I can't figure out the proper numbering method for large arenes. I have to synthesize trans-9-(2-phenylethenyl)-anthracene tomorrow, and I just want to understand the compound a little better. I'm clear on the rest of the molecule but I can't understand the 9. I know that it is speaking of the substituent location of the Phenylethenyl group, on the anthracene group. I just don't understand why the number is so High. I could guess that joined rings would be named similar to bi-cyclic rings but if that was the case I would expect a locant of 7. can someone please explain.