By making use of an 80-year-old reaction, chemists have developed a positively popping way to deliver fragrances, agrochemicals, and other volatile compounds. Researchers at fragrance and flavor maker Firmenich, led by Damien L. Berthier and Andreas Herrmann, report using the photochemical degradation of 2-oxoacetates to burst open polyurea microcapsules (Angew. Chem. Int. Ed. 2015, DOI: 10.1002/anie.201410778). In the presence of ultraviolet light and oxygen, 2-oxoacetates react to form ketones, carboxylic acids, and carbon dioxide (shown). When there’s no oxygen around, they form ketones, aldehydes, and carbon monoxide. The Firmenich team reasoned the gas generated in these reactions might be sufficient to make microcapsules pop open. Chemists reported a similar strategy using light-generated nitrogen gas to break microcapsule walls more than 30 years ago. But no one ever used the chemistry to deliver active compounds. The Firmenich scientists demonstrated they could combine 2-oxoacetates with fragrance compounds in the microcapsule, or they could create precursor fragrance molecules out of the 2-oxoacetates.