Problem : Which of the following pairs are resonance structure? For pairs that are resonance structures, use the curved-arrow formalism to derive the second structure from the first.
One of the resonance structures of phenanthrene, a hydrocarbon found
naturally in coal tar, is shown below. It turns out that this is only one
of five resonance structures that can be drawn for this compound.
(a) Using the curved-arrow formalism to aid you, find the other four resonance structures of phenanthrene (fill in the incomplete structures).