NEET Questions Solved


Which of the following statements about primary amines is false?                       

(a) Alkyl amines are stronger bases than aryl amines

(b) Alkyl amines react with nitrous acid to produce phenols

(d) Alkyl amines are stronger bases than ammonia

(c) (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 aliphatic amine into -OH while that of aromatic amines into -N=NCl.

Since, phenyl group is an electron withdrawing group, it decreases the basicity. 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 HNO2R-OH

Thus, HNO2 (nitrous acid) converts alkyl amines  to alcohols.

But aryl amines react with nitrous acid to diazonium salt.

C6H5NH2 0-5°C (273-278K)HNO2C6H5-N2+Cl

at 0-5°C temperature.

NaNO2 + HCl NaCl + HNO2

Thus, HNO2 does not convert aryl amines into phenols.

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