(i) A Friedel-Crafts reaction is carried out in the presence of AlCl3. But AlCl3 used as catalyst and is acidic in nature i.e ., Lewis acid whereas aniline is a strong Lewis base. Thus, aniline reacts with AlCl3 to form a salt.
Due to the positive charge on the N-atom, electrophilic substitution in the benzene ring is deactivated. Hence, aniline does not undergo Friedel-Crafts reaction.
(ii) (CH3)2 NH is more basic than (CH3)3 N in an aqueous solution. +I effect will increase in alkyl group that results in increasing the case of donation of lone pair electron. Amine accepts a proton and forms cation which will be stabilised in water by solvation. Higher the solvation by hydrogen bonding, higher will be the basic strength.
Therefore, with the increase in methyl group, hydrogen bonding, and stabilisation by solvation decreases. This net effect results in a decrease of basic strength from secondary to the tertiary amine.
(iii) In tertiary amine, there are no H-atoms whereas in primary amines, two H-atoms are present. Due to the presence of H-atoms, primary amines undergo extensive intermolecular H-bonding.
As a result, extra energy is required to separate the molecules of primary amine, Therefore, primary amines have a higher boiling point than a tertiary amine.
