3,5-Dimethylpyrazole

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, P261, 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

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.

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]

References

Reger, Daniel L.; Grattan, T.Christian; Brown, Kenneth J.; Little, Christine A.; Lamba, Jaydeep J.S.; Rheingold, Arnold L.; Sommer, Roger D. (2000). "Syntheses of tris(pyrazolyl)methane ligands and {[tris(pyrazolyl)methane]Mn(CO)3}SO3CF3 complexes: Comparison of ligand donor properties". Journal of Organometallic Chemistry. 607 (1–2): 120–128. doi:10.1016/S0022-328X(00)00290-4.
Schenck, Terry G.; Downes, J. M.; Milne, C. R. C.; MacKenzie, Peter B.; Boucher, Terry G.; Whelan, John; Bosnich, B. (1985). "Bimetallic reactivity. Synthesis of bimetallic complexes containing a bis(phosphino)pyrazole ligand". Inorganic Chemistry. 24 (15): 2334–2337. doi:10.1021/ic00209a003.
Johnson, William S.; Highet, Robert J. (1951). "3,5-Dimethylpyrazole". Organic Syntheses. 31: 43. doi:10.15227/orgsyn.031.0043.
"Blocked Isocyanates" (PDF). Lanxess. June 2020. Archived (PDF) from the original on 2020-09-27.

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[1] Reger, Daniel L.; Grattan, T.Christian; Brown, Kenneth J.; Little, Christine A.; Lamba, Jaydeep J.S.; Rheingold, Arnold L.; Sommer, Roger D. (2000). "Syntheses of tris(pyrazolyl)methane ligands and {[tris(pyrazolyl)methane]Mn(CO)3}SO3CF3 complexes: Comparison of ligand donor properties". Journal of Organometallic Chemistry. 607 (1–2): 120–128. doi:10.1016/S0022-328X(00)00290-4.

[2] Schenck, Terry G.; Downes, J. M.; Milne, C. R. C.; MacKenzie, Peter B.; Boucher, Terry G.; Whelan, John; Bosnich, B. (1985). "Bimetallic reactivity. Synthesis of bimetallic complexes containing a bis(phosphino)pyrazole ligand". Inorganic Chemistry. 24 (15): 2334–2337. doi:10.1021/ic00209a003.

[3] Johnson, William S.; Highet, Robert J. (1951). "3,5-Dimethylpyrazole". Organic Syntheses. 31: 43. doi:10.15227/orgsyn.031.0043.

[4] "Blocked Isocyanates" (PDF). Lanxess. June 2020. Archived (PDF) from the original on 2020-09-27.