Mercaptans


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Mercaptans

 

thioalcohols, thiols, sulfur analogues of alcohols, general formula, RSH, where R is a hydrocarbon radical.

With the exception of methyl mercaptan (boiling point, 6.0°C), the mercaptans are liquids with an unpleasant specific odor. They occur in nature mainly in the products of protein decay. Their weakly acidic properties make mercaptans capable of forming salts, called mercaptides [for example, of mercury— (RS)2Hg—hence the name, from the Late Latin mercurium captans,“mercury-binding”]. Mercaptans are easily oxidized to disulfides (RSSR) and sulfonic acids (RSO3H).

Mercaptans are prepared by the alkylation of hydrosulfides of the alkaline metals: NaSH + RX → RSH + NaX (where R is alkyl and X is a halogen). They are also obtained by the condensation of thiourea S = C(NH2)2 with alkyl halides (RX), followed by the hydrolysis of the resultant S-alkylisothiouronium salts. Thiophenols are also frequently included among the mercaptans.

Mercaptans and their derivatives (salts, sulfides, and disulfides) are used as accelerators in the vulcanization of natural and synthetic rubbers (for example, 2-mercaptobenzothiazole, or Kaptaks), as accelerators in the plastication of rubbers (for ex-ample, pentachlorothiophenol, or Renatsit, and dodecyl mercaptan), in certain medicinal preparations (methionine, Sulfonal), and in insecticides. A mixture of mercaptans (mostly of butyl and amyl mercaptans) is used to add an odor to harmful odorless gases.

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