During the dehydration of 3‑methyl‑2‑butanol () in conc. at , what is the major alkene product? Briefly explain the rationale.
Answer
3‑Methyl‑2‑butene
The correct answer is 3‑Methyl‑2‑butene — Conclusion: 3‑methyl‑2‑butene is the major product.
Step-by-step solution
- 1. Identify the ‑hydrogen atoms that can be removed. 2. Dehydration removes , leaving a double bond between the ‑carbons. 3. Evaluate the substitution pattern of the potential alkenes. 4. Apply Zaitsev’s rule: the more substituted alkene is favored. 5. The double bond between C2 and C3 gives a trisubstituted alkene, 3‑methyl‑2‑butene. 6. Less substituted alkenes are less stable and formed in minor amounts.
- Conclusion: 3‑methyl‑2‑butene is the major product.
Common mistake: Predicting the less substituted alkene or ignoring the rule
Concept tested: Dehydration of alcohols, Zaitsev’s rule
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