QJEEM21Chd870: JEE Main 2021 Chemistry - Class 12 JEEM21Chd870 Solution: A. Phenyl methanamine B. N,N-Dimethylaniline C. N-Methyl…
B. N,N-Dimethylaniline
C. N-Methyl aniline
D. Benzenamine
Choose the correct order of basic nature of the above amines.
Multiple Choice Options
- A D > C > B > A
- B A > C > B > D
- C D > B > C > A
- D A > B > C > D
Step-by-Step Verified Solution
In phenyl methanamine, the lone pair on nitrogen of -NH2 group is localised and does not undergoes resonance.
(B), (C) and (D) are aromatic amines in which lone pair of electrons of N-atoms goes in resonance (+R effect) with the benzene ring. So, Lewis basicity or donation of lone of electrons of these amines will be decreased in comparison to (A).
+ I effects of two -CH3 groups increases electron density on N atom while lone pair of N atom take part in resonance with the benzene ring and decreases electron density on N atom. Both this effect try to compensate each other.
+ I effects of one -CH3 groups increases electron density on N atom while lone pair of N atom take part in resonance with the benzene ring and decreases electron density on N atom. Both this effect try to compensate each other.
It has no + I-effect on N-atom to increase electron density on the N atom which was decreased due to lone pair of N atom take part in resonance with the benzene ring. So, A is purely aliphatic 1°-amine. B is aromatic. 3°-amine with more aliphatic nature (for two -CH3 groups). C is aromatic 2°-amine with less aliphatic nature (for one -CH3 group).
D is purely aromatic 1°-amine.
Hence basicity order is A > B > C > D.