The dehydration of tertiary alcohols typically occurs by which reaction mechanism?

• A. $S_{\mathrm{N}}2$ (bimolecular nucleophilic substitution)
• B. $E_2$ (bimolecular elimination)
• C. $E_1$ (unimolecular elimination)
• D. $S_{\mathrm{N}}1$ (unimolecular nucleophilic substitution)

Answer: (C)

Verified step by step guidance

1. Identify the type of alcohol involved: tertiary alcohols have a carbon atom bonded to three other carbons and one hydroxyl group (-OH). This structure greatly influences the reaction mechanism.
2. Understand that dehydration of alcohols involves the removal of a water molecule, typically resulting in the formation of an alkene through an elimination reaction.
3. Recall that tertiary carbocations are relatively stable due to alkyl group electron-donating effects, which favors a mechanism involving carbocation intermediates.
4. Recognize that the dehydration of tertiary alcohols proceeds via a unimolecular elimination mechanism, known as the E1 mechanism, where the rate-determining step is the formation of the carbocation intermediate.
5. Summarize the E1 mechanism steps: first, the protonation of the hydroxyl group to form a good leaving group (water), second, the loss of water to form a tertiary carbocation, and third, the elimination of a proton from a beta-carbon to form the alkene.