3,5-Dimethylpyrazole

3,5-Dimethylpyrazole is an organic compound with the formula (CH₃C)₂CHN₂H. It is one of several isomeric derivatives of pyrazole that contain two methyl substituents. The compound is unsymmetrical but the corresponding conjugate acid (pyrazolium) and conjugate base (pyrazolide) have C_2v symmetry. It is a white solid that dissolves well in polar organic solvents.

Quick facts Names, Identifiers ...

3,5-Dimethylpyrazole

Names
Preferred IUPAC name 3,5-Dimethyl-1H-pyrazole
Identifiers
CAS Number	67-51-6
3D model (JSmol)	Interactive image
ChEMBL	ChEMBL1828957
ChemSpider	5975
ECHA InfoCard	100.000.597
EC Number	200-657-5
PubChem CID	6210
UNII	H21N865K9J
CompTox Dashboard (EPA)	DTXSID5058777
InChI InChI=1S/C5H8N2/c1-4-3-5(2)7-6-4/h3H,1-2H3,(H,6,7) Key: SDXAWLJRERMRKF-UHFFFAOYSA-N
SMILES CC1=CC(=NN1)C
Properties
Chemical formula	C5H8N2
Molar mass	96.133 g·mol−1
Appearance	White solid
Density	1.027 g/cm3
Melting point	107.5 °C (225.5 °F; 380.6 K)
Boiling point	218 °C (424 °F; 491 K)
Hazards
GHS labelling:
Pictograms
Signal word	Warning
Hazard statements	H302, H315, H319, H335, H361, H373
Precautionary statements	P201, P202, P260, P264, P270, P271, P280, P281, P301+P312, P302+P352, P304+P340, P305+P351+P338, P308+P313, P312, P314, P321, P330, P332+P313, P337+P313, P362, P403+P233, P405, P501
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

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It is a precursor to a variety of ligands that are widely studied in coordination chemistry including trispyrazolylborate, a trispyrazolylmethane, and a pyrazolyldiphosphine.^[1][2]

Condensation of acetylacetone and hydrazine gives 3,5-dimethylpyrazole:^[3]

CH₃C(O)CH₂C(O)CH₃   +   N₂H₄   →   (CH₃C)₂CHN₂H   +   2 H₂O

It has found use as a blocking agent for isocyanates.^[4]