I have synthesized two different compounds. However, what a coincident both nmr spectrum showed an unknown peak (singlet, very intense) at the region of 2.4 - 2.6 ppm in proton nmr, 28 - 30 ppm in carbon NMR which doesn't belong to my synthesized compounds, solvent impurities or catalyst been used. i have checked through the list of solvent impurities as well but still unable to figure out what is that.
Both compounds purified using column chromatography. Solvent system used is hexane, dcm and methanol.
Anyone of you have encountered before or do you have any idea about it? i will be much appreciated for your precious opinions.
That region possibly refers to the alpha proton of ketone or 1-C of amine.
Dear withsakorn...my compound is as shown below
R-NHCO-CH2COOH
R-SO2NHCOCH2COOH
R: heterocyclic group
So, i shall exclude the possibility of alpha proton. What do u mean 1-C of amine? carbon of primary amine ?
I mean "RCHNHR". I follow the table in this website http://simulab.ltt.com.au/5/Laboratory/StudyNotes/snTheInterNucMagResSpect.htm
Just take a look.
Is there any chance that you cleaned the nmr tube with acetone and didn't evaporate all of it? The proton signal is a little far downfield for acetone, but the carbon is on the money for acetone. Does the carbon show a weak signal at ~207?
It could come from hexane. If you use distilled hexane, you can avoid those peaks. It is very usual peaks at 28-30 ppm in 13C, from hexane belong to some petroleum product. Give a one try to use all distilled solvents for extraction and column purification.
Dear sir,
i think it is due to amine group which is attached to primary carbon..or DMSO peak which may comes between 2.4-2.6ppm.
Dear Sir Kenneth, do you have any reference on these shift? Especially MeNH2+ ?
Dear Sir Robert, i truly believe the acetone has been fully evaporated as the nmr tube been placed in oven for weeks before i am using it. Furthermore, i did not spot any signal at ~ 207ppm
Dear Sir Hiren, all the solvent that i am using are distilled solvent.
Dear Sir Uday, there is another signal in my nmr belongs to DMSO, so this unknown peak shouldnt belong to DMSO. However, do you have any reference regarding on the "amine group attach to primary carbon" ?
Dear everyone, the integration on the unknown peak is about 0.2++ compared to 1H proton. Regarding on the MeNH2+, may i know why it exist as MeNH2+ ? due to incomplete reaction? For your information, my desired compound R-NH-CO-R, where NH is attached to a saturated carbon of oxazol ring....Does anyone can give me some further explanation about this? Thanks in advance.
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