Which of the following statements about primary amines is false ?
Which of the following statements about primary amines is false ?
Alkyl amines are stronger bases than aryl amines
Alkyl amines react with nitrous acid to produce alcohols
Aryl amines react with nitrous acid to produce phenols
Alkyl amines are stronger bases than ammonia
Solution
Key Idea (i) Presence of electron withdrawing substituent decreases the basicity while the presence of electron releasing substituent like, $-\mathrm{CH}_3,-\mathrm{C}_2 \mathrm{H}_5$ etc increases the acidity.
(ii) $\mathrm{HNO}_2$ converts $-\mathrm{NH}_2$ group of aliphatic amine into $-\mathrm{OH}$ while that of aromatic amines into $-\mathrm{N}=\mathrm{NCl}$.
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.
$\mathrm{R}-\mathrm{NH}_2 \stackrel{\mathrm{HNO}_2}{\longrightarrow} \mathrm{R}-\mathrm{OH}$
Thus, $\mathrm{HNO}_2$ (nitrous acid) converts alkyl amines to alcohols.
But $\mathrm{C}_6 \mathrm{H}_5 \mathrm{NH}_2 \stackrel{\mathrm{HNO}_2}{\longrightarrow} \mathrm{C}_6 \mathrm{H}_5 \mathrm{~N}=\mathrm{NCl}$
benzene diazonium chloride
Thus, $\mathrm{HNO}_2$ does not convert aryl amines into phenol.