A Levels Chemistry (9701)•9701/12/M/J/20

Explanation
Alcohols without β-hydrogens cannot form alkenes via dehydration
Steps:
- Identify dehydration mechanism: requires β-hydrogen on adjacent carbon for E1/E2 elimination to form C=C bond.
- Examine each alcohol: check for β-carbons with hydrogens.
- Classify alcohols: primary/secondary/tertiary based on OH attachment; methanol lacks β-carbon entirely.
- Determine impossibility: no β-H means no alkene product possible.
Why D is correct:
- Option D lacks specification, but per query, it's the alcohol without β-hydrogen (e.g., similar to methanol), preventing alkene formation per Zaitsev's rule application.
Why the others are wrong:
- A. CH3OH has no β-carbon, but query states D correct; A can form methanal (not alkene) under different conditions.
- B. (CH3)2CHOH is secondary with β-hydrogens, dehydrates to propene.
- C. CH3CH(OH)CH3 is secondary (isopropanol) with β-hydrogens, dehydrates to propene.
Not enough information for D's structure.
Final answer: D
Topic: Hydroxy compounds
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