Question

Write the reactions of (i) aromatic and (ii) aliphatic primary amines with nitrous acid.

Answer 1

(i) Aromatic primary amines react with nitrous acid at low temperatures (273-278K) to form diazonium salts.

$\underset{Aniline}{C_6{H}_5-N{H}_2}\underset{273-278K}{\overset{NaN{o}_2+HCl}{\to }}\underset{Benzenediazoniumchloride}{C_6{H}_5-{\stackrel{+}{N}}_2\stackrel{-}{Cl}}+NaCl+2H_{2}O$

Note : Nitrous acid is produced by the reaction of NaNO_2 and HCl

(ii) Aliphatic primary amines react with nitrous acid to form aliphatic diazonium salts (unstable), which produce nitrogen gas and alcohols after decompostion.

$\underset{Alkylamine}{R-N{H}_2+HN{O}_2}\stackrel{NaN{o}_2+HCl}{\to }\underset{Benzenediazoniumchloride}{[R-{\stackrel{+}{N}}_2\stackrel{-}{Cl}]}\stackrel{H_{2}O}{\to }\underset{Alcohol}{ROH}+N_2+HCl$