Chemical Forums
Chemistry Forums for Students => Organic Chemistry Forum => Organic Spectroscopy => Topic started by: Exproxsul on June 13, 2012, 02:16:58 PM
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I ran a HNMR spec of C9H12O, and I am having trouble figuring out the molecular structure.The solvent that was used is CDCL3 (had TMS inside). Obviously this molecules has a benzene ring according to the spec data. The peak at O is TMS. As far as I can tell, there is no OH coming off the ring, and since there are only 3 (main) peaks, maybe 4, that I can observe there is probably some sort of symmetry for the proton environments. Any help would be appreciated.
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Do you have any integration on your spectra?
What do the splitting patterns in the alkyl region tell you? What about the positions of the peaks in the alkyl region? Anything special about 1 ppm, or 2.5-3 ppm?
Can you draw the pieces of your puzzle? You have mentioned a benzene ring, any other groups you can identify?
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I'm sorry but without intergration your proton nmr is useless
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here is the integration as calculated by the spectra, however , It looks faulty...as the hydrogen count is past 12. The peak at 1 ppm suggests a Ch3 group but i cannot figure out what the 2.5-3ppm peak means. ch2 next to a carbonyl?
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I wonder if the signal at 2.5 is just a quintet, or a septet.
I'm sorry but without intergration your proton nmr is useless
It is not, it gives plenty of information.
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here is the integration as calculated by the spectra, however , It looks faulty...as the hydrogen count is past 12. The peak at 1 ppm suggests a Ch3 group but i cannot figure out what the 2.5-3ppm peak means. ch2 next to a carbonyl?
There is not a match 1 peak : 1 proton, if that's what you mean by "the hydrogen count is past 12". Taking a quick glance at the spectra, what are your J-values? The peaks at ~ δ2.5 and 1 seem to be fairly diagnostic of a particular group
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i thought the numbers calculated below the peak was the integration and therfore the number of protons that were in that particular peak/multiplet
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i thought the numbers calculated below the peak was the integration and therfore the number of protons that were in that particular peak/multiplet
The pattern of the aromatic protons is pretty characteristic for the ring substitution.
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the closest I've come to matching the structure to the nmr is 2-phenylpropan-1-ol , however I have doubts that this is a match.
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the closest I've come to matching the structure to the nmr is 2-phenylpropan-1-ol , however I have doubts that this is a match.
The aromatic signal suggests a 1,4 disubstituted phenyl ring. But is there something else hiding there?
You really need to integrate the spectrum.
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I did, the second post had a pdf with the integration calculated but i think it may be wrong.
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I did, the second post had a pdf with the integration calculated but i think it may be wrong.
The integration does not look correct to me, try it again, setting the peak at 2.5-3.0 to 1H as a reference.
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K here we go, i redid the integration calculations. benzene ring has 5 protons, the quintet at 2.5-3 has 1 and the doublet at 1 ppm has 6 protons.
The nmr spec is attached below.
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the closest I've come to matching the structure to the nmr is 2-phenylpropan-1-ol , however I have doubts that this is a match.
You almost have it here - can you reshuffle the pieces so it matches your integration?
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K here we go, i redid the integration calculations. benzene ring has 5 protons, the quintet at 2.5-3 has 1 and the doublet at 1 ppm has 6 protons.
The nmr spec is attached below.
The aromatic region has 5 protons, it does not mean that the phenyl ring has 5 attached to it, look at the symmetrical pattern, I suggested a 1,4 disubstituted phenyl ring.
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K here we go, i redid the integration calculations. benzene ring has 5 protons, the quintet at 2.5-3 has 1 and the doublet at 1 ppm has 6 protons.
The nmr spec is attached below.
The aromatic region has 5 protons, it does not mean that the phenyl ring has 5 attached to it, look at the symmetrical pattern, I suggested a 1,4 disubstituted phenyl ring.
i tried out all different 1,4 substituents , did not work out.
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K here we go, i redid the integration calculations. benzene ring has 5 protons, the quintet at 2.5-3 has 1 and the doublet at 1 ppm has 6 protons.
The nmr spec is attached below.
The aromatic region has 5 protons, it does not mean that the phenyl ring has 5 attached to it, look at the symmetrical pattern, I suggested a 1,4 disubstituted phenyl ring.
i tried out all different 1,4 substituents , did not work out.
I simulated the NMR of the compound I think it is, the shifts differ slightly but don't worry about that, look at the patterns.
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4-(propan-2-yl)phenol im assuming that small peak is the OH?
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4-(propan-2-yl)phenol im assuming that small peak is the OH?
That's what I think it is, and the small peak is the OH, in your actual spectrum it is under the aromatic signals.
If you did an exchange with D2O the OH would become OD and the integration would change from 5 to 4.
Or you could expand the aromatic portion of the spectrum and then you would see it a bit clearer.
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4-(propan-2-yl)phenol im assuming that small peak is the OH?
That's what I think it is, and the small peak is the OH, in your actual spectrum it is under the aromatic signals.
If you did an exchange with D2O the OH would become OD and the integration would change from 5 to 4.
Or you could expand the aromatic portion of the spectrum and then you would see it a bit clearer.
Thank you very much for all the time and help you have given me. :) I really appreciate it.
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4-(propan-2-yl)phenol im assuming that small peak is the OH?
That's what I think it is, and the small peak is the OH, in your actual spectrum it is under the aromatic signals.
If you did an exchange with D2O the OH would become OD and the integration would change from 5 to 4.
Or you could expand the aromatic portion of the spectrum and then you would see it a bit clearer.
Thank you very much for all the time and help you have given me. :) I really appreciate it.
No problem ;D