Chemistry - GOC Question with Solution | TestHub

Charge on O : the naphthalene unit has 3 Kekule forms, so 3 structures.

Charge on a ring carbon (O becomes $\mathrm{C}=\mathrm{O}$) : the carbanion can sit on ${\mathrm{C}}_1$ (2 Kekule forms), ${\mathrm{C}}_3$, C4a, ${\mathrm{C}}_6$ or ${\mathrm{C}}_8$, wherever the remaining carbons can still pair up : 6 structures.

Total = 3 + 6 = 9.