Essential Single and Double Bonds General Rules for Aromaticity

14 Essential Single and Double Bonds General Rules for Aromaticity 

One can usually write two or more classical structures for a given cyclic conjugated molecule the Kekule structures for benzene are of course the classic example. However, one often finds that even in the case of molecules containing conjugated rings, certain bonds are single or double in all the possible classical structures that one can write. Such a bond is described as an 

FIGURE 3.14. The bonds marked with asterisks are single or double in all the possible classical structures that one can write. 

Delete all essential single and essential double bonds. 

If charges or unpaired electrons are present, write a structure in which the charges or odd electrons are localized in odd-numbered rings. 

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