Editing Pyrazine

{{Short description|Chemical compound}}
{{chembox
| Watchedfields = changed
| verifiedrevid = 417947419
| ImageFileL1 = Pyrazine 2D aromatic full.svg
| ImageFileR1 = Pyrazine 2D numbers.svg
| ImageFileL2 = Pyrazine-3D-balls-2.png
| ImageAltL2 = Pyrazine molecule
| ImageFileR2 = Pyrazine-3D-spacefill.png
| ImageAltR2 = Pyrazine molecule
| PIN = Pyrazine<ref>{{cite book |author=[[International Union of Pure and Applied Chemistry]] |date=2014 |title=Nomenclature of Organic Chemistry: IUPAC Recommendations and Preferred Names 2013 |publisher=[[Royal Society of Chemistry|The Royal Society of Chemistry]] |pages=141 |doi=10.1039/9781849733069 |isbn=978-0-85404-182-4}}</ref>
| OtherNames = 1,4-Diazabenzene, p-Diazine, 1,4-Diazine, Paradiazine, Piazine, UN 1325
|Section1={{Chembox Identifiers
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| ChemSpiderID = 8904
| ChEMBL_Ref = {{ebicite|correct|EBI}}
| ChEMBL = 15797
| StdInChI_Ref = {{stdinchicite|correct|chemspider}}
| StdInChI = 1S/C4H4N2/c1-2-6-4-3-5-1/h1-4H
| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
| StdInChIKey = KYQCOXFCLRTKLS-UHFFFAOYSA-N
| CASNo_Ref = {{cascite|correct|CAS}}
| CASNo = 290-37-9
| UNII_Ref = {{fdacite|correct|FDA}}
| UNII = 2JKE371789
| EINECS = 206-027-6
| PubChem = 9261
| SMILES = c1cnccn1
| InChI = 1/C4H4N2/c1-2-6-4-3-5-1/h1-4H
| ChEBI_Ref = {{ebicite|correct|EBI}}
| ChEBI = 30953
}}
|Section2={{Chembox Properties
| Formula = C<sub>4</sub>H<sub>4</sub>N<sub>2</sub>
| MolarMass = 80.09 g/mol
| Appearance = White crystals
| Density = 1.031 g/cm<sup>3</sup>
| MeltingPtC = 52
| BoilingPtC = 115
| Solubility = Soluble
| pKa =0.37<ref>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.</ref> (protonated pyrazine)
| MagSus = −37.6·10<sup>−6</sup> cm<sup>3</sup>/mol
}}
|Section3={{Chembox Hazards
| MainHazards = 
| FlashPtC = 55
| FlashPt_notes = c.c.
| AutoignitionPt = 
| NFPA-H = 2
| NFPA-F = 2
| NFPA-R = 0
| NFPA-S = 
| GHSPictograms = {{GHS05}}{{GHS07}}
| GHSSignalWord = Danger
| HPhrases = {{H-phrases|228|315|319|335}}
| PPhrases = {{P-phrases|210|261|305+351+338}}
}}
}}

'''Pyrazine''' is a [[heterocyclic]] [[aromatic]] [[organic compound]] with the [[chemical formula]] C<sub>4</sub>H<sub>4</sub>N<sub>2</sub>. It is a symmetrical molecule with [[point group]] D<sub>2h</sub>. 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"''.<ref>{{cite web |title=Pyrazine {{!}} C4H4N2 {{!}} ChemSpider |url=https://www.chemspider.com/Chemical-Structure.8904.html?rid=e2532a2c-d5cb-457e-884b-ca9e4c8bd96b |website=www.chemspider.com |access-date=4 January 2022}}</ref>

Pyrazine and a variety of [[alkylpyrazine]]s are flavor and aroma compounds found in baked and roasted goods. [[Tetramethylpyrazine]] (also known as ligustrazine) is reported to scavenge [[Superoxide|superoxide anions]] and decrease [[nitric oxide]] production in human [[granulocytes]].<ref>{{cite journal | doi = 10.1016/S0024-3205(03)00139-5 | title=Tetramethylpyrazine scavenges superoxide anion and decreases nitric oxide production in human polymorphonuclear leukocytes | journal=Life Sciences | date=2003 | volume=72 | issue=22 | pages=2465–2472 | first1=Zhaohui | last1=Zhang|last2=Wei|first2=Taotao|last3=Hou|first3=Jingwu|last4=Li|first4=Gengshan|last5=Yu|first5=Shaozu|last6=Xin|first6=Wenjuan|pmid=12650854}}</ref>

== 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|2-chloroacetophenone]] is reacted with [[ammonia]] to the amino ketone, then condensed and then oxidized to a pyrazine.<ref>{{cite journal | doi = 10.1002/cber.187600901174 | title = Ueber die Einwirkung von Ammoniak auf Chloracetylbenzol | date = 1876 | last1 = Staedel | first1 = W. | last2 = Rügheimer | first2 = L. | journal = Berichte der Deutschen Chemischen Gesellschaft | volume = 9 | pages = 563–564 }}</ref> A variation is the '''Gutknecht pyrazine synthesis''' (1879) also based on this  [[selfcondensation]], but differing in the way the alpha-ketoamine is synthesised.<ref>{{cite journal | doi = 10.1002/cber.187901202284 | title = Ueber Nitrosoäthylmethylketon | journal = Berichte der Deutschen Chemischen Gesellschaft | date = 1879 | volume = 12 | issue = 2 | pages = 2290–2292 }}</ref><ref>''Heterocyclic chemistry'' T.L. Gilchrist {{ISBN|0-582-01421-2}}</ref>

:[[File:Gutknecht Pyrazine Synthesis.svg|500px|Gutknecht pyrazine synthesis]]

The '''Gastaldi synthesis''' (1921) is another variation:<ref>G. Gastaldi, Gazz. Chim. Ital. 51, ('''1921''') 233</ref><ref>''Amines: Synthesis, Properties and Applications'' Stephen A. Lawrence 2004 Cambridge University Press {{ISBN|0-521-78284-8}}</ref>

:[[File:GastaldiSynthesis.svg|400px|Gastaldi synthesis]]

== See also ==
* [[Alkylpyrazine]]s
* [[Methoxypyrazines]]
* [[Simple aromatic ring]]s
* [[Benzene]], an analog without the nitrogen atoms
* [[Pyridazine]], an analog with the second nitrogen atom in position 2
* [[Pyridine]], an analog with only one nitrogen atom
* [[Pyrimidine]], an analog with the second [[nitrogen]] [[atom]] in position 3
* [[Piperazine]], the saturated analog

== References ==
{{reflist}}

== External links ==
* [http://www.inchem.org/documents/jecfa/jecmono/v48je12.htm Safety evaluation of food additives – pyrazine derivatives]

{{Simple aromatic rings}}

{{Authority control}}

[[Category:Pyrazines| ]]
[[Category:Simple aromatic rings]]