Chemical Forums
Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: Rutherford on August 16, 2012, 07:27:20 AM
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Is there a method to determine if these compounds are enantiomers or not? I had a hard time rotating those molecules in my head.
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Is there a method to determine if these compounds are enantiomers or not? I had a hard time rotating those molecules in my head.
Make models? Try naming them?
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I tried but I don't know how to rotate the molecules that have the H atom on the top. They should be on the back because of the lowest priority.
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Naming them requires that you mentally rotate them so that the hydrogen is in the back.
Make models. Make models. Make more models.
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I improvised somehow, and only practice is needed now. Solved, A)same compound (R,R); B)enantiomers.
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I improvised somehow, and only practice is needed now. Solved, A)same compound (R,R); B)enantiomers.
Have you got a models set? You can get them cheap.
Or use cocktail sticks and olives, cherries etc. Then you can break the bonds by eating the atoms!
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Or gumdrops and toothpicks, or my personal favorite, those mini colored marshmallows :D
Do they still have those? Either gumdrops or mini colored marshmallows, I mean... ???
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I improvised somehow, and only practice is needed now. Solved, A)same compound (R,R); B)enantiomers.
Have you got a models set? You can get them cheap.
Or use cocktail sticks and olives, cherries etc. Then you can break the bonds by eating the atoms!
Sticks and plasticine :D.
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I improvised somehow, and only practice is needed now. Solved, A)same compound (R,R); B)enantiomers.
Have you got a models set? You can get them cheap.
Or use cocktail sticks and olives, cherries etc. Then you can break the bonds by eating the atoms!
Sticks and plasticine :D.
Prefer cocktail sticks etc.
At least you can eat your mistakes and nobody will ever know.
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Now a tougher problem: http://orgchem.chem.uconn.edu/courses/243f97-rs-pract-04.html
Why is in (i) the C atom that has an OH group attached R? The H atom is towards me, the OH group is away, if I exchange those two shouldn't I get the S configuration?
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Now a tougher problem: http://orgchem.chem.uconn.edu/courses/243f97-rs-pract-04.html
Why is in (i) the C atom that has an OH group attached R? The H atom is towards me, the OH group is away, if I exchange those two shouldn't I get the S configuration?
Yes you get the (S) configuration.
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Okay, then it is a mistake. Thanks.
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One way to "rotate" a molecule on paper is to hold one bond constant (making it the axis of rotation), and spinning the other three groups as if they were a propeller. This way you can always put the H in the back. I like models very much, but I have sometimes found this trick to be handy.
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The fastest way is this:
After double checking to see that they have the same connectivity, determine (R) and (S) for each stereocenter. Enantiomers will always have opposite (R)/(S) values.
This is far, far simpler and faster than making models or doing bond rotations.
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The purpose of building models or of rotating them on paper is to facilitate the R,S assigment process.