Pyrazine: Difference between revisions

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{{Short description|Chemical compound}}

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{{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 = C₄H₄N₂

| MolarMass = 80.09 g/mol

| Appearance = White crystals

| Density = 1.031 g/cm³

| 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 = −37.6·10⁻⁶ cm³/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]] C₄H₄N₂. It is a symmetrical molecule with [[point group]] D_2h. 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>

<table border="1" cellpadding="2" cellspacing="0" align="right" style="margin-left:1em">

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>

<tr><th colspan="2" align=center bgcolor="#cccccc">'''Pyrazine'''</th></tr>

== Synthesis ==

<tr><td>[[IUPAC nomenclature|Chemical name]]</td><td>Pyrazine</td></tr>

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>

<tr><td>[[Chemical formula]]</td><td>C₄H₄N₂</td></tr>

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

<tr><td>[[Molecular mass]]</td><td>80.09 g/mol</td></tr>

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>

<tr><td>[[Melting point]]</td><td>52 °C</td></tr>

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

<tr><td>[[Boiling point]]</td><td>115 °C</td></tr>

== See also ==

<tr><td>[[CAS registry number|CAS number]]</td><td>290-37-9</td></tr>

* [[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 ==

<tr><td>[[Simplified molecular input line entry specification|SMILES]]</td><td>C1=NC=CN=C1</td></tr>

{{reflist}}

== External links ==

<tr><td colspan="2" align="center">[[Image:Pyrazine_chemical_structure.png|Chemical structure of pyrazine]]</td></tr>

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

</table>

'''Pyrazine''' is a [[heterocyclic]] [[aromatic]] [[organic compound]].

== See also ==

* [[Pyrimidine]], an analog with the second [[nitrogen]] [[atom]] in position 3.

* [[Pyridine]], an analog with only one nitrogen atom.

* [[Benzene]], an analog without the nitrogen atoms.

* [[Simple aromatic ring]]s

{{Simple aromatic rings}}

{{Authority control}}

{{chem-stub}}

[[Category:Simple_aromatic_ringsPyrazines| ]]

[[Category:Basic_aromatic_ringsSimple aromatic rings]]