Chemical Forums
Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: Rutherford on July 30, 2013, 10:43:08 AM
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As I couldn't find any good text about this topic, I have to ask a question:
Why are axial enantiomers represented as this:
(http://upload.wikimedia.org/wikipedia/commons/7/7b/Atropisomer.svg)
but not as in the attached picture?
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Because they are not planar. If they were planar, as you have drawn, they would not be chiral (mirror plane in the plane of the page). Your representations do not indicate which enantiomer you have.
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I think also that these conformations I drew would be very unstable, because of steric hindrances. Then that's why the true enantiomers can't interconvert easily. How do I know which one is Sa, and which one is Ra?
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R/S assignment example here (http://www.chemgapedia.de/vsengine/vlu/vsc/en/ch/12/oc/vlu_organik/stereochemie/weitere_chiralitaetselem.vlu/Page/vsc/en/ch/12/oc/stereochemie/benennung_axial/benennung_axial.vscml.html).
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Ok, thanks.
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Why aren't allenes planar as alkenes?
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It's to do with the molecular obitals - you can easily google stuff like this yourself.
e.g. http://bouman.chem.georgetown.edu/S02/lect12/lect12.htm
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Sorry, I tried, but couldn't so easy. Thank you for the help, it is clear now.