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Topic: Is there a way to use NMR to determine the position of substituents in a benzene  (Read 6008 times)

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Offline Chaste

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Is there a way to use NMR to determine the position of substituents in a benzene
« on: October 29, 2010, 10:22:45 PM »
Hi,

as above. I wanna know if para, ortho, meta positions can be inferred from proton NMR or by other means? like IR or???
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Offline MissPhosgene

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Re: Is there a way to use NMR to determine the position of substituents in a benzene
« Reply #1 on: October 29, 2010, 10:42:13 PM »
Yes. Use 1H and 13C NMR.
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Stereograms of the 32 crystallographic point groups: little bike wheels of cold, hard, pure rationality.

Offline Chaste

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Re: Is there a way to use NMR to determine the position of substituents in a benzene
« Reply #2 on: October 30, 2010, 02:52:35 AM »
Sorry  , do you mind elaborating how carbon 13 nmr can determine its positions?
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Offline Doktor Nadon

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Re: Is there a way to use NMR to determine the position of substituents in a benzene
« Reply #3 on: November 01, 2010, 06:27:29 PM »
I don't know about ortho and meta, but for para there is a very typical pattern that appears in H NMR.

Here is an example.

http://chemistry.umeche.maine.edu/CHY251/Hnmr-2.html

On the left you can see the two symmetric doublets, which represent the two pairs of electrons which are equivalents in the para substituted aryl.

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Offline ATMyller

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Re: Is there a way to use NMR to determine the position of substituents in a benzene
« Reply #4 on: November 02, 2010, 05:43:40 AM »
From IR spectrum you can easily determine the benzene subsititution from 2000-1600 cm-1 range (benzene fingers). And not only orto, meta, para substitutions, but tri and tetra substitued as well. Penta and hexa substitued are a bit difficult to distinquish thou.
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Chemists do it periodically on table.
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