Amines

This is a Short Type Questions as classified in NCERT Exemplar

Ans: The reaction of aniline with nitrous acid at 273-278 K produces benzene diazonium chloride. The reaction of sodium nitrite with hydrochloric acid produces nitrous acid in the reaction mixture. Diazotisation is the process of converting primary aromatic amines into diazonium salts. Because of its instability, the diazonium salt is generally not stored or used immediately after preparation.

The crystalline solid benzene diazonium chloride is colorless.

It is easily soluble in water and stable at room temperature, but it reacts with water when warmed.

In the dry state, it decomposes easily.

This is a Short Type Questions as classified in NCERT Exemplar

Ans: Hinsberg's reagent is also known as benzenesulphonyl chloride (C₆H₅SO₂Cl). When it reacts with primary and secondary amines, it produces sulphonamides. Allowing secondary and tertiary amines to react with Hinsberg's reagent allows them to be distinguished (benzenesulphonyl chloride C₆H₅SO₂Cl). Secondary amines react with Hinsberg's reagent to form an alkali-insoluble product. N, N-diethylamine, for example, reacts with Hinsberg's reagent to form N, N-diethylbenzenesulphonamide, which is insoluble in alkalis. Tertiary amines, on the other hand, are unaffected by Hinsberg's reagent.

This is a Short Type Questions as classified in NCERT Exemplar

Ans:

 Direct nitration of aniline is not possible on account of oxidation of -NH₂ group. However, nitration can be carried after protecting the -NH₂ group by acetylation to give acetanilide which is then nitrated and finally hydrolysed to give o- and p-nitroanilines.
The acetyl group being electron withdrawing attracts the lone pair of electrons of the N-atom towards carbonyl group.

As a result, the activating effect -NH₂ group is reduced i.e., the lone pair of electrons on nitrogen is less available for donation to benzene ring by resonance. Therefore, activating effect of —NHCOCH₃ group is less than that of —NH₂ group.

This is a Multiple Choice Questions as classified in NCERT Exemplar

Ans: Option (A and B)  

Benzene diazonium chloride reacts with phenol to form p-hydroxy azobenzene by coupling the phenol molecule at its para position with the diazonium salt. This is referred to as a coupling reaction. This is an illustration of an electrophilic substitution reaction. 

At room temperature, aniline reacts with bromine water to form a white precipitate of 2,4,6-tribromoaniline.

By acetylation with acetic anhydride to protect the −NH₂ group, then carrying out the desired substitution followed by hydrolysis of the substituted amide to the substituted amine.