Definition

Tertiary alcohol can be converted to tertiary alkyl iodide with hydroiodic acid (HI).

Structural reaction scheme for Alkyl iodide formation [HI], diagram 1 of 4
Figure 1. Alkyl iodide formation [HI]

Explanation

This reaction proceeds via an SN1 mechanism which consists of three steps:

1. An acid/base reaction. Protonated oxygen from the hydroxyl group of alcohol makes a better leaving group.



2. The rate-determining step. Loss of the leaving group and carbocation formation.

Structural reaction scheme for Alkyl iodide formation [HI], diagram 2 of 4
Figure 2. Alkyl iodide formation [HI]


3. Nucleophilic attack of iodide ion on the electron-deficient carbon make final product (alkyl iodide)

Structural reaction scheme for Alkyl iodide formation [HI], diagram 3 of 4
Figure 3. Alkyl iodide formation [HI]
Structural reaction scheme for Alkyl iodide formation [HI], diagram 4 of 4
Figure 4. Alkyl iodide formation [HI]