CCL: Correctly drawing aromatic compounds

 Sent to CCL by: Dr David N Haney [haney~~edusoft-lc.com]
 Prof Deskins,
 Actually the Fisher-type or Kekule-type projections of aromatic compounds
 that contain double bonds are a representation of a struction that is
 very misleading.  In these structures all the bonds are of identical
 length (slightly longer than an alkene double bond) and thus such
 stuctures are best represented by circles (or a line and dashes).  The
 best way to identify a bond type is by the bond length.  In this
 case the bond would be classified as a partial double bond.  If
 you want to give it a value it would be 1.5 not 2.
 On Wed, Mar 23, 2011 at 08:58:41AM -0400, Deskins, N Aaron nadeskins,WPI.EDU
 wrote:
 >
 > 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>;
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