SN2 reaction of water with alkyl halides to give alcohols

by James

Description: Primary or methyl halides (or tosylates) will react with water to give alcohols. This is an SN2 reaction.


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



Notes: Water is a poor nucleophile and generally isn’t strong enough to displace a leaving group from a secondary alkyl halide.

Mechanism: In this reaction water attacks the carbon in an SN2 reaction displacing the leaving group (bromide in this case) (Step 1, arrows A and B). The bromide ion then removes a proton from the oxygen, providing the neutral alcohol and HBr.


Notes: It’s also reasonable to use water as the base here in the second step instead of Br(-). In fact it’s probably more reasonable to do so since water is a stronger base than Br(-).



{ 6 comments… read them below or add one }

Rosemary Flynn May 13, 2013 at 11:30 pm

Why does it say NaOH instead of H20?


james May 16, 2013 at 12:40 pm

NaOH is a much better nucleophile than water; for practical purposes it’s much faster to use than H2O.


Alexander Peltekoff January 11, 2014 at 2:40 pm

But isn’t the point of this slide to show “SN2 reaction of water with alkyl halides to give alcohols”?


James January 21, 2014 at 12:36 pm

Thank you, I need to fix this!


Rhiannon Spritzer March 19, 2014 at 4:12 am

is this going to be changed soon?


James May 27, 2014 at 1:29 pm



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