Pyrazine

Pyrazine
IUPAC name Pyrazine
Other names 1,4-Diazabenzene, p-Diazine, 1,4-Diazine, Paradiazine, Piazine, UN 1325
Identifiers
CAS number	290-37-9 Y
PubChem	9261
ChemSpider	8904 Y
EC number	206-027-6
ChEBI	CHEBI:30953 Y
ChEMBL	CHEMBL15797 Y
Jmol-3D images	Image 1
SMILES c1cnccn1
InChI InChI=1S/C4H4N2/c1-2-6-4-3-5-1/h1-4H Y Key: KYQCOXFCLRTKLS-UHFFFAOYSA-N Y InChI=1/C4H4N2/c1-2-6-4-3-5-1/h1-4H
Properties
Molecular formula	C4H4N2
Molar mass	80.09 g/mol
Appearance	White crystals
Density	1.031 g/cm3
Melting point	52 °C, 325 K, 126 °F
Boiling point	115 °C, 388 K, 239 °F
Solubility in water	Soluble
Acidity (pKa)	0.37[1] (protonated pyrazine)
Hazards
R-phrases	R11, R36/37/38
S-phrases	S16, S26, S36
NFPA 704	2 2 0
Flash point	55 °C c.c.
Y (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

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

Pyrazine is a symmetrical molecule with point group D2h. Derivatives like phenazine are well known for their antitumor, antibiotic and diuretic activity. Pyrazine is less basic in nature 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]. Tetramethylpyrazine is also a component of some herbs in traditional Chinese medicine^[3].

Synthesis

Many methods exist for the organic synthesis of pyrazine and derivatives and some of them very old.

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 (the chlorine compound in the above method is a lachrymatory agent) ^{[5] [6]}

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

See also

• Pyrimidine, an analog with the second nitrogen atom in position 3.
• Pyridazine, an analog with the second nitrogen atom in position 2.
• Pyridine, an analog with only one nitrogen atom.
• Benzene, an analog without the nitrogen atoms.
• Simple aromatic rings
• Methoxypyrazines

External links

• Safety MSDS data
• Safety evaluation of food additives - pyrazine derivatives

References

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. ^ Life Sciences, 2003, 72, 2465-2472, DOI: http://dx.doi.org/10.1016/S0024-3205(03)00139-5
3. ^ http://www.itmonline.org/arts/ligustrazine.htm
4. ^ Ueber die Einwirkung von Ammoniak auf Chloracetylbenzol (p 563-564) W. Staedel, L. Rügheimer doi:10.1002/cber.187600901174 Berichte der deutschen chemischen Gesellschaft Volume 9, Issue 1 , Pages 563 - 564 1876
5. ^ Mittheilungen Ueber Nitrosoäthylmethylketon H. Gutknecht Berichte der deutschen chemischen Gesellschaft Volume 12, Issue 2 , Pages 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 0521782848