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Chemistry Forums for Students => Organic Chemistry Forum => Organic Spectroscopy => Topic started by: aspiringphysician on November 10, 2011, 06:52:21 PM

Title: NMR Spectroscopy for a Carboxylic Acid
Post by: aspiringphysician on November 10, 2011, 06:52:21 PM
Today, I performed an NMR Spectroscopy on an unknown solution containing an arene and a carboxylic acid. I am having a difficult time figuring out the chemical structure based on the NMR spectra. Below is the data:

Chemical Formula:
C9H10O4

Proton NMR:
7.0 ppm - multiplet - four hydrogens
4.6 ppm - singlet - two hydrogens
3.9 ppm - singlet - three hydrogens
11.0 ppm - singlet - one hydrogen

Carbon NMR:
Peaks at 173.0, 149.9, 147.2, 123.7, 121.2, 116.4, 112.3, 67.6, and 55.9

The multiplet at 7.0 ppm are the arene hydrogens, and the singlet at 11.0 is an OH group, correct?

(See attached picture for the structure I came up with; is it correct?)

Title: Re: NMR Spectroscopy for a Carboxylic Acid
Post by: Honclbrif on November 10, 2011, 10:37:55 PM
Seems pretty reasonable. Might also be the meta isomer, but without seeing the spec who knows?
Title: Re: NMR Spectroscopy for a Carboxylic Acid
Post by: linh_ngt on November 11, 2011, 04:54:34 AM
I think the structure u give is quite reasonable and I think it can not be the isomer of meta because the different chemical shift of 4 hydrogens in the aromatic ring.
U can use chemdraw sofware to check the structure with the function of predicting 1H-NMR and 13C-NMR. This function works quite well, lol.

The other way to know whether it is correct or not is that u use the natural dictionary and find out the reference to compare.
Good luck!