Question

Among these compounds, the correct order of resonance energy is

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

Answer 1

The correct option is C II > III > I

Negative charge is delocalised more than the lone pair of electrons, moreover II has 2 equivalent resonating structurs. Hence, II has more resonance energy than (I) and (III)
Comparing (I) and (III):
In (I), the lone pair of $O$ is involved in resonance whereas in (III) lone pair of $N$ is involved. Since $O$ is more electronegative than $N$, $O$ lone pairs are not readily available for delocalisation as compared to $N$ so (III) has more resonance energy than (I)
Thus, the order of resonance energy is
II > III > I