Cleavage of Butyl Isopropyl Ether with HI at 100°C

What is the mechanism for the cleavage of butyl isopropyl ether with HI at 100°C?

Why are butyl alcohol and isopropyl iodide not formed in the reaction?

Answer:

Explanation:

In this reaction, the ether is cleaved by SN2 mechanism, as I⁻ is a strong nucleophile.

So we have the following steps:

1. Protonation of oxygen in the ether, improving the ability of both sides to be a leaving group as alcohols.

2. I⁻ performs a nucleophilic attack on the 1st carbon of the butyl side, releasing isopropanol as the leaving group and leaving 1-iodobutane behind.

Now, even though butanol can become a leaving group in this reaction, this is unfavorable, as the isopropyl group has large steric hindrance which prevents nucleophilic attack on the isopropyl side of the ether.