Enrichment of heavy oxygen (18O) from its level at natural abundance is widely used to probe O2-dependent processes in the atmospheric and biological sciences.[1–4] Here we describe the first application of this technique to O2-binding reactions of classic inorganic compounds. Competitive 18O kinetic isotope effects (KIEs)[5–7] reflecting the ratio of secondorder rate constants for the formation of η2-peroxide compounds from 16, 16O2 ...
