AIPMT 2010 Physics and Chemistry Paper

(i) Presence of electron withdrawing substituent decreases the basicity while the presence of electron releasing substituent like, −CH3,−C2H5 etc increases the acidity.
(ii) HNO2 converts −NH2 group of alphatic amine into −OH while that of aromatic amines into −N=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.
R−NH2

HNO2

⟶

R−OH
Thus, HNO2 (nitrous acid) converts alkyl amines to alcohols.
But C6H5NH2

HNO2

⟶

C6H5N=NCl

benzene diazonium chloride

Thus, HNO2 does not convert aryl amines into phenol.