Given below are two statements, one is labelled as Assertion (A) and other is labelled as Reason (R). Assertion (A) : Gabriel phthalimide synthesis cannot be used to prepare aromatic primary amines. Reason (R) : Aryl halides do not undergo nucleophilic substitution reaction. In the light of the above statements, choose the correct answer from the options given below :

Both (A) and (R) true and (R) is correct explanation of (A).

Both (A) and (R) true but (R) is not the correct explanation of (A)

Compounds Containing Nitrogen PYQ — JEE Main 2021 · 25 Jul · Shift 1 · Q6 with Solution

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Correct answer: C

Understand Gabriel phthalimide synthesis

Gabriel phthalimide synthesis is used to prepare primary alkyl amines.

The key step is nucleophilic substitution of an alkyl halide by potassium phthalimide: $\text{R-X} + \text{K-phthalimide} \rightarrow \text{R-N-phthalimide} \xrightarrow{\text{hydrolysis}} \text{R-NH}_2$
Check Assertion (A)

Assertion: Gabriel phthalimide synthesis cannot be used to prepare aromatic primary amines.

This is true.

Aromatic primary amines such as aniline would require reaction of aryl halides like chlorobenzene with potassium phthalimide. But this substitution does not occur under normal Gabriel conditions.
Check Reason (R)

Reason: Aryl halides do not undergo nucleophilic substitution reaction.

In the context of standard JEE chemistry, this statement is taken as true: aryl halides are generally resistant to nucleophilic substitution because:
- the carbon-halogen bond has partial double bond character due to resonance,
- the carbon is $sp^2$ hybridized,
- neither $S_N1$ nor $S_N2$ occurs easily.
Does (R) explain (A)?

Yes.

Gabriel synthesis fails for aromatic primary amines precisely because it requires nucleophilic substitution on a halide substrate, and aryl halides do not undergo this reaction easily.
Evaluate options
- A: Both true, but R not explanation of A → Incorrect
- B: A false, R true → Incorrect
- C: Both true and R is correct explanation of A → Correct
- D: A true, R false → Incorrect

Therefore, the correct answer is C.

View written solutionFree

Correct answer: C

Understand Gabriel phthalimide synthesis

Gabriel phthalimide synthesis is used to prepare primary alkyl amines.

The key step is nucleophilic substitution of an alkyl halide by potassium phthalimide: $\text{R-X} + \text{K-phthalimide} \rightarrow \text{R-N-phthalimide} \xrightarrow{\text{hydrolysis}} \text{R-NH}_2$
Check Assertion (A)

Assertion: Gabriel phthalimide synthesis cannot be used to prepare aromatic primary amines.

This is true.

Aromatic primary amines such as aniline would require reaction of aryl halides like chlorobenzene with potassium phthalimide. But this substitution does not occur under normal Gabriel conditions.
Check Reason (R)

Reason: Aryl halides do not undergo nucleophilic substitution reaction.

In the context of standard JEE chemistry, this statement is taken as true: aryl halides are generally resistant to nucleophilic substitution because:
- the carbon-halogen bond has partial double bond character due to resonance,
- the carbon is $sp^2$ hybridized,
- neither $S_N1$ nor $S_N2$ occurs easily.
Does (R) explain (A)?

Yes.

Gabriel synthesis fails for aromatic primary amines precisely because it requires nucleophilic substitution on a halide substrate, and aryl halides do not undergo this reaction easily.
Evaluate options
- A: Both true, but R not explanation of A → Incorrect
- B: A false, R true → Incorrect
- C: Both true and R is correct explanation of A → Correct
- D: A true, R false → Incorrect

Therefore, the correct answer is C.