Hydrolytic stability of hydrazones and oximes.

Molecules containing carbon–nitrogen double bonds are prevalent in both chemical and biological contexts. The foundations for our current understanding of carbon–nitrogen double-bond formation and hydrolysis were laid by seminal work on hydrazone hydrolysis and formation, and by contributions from mechanistic studies on enzymes that utilize pyridoxal phosphate. In particular, the meticulous kinetic analyses of Jencks resulted in the delineation of a carbinolamine intermediate in carbon–nitrogen double-bond formation and hydrolysis, and elucidation of the general mechanism of carbonyl-group addition reactions. These principles were summarized in a landmark review. Hydrazones and oximes (C=N X) possess greater intrinsic hydrolytic stability than do imines. The textbook explanation for this greater stability invokes the participation of X in electron delocalization (Scheme 1). The contribu-