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Topic: 1,2 cyclohexanediol NMR E/Z cis trans  (Read 5288 times)

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Offline TPope

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1,2 cyclohexanediol NMR E/Z cis trans
« on: January 04, 2015, 11:56:33 AM »
How do you work out whether this compound is cis or trans from just the H1 and C13 NMR? Is it through J couplings or differences in shift or something?

Many thanks,

TPope
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Offline Rutherford

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Re: 1,2 cyclohexanediol NMR E/Z cis trans
« Reply #1 on: January 04, 2015, 12:38:13 PM »
The coupling constant for cis-hydrogen atoms is 10-12Hz, while for the trans it is 14-18Hz.
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Offline TPope

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Re: 1,2 cyclohexanediol NMR E/Z cis trans
« Reply #2 on: January 04, 2015, 02:24:47 PM »
Is that the same for OH hydrogens?
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Offline kriggy

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Re: 1,2 cyclohexanediol NMR E/Z cis trans
« Reply #3 on: January 04, 2015, 02:58:56 PM »
How could you have vicinal OH groups on double bond? Or am I missing something?
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Offline TPope

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Re: 1,2 cyclohexanediol NMR E/Z cis trans
« Reply #4 on: January 04, 2015, 06:01:01 PM »
It's a cyclohexane ring that acts as a double bond basically.
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Offline kriggy

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Re: 1,2 cyclohexanediol NMR E/Z cis trans
« Reply #5 on: January 05, 2015, 04:52:18 PM »
I see. Well Im not expert on NMR but the H-H interaction would be over 5 bonds and that seems too much to see. Probably depends on your NMR machine and type of experiment but to me It seems unlikely to see in 1H NMR.
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Offline Rutherford

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Re: 1,2 cyclohexanediol NMR E/Z cis trans
« Reply #6 on: January 06, 2015, 06:11:36 AM »
Sorry, I was thinking about regular alkenes.

The coupling constant for the hydrogen atoms bonded to the same carbon as the hydroxyl groups are different depending on their relative position: equatorial-equatorial≈2-3Hz, axial-equatorial≈3-5Hz and axial-axial≈10-12Hz.
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Offline Babcock_Hall

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Re: 1,2 cyclohexanediol NMR E/Z cis trans
« Reply #7 on: January 06, 2015, 06:30:51 PM »
@OP, Can you explain why one might expect to see differences based upon the axial or equatorial position of the hydrogen atoms in a cyclohexane derivative.  With what does it correlate?
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