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Question #44929

Difficulty: 8/10 | 🟢 Free

The Question

Consider the polyfunctional compound $X$ , Ethyl 3,3,5-trimethyl-5-nitro-2-oxohexanoate. $X$ is subjected to two different reduction sequences:

Sequence 1: $X \xrightarrow{\text{Sn/HCl, } \Delta} \xrightarrow{\text{NaOH (aq), cold}} P$ (Major Product) Sequence 2: $X \xrightarrow{\text{LiAlH}_4 \text{ (excess), THF}} \xrightarrow{H_3O^+} Q$ (Major Product)

Assuming no ester hydrolysis occurs in Sequence 1, identify the major products $P$ and $Q$ .

Options

A.
$P$ = Ethyl 3,3,5,5-tetramethyl-4,5-dihydro-3H-pyrrole-2-carboxylate ; $Q$ = 5-amino-3,3,5-trimethylhexane-1,2-diol
B.
$P$ = Ethyl 5-amino-3,3,5-trimethyl-2-oxohexanoate ; $Q$ = (3,3,5,5-tetramethylpyrrolidin-2-yl)methanol
C.
$P$ = Ethyl 3,3,5,5-tetramethyl-4,5-dihydro-3H-pyrrole-2-carboxylate ; $Q$ = (3,3,5,5-tetramethylpyrrolidin-2-yl)methanol
D.
$P$ = Ethyl 5-amino-3,3,5-trimethylhexanoate ; $Q$ = 5-amino-3,3,5-trimethylhexane-1,2-diol

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Correct Answer

Step-by-Step Solution

Explanation

How the Examiner Thinks

Exception_Exposure

Learn to identify edge cases and boundary exceptions that JEE examiners hide in math problems.

Concepts Behind This Question

Reduction Selectivity (Sn/HCl vs LiAlH4)|Nucleophilic Acyl Substitution|Esterification Reversibility

Why This Question Is Tricky

Common Mistakes

The question tests chemoselectivity and kinetic vs. thermodynamic control in polyfunctional molecule reductions.

The 'hidden variable' is the relative rate of reduction by LiAlH4.

Students often assume that since LiAlH4 reduces all groups, the amine will form and cyclize just like in the Sn/HCl case, leading to a pyrrolidine derivative (Option C).

However, they fail to account for the fact that ketone reduction by hydride is diffusion-controlled and orders of magnitude faster than nitro reduction.

Thus, the ketone is 'masked' as a secondary alcohol before the amine is even generated, completely preventing the cyclization trap.

Furthermore, the Thorpe-Ingold effect from the gem-dimethyl groups ensures rapid cyclization in Sequence 1.

Quick Facts About This Question

Question Information

Subject	Chemistry
Chapter	Amines - Class 12
Concept	Reduction Selectivity (Sn/HCl vs LiAlH4)
Difficulty	8
Cognitive Load	7
Target Solve Time	160 sec
Access	Free