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SN2 reaction of thiolates with alkyl halides to give thioethers (sulfides)

Description: Alkyl halides (or tosylates) will react with thiolate ions to form sulfides [also known as thioethers]


  • Sulfides are the sulfur-containing equivalents of ethers. This reaction is analogous to the Williamson synthesis of ethers.
  • X here is a halide (Cl, Br, I) or sulfonate (OTs, OMs)
  • The counter-ion for RS(-) can be any alkali ion, such as Li, Na (as shown) or K.
Notes: Note that since this is an SN2 reaction and proceeds via backside attack, there will be inversion of configuration at the carbon (note the last two examples).
Mechanism: In the SN2 reaction here the nucleophile (RS-) attacks the carbon with the good leaving group, forming a C–S bond and breaking the C–Br bond (Step 1, arrows A and B).