Question

Amine that can't be prepare by Gabriel phthalimide synthesis:
Aniline
Benzyl amine
Methyl amine
Iso butylamine
Tertiary butylamine
please explain

Answer 1

In Gabriel phthalimide synthesis, phthalimide reacts with ethanolic potassium hydroxide to form potassium salt of phthalimide.The salt is heated with alkyl halide followed by alkaline hydrolysis to give the corresponding primary amine.Now, aromatic halides do not undergo nucleophilic substitution with the salt formed by phthalimide.Therefore, aromatic amines cannot be prepared by Gabriel phthalimide reaction.Also it involvesnucleophilicsubstitution (SN2) of alkyl halides by the anion formed by the phthalimide.
But aryl halides do not undergo nucleophilic substitution with the anion formed by the phthalimide.
Hence aniline cannot be prepared by this method.



the thing to note is benzyl amide is not aromatic...as nh2 group is not directly attached to benzene ring...