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Question #44931

Difficulty: 8/10 | 🟢 Free

The Question

Consider the compound $\textbf{X}$ , which is 2,4,6-tri-\textit{tert}-butylnitrobenzene. Reaction 1: $\textbf{X}$ is treated with excess $\ce{LiAlH4}$ in dry ether at reflux to yield major product $\textbf{P}$ . Reaction 2: $\textbf{X}$ is treated with $\ce{Sn/HCl}$ followed by aqueous $\ce{NaOH}$ to yield major product $\textbf{Q}$ . Identify $\textbf{P}$ , $\textbf{Q}$ , and the correct relationship between the basicity constant ( $K_b$ ) of $\textbf{Q}$ and aniline.

Options

A.
$\textbf{P}$ = 2,4,6-tri-\textit{tert}-butylaniline; $\textbf{Q}$ = 2,4,6-tri-\textit{tert}-butylaniline; $K_b(\textbf{Q}) > K_b(\text{aniline})$
B.
$\textbf{P}$ = 2,2',4,4',6,6'-hexa-\textit{tert}-butylazobenzene; $\textbf{Q}$ = 2,4,6-tri-\textit{tert}-butylaniline; $K_b(\textbf{Q}) < K_b(\text{aniline})$
C.
$\textbf{P}$ = 2,2',4,4',6,6'-hexa-\textit{tert}-butylazobenzene; $\textbf{Q}$ = 2,4,6-tri-\textit{tert}-butylaniline; $K_b(\textbf{Q}) > K_b(\text{aniline})$
D.
$\textbf{P}$ = 2,4,6-tri-\textit{tert}-butylphenylhydroxylamine; $\textbf{Q}$ = 2,4,6-tri-\textit{tert}-butylaniline; $K_b(\textbf{Q}) < K_b(\text{aniline})$

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Correct Answer

Step-by-Step Solution

Explanation

How the Examiner Thinks

Mechanism_Trap

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Concepts Behind This Question

Reduction Selectivity (Sn/HCl vs LiAlH4)|Ortho-Effect in Anilines|Electrophilic Substitution Control

Why This Question Is Tricky

Common Mistakes

This problem tests two major exceptions to standard rules.

First, it traps students who blindly apply the rule that 'LiAlH4 reduces nitrobenzene to azobenzene', ignoring that extreme steric hindrance prevents the necessary bimolecular coupling, leading to the primary amine instead.

Second, it subverts the standard 'Ortho-Effect in Anilines' (which states ortho-anilines are less basic due to hindered solvation) by using a substituent so bulky that Steric Inhibition of Resonance (SIR) forces the amine out-of-plane, localizing the lone pair and drastically increasing basicity.

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