Spotlights on Recent JACS Publications

Tetravalent oxygen, which has four bonds and a double positive charge, has long been believed to exist in theory but has never been unequivocally observed. Protonation of one of the two lone pairs on H2O to form H3O + is the well-known basis of aqueous acid chemistry, but protonation of the remaining lone pair to form the H4O 2+ dication is challenging to demonstrate. George Olah and co-workers previously proposed the intermediacy of such an oxadionium cation in reactions of H3O + in a superacidstronger than 100% sulfuric acid. Now a group led by Evgenii Stoyanov, Mark Mascal, and Christopher Reed has used infrared spectroscopy to demonstrate hydrogen bonding between an oxatriquinane and the strongest known acid, a carborane superacid (DOI: 10.1021/ ja209942s). Oxatriquinanes are tricyclic analogues of the H3O +