Question

Explain the mechanism of dehydration of alcohol.

Hint:

Dehydration of alcohols usually follows an E1 mechanism and works best with tertiary alcohols, as they form more stable carbocations.

Answer 1

Step 1: Reaction Overview
Dehydration of alcohols typically occurs in the presence of a strong acid, such as sulfuric acid (\(H_2SO_4\)), resulting in the elimination of a water molecule to form an alkene.
Step 2: Mechanism
1. Protonation of the alcohol's hydroxyl group to form a better leaving group: \[ \text{R-OH} + \text{H}^+ \rightarrow \text{R-OH}_2^+ \] 2. The protonated alcohol undergoes loss of water to form a carbocation: \[ \text{R-OH}_2^+ \rightarrow \text{R}^+ + \text{H}_2\text{O} \] 3. The carbocation undergoes a rearrangement (if necessary) to form the most stable carbocation. 4. The carbocation then undergoes elimination of a proton (\(H^+\)) to form the alkene: \[ \text{R}^+ \rightarrow \text{C} = \text{C} + \text{H}^+ \] Final Answer: The dehydration of alcohols proceeds via the formation of a carbocation and elimination of a proton to form an alkene. Correct Answer: The mechanism involves protonation, carbocation formation, and proton elimination.