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SN2 reaction of alkyl halides with hydroxide ions to give alcohols

Description: Alkyl halides (or tosylates) will react with hydroxide ions to give alcohols. This is an SN2 reaction.

Notes: X here is a halide (Cl, Br, I) or sulfonate (OTs, OMs)

The counter-ion for the hydroxide ion is generally an alkali metal such as lithium, sodium (shown) or potassium.

In order to avoid competition with the E2 reaction, a polar aprotic solvent like DMSO or acetone can be used. This is particularly important for secondary alkyl halides/tosylates.


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 (HO–) attacks the carbon with the good leaving group, forming a C–OH bond and breaking the C–Br bond (Step 1, arrows A and B).