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syn-Propanethial-S-oxide
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<h2 id="onion-release">Onion release</h2> <p>The chemical is released from <a href="/facts/Onions/2ajXf00d">onions</a>, <i>Allium cepa</i>, as they are sliced. The release is due to the breaking open of the onion cells, which releases <a href="/facts/Enzymes/DSI1Fh7y">enzymes</a> called <a href="/facts/Alliinase/ILJgSy3m">alliinases</a>. Alliinases then break down <a href="/facts/Amino_acid/WDxYwBny">amino acid</a> <a href="/facts/Sulfoxide/Stk3Vnj9">sulfoxides</a>, generating <a href="/facts/Sulfenic_acid/kthmLHtJ">sulfenic acids</a>. A specific sulfenic acid, <a href="/facts/Allicin/tPLWtC2a">allicin</a> or 1-propenesulfenic acid, is rapidly rearranged by another enzyme, the lachrymatory factor synthase (LFS) to give <i>syn</i>-propanethial <i>S</i>-oxide.<a class="footnote-ref" id="fnref:2" href="#fn:2"><sup>2</sup></a> Vapors from this volatile liquid induces tearing.<a class="footnote-ref" id="fnref:3" href="#fn:3"><sup>3</sup></a> </p> <h2 id="related-compounds">Related compounds</h2> <p>A structurally related lachrymatory compound, <i>syn</i>-butanethial <i>S</i>-oxide, C4H8OS, has been found in another genus <i>Allium</i> plant, <i><a href="/facts/Allium_siculum/VPSYFEI5">Allium siculum</a></i>.<a class="footnote-ref" id="fnref:4" href="#fn:4"><sup>4</sup></a> </p> <p>Propanethial S-oxide forms a stable thio<a href="/facts/Sultone/ApbgQMXB">sultone</a> dimer, <i>trans</i>-3,4-diethyl-1,2-dithietane 1,1-dioxide.<a class="footnote-ref" id="fnref:5" href="#fn:5"><sup>5</sup></a> </p> <h2 id="references">References</h2> <ol> <li id="fn:1"><p>Zwanenburg, B. (2004). "Thioaldehyde and Thioketone S-Oxides and S-Imides (Sulfines and Derivatives)". In Padwa, A. (ed.). Heteroatom Analogues of Aldehydes and Ketones. Science of Synthesis. Vol. 27. pp. 135–176. ISBN 978-1-58890-204-7. <a href="978-1-58890-204-7" target="_blank">978-1-58890-204-7</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li> <li id="fn:2"><p>Block, E. (2010). Garlic and Other Alliums: The Lore and the Science. Royal Society of Chemistry. p. 132. ISBN 978-0-85404-190-9. <a href="978-0-85404-190-9" target="_blank">978-0-85404-190-9</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li> <li id="fn:3"><p>Scott, T. (1999-10-21). "What is the chemical process that causes my eyes to tear when I peel an onion?". Ask the Experts: Chemistry. Scientific American. Retrieved 2012-04-03. <a href="http://www.sciam.com/article.cfm?id=what-is-the-chemical-proc" target="_blank">http://www.sciam.com/article.cfm?id=what-is-the-chemical-proc</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li> <li id="fn:4"><p>Kubec, R.; Cody, R. B.; Dane, A. J.; Musah, R. A.; Schraml, J.; Vattekkatte, A.; Block, E. (2010). "Applications of DART Mass Spectrometry in Allium Chemistry. (Z)-Butanethial S-Oxide and 1-Butenyl Thiosulfinates and their S-(E)-1-Butenylcysteine S-Oxide Precursor from Allium siculum". Journal of Agricultural and Food Chemistry. 58 (2): 1121–1128. doi:10.1021/jf903733e. PMID 20047275. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li> <li id="fn:5"><p>Block, E; Bazzi, AA; Revelle, LK (1980). "The chemistry of sulfines. 6. Dimer of the onion lachrymatory factor: the first stable 1,2-dithietane derivative". J. Am. Chem. Soc. 102 (7): 2490–2491. Bibcode:1980JAChS.102.2490B. doi:10.1021/ja00527a074. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></p></li> </ol>