Identification of dimethyl sulfide in dimethyl sulfoxide and implications for metal-thiolate disulfide exchange reactions

Abstract

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...

Symmetry Breaking in Seed-Mediated Silver Nanorod Growth Induced by Dimethyl Sulfoxide

“…Finally, the potential effect of impurities in DMSO on the directed growth of the Ag rods on the AuBPs seed was investigated. Although a DMSO batch with a purity above 99.9% was used, impurities such as dimethyl sulfide (DMS) were also present at a concentration around 0.5 mM, 46 corresponding to a range of 0−0.2 mM in the reaction medium (DMSO concentrations between 0% and 40%). The synthesis was performed in the presence of DMS concentrations ranging from 0 to 10 mM (Figure S12) and a modification of the shape of the Au@Ag rods was noticed, but only for 10 mM DMS.…”

Radical Chain Reduction via Carbon Dioxide Radical Anion (CO2•–)

“…While light and formate were critical to substrate conversion under these conditions (see the Supporting Information for details), quantitative reduction was observed when thiyl generation was performed via photolysis of dimethyl disulfide (no photoredox catalyst) or with thiol and persulfate (20 mol %) at 100 °C. However, because trace amounts of thiol impurities that are present in DMSO − are capable of promoting this reaction, mechanistic experiments were conducted with freshly purified DMSO (however, solvent from particularly old bottles was capable of promoting this reactivity without added thiol cocatalyst). We found the quantum yield (Φ) of the reaction under our standard conditions ( P1 , mesna) to be 2.63, which strongly indicates radical chain character.…”

Carbon Dioxide Radical Anion by Photoinduced Equilibration between Formate Salts and [11C, 13C, 14C]CO2: Application to Carbon Isotope Radiolabeling

“…On the other hand, without both PC and T1 under light irradiation (∼40 °C), a non-negligible 9% IE was observed in DMSO (entry 9). 18 This background equilibration seems solvent-dependent as in DMF no IE was detected. 19 The photoinduced equilibration was next performed in a two-chamber reactor (Ch.A), and in the adjacent chamber (Ch.B), a Staudinger/aza-Wittig sequence 20 was set to react with the residual [ 13 C]CO 2 (Scheme 2B).…”