(a) Account for the following: (i) pk_b of aniline is more than that of methylamine. (ii) Aniline does not undergo Friedel-Crafts reaction. (iii)…

(a) (i) lone pair of electrons are delocalised over benzene ring due to resonance, electron density decreases and hence less available for protonation / Due to electron withdrawing nature of the aryl group in aniline while electron donating nature of methyl group in methyl amine /Aniline is a weaker base than methylamine.

(ii) Aniline is a Lewis base and it reacts with \(\displaystyle \mathrm{AlCl}_{3}\) to form a salt / N of aniline acquires positive charge with \(\displaystyle \mathrm{AlCl}_{3}\) and hence is a deactivating group.

(iii) Presence of intermolecular hydrogen bonding in primary amines which is absent in tertiary amines.

(b) (i) \(\displaystyle \left(\mathrm{CH}_{3}\right)_{3} \mathrm{~N}<\mathrm{CH}_{3} \mathrm{NH}_{2}<\left(\mathrm{CH}_{3}\right)_{2} \mathrm{NH}\)

(ii) \(\displaystyle \mathrm{C}_{6} \mathrm{H}_{5} \mathrm{SO}_{2} \mathrm{Cl}\) / Benzenesulphonyl chloride

(iii) Pyridine is used to remove HCl from the reaction mixture.