Isomeric structures of protonated ozone: A theoretical study

Ab initio molecular orbital calculations have been used to determine the structure of protonated ozone. Four stable minima were found on the O₃H⁺ singlet potential energy surface. Three forms correspond to ozone protonated at the central oxygen (C_2v) or at the terminal oxygen (two C_s isomers, E and Z). The fourth isomer (C_s) is a derivative of trioxirane. The most stable structure is the planar E form I. The proton affinity of ozone (to give I) is given as 123.6 kcal/mole (MP2/6-31G*//4-31G). The energy difference between I and protonated trioxirane VI is greater than that between ozone and trioxirane.