April 15, 2009
by Arvin Moser, Team Manager, Application Scientists, ACD/Labs
Chemical shift information offers a clue into an atom’s hybridization state. For example, carbon atoms with a carbon chemical shift greater than 90 ppm are typically considered as sp2 carbons. If 4 sp2 carbons are present, one can infer 2 alkene pairs. Five sp2 carbons and an available oxygen and nitrogen atom suggest the possibility of a pyridinone fragment.
The example below shows a 5 sp2 carbons and 2 sp3 carbons, coloured pink and blue, respectively. The chemical shift at 167 ppm for the quaternary carbon suggests the presence of an amide group.
Using the information described above, a set of 6 possible candidate structures can be pieced together.