Question

The product expected along with primary amine, when phthalmide is treated with alc. $KOH$, alkyl halide and aq. $NaOH$ is :

• A.
• B.
• C.
• D.

Answer 1

The correct option is C

Gabriel phthalimide synthesis is a method for preparation of primary amine.
The Gabriel phthalimide synthesis reaction is as follows:Thus the major product expected is sodium salt of phthalic acid i.e. option (c).
Mechanism of Gabriel phthalimide synthesis
Step 1: When potassium hydroxide is introduced to the phthalimide, an acid-base reaction occur. The hydroxide ion deprotonates the imide. The resulting proton is more acidic than any simple amine, generating a strong nucleophile – the potassium phthalimide​ ion.

Step 2:
The nucleophilic potassium imide ion attacks the electrophilic carbon of the alkyl halide. The nitrogen atom subsequently replaces the halogen (Fluorine, Chlorine, Bromine or Iodine) in the alkyl halide and bonds with the carbon itself. This results in the formation of an N-Alkyl Phthalimide.
Step 3:
The product N-Alkyl phthalimide is hydrolysed with aq. $NaOH$ to form primary amine, i.e. Alkylamine.