Compounds Containing Nitrogen

Rhumann’s purple is confirmatory test for the presence of protein. The correct structure of Rhumann’s Purple, the compound formed in the reaction of ninhydrin with proteins is an follows

Primary amine reacts in presence of chloroform gives isonitrile which is toxic in nature which further reacts in presence of HCl/H₃O⁺ to give primary amine and acid.

Hence, A-primary amine, B-isonitrile compound and C-conc. HCl.

In phenyl methanamine, the lone pair on nitrogen of -NH₂ group is localised and does not undergoes resonance.

(B), (C) and (D) are aromatic amines in which lone pair of electrons of N-atoms goes in resonance (+R effect) with the benzene ring. So, Lewis basicity or donation of lone of electrons of these amines will be decreased in comparison to (A).

+ I effects of two -CH₃ groups increases electron density on N atom while lone pair of N atom take part in resonance with the benzene ring and decreases electron density on N atom. Both this effect try to compensate each other.

+ I effects of one -CH₃ groups increases electron density on N atom while lone pair of N atom take part in resonance with the benzene ring and decreases electron density on N atom. Both this effect try to compensate each other.

It has no + I-effect on N-atom to increase electron density on the N atom which was decreased due to lone pair of N atom take part in resonance with the benzene ring. So, A is purely aliphatic 1°-amine. B is aromatic. 3°-amine with more aliphatic nature (for two -CH₃ groups). C is aromatic 2°-amine with less aliphatic nature (for one -CH₃ group).
D is purely aromatic 1°-amine.

Hence basicity order is A > B > C > D.

Nitrating mixture is mixture of conc. HNO₃ and a conc. H₂SO₄.

When aniline is reacted with nitrating mixture ortho, meta and para nitroanilines are obtained.

Aniline being basic in nature, reacts with acids to form anilinium ion which is meta directing.

The Gabriel phthalimide synthesis is a method used to prepare primary aliphatic and aromatic amines. The process begins with phthalimide being treated with ethanolic potassium hydroxide (KOH), forming the potassium salt of phthalimide. This salt is then heated with an alkyl halide (RX), and subsequent treatment with either alkaline hydrolysis or hydrazinolysis (using hydrazine, $ \mathrm{H}_2\mathrm{N} \cdot \mathrm{NH}_2 $) yields the corresponding primary amine. However, this method cannot be used to synthesize primary aromatic amines that have electron-withdrawing groups (EWGs) at the ortho- and para-positions, such as the nitro group ($ -\mathrm{NO}_2 $). This limitation arises because aryl halides (ArX) do not undergo nucleophilic substitution ($\mathrm{S}_{\mathrm{N}}$) reactions with the anion formed by phthalimide.