Question

The order of basicity among the following compound is:

• A. II > I > IV > III
• B. IV > II > III > I
• C. IV > I > II > III
• D. I > IV > III > II

Answer 1

The correct option is C IV > I > II > III


Conjugate acid of structure IV has three equivalent canonical forms it is stabalised by resonance with two nitrogen lone pair so due to efficient resonance stabilisation of charge it is most basic.

Conjugate acid of structures I, II, III have two equivalent canonical forms respectively.

I is more basic than II because conjugate acid formed is more stablised by +$I$ effect of $-C{H}_3$

But III is least basic because of electron withdrawing effect of $-CH=CH-$ group. Also, the lone pairs of one of the nitrogen is involved in resonace and hence aromaticity and the other nitrogen is $s{p}^2$ hybridised which makes it least basic amongst all .