Unexpected Epoxide Formation in the Gas-Phase Photooxidation of Isoprene

<jats:title>No NO</jats:title> <jats:p> Isoprene, a five-carbon diene produced by plants, is the most abundant nonmethane hydrocarbon released into the atmosphere and plays an important role in tropospheric chemistry. Isoprene is also thought to affect climate by acting as a source of atmospheric aerosols. <jats:bold> Paulot <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="730" related-article-type="in-this-issue" vol="325" xlink:href="10.1126/science.1172910">730</jats:related-article> ; see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="5941" page="687" related-article-type="in-this-issue" vol="325" xlink:href="10.1126/science.1178324">Kleindienst</jats:related-article> </jats:bold> ) now describe how isoprene may lead to the formation of secondary organic aerosols. In laboratory experiments, the photooxidation of isoprene in low-NO conditions, such as those which occur in vegetated regions far from anthropogenic influence, produced high yields of dihydroxy epoxides, a suspected precursor of the aerosols. This discovery could help to explain some of the more puzzling aspects of isoprene chemistry in remote regions. </jats:p>