Sulfide, Organic

an organosulfur compound with the general formula R—S_n—R’, where R and R’ are identical or different aliphatic or aromatic hydrocarbon residues and n ≥ 1. Organic sulfides for which n = 1 are called monosulfides, or thioethers, whereas those with n = 2 and n > 2 are called disulfides, trisulfides, and so on.

Monosulfides boil at higher temperatures than the corresponding ethers ROR’, of which they are the sulfur analogues. Thus, methyl sulfide, (CH₃)₂S, boils at 38.0°C, whereas (CH₃)₂0 boils at –23.6°C. Monosulfides are oxidized, for example, to sulfoxides by hydrogen peroxide and to sulfones by concentrated nitric acid; they also add halogens, alkyl halides, and alkyl sulfates.

Organic sulfides are abundant in nature. Some petroleums contain up to 4–5 percent sulfur, most of which is bound in the form of sulfides. The biologically important natural products methionine and biotin are organic sulfides. Allyl sulfide is found in garlic. Organic sulfides are used as antioxidants and stabilizers in motor fuels and lubricating oils. They are also used as medicinal preparations, dyes, and solvents. Some synthetic disulfides and polysulfides have great industrial importance, among them polysulfide rubbers (Thiokols) and tetramethylthiuram disulfide, which is used in vulcanizing raw rubber. Halogenated organic sulfides, such as mustard gas, are toxic.