1H-Pyrazol-5(4H)-one
[CAS# 137-44-0]

Identification

• Name: 1H-Pyrazol-5(4H)-one
• Synonyms: 2,4-Dihydro-3H-pyrazol-3-one; 5-Pyrazolone; NSC 243823
• Molecular Formula: C₃H₄N₂O
• Molecular Weight: 84.08
• CAS Registry Number: 137-44-0
• EC Number: 824-477-7

Properties

• Solubility: Freely soluble (108 g/L) (25 ºC), Calc.^*
• Density: 1.44±0.1 g/cm³ (20 ºC 760 Torr), Calc.^*
• Melting point: 268 ºC^**
• Boiling point: 143-144 ºC (0.3 Torr)^***

^* Calculated using Advanced Chemistry Development (ACD/Labs) Software V11.02 (©1994-2013 ACD/Labs)

^** Clemo, George R.; Journal of the Chemical Society 1934, P1739-41.

^*** Makisumi, Yasuo; Tetrahedron Letters 1966, (52), P6413-17.

Safety Data

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Skin irritation	Skin Irrit.	2	H315
Specific target organ toxicity - single exposure	STOT SE	3	H335
Eye irritation	Eye Irrit.	2A	H319
Eye irritation	Eye Irrit.	2	H319