Protonated Ozone: Experimental Detection of O3H+ and Evaluation of the Proton Affinity of Ozone

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Science  08 Jul 1994:
Vol. 265, Issue 5169, pp. 208-209
DOI: 10.1126/science.265.5169.208


The elusive protonated ozone ion (O3H+) has been long postulated as a reactive intermediate but never experimentally observed. This ion has been detected here in mass spectrometric experiments with the use of Fourier transform ion cyclotron resonance. In these experiments, ozone (O3) was protonated by strong acids—for example, H3+, KrH+, XeH+, and CH5+. The hitherto experimentally unknown proton affinity of O3 was evaluated by a "bracketing" technique and determined to be 148 ∓ 3 kilocalories mole-1 at 298 kelvin, in excellent agreement with a value determined in a recent theoretical study of the O3/O3H+ system, which was 148 kilocalories mole-1 at zero temperature (∼149.5 kilocalories mole-1 at 298 kelvin).