Question

Question: Dehydration of 1,2,2-trimethylcyclohexanol with ${\mathbf{H}}_{\mathbf{2}}{\mathbf{SO}}_{\mathbf{4}}$ affords 1-tert-butylcyclopentene as a minor product. (a) Draw a stepwise mechanism to show how this alkene is formed. (b) Draw other alkenes formed in this dehydration. At least one must contain a five-membered ring.

Short answer

Answer

a.

Mechanism of the given reaction

b.

Other alkenes

Step-by-step solution

Step-by-Step SolutionStep 1: Reaction of ROH with strong acids

ROH undergo a dehydration reaction to form alkene in the presence of a strong acid like ${\mathbf{H}}_{\mathbf{2}}{\mathbf{SO}}_{\mathbf{4}}$.

Ring contraction/expansion

The carbocation formed during the reaction undergoes an alkyl shift to achieve higher stability. So the cyclic ROH undergoes ring expansion or contraction.

Mechanism of the given reaction.

a. The stepwise mechanism of the given reaction showing the formation of alkene is given hereunder:

Mechanism of the given reaction

b. The other alkenes formed are shown here below:

Mechanism of other alkenes