Compounds derived from oxoacids $\ce{R_{k}E(=O)_{l}(OH)_{m}}$ ($l \neq 0$) by replacing $\ce{–OH}$ by $\ce{–NRNR2}$ ($\ce{R}$ groups are commonly $\ce{H}$), as in carbohydrazides, $\ce{RC(=O)NHNH2}$, sulfonohydrazides, $\ce{RS(=O)2NHNH2}$, and phosphonic dihydrazides, $\ce{RP(=O)(NHNH2)2}$.