Chemical Forums
Chemistry Forums for Students => Organic Chemistry Forum => Organic Spectroscopy => Topic started by: HB on July 08, 2013, 03:39:08 PM
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I have conducted a reaction of pyran-2-amino-3-carbonitrile with formic acid to obtain pyranopyrimidine derivative. the IR showed C=O band at 1680 cm-1, however, the 1H NMR showed no protons in the olefinic region and no NH and only aromatic protons appeared. cna any one help me in explaining this
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Hello HB,
If you attached your 1H NMR/IR data with integrations it would be very helpful (13C as well if you have it). An explanation of experimental setup and conditions would be beneficial as well.
Note: I assume you refluxed at one point in your experiment, did you regulate temperature well? Strongly overheating may cause unwanted hetero-cyclic rearrangement or even thermal degradation, which can result in your material transforming/ breaking down into more stable molecules.
Anticipating.
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Also, there's a slight possibility that the ring on the ring may be in the pyrimidine form (i.e., aromatic; think tautomery). Personally I don't think it's likely, but it can't be excluded.
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Can you see the single proton in the aliphatic region?
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no I did not see any aliphatic protons in NMR, only aromatic
the reaction was done by refluxing in 85% formic acid for 5 hours, then cooling and pouring onto ice- cold water
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It sounds distinctly possible that all of the bonds have tautomerised to give the most conjugated product. Plus loss of H2 through oxidation.
Are there all the protons that you expected, in number, except from the NH?
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Seems to me that you need MS to determine the MW and the N atom count.
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There's no olefin in the product, why would there be olefinic CH?