allene oxide
{{cs1 config|name-list-style=vanc|display-authors=6}}
In organic chemistry, an allene oxide is an epoxide of an allene. The parent allene oxide is CH2=C(O)CH2 (CAS RN 40079-14-9), a rare and reactive species of only theoretical interest. Typical allene oxides require steric protection for their isolation. Certain derivatives can be prepared by epoxidation of the allenes with peracetic acid. Allene oxides tend to rearrange to cyclopropanones.{{cite journal|journal=Tetrahedron|volume=36| date = January 1980 |pages=2269–2289|title=Chemistry of Allene Oxides| vauthors = Chan TH, Ong BS |issue=16 |doi=10.1016/0040-4020(80)80123-2}}
Despite the esoteric character of synthetic allene oxides, allene oxides occur naturally. They are intermediates in the chemical defense of some plants against attack by herbivores. Specifically, a hydroperoxide of linolenic acid is the substrate for the enzyme allene oxide synthase. The resulting allene oxide in turn is converted by allene oxide cyclase to jasmonic acid.{{cite journal | vauthors = Schaller A, Stintzi A | title = Enzymes in jasmonate biosynthesis - structure, function, regulation | journal = Phytochemistry | volume = 70 | issue = 13–14 | pages = 1532–1538 | date = September 2009 | pmid = 19703696 | doi = 10.1016/j.phytochem.2009.07.032 | bibcode = 2009PChem..70.1532S }}
File:JasmonicAcidBiosyn.pngNevertheless, allene oxides are extremely unstable even in biological contexts, decomposing with a half-life of approximately 15-30 s.{{cite journal | vauthors = Brash AR, Baertschi SW, Ingram CD, Harris TM | title = Isolation and characterization of natural allene oxides: unstable intermediates in the metabolism of lipid hydroperoxides | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 85 | issue = 10 | pages = 3382–3386 | date = May 1988 | pmid = 2835769 | pmc = 280213 | doi = 10.1073/pnas.85.10.3382 | doi-access = free | bibcode = 1988PNAS...85.3382B }}
