Reaction of alkyl halides with water to form alcohols (SN1)

by James

Description: Alkyl halides will react with water to form alcohols through an SN1 mechanism.

Notes: X is a halide such as Cl, Br, or I (never F). The R group must be able to form a stable carbocation (e.g. tertiary, benzylic or allylic).

In these reactions water is generally used as the solvent.


Notes: Note that if the alkyl halide is on a stereocenter, a 1:1 mixture of stereoisomers will be obtained (example 3).

Mechanism: Cleavage of the C–Cl bond (Step 1, arow A) leads to the carbocation, which is attacked by water (Step 2, arrows B). Deprotonation of the oxygen (Step 3, arrows C and D) leads to the alcohol. This is an SN1 reaction.

Notes: It’s probably more reasonable to show water as the base in step C. Note that if C-2 was a stereocenter, this reaction would end up as a mixture of stereoisomers.


{ 3 comments… read them below or add one }

Omar Sadek October 29, 2012 at 11:30 pm

Looking forward to becoming a member. This is a great site. I wish I would have found it earlier.


Michel Carroll February 6, 2014 at 11:46 pm

I’ve heard it mentioned that dilute acid can be used to transform RX into ROH. In that case, would the reaction follow this same pathway (Sn1), or would it be a different mechanism?


Mark Quercioli April 30, 2015 at 12:35 am

Great example!! I think you were suppose to say cleavage of C-Cl in step 1 instead of C-Br though. Regardless, X is a halide. Thank you for this awesome website. I love being a member!!


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