On the bonding and structure in dihydroperoxyl (HO2)2 and H2O4

Ultraviolet photolysis of H2CO and C2H2O2 in an O2 matrix at 12–20 K gives (HO2)2. The infrared absorption spectrum of (HO2)2 shows internal hydrogen bonding. A head-to-tail, six-membered cyclic dimer structure is proposed. On warming to 30 K, (HO2)2 disappears and H2O2 is formed.