Le 11/03/2016 10:38, Giuseppe Marco Randazzo a écrit :
An example can be the case of this isomerism is given by
triphenylphosphorane (Witting reagents).
Wittig reagents with their three identical phenyl groups on the
phosphorus atom
do not present any intriguing configuration problem around the P=C bond,
contrarily to the compound that it was about in Greg's first message on
this topic.
I also wanted to point out that chirality is not necessarily centered on
an atom
but may be axial, like in allenes:
https://en.wikipedia.org/wiki/Axial_chirality
All the best,
Jean-Marc
Here i give to you some publications were can find a clear publication
about cis/trans isomerism and the importance.
[1] Conformation isomerism and coupling constants of formylmethylene
triphenylphosphorane (C6H5)3P=CH-CHO
Comptes Rendus des Seances de l'Academie des Sciences, Serie C:
Sciences Chimiques (1970), 270, (21), 1747-9.
[2] Structural and conformational analysis of
2-triphenylphosphoranylidene succinic acid derivatives by 1H, 13C
and 31P one and two dimensional NMR spectroscopy and molecular modelling
Radu Bacaloglu, Andrei Blaskó, Clifford A. Bunton, Giorgio
Cerichelli, Fernando Castaneda and Enrique Rivera
J. Chem. Soc., Perkin Trans. 2, 1995, 965-972
DOI: 10.1039/P29950000965
[3] Favoured conformations of methyl isopropyl, ethyl isopropyl,
methyl tert-butyl, and ethyl tert-butyl
2-(triphenylphosphoranylidene)malonate
[4] Conformations of diester triphenylphosphonium ylides with an
ylidic ester or keto and ester ylidic groups
Best regards
Marco
On 11 Mar 2016, at 10:12, Greg Landrum <greg.land...@gmail.com
<mailto:greg.land...@gmail.com>> wrote:
On Fri, Mar 11, 2016 at 10:05 AM, Jean-Marc Nuzillard
<jm.nuzill...@univ-reims.fr <mailto:jm.nuzill...@univ-reims.fr>> wrote:
Le 11/03/2016 05:11, Greg Landrum a écrit :
Here's a question for the chemists in the group: do we need to
be concerned about representing the stereochemistry of the P=C
bond in substructures like O=P(/O)=C/C under normal circumstances?
It has a meaning to write that the configuration of the P=C bond
is Z or E.
If this is the case, I'd love to add some real examples to the test
suite. Can you point me to some examples (or a paper/web page talking
about the topic)?
-greg
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Institut de Chimie Moléculaire de Reims
CNRS UMR 7312
Moulin de la Housse
CPCBAI, Bâtiment 18
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51687 REIMS Cedex 2
France
Tel : 03 26 91 82 10
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http://www.univ-reims.fr/LSD/JmnSoft/
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