Sorry for my silly question: To my best knowledge, C=C means a double bond between C and C, like in butene and the likes. Vaguely remembering high school chemistry, I think benzene does not contain such a double bond, instead its six excess electrons for some funny orbital, hence neither hydroquinone, nor catechol have any real C=C in their structure. If that is correct, how does this Kendall-Pelz rule really work? What did I miss?