Question

How can you use solid derivatives to confirm the structures of your “unknown” aldehyde and ketone?

Answer 1

Both aldehydes and ketones usually undergo rapid reaction with arylhydrazines such as phenylhydrazine

or 2,4-dinitrophenylhydrazine:

These hydrazones are normally highmelting-point solids, especially in the case of the deeply

colored 2,4-dinitrophenylhydrazones. Their melting points can serve as aids in identifying your starting

carbonyl compounds. Before the advent of modern infared and NMR spectroscopy, the use of

solid derivatives of liquid compounds was widespread in organic chemistry.

You will prepare a 2,4-dinitrophenylhydrazone derivative of your ketone, and you have the choice of preparing the phenylhydrazone or the 2,4-ditrophenylhydrazone derivative of your aldehyde.