Question

Arrange the following in decreasing order of basicity:

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

Answer 1

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

In case of halides, -I effect is more dominating than +R effect.
Lone pair of nitrogen is involved in conjugation in all the cases.
In D, since Br is attached at ortho position, it has steric inhibition of protonation i.e. after protonation the conjugate acid becomes destabilised due to steric hindrance. So D is the least basic
In A and B ,since Br shows -I effect, so it decreases the electron density on nitrogen as compared to C where there is no $Br$ group present.
So C is the most basic than all other compounds.
In A halide is attached at meta position, whereas in B the halide is at para position. More -I effect is there at meta position as compared to para position.
So, basic stength of A is more than that of B.
Correct order is:
C > A > B > D