(i) A - C₆H₅NO₂ - Nitro benzene
(ii) B - C₆H₅NH₂ - Aniline
(iii) C - C₆H₅NC - Phenyl Carbylamine

Structure of amines:
(i) Like, ammonia, nitrogen atom of amines is trivalent and carries a lone pair of electron and sp³ hybridised, out of the four sp³ hybridised orbitals of nitrogen, three sp³ orbitals overlap with orbitals of hydrogen (or) alkyl groups of carbon, the fourth sp³ orbital contains a lone pair of electron.
(ii) Hence, amines possess pyramidal geometry. Due to presence of lone pair of electron C-N-H (or) C-N-C bond angle is less than the normal tetrahedral bond angle 109.5°.
For example, the C-N-C bond angle of trimethylamine is 108° which is lower than tetrahedral angle and higher than the H-N-H bond angle of 107°.
(iii) This increase is due to the repulsion between the bulky methyl groups.

(i) Repl cementby-OH: When the aqueous solution is boiled, phenol is obtained

This is an example of SN₁ reaction in which C₆H₅N₂CI initially gives C₆H₅⁺ and water is the nudeophile.
(ii) Replacement of RO- (or) RCOO- groups Similarly -N₂CI can be replaced acyloxy group by boiling with carboxylic acids.

(iii) Diazonlum coupling reaction: Diazonium salt reacts with aromatic amine and phenols to give azo compounds of the general formula.
Ar - N = N - Ar'
This reaction is known as Coupling reaction since all these compounds are intensely coloured and used as dyes, thousands of azodyes have been synthesised by this procedure.

(i) 
(ii) 
(iii) 
(iv) 

(i) The nitriles containing a-hydrogen also undergo condensation with esters in the presence of sodamide in ether to form ketonitriles.
(ii) This reaction is known as "Levine and hauser" acetylation.
(iii) This reaction involves replacement of ethoxy (OC₂H₅) group by methylnitrile (-CH₂CN) group and is called as cyanomethylation reaction.