The first detection of the chiral cyclic compound propylene oxide (CH₃CHCH₂O) was reported in 2016 by McGuire and coworkers toward the Sgr B2(N) star-forming region. Three rotational transitions were identified using two telescopes: two transitions recorded by PRIMOS using the 100m GBT and the third with the 64m telescope at Parkes Observatory. The detection was based upon the 1957 laboratory data of Swallen & Hershbach. Mesko and coworkers remeasured the rotational spectrum of propylene oxide in 2017. Rotational ata for singly-deuterated isotopologues were published by Imachi and Kuczkowski in 1983, while data for one of the doubly deuterated forms was published by Stahl and coworkers in 2021.

Propylene oxide (or methyloxirane) is a chiral molecule with two energetically equivalent stereoisomers that cannot be interconverted. Chirality is an important part of the only form of life we know, and its origin remains mysterious. Propylene oxide also happens to be "acutely toxic and carcinogenic."