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Topic: Number of peaks for low resolution nmr of nitrobenzoic acid  (Read 4802 times)

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Offline mystreet123

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Is it true that 2-nitrobenzoic acid and 3-nitrobenzoic acid have 5 peaks while 4-nitrobenzoic acid has 3 peaks?

Is my drawing correct?

Thanks in advance! ;D
« Last Edit: May 17, 2016, 03:52:25 AM by mystreet123 »

Offline ATMyller

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Re: Number of peaks for low resolution nmr of nitrobenzoic acid
« Reply #1 on: May 17, 2016, 05:14:21 AM »
In theory yes, but the triplets of 2-Nitrobenzoic acid are difficult to distinguish from eachother. Also the benzoic acid can exchange protons with protic solvents, so its singlet might be very broad depending on solvent.
Chemists do it periodically on table.

Offline mystreet123

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Re: Number of peaks for low resolution nmr of nitrobenzoic acid
« Reply #2 on: May 17, 2016, 05:21:40 AM »
In theory yes, but the triplets of 2-Nitrobenzoic acid are difficult to distinguish from eachother. Also the benzoic acid can exchange protons with protic solvents, so its singlet might be very broad depending on solvent.
Thanks for replying!

Is the reason for the two triplets being two different proton environments is that the two protons are at different distance from the -NO2 and -COOH groups?

Offline Babcock_Hall

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Re: Number of peaks for low resolution nmr of nitrobenzoic acid
« Reply #3 on: May 17, 2016, 09:41:07 AM »
In the case of 4-nitrobenzoic acid, first order coupling rules do not apply, although the spectrum looks something like two doublets in the aromatic region.  The two hydrogen atoms that have ortho-relationships to the nitro group are isochronous but are not magnetically equivalent.   That may be beyond what you need to know for now.

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