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Is it possible to elucidate an unknown with just a 1H NMR spectrum? … Part 1

May 11, 2009

Yes, it is possible to elucidate an unknown with just a 1H NMR spectrum but only for specific cases*. Case 1: an unknown with a low molecular weight and a “well-resolved” 1H NMR spectrum. Case 2: the unknown has been identified previously, or at least part of it, in a database/library/literature and a spectrum search produced a hit(s).

*Please note that as I write this blog, only two cases come to mind perhaps there are more. If anyone can think of more cases, please feel free to comment so I may expand this blog.

Elucidations based solely on a 1H NMR spectrum can fail when:

-peaks are poorly resolved or crowding each other,

1HElucidationOnlyPart1_1_Apr112009

-the 1H NMR spectrum exhibits low signal-to-noise,

1HElucidationOnlyPart1_2_Apr112009

-the peaks for the unknown are not clearly distinguished from impurities or artifacts,

-the 1H NMR spectrum is too complicated,

1HElucidationOnlyPart1_3_Apr112009

-the unknown contains few characteristic proton signals and/or numerous heteroatoms.

1HElucidationOnlyPart1_4_Apr112009

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