Before You Begin

Question #44937

Difficulty: 8/10 | 🟢 Free

The Question

An optically active alkyl halide $A$ (\ce{C4H9Br}) with $(S)$ -configuration is subjected to the following reaction sequence to synthesize a primary amine $F$ : $A \xrightarrow{\text{KCN (alc.)}} B \xrightarrow{H_3O^+, \Delta} C \xrightarrow{SOCl_2} D \xrightarrow{NH_3 \text{ (excess)}} E \xrightarrow{Br_2, NaOH} F$ In an independent experiment, $A$ is heated with a large excess of ethanolic \ce{NH3} in a sealed tube at 373 K to yield a major product $G$ . Which of the following statements correctly describes the relationship and properties of $F$ and $G$ ?

Options

A.
$F$ and $G$ are identical compounds with $(R)$ -configuration, but $F$ is synthesized free from secondary and tertiary amine impurities.
B.
$F$ is $(S)$ -butan-2-amine because the Hoffmann rearrangement proceeds with inversion of the migrating group, whereas $G$ is $(R)$ -butan-2-amine.
C.
$F$ is $(R)$ -2-methylbutan-1-amine due to chain extension, whereas $G$ is $(S)$ -butan-2-amine due to retention during ammonolysis.
D.
$F$ and $G$ are identical compounds with $(S)$ -configuration, because the initial cyanide substitution proceeds with retention of configuration via an $S_Ni$ mechanism.

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

Ammonolysis Complexity|Hoffmann Bromamide Rearrangement

Why This Question Is Tricky

Common Mistakes

The question tests the student's ability to track stereochemistry through a multi-step synthesis involving both chain extension and contraction.

The core trap lies in the stereochemical outcomes: $S_N2$ with KCN causes inversion, while the Hoffmann bromamide degradation proceeds with retention of configuration at the migrating chiral center.

Students often mistakenly assume Hoffmann causes inversion or forget the initial $S_N2$ inversion.

Furthermore, it tests the practical difference between Ammonolysis (which yields a mixture of amines) and the Hoffmann degradation (which yields a pure primary amine), a critical distinction in organic synthesis.

Quick Facts About This Question

Question Information

Subject	Chemistry
Chapter	Amines - Class 12
Concept	Ammonolysis Complexity
Difficulty	8
Cognitive Load	7
Target Solve Time	160 sec
Access	Free