Conversion of tertiary alcohols to alkyl iodides with HI

by James

Description: Tertiary alcohols can be converted to tertiary alkyl iodides with hydroiodic acid (HI).
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Notes: This reaction proceeds through an SN1 mechanism. This reaction is also effective for alcohols which can form stable carbocations, such as allylic and benzylic alcohols.

Examples: 

Notes: Note that if the tertiary alcohol is on a stereocenter there will be a mixture of stereoisomers formed.

Mechanism: The reaction proceeds first with protonation of the alcohol (Step 1, arrows A and B) followed by departure of the leaving group to give a carbocation (Step 2, arrow C) and then attack of iodide on the carbocation (Step 3, arrow D).

Notes: The net result of this reaction is replacement of the alcohol (OH) with iodine (I). This is a substitution reaction.

Note that if the alcohol were on a stereocenter there would be a mixture of stereoisomers formed.

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