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. It is a colorless liquid with a boiling point of 208 °C. It is isomeric with two other (CH)4N2 rings, pyrimidine and pyrazine.
|Preferred IUPAC name|
|Systematic IUPAC name
3D model (JSmol)
CompTox Dashboard (EPA)
|Molar mass||80.090 g·mol−1|
|Melting point||−8 °C (18 °F; 265 K)|
|Boiling point||208 °C (406 °F; 481 K)|
|Solubility||miscible in dioxane, ethanol |
soluble in benzene, diethyl ether
negligible in cyclohexane, ligroin
Refractive index (nD)
|1.52311 (23.5 °C)|
Std enthalpy of
|Flash point||85 °C (185 °F; 358 K)|
|pyridine, pyrimidine, pyrazine|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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.
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. 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.
- "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.
- 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.