Answers are given in the end-
1.Amines are basic in nature . Why?
2.Arrange the following amines in decreasing order of their basic strength. Give reason also.
(CH3)3N > (CH3)2NH > CH3NH2 > NH3 In aqueous phase
3. Arrange the following amines in decreasing order of their basic strength. Give reason also.
C2H5NH2 > (C2H5)2NH > (C2H5)3N > NH3 In aqueous phase
4. Arrange the following amines in decreasing order of their basic strength. Give reason also.
(CH3)2NH > (CH3)3N > CH3NH2 > NH3 in gaseous phase
5.Arrange the following amines in decreasing order of their basic strength. Give reason also.
6. Methanamine is less basic than aniline. Why?
7.Anilene does not gives friedal craft,s reaction.Why?
8.Why does amine group is protected by acetylating it?
9. Explain briefly
(a) Carbylamine reaction( Isocyanide test)
10. pKb value of ethylamine is lower than benzylamine
Answer
1.Basic nature of amine is attributed to presence of lone pair of electron on nitrogen atom of amine group which can be donated.
2. (CH3)2NH > CH3NH2 > (CH3)3N > NH3 (This order is combine effect of three factors.In aqueous phase, inductive effect, solvation effect and steric hindrance also play important roles)
3.(C2H5)2NH > (C2H5)3N > C2H5NH2 > NH3 (This order is combine effect of three factors.In aqueous phase, inductive effect, solvation effect and steric hindrance also play important roles)
4. (CH3)3N > (CH3)2NH > CH3NH2 > NH3 ( Due to Steric hinderance increases from primary to tertiary amine which hinder to donate lone pair of electron.)
5.
Methyl group, having +I effect increases the electron density on Nitrogen of amine whereas electron withdrawing(-I and –M effect) nitro group decreases electron density on nitrogen of benzene ring.
6.Due to +I effect of methyl group electron density increases in N of amine group whereas electron density decreases due to involvement of lone pair of electrons in resonance.
7. Because basic group amine (-NH2) reacts with friedal craft,s reagents which is acidic in nature and nitrogen bears +ive charge. This +vely charged nitrogen deactivate to the benzene ring due to its elecrtron withdrawing effect.
8. Amine group is protected by acetylating ( addition of -COCH3) it therefore it does not react with friedal craft,s reagens and able to perform friedal craft reaction.
9.When primary amine is treated with chloroform (CHCl3) in presence of base (KOH) yields isocyanide having offensive smell.
R-NH2 + CHCl3 +3 KOH –> R-NC + 3KCl + H2O
10.( pKb value lower mean basic strength is higher) Due to +I effect of ethyl group electron density increases in N of amine group, therefore ethamine is more basic whereas aniline is less basic as electron density decreases due to involvement of lone pair of electrons in resonance.
CHEMIGOD 