Pyridazine

Pyridazine is an aromatic, heterocyclic, organic compound with the molecular formula C4H4N2. It contains a six-membered ring with two adjacent nitrogen atoms.[2] 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)
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.005.478
EC Number
  • 206-025-5
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
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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Infobox references

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
  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. Vol. 9. pp. 211–320. doi:10.1016/S0065-2725(08)60374-8. ISBN 9780120206094.
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