Sulfenyl chloride

File:Sulfenyl-chloride-general-RSCl-2D.png

General structural formula of sulfenyl chlorides, RSCl

A sulfenyl chloride is a functional group with the connectivity R–S–Cl, where R is alkyl or aryl. Sulfenyl chlorides are reactive compounds that behave as sources of RS⁺. They are used in the formation of RS–N and RS–O bonds. According to IUPAC nomenclature they are named as alkyl thiohypochlorites, i.e. esters of thiohypochlorous acid.

Preparation

Sulfenyl chlorides are typically prepared by chlorination of disulfides:

R₂S₂ + Cl₂ → 2 RSCl

This reaction is sometimes called the Zincke disulfide reaction, in recognition of Theodor Zincke. Typically, sulfenyl halides are stabilized by electronegative substituents. This trend is illustrated by the stability of CCl₃SCl obtained by chlorination of carbon disulfide.

File:Perchloromethyl mercaptan.svg

Trichloromethanesulfenyl chloride is a stable sulfenyl chloride.

Reactions

CCl₃SCl reacts with N-H-containing compounds in the presence of base to give the sulfenamides:

CCl₃SCl + R₂NH → CCl₃SNR₂ + HCl

This method is used in the production of the fungicide captan.

Sulfenyl chlorides add across alkenes:

CH₂=CH₂ + RSCl → RSCH₂CH₂Cl

Related compounds

Sulfenyl bromides are also known. Simple sulfenyl iodides are unknown because they are unstable with respect to the disulfide and iodine:

2 RSI → (RS)₂ + I₂

Sulfenyl iodides can be isolated as stable compounds if they bear alkyl steric protecting groups as part of a cavity-shaped framework, illustrating the technique of kinetic stabilization of a reactive functionality, as in the case of sulfenic acids.

A related class of compounds are the alkylsulfur trichlorides, as exemplified by methylsulfur trichloride, CH₃SCl₃.

The corresponding selenenyl halides, e.g. C₆H₅SeCl, are more commonly encountered in the laboratory. Sulfenyl chlorides are used in the production of agents used in the vulcanization of rubber.