Question

The correct decreasing order of basic strength of following compounds is:

• A. A > B > C > D
• B. B > A > C > D
• C. C > B > A > D
• D. C > B > D > A

Answer 1

The correct option is C C > B > A > D

The lone pair of nitrogen is involved in resonance/delocalisation in all the cases.
In B and C :
Due to $+I$ of effect of alkyl group(s) attached to nitrogen basic strength increases.
In B there is one alkyl group, whereas in C there are two alkyl groups attached.
More the alkyl groups, more is the electron density at nitrogen, so C is more basic than B.
Between A and D:
lone pair of nitrogen is involved in resonance in both, but in case of D , $-R$ effect of $-N{O}_2$ decreases the electron density and makes it the least basic.
So, correct order is :
C > B > A > D