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Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: Joules23 on June 02, 2008, 06:45:02 PM

Title: Stereochemistry - Chair conformations of Cyclohexane
Post by: Joules23 on June 02, 2008, 06:45:02 PM
(https://www.chemicalforums.com/proxy.php?request=http%3A%2F%2Fi2.photobucket.com%2Falbums%2Fy46%2Fjumpman6235%2Fenantiomers.jpg&hash=51ec331258be6b7c5be8def9124cf551ea652a80)

Please explain how these are enantiomers, i thought enantiomers were mirror images of each other, these are not mirror images.

also, im not to sure what conformers are, so please feel free to explain that too :)
Title: Re: Stereochemistry - Chair conformations of Cyclohexane
Post by: macman104 on June 02, 2008, 06:56:35 PM
What happens if you do a chair-chair interconversion (chair flip) to the conformer on the left?  If you have an axial chlorine and chair flip it, is it still axial?

A conformer is just a possible conformation of the molecule you are looking at.  It represents one possible existence of the entity you are looking at.
Title: Re: Stereochemistry - Chair conformations of Cyclohexane
Post by: Joules23 on June 02, 2008, 07:04:37 PM
ahh ok, so when you flip it, the axials turn into equatorials.. but then why wouldnt they be identical molecules?

EDIT: okay i just did it with my models, now i see, thanks!
Title: Re: Stereochemistry - Chair conformations of Cyclohexane
Post by: macman104 on June 02, 2008, 07:41:25 PM
ahh ok, so when you flip it, the axials turn into equatorials.. but then why wouldnt they be identical molecules?

EDIT: okay i just did it with my models, now i see, thanks!
Ah  models, very good that you have them.  They will be invaluable for stereochemistry and such.  Also, if you know how to assign priorities, you would see that the R,S assignments are flipped, which indicates enantiomers.
Title: Re: Stereochemistry - Chair conformations of Cyclohexane
Post by: Joules23 on June 05, 2008, 08:26:18 PM
(https://www.chemicalforums.com/proxy.php?request=http%3A%2F%2Fi2.photobucket.com%2Falbums%2Fy46%2Fjumpman6235%2Fconformer.jpg&hash=4686b6054d905d5e8cff867385f4c07f90177640)

Why arent these molecules identical ?? If you flip the chair conformation of either molecule you will get the other molecule...

Or is that what is meant by "conformer" they are the same (when one is flipped) but not the same (when left alone)?
Title: Re: Stereochemistry - Chair conformations of Cyclohexane
Post by: Yggdrasil on June 05, 2008, 10:36:56 PM
Conformer means that they are molecules with identical connectivity and stereochemistry that differ by rotation about one or more bonds (i.e. they have different conformations).