One base in Figure 5.5 (IV or V) has two equivalent resonance structures; the other base...

One base in Figure 5.5 (IV or V) has two equivalent resonance structures; the other base has two resonance structures that are NOT equivalent.

a. Write equivalent below one pair of resonance structures and NOT equivalent below the other pair of resonance structures.

b. For the pair labeled NOT equivalent, circle the lower potential energy resonance structure, and explain your reasoning.

(Reference Figure 5.5)