CCL: Correctly drawing aromatic compounds

From: "Deskins, N Aaron" <nadeskins^^WPI.EDU>
Subject: CCL: Correctly drawing aromatic compounds
Date: Wed, 23 Mar 2011 08:58:41 -0400

 Sent to CCL by: "Deskins, N Aaron" [nadeskins*o*WPI.EDU]
 Hello all,
   I'm trying to draw (2-D) some aromatic compounds but can't seem to get them
 right. For instance, all the pictures of coronene I've seen show 12 C=C bonds
 (see for example  en.wikipedia.org/wiki/File:Coronene_structure.png). But I
 tried making coronene in ChemSketch but it puts draws a structure with 10-11 C=C
 bonds depending on the order I put the benzene rings together. Same problem with
 pyrene. My drawings show 7 C=C bonds, while I believe it should have 8.
   More importantly, I'd like to figure out how many C=C bonds different large
 aromatic compounds have for a series of isodesmic reactions I'm interested in.
   Any ideas?
   Thank you,
 N. Aaron Deskins
 Assistant Professor
 Chemical Engineering Department
 Worcester Polytechnic Institute
 http://users.wpi.edu/~nadeskins