[HB]

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

[Illuminatus]

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.

[mamid]

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.

[Archer]

Can you see the single proton in the aliphatic region?

[HB]

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

[Archer]

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?

[MOTOBALL]

Seems to me that you need MS to determine the MW and the N atom count.

[opsomath]

There's no olefin in the product, why would there be olefinic CH?