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SN2 reaction of hydrosulfide ion with alkyl halides to give thiols

Description: Alkyl halides (or tosylates) will react with the hydrosulfide ion (HS–) to give thiols.

Notes: X here is a halide (Cl, Br, I) or sulfonate (OTs, OMs). Although Na is shown here as the counter-ion for HS(-), any alkali metal can be used (e.g. Li, Na, 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 the nucleophile (HS-) 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).

Notes: For more information on the SN2 see the summary sheet on this reaction. It isn’t crucial to show the sodium (Na) here.