Hello, guys! Recently I recorded NMR spectrum (1H) for one of the samples and found several peaks I can't recognize. Please, take a look, maybe someone has faced similar splitting. Sorry for showing the only piece of spectrum. But I can assure you, there are no aromatic systems here. Could anyone suggest at least what type of interactions between protons we are observing? Thanks
Hello,
This splitting may caused by coupling of CH2 protons, in which the two geminal protons are cemically not equivalent. Therefore this splitting is the sum of a triplet (coupling of vicinal CH2s) and an AB doublet (coupling of A and B protons in CH(A)H(B)). If your molecule containes a longer aliphatic chain (propyl, butyl etc.) these peaks cannot be the signals of the coupling partnes, but those of the therminal CH2 protons.
András, thank you for your thoughts on the spectrum. If I am getting it right you think a coupling system like XCH2CH(A)H(B)Y is an option here. It really could be the case, I guess. However for both triplets J = 1.7 Hz, which doesn't look like vicinal coupling in my opinion. In addition, there is no evidence of return interaction between CH2 and CH(A)H(B) in the spectrum. Do you have some similar molecules in mind with such coupling? I'd be glad to see if it looks the same or not:)
Vasilii, You are absolutely right, this is an unusual J value. To the best of my knowledge, the vicinal coupling constant depends on the conformation, as the attached figure shows below. I don't know too much about your molecule, but I can recommend this great NMR note for you from University of Wisconsin-Madison :
http://www.chem.wisc.edu/areas/reich/nmr/index.htm
(The figure was taken from this note)
I hope you can find the answer for your question. :)
- Badges
- Science topic
- Similar topics
- Physics
- Condensed Matter Physics
- Solid State Physics
- PEAKS