Question

Which among following statements is NOT true about Gabriel phthalimide synthesis?

• A. In this method formation of N-alkyl phthalimide is involved.
• B. In this method sodium phthalate is also obtained.
• C. This method is useful for preparation of aromatic amines.
• D. In this method potassium salt of phthalimide is formed as an intermediate product.

Hint:

Gabriel phthalimide synthesis is strictly reserved for creating pure aliphatic $1^\circ$ amines. Aryl halides are too stubborn to undergo the necessary nucleophilic substitution step, completely ruling out aromatic amines!

Answer 1

The Correct Option is C

Step 1: Understanding the Question:
The question asks us to identify the incorrect statement regarding the Gabriel phthalimide synthesis reaction sequence from the given choices.

Step 2: Detailed Explanation:
Let's analyze the steps and scope of the Gabriel phthalimide synthesis:

• Phthalimide is first treated with ethanolic KOH to form the potassium salt of phthalimide, making statement (D) true.

• This potassium salt undergoes nucleophilic substitution ($\text{S}_\text{N}2$) with an alkyl halide to produce an N-alkyl phthalimide, making statement (A) true.

• Subsequent alkaline hydrolysis of N-alkyl phthalimide using aqueous NaOH yields a primary aliphatic amine along with sodium phthalate as a side product, making statement (B) true.

• Aromatic primary amines (like aniline) cannot be prepared by this method. This is because aryl halides (Ar-X) do not easily undergo nucleophilic substitution reactions with the bulky phthalimide anion due to partial double-bond character of the C-X bond and steric hindrance. Therefore, statement (C) is completely false.


Step 3: Final Answer: The statement that is not true is option (C).