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.