HOON’s O–O Bond Is The Longest Yet

A team led by scientists at the Harvard-Smithsonian Center for Astrophysics has isolated a previously undetected molecule and found that it has the longest oxygen-oxygen bond yet discovered (Science 2013, DOI: 10.1126/science.1244180). Researchers have long known that nitrous acid (HONO) plays an important role in atmospheric chemistry. But most people dismissed the existence of the compound’s isomer, nitrosyl O-hydroxide (HOON), predicting that it wouldn’t be stable, says team leader Michael C. McCarthy. Still, earlier this year a computational study suggested HOON’s plausibility at low temperatures (J. Phys. Chem. A 2013, DOI:10.1021/jp3110858). Following up, McCarthy’s group generated trans-HOON by combining nitric oxide, water vapor, and neon; applying an electrical discharge to the mix; and then cooling the resulting products with a method called supersonic expansion. The researchers detected the never-before-seen HOON with microwave spectroscopy and determined its O–O bond length to be 1.9 Å, 32% longer than a standard O–O single bond, such as the one in hydrogen peroxide (HOOH).