What is "pyrazolone"

n. (context organic compound English) A five-membered unsaturated heterocyclic ketone (or lactam), derived from pyrazole, that is the basis of several pharmaceuticals

Pyrazolone, a five-membered-ring lactam, is a derivative of pyrazole that has an additional keto (=O) group. It has a molecular formula of CHNO. There are three possible isomers: 3-pyrazolone, 4-pyrazolone, and 5-pyrazolone.

Examples of derivatives include:

• Ampyrone, a pharmaceutical
• Metamizole, a pharmaceutical used as an analgesic, antispasmodic, antipyretic
• Pigment Yellow 10, a yellow colorant
• Phenidone, a dihydropyrazolone