Hydrazides in organic chemistry are a class of organic compounds sharing a common functional group characterized by a nitrogen to nitrogen covalent bond with 4 substituents with at least one of them this acyl group. The general structure for an hydrazide is R1R2-N-N-R3R4. A related class of compounds called hydrazines do not carry an acyl group. Important members of this class are sulfonylhydrazides such as p-toluenesulfonylhydrazide which are useful reagents in organic chemistry for example in the Shapiro reaction. This reagent can be prepared by reaction of tosyl chloride with hydrazine.