I can't seem to find any clear explanation of how benzene ring protons couple with each other when mono and disubstituted with the same constituent.
My professor claims that if a benzene ring is para disubstituted with X, the remaining 4 protons exhibit a doublet interference pattern. This seems strange to me because they are equivalent, and my last two organic chemistry professors said the information isn't useful diagnostically, but never explained why.
Also, he claims that if a benzene ring is monosubstituted the proton in the para position will display a triplet interference pattern. Is this right? Symmetry seems to say that the proton would be a doublet.
Do benzene rings have their own rules for coupling?