Organic YadaYada

[PreDentJennifer]

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Hope you're all out having fun on this Saturday!

 

[croco]

I honestly have never heard of dianiomers. I have heard of diasteroisomers if that's what you mean? No, not all molecules containing a chiral carbon contain an enantiomer. Some molecules w/chiral carbons are called meso compounds (represented by a line a symmetry).

 

[PreDentJennifer]

yes you are correct. Diasteroisomers is what I mean. Shows how much I know! Hopefully I'll get it soon. Thanks!

 

[Balki]

I think you are mixing up some things here and actually making it more difficult for yourself. Let me try to help.
First of all one molecule can be Chiral, it doesn't have a plane of symmetry: Usually a carbon will be attached to four different molecules. Now In order to decide on isomers if any you must compare that molecule to something. There is a broad range of isomers:
Structural Isomers: These are the least related to each other. The only relation they have is the same molecular formulae but a completely different connectivity. And you must know that structure defines property. Example of structural isomers.
CH3Ch2OH end CH3-O-CH3
Then you have Stereo Isomers which are divided in half.
If the Molecules have the same connectivity and are mirror images of each other they are considered ENANTIOMERS.
If the molecules have the same connectivity but are not mirror images of each other they are said to be DIASTERIOMERS.
Consider (3S, 4R)-BLAH-Blah molecule.
Enantiomer would be (3R, 4S) Blah Blah
and Diasteriomer (3R, 4R) Blah Blah
The last class of isomers are Geometric
Isomers, these are the ones that are different only in the position of groups with respect to the double bond. (i.e Z and E isomer of a molecule )
You can also have meso, that's when you have a plane of semetry.

I certainly hope this works, but ask more if anything

-Balki-

 

[Balki]

Hey,
I don't think this relates to DAT because on DAT they most likely will never ask this but I'll try to answer . In case of Cyclohexne it's a little more complicated. Make sure you understand the theory with a simplier molecule first, For example CHClBr-CH3. Make models and look at it. Rmember mirror image means not superimposable.

Now cyclohexane, I don't think I should descuss it simply as 2 going in page coming out of page because it's a little more than that. You should know the terminalogy as well AXIAL means = vertical, or along y axis or simply up. Equatorial means = along the "equator" along the x axis or the plane perpendicular to Axial. Go this website and you'll find a rather detailed explanation of how that works along with the answer on your question.
http://www.elcamino.cc.ca.us/Faculty/jshankweiler/new_page_2.htm

I hope the explanation and pictures there make it clearer for you now. Again much of stereo chem you'll see on the DAT will be related to finding the number of stereoismers (2^(number of sterocenters)) Working with fisher projections to determine absolute conformation and determining if the molecule is enantiomer, meso, identical or diosteriomer. Orgo section is over probaly the easiest section on DAT so good luck

-Balki-