A number of acyclic acyl alkyl diimides have been obtained by oxidation of the corresponding alkyl hydrazides. A new method for the synthesis of α-cyanoalkyl hydrazides, the reaction of acid hydrazides with ketones in the presence of sodium cyanide, has been explored. All the acyl alkyl diimides so obtained exhibit a medium to weak i.r. band at ca. 1550 cm−1; evidence supporting the assignment of this band to the —N=N— stretch is given. The results of oxidation of 5-methyl and 5-phenyl-pyrazolidin-3-one are reported, together with the synthesis and oxidation of tetrahydro-6-methyl-3(2H)-pyridazinone.