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60 CHAPTER 2 
 
This aromatic ring has eight significant resonance structures, shown below: 
 
OR
RO
OR
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OR
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OR
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OR
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OR
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OR
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OR
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resonance
structure
1
resonance
structure
2
resonance
structure
1
resonance
structure
3
resonance
structure
4
resonance
structure
5
resonance
structure
1
resonance
structure
6
resonance
structure
7
resonance
structure
8 
 
The resonance hybrid is a weighted average of these eight resonance structures. Resonance structures 1 and 2 are 
equally most significant because all atoms have an octet AND there are no formal charges. Resonance structures 3-8 
are less significant than 1 and 2 but equally significant to each other because every atom has a full octet with a positive 
charge on an oxygen atom and a negative charge on a carbon atom. Since the partial negative charge is delocalized onto 
three carbon atoms and the partial positive charge is delocalized onto only two oxygen atoms, the partial positive 
charges are drawn slightly larger than the partial negative charges. The analysis allows us to draw the resonance hybrid 
for this portion of the molecule, and it demonstrates that the highlighted carbon atom is -. 
 
 
Now let’s focus on our attention on the other highlighted carbon atom (the one that is part of a carboxylic acid group). 
Just as we did before, we will draw only the portion of the molecule that is of interest: 
 
 
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