The correct order of the basic strength of methyl substituted amines in aqueous solution is :
- (CH3)3N > (CH3)2NH > CH3NH2
- CH3NH2 > (CH3)2NH > (CH3)3N
- (CH3)2NH > CH3NH2 > (CH3)3N
- (CH3)3N > CH3NH2 > (CH3)2NH
Answer
(3) (CH3)2NH > CH3NH2 > (CH3)3N
Solution
As per NCERT, in aqueous solution the basic strength of amines is decided by the combined effect of
(i) +I effect of alkyl groups (increases electron density on N),
(ii) solvation of the substituted ammonium cation by H-bonding with water (more N–H bonds, more stabilisation), and
(iii) steric hindrance to H-bonding.
For methyl substituted amines the net order is
(CH3)2NH > CH3NH2 > (CH3)3N > NH3
Answer: (3)