18-18-8P - Organic Chemistry (Mcmurry)

Question

Write the mechanism of the acid-induced cleavage of tert-butyl cyclohexyl ether to yield cyclohexanol and 2-methylpropene.

Step-by-Step Solution

Answer

The mechanism of the acid-induced cleavage of tert-butyl cyclohexyl ether is,

Acid-induced cleavage of ether

In acid-induced cleavage of ether, ether is treated with strong acid. It generates oxonium ion, collapsing to form an alcohol and a tertiary carbocation which further forms an alkene.

Explanation for the mechanism of the reaction

In the acid-catalyzed ether cleavage, the first step is the protonation of ether oxygen, forming an intermediate oxonium ion. This ion collapses to form an alcohol and a tertiary carbocation. 

An alkene 2-methylpropene is formed when a carbocation loses a proton. This reaction is an example of E1 elimination. The acid used for the cleavage is often trifluoroacetic acid. The products obtained are cyclohexanol and 2-methylpropene.

The mechanism of the reaction

The mechanism of the acid-induced cleavage of tert-butyl cyclohexyl ether is shown below,

                           The mechanism of the reaction