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Pyrazine 2D aromatic full.svg
Pyrazine 2D numbers.svg
Pyrazine molecule
Pyrazine molecule
IUPAC name
Other names
1,4-Diazabenzene, p-Diazine, 1,4-Diazine, Paradiazine, Piazine, UN 1325
290-37-9 YesY
ChEBI CHEBI:30953 YesY
ChemSpider 8904 YesY
EC Number 206-027-6
Jmol interactive 3D Image
PubChem 9261
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)
Acidity (pKa) 0.37[1] (protonated pyrazine)
R-phrases R11, R36/37/38
S-phrases S16, S26, S36
NFPA 704
Flammability code 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 fuel Health code 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g., chloroform Reactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g., liquid nitrogen Special hazards (white): no codeNFPA 704 four-colored diamond
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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Infobox references

Pyrazine is a heterocyclic aromatic organic compound with the chemical formula C4H4N2.

Pyrazine is a symmetrical molecule with point group D2h. Derivatives such as phenazine are well known for their antitumor, antibiotic and diuretic activities. Pyrazine is less basic than pyridine, pyridazine and pyrimidine. Tetramethylpyrazine (also known as ligustrazine) is reported to scavenge superoxide anion and decrease nitric oxide production in human polymorphonuclear leukocytes,[2] and is a component of some herbs in traditional Chinese medicine.[3]


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. [4] A variation is the Gutknecht pyrazine synthesis (1879) also based on this selfcondensation, but differing in the way the alpha-ketoamine is synthesised [5][6]

Gutknecht pyrazine synthesis

The Gastaldi synthesis (1921) is another variation:[7][8]

Gastaldi synthesis

See also[edit]

External links[edit]


  1. ^ 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.
  2. ^ Zhang, Zhaohui (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. 
  3. ^
  4. ^ Ueber die Einwirkung von Ammoniak auf Chloracetylbenzol (pp. 563–564) W. Staedel, L. Rügheimer doi:10.1002/cber.187600901174 Berichte der deutschen chemischen Gesellschaft Volume 9, Issue 1, pp. 563–564, 1876
  5. ^ Mittheilungen Ueber Nitrosoäthylmethylketon H. Gutknecht Berichte der deutschen chemischen Gesellschaft Volume 12, Issue 2 , pp. 2290–2292, 1879 doi:10.1002/cber.187901202284
  6. ^ Heterocyclic chemistry T.L. Gilchrist ISBN 0-582-01421-2
  7. ^ G. Gastaldi, Gazz. Chim. Ital. 51, (1921) 233
  8. ^ Amines: Synthesis, Properties and Applications Stephen A. Lawrence 2004 Cambridge University Press ISBN 0-521-78284-8