Pyrazine

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Pyrazine
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Names
Preferred IUPAC name
Pyrazine[1]
Other names
1,4-Diazabenzene, p-Diazine, 1,4-Diazine, Paradiazine, Piazine, UN 1325
Identifiers
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  • InChI=1S/C4H4N2/c1-2-6-4-3-5-1/h1-4H checkY
    Key: KYQCOXFCLRTKLS-UHFFFAOYSA-N checkY
  • InChI=1/C4H4N2/c1-2-6-4-3-5-1/h1-4H
  • c1cnccn1
Properties
C4H4N2
Molar mass 80.09 g/mol
Appearance White crystals
Density 1.031 g/cm3
Melting point 52 °C (126 °F; 325 K)
Boiling point 115 °C (239 °F; 388 K)
Soluble
Acidity (pKa) 0.37[2] (protonated pyrazine)
−37.6·10−6 cm3/mol
Hazards
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NFPA 704 four-colored diamondHealth 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g. chloroformFlammability 2: Must be moderately heated or exposed to relatively high ambient temperature before ignition can occur. Flash point between 38 and 93 °C (100 and 200 °F). E.g. diesel fuelInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
2
2
0
Flash point 55 °C (131 °F; 328 K) c.c.
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Pyrazine is a heterocyclic aromatic organic compound with the chemical formula C4H4N2. It is a symmetrical molecule with point group D2h. Pyrazine is less basic than pyridine, pyridazine and pyrimidine. It is a "deliquescent crystal or wax-like solid with a pungent, sweet, corn-like, nutty odour".[3]

Pyrazine and a variety of alkylpyrazines are flavor and aroma compounds found in baked and roasted goods. Tetramethylpyrazine (also known as ligustrazine) is reported to scavenge superoxide anions and decrease nitric oxide production in human granulocytes.[4]

Synthesis

Many methods exist for the organic synthesis of pyrazine and its derivatives. Some of these are among the oldest synthesis reactions still in use.

In the Staedel–Rugheimer pyrazine synthesis (1876), 2-chloroacetophenone is reacted with ammonia to the amino ketone, then condensed and then oxidized to a pyrazine.[5] A variation is the Gutknecht pyrazine synthesis (1879) also based on this selfcondensation, but differing in the way the alpha-ketoamine is synthesised.[6][7]

Gutknecht pyrazine synthesis

The Gastaldi synthesis (1921) is another variation:[8][9]

Gastaldi synthesis

See also

References

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  1. ^ Page Module:Citation/CS1/styles.css has no content.International Union of Pure and Applied Chemistry (2014). Nomenclature of Organic Chemistry: IUPAC Recommendations and Preferred Names 2013. The Royal Society of Chemistry. p. 141. doi:10.1039/9781849733069. ISBN 978-0-85404-182-4.
  2. ^ Brown, H.C., et al., in Baude, E.A. and Nachod, F.C., Determination of Organic Structures by Physical Methods, Academic Press, New York, 1955.
  3. ^ Page Module:Citation/CS1/styles.css has no content."Pyrazine | C4H4N2 | ChemSpider". www.chemspider.com. Retrieved 4 January 2022.
  4. ^ Page Module:Citation/CS1/styles.css has no content.Zhang, Zhaohui; Wei, Taotao; Hou, Jingwu; Li, Gengshan; Yu, Shaozu; Xin, Wenjuan (2003). "Tetramethylpyrazine scavenges superoxide anion and decreases nitric oxide production in human polymorphonuclear leukocytes". Life Sciences. 72 (22): 2465–2472. doi:10.1016/S0024-3205(03)00139-5. PMID 12650854.
  5. ^ Page Module:Citation/CS1/styles.css has no content.Staedel, W.; Rügheimer, L. (1876). "Ueber die Einwirkung von Ammoniak auf Chloracetylbenzol". Berichte der Deutschen Chemischen Gesellschaft. 9: 563–564. doi:10.1002/cber.187600901174.
  6. ^ Page Module:Citation/CS1/styles.css has no content."Ueber Nitrosoäthylmethylketon". Berichte der Deutschen Chemischen Gesellschaft. 12 (2): 2290–2292. 1879. doi:10.1002/cber.187901202284.
  7. ^ Heterocyclic chemistry T.L. Gilchrist Template:ISBN
  8. ^ G. Gastaldi, Gazz. Chim. Ital. 51, (1921) 233
  9. ^ Amines: Synthesis, Properties and Applications Stephen A. Lawrence 2004 Cambridge University Press Template:ISBN

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