[mreff555]

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.

[James Newby]

http://en.wikipedia.org/wiki/Anthracene

The numbering is just how IUPAC chose to do it, the central ring is the one that does all the interesting chemistry, so i assume its like that to separate it from the 'benzene like' carbons.  All research journals you read will number it like this as well

[mreff555]

What about those four unnumbered bridge carbons?

http://en.wikipedia.org/wiki/Anthracene

The numbering is just how IUPAC chose to do it, the central ring is the one that does all the interesting chemistry, so i assume its like that to separate it from the 'benzene like' carbons.  All research journals you read will number it like this as well

[James Newby]

Im not sure to be honest! You cannot add substituents to them as they are saturated already, maybe that plays a part.  How was your synthesis?  Ive applied for a PhD involving using anthracene so im interested in the area

[sjb]

What about those four unnumbered bridge carbons?

The bridge atoms will be numbered using things like 4a, 4b etc. See http://www.chemsynthesis.com/base/chemical-structure-22928.html for an example.