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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