Question

Among these canonical structures, the correct order of stability is

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

Answer 1

Answer: (C)

Uncharged resonating structure is more stable than charged resonating structure. Therefore, $I$ is more stable than both $II$ and $III$ .
In case of charged structure that will be more stable in which octet of each atom is completed. In structure $III$ octet of each atom is completed whereas in structure $II$ octet of carbon having positive charge is not completed. Therefore, III is more stable than II.
Overall stability order is $\Rightarrow I>III>II$