CH 9-2: HD/IR Example (step-by-step) An unknown organic compound has a formula of C4H6O. (1) What is the Hydrogen Deficiency? 4 HD = _____ (2) What functional groups might be present as suggested by the HD and formula? (3) What functional group information can we get from the IR spectrum: 1712 cm-1 carbonyl IR spectrum = ______________ (4) Now we can refine our original ideas for the type(s) of functional group(s) present, based on: formula = C4H6O Carbonyl and alkene HD = 4 carbonyl group Carbonyl and ring (5) More Info: There is one 1o carbon and no 2o or 3o carbons. Suggest one or more reasonable structures: Note that based on this information, no rings are possible as they would have 2o & 3o carbon atoms.