Pyridazine is an aromatic, heterocyclic, organic compound with the molecular formula C4H4N2. It contains a six-membered ring with two adjacent nitrogen atoms.[3] It is a colorless liquid with a boiling point of 208 °C. It is isomeric with two other diazine (C4H4N2) rings, pyrimidine and pyrazine.

Pyridazine
Skeletal formula with numbering convention
Pyridazine molecule
C=black, H=white, N=blue
Pyridazine molecule
C=black, H=white, N=blue
Names
Preferred IUPAC name
Pyridazine[1]
Systematic IUPAC name
1,2-Diazabenzene
Other names
1,2-Diazine
Orthodiazine
Oizine
Identifiers
3D model (JSmol)
103906
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.005.478 Edit this at Wikidata
EC Number
  • 206-025-5
49310
UNII
  • InChI=1S/C4H4N2/c1-2-4-6-5-3-1/h1-4H checkY
    Key: PBMFSQRYOILNGV-UHFFFAOYSA-N checkY
  • InChI=1/C4H4N2/c1-2-4-6-5-3-1/h1-4H
    Key: PBMFSQRYOILNGV-UHFFFAOYAA
  • n1ncccc1
Properties
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)
miscible
Solubility miscible in dioxane, ethanol
soluble in benzene, diethyl ether
negligible in cyclohexane, ligroin
1.52311 (23.5 °C)
Thermochemistry
224.9 kJ/mol
Hazards
GHS labelling:[2]
GHS07: Exclamation mark
Warning
H302, H315, H319, H335
P261, P264, P264+P265, P270, P271, P280, P301+P317, P302+P352, P304+P340, P305+P351+P338, P319, P321, P330, P332+P317, P337+P317, P362+P364, P403+P233, P405, P501
Flash point 85 °C (185 °F; 358 K)
Related compounds
Related compounds
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Occurrence

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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

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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.[4] 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.[5]

References

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  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. ^ "Pyridazine". pubchem.ncbi.nlm.nih.gov.
  3. ^ 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.
  4. ^ Fischer, E. (1886). "Indole aus Phenylhydrazin". Justus Liebigs Annalen der Chemie. 236 (1–2): 126–151. doi:10.1002/jlac.18862360107.
  5. ^ Tišler, M.; Stanovnik, B. (1968). "Pyridazines". Advances in Heterocyclic Chemistry Volume 9. Vol. 9. pp. 211–320. doi:10.1016/S0065-2725(08)60374-8. ISBN 9780120206094.