Correlation of relative rates of chromyl chloride oxidation and chromic acid oxidation of acyclic alkenes versus alkene IPs and HOMOs

Plots of logarithms of relative reaction rates of chromyl chloride oxidation and of chromic acid oxidation of alkenes (log k rel values) versus alkene ionization potentials (IPs) and versus their highest occupied molecular orbital energy levels (HOMOs) demonstrate excellent correlations. Each plot has a similar appearance and shows a single line with a positive slope. The results indicate that the rate‐determining step of each title reaction involves an electrophilic attack on the alkene π‐bond without significant steric effects; this supports a proposed 2 + 3 cycloaddition mechanism and disfavors a proposed stepwise 2 + 2 cycloaddition mechanism. Comparison is made with other d 0 transition metal complexes that oxidize alkenes.