English

Noun

sulfnium

1. the univalent H3S+ cation, derived from sulfane

A sulfonium ion, also known as sulphonium ion and sulfanium ion, is a positively charged sulfur ion carrying three alkyl groups as substituents (S+R3). Ionic compounds consisting of a positively charged sulfonium cation and a negatively charged anion are called sulfonium salts.

Sulfonium compounds can be synthesized from the reaction of dialkylsulfides with alkyl halides:

CH3-S-CH3 + CH3-I → (CH3)3S+ I− (trimethylsulfonium iodide)

In the above reaction, the alkylation of a sulfide, the sulfur atom has two lone electron pairs. Using those lone pairs, the sulfide acts as a nucleophile, and attacks the carbon of iodomethane. At the same time, as part of a concerted nucleophilic substitution mechanism (SN2), the iodide leaving group comes off; this leaves a positively charged trimethylsulfonium ion. This cation is attracted to the negatively charged iodide, so the two form an ionic bond, giving trimethylsulfonium iodide.

See also

• Sulfide R-S-R
• Sulfate R-SO4-R
• Sulfite R-SO3-R
• Sulfonate R-SO3−
• Onium compounds

References

External links

• IUPAC definition (short pdf)