Drawing Enantiomer Substituents

[ieatshrimp24]

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When drawing a pair of enantiomers, how do I choose which group goes on a wedge or dash? For example, I have a cyclopentane with a C2H5O group hanging on it (sorry I don't know the IUPAC name for it). I don't know whether the OH group is on a wedge or if the CH3 group is on a wedge.

 

[Bru]

With the limited information you have provided, there is really no way to tell anything.

 

[Life Eternal]

If one Enantiomer is s make the other r and vice versa.

 

[ieatshrimp24]

http://imgur.com/HGlYYHz

So this is my molecule. How do I know if I put the OH group on a wedge or dash? Or is it the methyl group on a wedge and the H on a dash? Do these placements even matter?

 

[Clinicall]

Am I the only one that doesn't understand this molecule? Where is the OH supposed to be

 

[Life Eternal]

It doesn't matter what is wedged or dashed as long as the absolute configurations are correct

 

[MedSprinter]

As Life Eternal posted, it is irrelevant whether the OH group or the CH3 group is a wedge or a dash as long as you draw the enantiomer as it's mirror image and the absolute configurations are opposite.

For example, if you have the OH group as a wedge and the hydrogen as a dash, then the configuration will be S since the OH group has the highest priority, the carbon that is part of the cyclopentane has the second highest priority, the methyl group has the third highest priority, and the hydrogen has the lowest priority and is also facing away from you, which forms a counterclockwise rotation when drawn out.

It's enantiomer should have an R configuration with the cyclopentane on the right and the methyl group on the left with both the OH group and H remaining in the same positions. Just imagine a mirror placed to the right of your compound and draw out what it's image in the mirror would look like.

Hope this helps.

 

[PostBaccHopeful]

Yes, I agree with Medsprinter and Life Eternal. The dashes and wedges do not really matter as long as you draw the correct enantionmer.

When dealing with enantiomers, diastereomers, etc. I usually follow the numbering system that a few books suggest. Plus, it makes the molecule look a lot simpler to deal with. If you don't know it yet, give the highest priority #1 and the lowest priority #4. And, to figure out whether R or S you still follow the clockwise/counter-clockwise rule.

Here's a trick that you will never get wrong: switch two numbers (ie. 1 and 3, or 2 and 3, or any other two) and you'll get the enantiomer of that molecule. And, if you go further and switch two more numbers you'll end up with the same molecule. This trick will work wonders and very easy to manage.