Write a note on Gabriel phthalimide synthesis.
Alkylation of phthalimide is known as Gabriel phthalimide synthesis. Phthalimide reacts with ethanolic potassium salt of phthalimide. In this step, N–H proton is removed to give imide ion. It is then heated with alkyl halide to give N-alkyl phthalimide, which gives a primary amine on alkaline hydrolysis.
Advantage:- Overalkylation is avoided, so secondary or tertiary amines are not obtained.
Limitation:- Aromatic primary amines cannot be prepared by this method because aryl halides do not undergo nucleophilic substitution with the anion formed by phthalimide.
Gabriel phthalimide synthesis - Gabriel phthalimide synthesis is a very useful method for the preparation of aliphatic primary amines. It involves the treatment of phthalimide with ethanolic potassium hydroxide to form potassium salt of phthalimide. This salt is further heated with alkyl halide, followed by alkaline hydrolysis to yield the corresponding primary amine.