Solvent effects. A model reaction between dimethyl trisulfide and di-n-propyl trisulfide was used to assess the influence of solvent on this unusual S-S exchange process (Figure ). Control reactions in which no solvent was used (both trisulfides are liquids) resulted in no reaction after 24 hours, and only trace amounts of metathesis product (MeS3 n Pr) were observed over 7 days at room temperature, as assessed by gas chromatography-mass spectrometry (GC-MS) analysis (S7-S8). Heating the neat reaction to 80 ºC led to no reaction over 24 hours. In contrast, rapid S-S metathesis was observed when the trisulfides were treated with 1 molar equivalent of DMF. The result was the same in ambient light and when light was excluded from the reaction (S9-S10). The amount of DMF was important with no reaction observed when only 5% of the reaction volume was comprised of DMF (~0.2 molar equivalents relative to trisulfide) and increasing reaction rates were observed with increasing amounts of DMF. When >50% of the reaction volume was DMF (>3.6 molar equivalents DMF relative to trisulfide), equilibrium was reached in less than 2 minutes at room temperature (S11-S24). Rapid S-S metathesis was also observed in other amide containing solvents (DMA, NMP), urea-based solvents, phosphoramides and DMSO (Figure , Category 1 solvents). In all cases, equilibrium was reached in seconds when the reaction was run in an excess of these polar, aprotic solvents (S25-S29). Interestingly, the rate of S-S metathesis in these solvents was reduced when water or acetic acid was added to the reaction. For this reason, it was important to dry the solvents to promote rapid metathesis (S30-S35).