JEE Main 2023 · 29 January · morning · Single correct · +4 / −1
The major product 'P' for the following sequence of reactions is :
- (a)
- (b)
- (c)
- (d)
Answer and solution
Answer (b)
Solution
Chemistry ma’am · 4 steps
Clemmensen strips the ketone to CH₂ first, then LiAlH₄ turns the amide into CH₂NH₂.
- Two carbonyls. The starting compound has a ketone next to the benzene ring and an amide, CONH₂, at the other end of the chain. Each reagent attacks a different one.
- Clemmensen step. Zn/Hg with HCl reduces an aldehyde or ketone C=O all the way to CH₂. It leaves the amide alone, which gives Ph-CH₂CH₂CH₂CH₂-CONH₂.
- LiAlH4 step. LiAlH₄ reduces an amide by removing its oxygen. The C=O becomes CH₂ and the nitrogen stays, so -CONH₂ becomes -CH₂NH₂. H₃O⁺ only works up the reaction.
Ph-CO-(CH₂)₃-CONH₂ →(Zn/Hg, HCl) Ph-(CH₂)₄-CONH₂ →(1) LiAlH₄, 2) H₃O⁺) Ph-(CH₂)₅-NH₂
- So. P is 5-phenylpentan-1-amine. It has no OH group anywhere and an NH₂ at the end of a five-carbon chain, which is option (b).
The idea to keep. Clemmensen turns a ketone C=O into CH₂ and leaves amides alone. LiAlH₄ turns an amide into an amine with one more CH₂: RCONH₂ → RCH₂NH₂. The oxygen goes, the nitrogen stays.
Answer from the NTA final answer key. Solution by PrepWiser.