I have a sample which is an isoxazole derivative. It has an =N-OH group. In the H1-NMR spectra there are three and more singlet peaks aprox. 11ppm. Please can someone explain why?
Check (in the HSQC spectrum) if there are crosspeaks for those protons. If not, then those protons are not attached to carbons. NOH protons appear at around 10 ppm, and oximes exist as mixtures of stereoisomers, so those signals might be NOH signals. Your sample is probably a mixture of (E)- and (Z)- isomers, also there might be some impurity (intermediate, starting compound?). Can you send as a structure of the expected product?
yes of course. A vinilic carbon attached to the ring and also to N-OH.
but i see Hs of ring at 6-7 ppm. and is it possible to see the ring's Hs at 11 ppm?
Check (in the HSQC spectrum) if there are crosspeaks for those protons. If not, then those protons are not attached to carbons. NOH protons appear at around 10 ppm, and oximes exist as mixtures of stereoisomers, so those signals might be NOH signals. Your sample is probably a mixture of (E)- and (Z)- isomers, also there might be some impurity (intermediate, starting compound?). Can you send as a structure of the expected product?
Carboxylic acids in the structure? With just a 1H 1D and no structure, this question may not be answerable. HSQC would also help.
there is no carboxylic acid. I' ll have 2D or noesy spectrum. thanks all for your attentions...
what about the IR spectrum? is there nay indication of N=O, if then there may be enitroso oxime and the tautomeric protons may be seen even more downfield than this................ IR may be used for some functional group hint............?
Would you please let us know the starting materials of the reaction?
- Badges
- Science topic
- Similar topics
- Chemistry
- Organic Chemistry