Count the distinct resonance structures of the phenoxide ion $C X_{6} H X_{5} O X^{-}$ , counting each different Kekule arrangement separately: the negative charge on oxygen (with each of the two Kekule rings), and the negative charge on each ortho and the para carbon of the ring (where the ring has a single arrangement of double bonds). Give the total number of structures.

Numerical answer type, tolerance 0.5.

Answer: 5

With the charge on oxygen there are 2 Kekule forms. Moving a lone pair of oxygen into the ring gives a C=O bond, with the negative charge on a carbon: 2 ortho positions and 1 para position, each with only one possible arrangement of the remaining double bonds. The total is

2 + 2 + 1 = 5

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