GBALA Posted March 30, 2013 Posted March 30, 2013 Recently took a NMR spectrum, of my natural product sample and it showed intense -CH2 peak at 1.2 ppm in the H NMR spectrum. But the integration value mentioned is 69. Is it an error? If so how can i overcome this? Appreciate your suggestions. Note that C13 showed only 13 peaks
Knumbnuts Posted March 31, 2013 Posted March 31, 2013 How can it be 69 protons? 68 or 70 would make more sense. It must be a solvent peak, hexane or what ever you used to extract the natural product.
John Cuthber Posted March 31, 2013 Posted March 31, 2013 It might be easier if you told us what the product is and what the NMR looks like.
Caffeinated Chemist Posted April 3, 2013 Posted April 3, 2013 Common contaminants around 1.2ppm are t-butyl methyl ether - CCH3 - 1.19 (s) diethyl ether - CH3 - 1.21 (t) ethanol - CH3 - 1.25 (t) silicone grease - CH2 - 1.26 (br s) t-butyl alcohol - CH3 - 1.28 (s) H2O - 1.56 (s) (Taken from J. Org. Chem., Vol. 62, No. 21, 1997 - This is a must have article for anyone who regularly does NMR!! Look it up!) From my own experience I'm inclined to think it is water as it isn't showing up in your 13C and it is such a large peak. I have seen water contamination as far off as 1.2ppm and it is always the same enormous sharp peak. I had a similar problem just recently and discovered that the CDCl3 had gone bad and it had turned to water because people were refluxing their pipette in the solution and essentially aerating the solvent (big no-no). Run a 1H NMR on the CDCl3 to make sure the solvent is okay then, if your product is stable enough, try sticking it on an oil pump or rotavap. That should get off whatever it is if it isn't in the CDCl3 Good luck! If possible, upload a picture of your 1H NMR and 13C NMR. That would be a big help!
GBALA Posted April 3, 2013 Author Posted April 3, 2013 How can it be 69 protons? 68 or 70 would make more sense. It must be a solvent peak, hexane or what ever you used to extract the natural product. What if it is 68 or 70 protons? Please explain me a bit. Also how a solvent that is used for extraction and isolation influence NMR spectrum? Please share your thoughts. It would be more helpful. Common contaminants around 1.2ppm are t-butyl methyl ether - CCH3 - 1.19 (s) diethyl ether - CH3 - 1.21 (t) ethanol - CH3 - 1.25 (t) silicone grease - CH2 - 1.26 (br s) t-butyl alcohol - CH3 - 1.28 (s) H2O - 1.56 (s) (Taken from J. Org. Chem., Vol. 62, No. 21, 1997 - This is a must have article for anyone who regularly does NMR!! Look it up!) From my own experience I'm inclined to think it is water as it isn't showing up in your 13C and it is such a large peak. I have seen water contamination as far off as 1.2ppm and it is always the same enormous sharp peak. I had a similar problem just recently and discovered that the CDCl3 had gone bad and it had turned to water because people were refluxing their pipette in the solution and essentially aerating the solvent (big no-no). Run a 1H NMR on the CDCl3 to make sure the solvent is okay then, if your product is stable enough, try sticking it on an oil pump or rotavap. That should get off whatever it is if it isn't in the CDCl3 Good luck! If possible, upload a picture of your 1H NMR and 13C NMR. That would be a big help! With my little experience it is not water contamination. Also I have taken NMR spectrum of this compound for three times and all three times I ended up with the same intense peak with slightly varying integral values. sorry that i couldnt attach the spectrum. It might be easier if you told us what the product is and what the NMR looks like. It is yet to be identified what it is.
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