Hello Researcher,
I would like to ask a question about crude (1H) NMR product yield calculation?
When we assign product integration and internal standard integration for percentage yield calculation does solvent (DMF. EtOAc and DMSO) which is used for reaction and workup affects percentage yield? Should I need to give a high vacuum before the crude 1H NMR?
Thanks in advance.
Assuming that the solvent signals do not overlap with the signals you use for calculation of conversion, then it shouldn't matter.
Dear Jivan,
what has been said is true if you can conclusively rule out slow chemical exchange (not always trivial) of the relvant signal with deuterated solvent. There were examples of slow exchange (even in DMSO) in our lab. But this shouln't be of relevance if you do your NMR quantification after dissolution. If I am not sure I normally repeat the quantification a few hours after dissolution.
Kind regards
Alfred
Some good answers already. If you have a very large amount of solvent, you may find that your product signal to noise is low as the receiver may be swamped with protonated signals. Also, be careful that the 13C satellites of your solvent signals don't overlap with signals that you need to measure.
When re-reading your question I see the phrase "....does solvent (DMF. EtOAc and DMSO) which is used for reaction and workup affects percentage yield...".
Based on this I conclude that your question actually is NOT a NMR question, but a synthesis question. With my very limited synthesis understanding it is clear that different solvents will induce different reaction kinetics related to differences in yield....
I hope this helps
Alfred
P.S. Thanks John for pointing out the 13C satellite problem! This sometimes is important to remember!
- Badges
- Science topic