$(ii)$ $H NO_{2}$ converts $-N H_{2}$ group of aliphatic amine into$-OH$ while that of aromatic amines into $-N=N C$. Since, phenyl group is a electron withdrawing group, it decreases the basicity. Alkyl group, on the other hand, being electron releasing, increases the basicity. Thus, alkyl amines are more basic as compared to aryl amines as well as ammonia.

$R-N H_{2} \stackrel{H N O_{2}}{\longrightarrow} R-O H$

Thus, $H NO_{2}$ (nitrous acid) converts alkyl amines to alcohols. But aryl amines react with nitrous acid to form diazonium salt.

$\quad C_{6} H_{5} N H_{2} \frac{H N O_{2}}{0.5\,^{o} C(273-278 \,K)} C_{6} H_{5}-N_{2}^{+} C l$ at $0.5\,^{o} \mathrm{C}$

temperature

$\mathrm{NaNO}_{2}+\mathrm{HCl} \longrightarrow \mathrm{HNO}_{2}+\mathrm{NaCl},$

Thus $\mathrm{HNO}_{2}$ does not convert aryl amines into phenol.