I had a question on a chem exam about which difluorobenzene isomer will have the highest boiling point. Obviously it is the ortho isomer, since the dipole will be stronger than the meta or para isomers. The question I have is more for my own curiosity than anything else really. Does it matter whether the fluorine groups are attached to the benzene across a double or single bond? I suspect that any difference (as far as dipole strength goes anyway) is either nonexistant or negligible, but I'm not a hundred percent sure. Could anyone clear this up for me?