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Question #44609

Difficulty: 8/10 | 🟢 Free

The Question

Consider the following two-step reaction sequence:

Step 1: $\text{(2S,3R)-2-bromo-3-deuteriobutane} + \ce{NaI} \xrightarrow[\text{298 K}]{\text{dry acetone}} \text{Major Product P}$

Step 2: $\text{Product P} + \ce{NaOEt} \xrightarrow[\text{350 K}]{\ce{EtOH}} \text{Major Product Q}$

Identify the major product Q.

Options

A.
$\text{(2E)-but-2-ene}$
B.
$\text{(2E)-2-deuteriobut-2-ene}$
C.
$\text{(2Z)-but-2-ene}$
D.
$\text{(2Z)-2-deuteriobut-2-ene}$

Check Your Answer

Correct Answer

Step-by-Step Solution

Explanation

How the Examiner Thinks

Mechanism_Trap

Don't get tricked by the process! Learn the mechanical traps used in competitive exam questions.

Concepts Behind This Question

C-X Bond Polarization and Polarizability|Finkelstein and Swarts Exchange|E1/E2 Solvent and Base Effects

Why This Question Is Tricky

Common Mistakes

This problem tests the stereochemical relay between two sequential stereospecific reactions.

The 'Hidden Variable' is the inversion of configuration in the Finkelstein reaction, which fundamentally alters the stereochemical outcome of the subsequent E2 elimination.

Students often rote-memorize Zaitsev's rule without performing rigorous conformational analysis.

If a student skips the $\text{S}_\text{N}2$ inversion or fails to identify the lowest-energy anti-periplanar conformer (where the methyl groups are anti), they will incorrectly predict the elimination of $\ce{HI}$ instead of $\ce{DI}$ , leading to the trap answer (2E)-2-deuteriobut-2-ene.

Quick Facts About This Question

Question Information

Subject	Chemistry
Chapter	Haloalkanes and Haloarenes - Class 12
Concept	C-X Bond Polarization and Polarizability
Difficulty	8
Cognitive Load	7
Target Solve Time	160 sec
Access	Free