Pyrazole

Pyrazole

Names
Preferred IUPAC name 1H-Pyrazole
Other names 1,2-Diazole
Identifiers
CAS Number	288-13-1 Y
3D model (Jmol)	Interactive image
ChEBI	CHEBI:17241 Y
ChEMBL	ChEMBL15967 Y
ChemSpider	1019 Y
DrugBank	DB02757 Y
ECHA InfoCard	100.005.471
KEGG	C00481 Y
PubChem	1048
InChI InChI=1S/C3H4N2/c1-2-4-5-3-1/h1-3H,(H,4,5) Y Key: WTKZEGDFNFYCGP-UHFFFAOYSA-N Y InChI=1/C3H4N2/c1-2-4-5-3-1/h1-3H,(H,4,5) Key: WTKZEGDFNFYCGP-UHFFFAOYAW
SMILES n1cccn1
Properties
Chemical formula	C3H4N2
Molar mass	68.08 g·mol−1
Melting point	66 to 70 °C (151 to 158 °F; 339 to 343 K)
Boiling point	186 to 188 °C (367 to 370 °F; 459 to 461 K)
Basicity (pKb)	11.5
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Y  (what is YN ?)
Infobox references

Pyrazole is an organic compound with the formula C₃H₃N₂H. It is a heterocycle characterized by a 5-membered ring of three carbon atoms and two adjacent nitrogen atoms. Pyrazole is a weak base, with pK_b 11.5 (pK_a of the conjugated acid 2.49 at 25 °C). Pyrazoles are also a class of compounds that have the ring C₃N₂ with adjacent nitrogen atoms. Notable drugs containing a pyrazole ring are celecoxib (Celebrex) and the anabolic steroid stanozolol.

Pyrazoles are synthesized by the reaction of α,β-unsaturated aldehydes with hydrazine and subsequent dehydrogenation:

Substituted pyrazoles are prepared by condensation of 1,3-diketones with hydrazine. For example, acetylacetone and hydrazine gives 3,5-dimethylpyrazole:

The term pyrazole was given to this class of compounds by German Chemist Ludwig Knorr in 1883. In a classical method developed by German chemist Hans von Pechmann in 1898, pyrazole was synthesized from acetylene and diazomethane.

Pyrazoles react with potassium borohydride to form a class of ligands known as scorpionate. Pyrazole itself reacts with potassium borohydride at high temperatures (~200 °C) to form a tridentate ligand known as Tp ligand:

In medicine, derivatives of pyrazoles are used for their analgesic, antinociceptive, anti-inflammatory, antipyretic, antiarrhythmic, tranquilizing, muscle relaxing, psychoanaleptic, anticonvulsant, monoamineoxidase inhibiting, antidiabetic, antifungal, and antibacterial activities.