Reactions involving other reagents of the type Y-NH₂

Imines are sometimes difficult to isolate and purify due to their sensitivity to hydrolysis. Consequently, other reagents of the type Y–NH₂ have been studied, and found to give stable products (R₂C=N–Y) useful in characterizing the aldehydes and ketones from which they are prepared. Some of these reagents are listed in the following table, together with the structures and names of their carbonyl reaction products.

With the exception of unsubstituted hydrazones, these derivatives are easily prepared and are often crystalline solids – even when the parent aldehyde or ketone is a liquid. Since melting points can be determined more quickly and precisely than boiling points, derivatives such as these are useful for comparison and identification of carbonyl compounds.  It should be noted that although semicarbazide has two amino groups (–NH₂) only one of them is a reactive amine. The other is amide-like and is deactivated by the adjacent carbonyl group.