Question

Can anyone explain the complete mechanism for preparation of amines via gabriel synthesis starting with phthalimide?

Answer 1

Gabriel Synthesis is an organic chemical reaction in which primary alkyl halides are transformed into primary amines using potassium phthalimide. This reaction is named after a German chemist Siegmund Gabriel.

Pure primary aliphatic amines are prepared from alkyl halides by this method. In this reaction, potassium phthalimide reacts with KOH. The potassium phthalimide on treatment with alkyl halides gives N - alkyl phthalimide which on hydrolysis with 20% hydrochloric acid gives pure primary amine.

Gabriel Synthesis

Gabriel Synthesis is an organic chemical reaction in which primary alkyl halides are transformed into primary amines using potassium phthalimide. This reaction is named after a German chemist Siegmund Gabriel.

Pure primary aliphatic amines are prepared from alkyl halides by this method. In this reaction, potassium phthalimide reacts with KOH. The potassium phthalimide on treatment with alkyl halides gives N - alkyl phthalimide which on hydrolysis with 20% hydrochloric acid gives pure primary amine.

Gabriel Synthesis Mechanism

• Deprotonation takes place and the proton is more acidic than the simple amine due to resonance stabilization.
• Nucleophile attacks the electrophile and alkyl halide displacing the bromide and creating the new C-N bond.
• Product is formed due to hydrolysis with a base leading to cyclic product.

Cleavage

Secondary and tertiary amines cannot be prepared by Gabriel amine synthesis. Also, aniline cannot be prepared by this method, as aryl halides do not undergo nucleophilic institution under ordinary condition.