What is "hydrazide"

n. (context chemistry English) any compound derived from an oxoacid by replacing the hydroxide group with -NHNH₂ or derived forms -NRNR₂

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 being an acyl group. The general structure for a hydrazide is E(=O)-NR-NR, where the R's are frequently hydrogens. Hydrazides can be further classified by atom attached to the oxygen: carbohydrazides (R-C(=O)-NH-NH), sulfonohydrazides (R-S(=O)-NH-NH), and phosphonic dihydrazides (R-P(=O)(-NH-NH). The related hydrazines do not carry an acyl group. Some important members of this class are sulfonylhydrazides such as p-toluenesulfonylhydrazide which are useful reagents in organic chemistry such as in the Shapiro reaction. This reagent can be prepared by reaction of tosyl chloride with hydrazine.