Subject: HyperChem: Incorrect geometries in amines

From: "Mr HG Kruger" <[email-masked]>
Date: Fri, 5 Dec 1997 12:42:29 +0200 (SAST)

Andy,

I support your view.  (At least for a single aniline molecule - not 
sure what will happen in a crystal).
  
> Unless I'm missing the point here what you see is not a problem - simply
> the correct answer. The nitrogen in these systems WILL be planar due to
> the pi systems delocalising over all conjugated atoms. This forces the
> nitrogen into planarity...something which won't happen with a saturated
> system as there is no opportunity for pi orbital delocalisation. Might I
> suggest reading something like 'A guidebook to mechanism in organic
> chemistry' by Peter Sykes which has an excellent chapter on atomic
> orbitals and hybridisation.

I think practical proof of the delocalised (planar) structure follows 
from the textbook explanation on the difference between the 
basicities of cyclohexaneamine (pKa 9.8) and aniline (pKa 4.6).

(Thanks to my colleaque Dr JP Gerber).

Best wishes
Gert Kruger
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Dr HG Kruger, Dept Chemistry, University of Natal,
PO Box 18091, Dalbridge 4014, Durban, South Afica
Tel  +27-31-2602181   Fax  +27-31-2603091
Email  [email-masked] 
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