suggested.

Effect of the Dioctyl Sodium Sulfosuccinate (AOT) Concentration on the Properties of the AOT-n-Heptane-DMSO-Water Micellar System

The effect of the concentration of sodium di-(2-ethylhexyl) sulfosuccinate (AOT) on the volume and transport properties of the AOT/n-heptane/dimethylsulfoxide-water reverse micellar systems at different sulfoxide to water volume ratios, constant degree of AOT hydration R = 10, and temperatures of 298.15–313.15 K was studied by densimetry and viscosimetry. The apparent volumes of the polar phases and the volume fractions of micelles were calculated using the densities of these systems. In the presence of dimethylsulfoxide, an increase in its concentration led to an increase in the apparent volume of the polar phase; an increase in the AOT concentration at increased viscosity of the system led to a decrease in the apparent volume of the micellar nucleus.

Physicochemical properties of aqueous solutions of dimethyl- and diethylsulfones

Aqueous solutions of dimethylsulfone (DMSO2) and diethylsulfone (DESO2) are studied by means of densimetry, surface tension, and calorimetry. The solution densities are defined and the apparent and partial molar volumes of DMSO2 and DESO2 are calculated in the temperature range of 293.15–323.15 K. It is revealed that in both cases the increase of sulfone concentration leads to the reduction of the surface tension. This is more expressed in the case of DESO2 than in the extension of the sulfone hydrocarbon chain. The calorimetric studies show that the dissolution enthalpies of DMSO2 and DESO2 do not differ substantially from one another; in both cases the dissolution of crystalline sulfones makes a crucial contribution to the enthalpy of dissolution values

Effect of dimethyl sulfoxide on electrochemical and antiradical properties of ascorbic acid

Solvent effect of dimethyl sulfoxide (DMSO) on the oxidation-reduction properties of ascorbic acid (AA) was studied by the electroanalytical method of differential pulse voltammetry (DPV) in a three-electrode cell at 37 °C. Dimethylsulfoxide was found to considerably decrease the oxidation ability of AA due to the formation of molecular complexes between AA and DMSO through the intermolecular hydrogen bonds and shift the anodic peak potential toward the positive values, with its intensity being decreased. Kinetic spectrophotometric measurements in the UV-vis regions of the reaction of the stable free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH·) with AA confirmed the stabilizing effect of the Lewis base DMSO on the reactivity of the neutral form of AA and its intermediates with respect to DPPH·. The mechanism of oxidation of AA with the radical DPPH· in the presence of DMSO was considered.

Photochemical transformations of 7-dehydrocholesterol

Photochemical transformations of 7-dehydrocholesterol were performed with a two-lamp experimental circulation installation equipped with a ferrioxalate actinometer and were monitored by UV spectroscopy and high-performance liquid chromatography. The quantum yields of the overall conversion of 7-dehydrocholesterol at wavelengths of 254, 313, and 365 nm were determined.

Dielectric Relaxation Spectroscopy Study of the Structure and Dynamics of Dialkyl Sulfoxide Solutions

The authors’ earlier works on the dielectric properties of different dialkyl sulfoxides and solutions of them are reviewed.

Use of Water-Insoluble Surfactants for the Removal of Small Amounts of Transition Metal Nitrates from Water

The removal of small amounts of cobalt and nickel nitrates from water with the use of water-insoluble surfactant, dioctadecyldimethylammonium bromide, was studied.

Interaction of Cholesterol with Dimethyl and Diethyl Sulfoxides

The complexing of cholesterol with dimethyl and diethyl sulfoxides in carbon tetrachloride is investigated by the method of IR spectroscopy. It is established that the hydrogen bond is formed between the oxygen of the sulfoxide group of sulfoxides and the hydrogen of the hydroxyl group of cholesterol. The equilibrium constants (Keq) of the complexes of cholesterol with dimethyl sulfoxide (Keq = 93 liters/mole) and diethyl sulfoxide (Keq = 98 liters/mole) at 23°C are determined.