Question

Account for the following:
(i) Direct nitration of aniline yields significant amount of meta derivative.
(ii) Primary aromatic amines cannot be prepared by Gabriel phthalimide synthesis.

Answer 1

(I) direct nitration of aniline yields significant amount of meta derivative

      aniline is protonated in strongly acidic medium to form the anilium ion which is meta directing.

(ii) primary aromatic amines cannot be prepared by Gabriel phthalimide  sythesis.

       We know, The Gabriel phthalimide synthesis is a chemical reaction that transforms primary alkyl halides into primary amines.  

We also know , aryl halides or alkyl halides do not undergoes nucleophilic substitution reaction with anion formed by phthalimide.

That’s why , primary aromatic cannot be prepared by Gabriel phthalimide sythesis.

Answer 2

1)The nitrogen atom of aniline is protonated in strongly acidic medium to form the anilium ion which is nothing but the electron withdrawing group.Due to its -M effect it is meta directing group.That's why direct nitration of aniline yields significant amount of meta derivative.

2) primary aromatic amines cannot be prepared by Gabriel phthalimide  sythesis because  Gabriel phthalimide  synthesis is a chemical process that transforms primary alkyl halides into primary amines.  

Again we know , aryl halides or alkyl halides do not undergoes any type of nucleophilic substitution reaction with anion formed by phthalimide.For this reason primary aromatic cannot be prepared by Gabriel phthalimide sythesis.