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The concentration of dimethyl sulfide (DMS) in seven different samples of research grade dimethyl sulfoxide (DMSO), including one deuterated sample, was measured by GC-MS. The average concentration of DMS is 0.48 AE 0.14 mM (range: 0.44-0.55 mM) and ca. 0.35 mM in DMSO-d 6 . The presence of DMS in DMSO is potentially problematic for compounds that are susceptible to reaction with DMS and are present at mM-mM concentrations. Standard methods of purification of DMSO were unsuccessful in removing all traces of DMS.Dimethyl sulfoxide (DMSO) is an aprotic, polar solvent that is widely used in chemistry and biology. It dissolves hydrophobic and hydrophilic solutes, 1-4 is used as a cryoprotectant for biological samples, 5 and is a component in drug delivery. 6 Researchers have taken advantage of the miscibility of DMSO with water, organic solvents, and ionic liquids (IL) to solubilize polymers and enhance reaction chemistry. For example, recent reports describe the benecial effects of a DMSO : IL co-solvent as a green solvent for hydrolysis of cellulose; 7 and a DMSO : water co-solvent to promote thiol-disulde dynamic combinatorial chemistry. 8 DMSO can also participate in reactions. Some examples include: playing an essential role as a ligand for transition metal catalysts, 9,10 an oxidant for the oxidation of thiols or alcohols, 11,12 and a participant in the oxidation of gold phosphine complexes. 13 We have employed DMSO as a solvent in our kinetic studies of the inuence of solvent dielectric on metal thiolate-disulde exchange reactions. 14-16 Our interest lies in comparing metalmediated thiolate-disulde exchange to metal-free thioldisulde exchange, the latter of which proceeds at a slower rate in high dielectric solvents, such as water or DMSO, than in low dielectric solvents such as THF or CH 2 Cl 2 . 17 Since the metal thiolate complexes and disuldes employed in our kinetic studies are not water-soluble, DMSO was selected as a solvent with a high dielectric constant (3 ¼ 46.45) 1 for these studies. During the course of kinetic investigations, we observed that addition of bis(4-nitrophenyl)disulde to DMSO, in the absence of any metal thiolate, formed a pale red solution with an absorbance near 500 nm. Bis(4-nitrophenyl)disulde is isolated as a pale yellow solid aer recrystallization from boiling nbutanol. When the disulde is dissolved in solvents such as CH 2 Cl 2 , CH 3 CN, acetone, or THF, the solution does not turn red (i.e. there is no absorbance at 500 nm). We suspected that the species responsible for the color in solutions of DMSO was 4-nitrophenylthiolate because addition of base (NEt 3 ) to a DMSO solution of 4-nitrophenylthiol produced a similar red solution with l max ¼ 502 nm. 18 Over the course of time, we observed that when bis(4-nitrophenyl)disulde is dissolved in a variety of DMSO solvents obtained from different commercial suppliers, a similar red color was produced. Thus, we hypothesized that an impurity in DMSO reacts with the disulde to form 4-nitrophenylthiolate. DMSO is an odorle...

A controlled-potential coulometric method is described for the titration of uranium(IV). At potentials more positive than +0.5 volt vs. the Ag/AgCI electrode, uranium(IV) is oxidized at a platinum electrode. The oxidation is sufficiently rapid and complete at a