Chemical Forums
Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: THECapedCaper on October 16, 2012, 12:47:27 PM
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I have a little confusion as to what determines a chiral center in the larger molecules, namely hydrocodone.
(https://www.chemicalforums.com/proxy.php?request=http%3A%2F%2Fupload.wikimedia.org%2Fwikipedia%2Fcommons%2Fc%2Fcc%2FHydrocodone.svg&hash=68197461fb11b7484ccf15b47c856ae06ff0665d)
As far as I can tell, anything that is a CH2 or CH3 cannot be considered chiral, but do C=O or C=C bonds fall under the same category because they're not bonded to four groups? What are the chiral centers of hydrocodone?
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C=O and C=C bonds cannot be chiral.
In your molecule there seem to be 4 chiral centers.
Simply put the same criteria apply for simple and complex molecules, 4 different substituents and non-superimposable on it's mirror image.
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C=O and C=C bonds cannot be chiral.
In your molecule there seem to be 4 chiral centers.
Simply put the same criteria apply for simple and complex molecules, 4 different substituents and non-superimposable on it's mirror image.
Silly question: Why isn't this (see below) atom considered chiral? Even accounting for resonance aren't there essentially four different substituents?
(https://www.chemicalforums.com/proxy.php?request=http%3A%2F%2Fi.imgur.com%2Fv3Zlv.png&hash=bd09aa6b26bcd393850caad48c8639aa1cfe1ac9)
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So, then these four carbons would be the chiral centers (marked with red stars)?
(https://www.chemicalforums.com/proxy.php?request=http%3A%2F%2Fi.imgur.com%2FDExPe.png&hash=c8427fdb4d8565d0955a1df1cc49030fc8842b06)
In that case, we have 16 stereoisomers (2^n) and 14 diasteroisomers (2^n - 2), correct?
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There are not 4 different substituents on that carbon atom. It's part of a phenyl ring. The double bonds are not static as you said.
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Yes, that is correct.
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There are not 4 different substituents on that carbon atom. It's part of a phenyl ring. The double bonds are not static as you said.
I see. Thanks!
Would that position (red box) become a Chiral Centre if I, say, brominated it there? {Bet it can't be done! But who knows! You wizards have all kinds of synthetic magic up you sleeves! ;D }
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Well assuming you could brominate there then it would give a new chiral centre.
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Well assuming you could brominate there then it would give a new chiral centre.
Thanks again!
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So, then these four carbons would be the chiral centers (marked with red stars)?
(https://www.chemicalforums.com/proxy.php?request=http%3A%2F%2Fi.imgur.com%2FDExPe.png&hash=c8427fdb4d8565d0955a1df1cc49030fc8842b06)
In that case, we have 16 stereoisomers (2^n) and 14 diasteroisomers (2^n - 2), correct?
Not really - build some models. Having ring structures will restrict the total number of possible stereoisomers. You will find that certain combinations of R and S just won't be possible to get the atoms to line up.