Question

Assertion (A) : Aromatic primary amines can easily be prepared by Gabriel phthalimide synthesis. Reason (R) : Gabriel phthalimide synthesis is used to prepare only aliphatic primary amines.

• A. Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
• B. Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
• C. Assertion (A) is true, but Reason (R) is false.
• D. Assertion (A) is false, but Reason (R) is true.

Hint:

Gabriel phthalimide synthesis is an excellent method for preparing pure aliphatic primary amines but is generally not applicable to aryl halides.

Answer 1

The Correct Option is D

Step 1: How Gabriel synthesis works.
Potassium phthalimide attacks an alkyl halide R-X via SN2 substitution. Hydrolysis of the N-alkylphthalimide gives a primary amine $\text{RNH}_2$. The reaction requires SN2-susceptible alkyl halides, not aryl halides.
Step 2: Verify the Assertion.
Aryl halides such as $\text{C}_6\text{H}_5\text{Cl}$ cannot undergo SN2 because the C-X bond has partial double-bond character from ring resonance, blocking backside attack. Aromatic primary amines CANNOT be prepared by Gabriel synthesis. Assertion is FALSE.
Step 3: Verify the Reason.
Gabriel synthesis produces only aliphatic primary amines; it is inapplicable to aryl halides because they resist SN2. Reason is TRUE. \[ \boxed{\text{Option (D): Assertion false, Reason true}} \]