Can only stereogenic centers create enantiomers?

[ipodtouch]

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Going through this BR problem with these two sets of compounds:
http://imgur.com/18Eq3
The two compounds are certified enantiomers, although they don't have any sp3 centers.


I was wondering if the middle sp hybridized carbon would be considered a stereogenic center (chiral center), or if that term is only reserved for sp3 carbons.

 

[folktale]

I would have guessed that that was a diastereomer. I've tried turning the first molecule around to see if it's mirror image, and can't really see a mirror image. All I see is a diastereomer. I'm confused.

 

[milski]

In that case you have a chirality axis, not a center. Slightly different terminology but nothing really that different from "regular" enantiomers.

It is not a diastereomer - the molecules are mirror images of each other and cannot be superimposed on one another, aka enantiomers.

 

[dmf2682]

Do these also exhibit optical activity? I'd think so, not positive.

 

[milski]

Yes, they are optically active.

 

[folktale]

In that case you have a chirality axis, not a center. Slightly different terminology but nothing really that different from "regular" enantiomers.

It is not a diastereomer - the molecules are mirror images of each other and cannot be superimposed on one another, aka enantiomers.

Wait, so the position of the dashed and solid lines for CH3 and Cl does not matter? as long as both CH3 is pointing outwards and Cl is pointing inwards? B/c when I try rotating the image, I get both CH3 pointing outwards, but on opposite sides (one is on the top and the other one is on the bottom).

 

[milski]

Wait, so the position of the dashed and solid lines for CH3 and Cl does not matter? as long as both CH3 is pointing outwards and Cl is pointing inwards? B/c when I try rotating the image, I get both CH3 pointing outwards, but on opposite sides (one is on the top and the other one is on the bottom).

Dashed/solid certainly matter. Don't rotate them, mirror them. If you mirror the left one you end up with something that can be rotated 180 degrees and it will be exactly the right one.

 

[folktale]

Dashed/solid certainly matter. Don't rotate them, mirror them. If you mirror the left one you end up with something that can be rotated 180 degrees and it will be exactly the right one.

Ahhhh I see. But if you mirror the first one, and compare its mirror image to the second one, you're not comparing the original two molecules anymore.

Or do you mean get the mirror image of the first one first, and see if that's the same as the second one? Isn't my method of rotating first and comparing the two molecules the SAME as your method?

 

[milski]

Ahhhh I see. But if you mirror the first one, and compare its mirror image to the second one, you're not comparing the original two molecules anymore.

Or do you mean get the mirror image of the first one first, and see if that's the same as the second one? Isn't my method of rotating first and comparing the two molecules the SAME as your method?

If you just rotate it, you are checking if it is exactly the same molecule.

If you are comparing one with the mirror image of the other, you are checking if they are enantiomers.

 

[folktale]

If you just rotate it, you are checking if it is exactly the same molecule.

If you are comparing one with the mirror image of the other, you are checking if they are enantiomers.

Well, not necessarily what I was doing. I was rotating the first molecule, and comparing it to the other one to see if they are mirror images to each other. But I don't see a mirror image when I rotate the first one by 180degrees/

EDIT: Nvm I see it now. I still did it my way, and both methods have the same results. Thank you for the help!

 

[milski]

Well, not necessarily what I was doing. I was rotating the first molecule, and comparing it to the other one to see if they are mirror images to each other. But I don't see a mirror image when I rotate the first one by 180degrees/

EDIT: Nvm I see it now. I still did it my way, and both methods have the same results. Thank you for the help!

Ah, I see what you are saying. Yes, the method is almost the same. I like to do the mirroring first since it's easier (at least for me) to check if something is the same as another thing vs trying to figure out if they are mirror images.