Interpreting an HNMR....
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Interpreting an HNMR....

[From: ] [author: ] [Date: 12-04-29] [Hit: ]
I thought this was dichloroacetic acid, but Im not sure.Any suggestions?I suck at NMR.-Hi,First off,......
My solvent was DMSO. I have a singlet at 0ppm, a quintet or sextet at 1.7ppm, a tripet or quartet at 2.2 (which might be acetone we used to clean the tubes), a tiny singlet at 2.4ppm, and a tallish singlet at 12ppm. I thought this was dichloroacetic acid, but I'm not sure. Any suggestions? I suck at NMR.

-
Hi,

First off, it'd be likely impossible to tell, without accompanying integral values at least. Is the "tiny peak" a relevant peak? Or just a small amount of impurity?

Acetone would only have one peak - it would not register as a triplet or quartet. (It'd likely be the tiny singlet at 2.4 ppm, if it shows up at all). Know that acetone is a symmetric molecule. Therefore, both the methyl groups are equivalent, as are their hydrogens.

A tallish singlet at 12 ppm likely comes from an aldehyde. Aldehydes generally have the largest chemical shift. (Usually from 9-10, I haven't seen many above 10, but I guess if that's what your readings show, then sure).

The tiny singlet at 2.4 ppm can also be an alcohol hydrogen, but since we don't know the integral values, it'd be hard to tell.

A triplet or quartet at 2.2 is probably an alkane hydrogen; the fact that it is a triplet/quartet indicates that there are at least 2 non-equivalent hydrogens nearby.
Quintet/sextet at 1.7 is the same; in this case, there are at least four non-equivalent hydrogens.

My guess: An aldehyde: O double bond to a C, which is bonded to an H on one side, then a CH2-CH2-CH3

The CH3 would be a doublet, the CH2 directly next to it a triplet (I'd guess they overlap at 1.7 ppm). The CH2 connected to the carbronyl carbon would show up as a triplet, probably around 2.2. And your aldehyde hydrogen would show up at 12 ppm.

Dichloroacetic acid would be a poor guess as it'd have only two peaks - both singlets.

http://en.wikipedia.org/wiki/Butyraldehy…

You can also reference HNMR charts here. Type butyraldehyde in the compound name. SDBS No. 1925. Hit the "Y" link under "HNMR" to view.
http://riodb01.ibase.aist.go.jp/sdbs/cgi…
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