Pyridazine

Pyridazine
Names
	Preferred IUPAC name Pyridazine
	Systematic IUPAC name 1,2-Diazabenzene
	Other names 1,2-Diazine; Orthodiazine; Oizine
Identifiers
CAS Number	289-80-5 ;
3D model (JSmol)	Interactive image;
ChEBI	CHEBI:30954 ;
ChEMBL	ChEMBL15719 ;
ChemSpider	8902 ;
ECHA InfoCard	100.005.478
EC Number	206-025-5;
PubChem CID	9259;
UNII	449GLA0653 ;
CompTox Dashboard (EPA)	DTXSID7059777 ;
	InChI InChI=1S/C4H4N2/c1-2-4-6-5-3-1/h1-4H Key: PBMFSQRYOILNGV-UHFFFAOYSA-N ; InChI=1/C4H4N2/c1-2-4-6-5-3-1/h1-4H Key: PBMFSQRYOILNGV-UHFFFAOYAA;
	SMILES n1ncccc1;
Properties
Chemical formula	C4H4N2
Molar mass	80.090 g·mol−1
Appearance	Colorless liquid
Density	1.107 g/cm3
Melting point	−8 °C (18 °F; 265 K)
Boiling point	208 °C (406 °F; 481 K)
Solubility in water	miscible
Solubility	miscible in dioxane, ethanol ; soluble in benzene, diethyl ether ; negligible in cyclohexane, ligroin
Refractive index (nD)	1.52311 (23.5 °C)
Thermochemistry
Std enthalpy of; formation (ΔfH⦵298)	224.9 kJ/mol
Hazards
Flash point	85 °C (185 °F; 358 K)
Related compounds
Related compounds	pyridine, pyrimidine, pyrazine
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Pyridazine is a heterocyclic organic compound with the molecular formula (CH)₄N₂. It contains a six-membered ring with two adjacent nitrogen atoms, and is aromatic.^[2] It is a colorless liquid with a boiling point of 208 °C. It is isomeric with two other (CH)₄N₂ rings, pyrimidine and pyrazine.

Occurrence

Pyridazines are rare in nature, possibly reflecting the scarcity of naturally occurring hydrazines, common building blocks for the synthesis of these heterocycles. The pyridazine structure is a popular pharmacophore which is found within a number of herbicides such as credazine, pyridafol and pyridate. It is also found within the structure of several drugs such as cefozopran, cadralazine, minaprine, pipofezine, and hydralazine.

Synthesis

In the course of his classic investigation on the Fischer indole synthesis, Emil Fischer prepared the first pyridazine via the condensation of phenylhydrazine and levulinic acid.^[3] The parent heterocycle was first prepared by oxidation of benzocinnoline to the pyridazinetetracarboxylic acid followed by decarboxylation. A better route to this otherwise esoteric compound starts with the maleic hydrazide. These heterocycles are often prepared via condensation of 1,4-diketones or 4-ketoacids with hydrazines.^[4]

References

^ "Front Matter". Nomenclature of Organic Chemistry : IUPAC Recommendations and Preferred Names 2013 (Blue Book). Cambridge: The Royal Society of Chemistry. 2014. p. 141. doi:10.1039/9781849733069-FP001. ISBN 978-0-85404-182-4.
^ Gumus, S. (2011). "A computational study on substituted diazabenzenes" (PDF). Turk J Chem. 35: 803–808. Archived from the original (PDF) on 2016-03-03. Retrieved 2014-04-10.
^ Fischer, E. (1886). "Indole aus Phenylhydrazin". Justus Liebigs Annalen der Chemie. 236 (1–2): 126–151. doi:10.1002/jlac.18862360107.
^ Tišler, M.; Stanovnik, B. (1968). "Pyridazines". Advances in Heterocyclic Chemistry. 9: 211–320. doi:10.1016/S0065-2725(08)60374-8. ISBN 9780120206094.

[iupac2013-1] "Front Matter". Nomenclature of Organic Chemistry : IUPAC Recommendations and Preferred Names 2013 (Blue Book). Cambridge: The Royal Society of Chemistry. 2014. p. 141. doi:10.1039/9781849733069-FP001. ISBN 978-0-85404-182-4.

[2] Gumus, S. (2011). "A computational study on substituted diazabenzenes" (PDF). Turk J Chem. 35: 803–808. Archived from the original (PDF) on 2016-03-03. Retrieved 2014-04-10.

[3] Fischer, E. (1886). "Indole aus Phenylhydrazin". Justus Liebigs Annalen der Chemie. 236 (1–2): 126–151. doi:10.1002/jlac.18862360107.

[4] Tišler, M.; Stanovnik, B. (1968). "Pyridazines". Advances in Heterocyclic Chemistry. 9: 211–320. doi:10.1016/S0065-2725(08)60374-8. ISBN 9780120206094.

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