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Topic: Chiral Molecules (Cyclohexane) and Configurational Stereoisomers  (Read 6956 times)

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Offline mklee90

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Hi I'm new to this forum and I am also new to Organic Chemistry (just started stereochemistry in class two weeks ago) and I am having trouble with some questions that my professor gave to us. Here's a couple:

1) Which of the following compounds is chiral (taking into consideration conformational interconversions)? -Refer to attached image

2) How many total configurational stereoisomers are possible with the following molecules?

I tried to work them out but I don't think my method of approach is correct... Can anyone help?

Greatly appreciated,

Mike

Offline UG

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Re: Chiral Molecules (Cyclohexane) and Configurational Stereoisomers
« Reply #1 on: March 23, 2009, 01:49:39 AM »
A compound which is not superimposable upon its mirror image is described as being chiral. Many such compounds contain an asymmetric carbon atom- a carbon atom with 4 different groups attached.

There are a few quick tests which will allow you to check whether a molecule is likely to be chiral. But just bare in mind that these are not infallible  :)

-The presence of an asymmetric carbon atom.
-A plane of symmetry. Compounds with a plane of symmetry are not chiral
 

Offline mklee90

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Re: Chiral Molecules (Cyclohexane) and Configurational Stereoisomers
« Reply #2 on: March 23, 2009, 02:03:51 AM »
Okay, I'm trying to draw them out and rotating them in my head.. see if their mirror images match.

For number 2, I get 4 stereoisomers rather than 3 (which is the answer). I drew a mirror image of the molecule and tried to see if is superimposable, but I got another configuration of that molecule that has a non-superimposable mirror image as well, doesn't that make it 4 possible stereoisomers?

Edit: How do I check for planes of symmetry for 3D molecules such as the one posted above? It's quite confusing...

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