Question

Identify the major product from the following reaction sequence:

• A.
• B.
• C.
• D.

Hint:

Grignard reagent adds alkyl group to carbonyl → alcohol → dehydration under heat forms alkene.

Answer 1

The Correct Option is C

Step-by-step mechanism:
1. Grignard reaction: CH\(_3\)MgCl adds CH\(_3\)⁻ to carbonyl carbon of cyclopentanone: \[ \text{Cyclopentanone} + \text{CH}_3\text{MgCl} \rightarrow \text{Tertiary alcohol} \] 2. Acidic workup (H\(_3\)O\(^+\)) protonates the alkoxide to form 1-methylcyclopentanol.
3. Elimination under acidic heat (E1):
- Alcohol is protonated → forms carbocation.
- Elimination of H\(^+\) leads to formation of double bond.
- Alkene forms as 1-methylene-cyclopentane (major due to stability).