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Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: 5cienceboy on January 16, 2010, 01:43:05 PM

Title: Symmetry
Post by: 5cienceboy on January 16, 2010, 01:43:05 PM
Why would Cr(ethenediamine)33+ be expected to be chiral?
Title: Re: Symmetry
Post by: cth on January 16, 2010, 03:50:24 PM
In http://en.wikipedia.org/wiki/Octahedral_molecular_geometry, there is the example of [Fe(ox)3]3- which has two configurations named respectively:
Λ-[Fe(ox)3]3− and Δ-[Fe(ox)3]3−
They are mirror image from one another. But, can you supperpose them?

Your case with Cr3+ and ethylenediamine works exactly the same.


I think the best way to see chirality in this case is to build models of both Λ and Δ configurations and to play with them until you're convinced there is no way you can superpose them without breaking a bond.
Title: Re: Symmetry
Post by: UG on January 16, 2010, 06:59:06 PM
Try and see if you can rotate it around in your head, and as cth said "play with them until you're convinced there is no way you can superpose them without breaking a bond."

Title: Re: Symmetry
Post by: Ligander on January 17, 2010, 07:43:26 PM
Quote from: 5cienceboy on January 16, 2010, 01:43:05 PM
Why would Cr(ethenediamine)33+ be expected to be chiral?
Formally a molecule is not chiral if:
It possesses plane of symmetry or it possesses inversion centre or it possesses improper rotation axis.