(i) Primary and secondary amines are engaged in intermolecular association due to hydrogen bonding between nitrogen of one and hydrogen of another molecule. This intermolecular association is more in primary amines than in secondary amines as there are two hydrogen atoms available for hydrogen bond formation in it. Tertiary amines do not have intermolecular association due to the absence of hydrogen atom available for hydrogen bond formation. Therefore, the order of boiling points of isomeric amines is as follows:
Primary > Secondary > Tertiary
(ii) Aniline does not undergo Friedel-Crafts reaction (alkylation and acetylation) due to salt formation with aluminium chloride, the Lewis acid, which is used as a catalyst. Due to this, nitrogen of aniline acquires positive charge and hence acts as a strong deactivating group for further reaction
(iii) In the aqueous phase, the substituted ammonium cations get stabilised not only by electron releasing effect of the alkyl group (+I) but also by solvation with water molecules. The greater the size of the ion, lesser will be the solvation and the less stabilised is the ion. Greater is the stability of the substituted ammonium cation, stronger should be the corresponding amine as a base. Thus, the order of basicity of aliphatic amines should be:
primary > secondary > tertiary.
OR
(i) C6H5NO2

Sn+HCl

───▸

C6H5NH2

Aniline

NaNO2+HCl

───────▸

C6H5− + N2 − Cl

Benzeediazonium‌chloride

H2O

───▸

C6H5‌OH

Phenol

(ii)

CH3‌CN

Methyl‌cyanide

H2O∕H+

───▸

CH3‌COOH

Ethanoic‌acid

NH3

───▸

CH3‌CO‌ + N ‌ − H2

Ethanamide

Br2+KOH

─────▸

CH3NH2

Methylamine