Novel five-membered ring intermediates in gas phase reactions

This review considers the role of closed-ring intermediates in chemistry, in general, and focuses on recent experimental and theoretical works that provide compelling evidence for a five-membered ring intermediate in the gas phase. The reactions of oxygen atoms with ethyl iodide and larger alkyl iodides produce HOI and a corresponding ethylenic compound via attack of the oxygen atom at the iodine and closure of the five-membered ring between the oxygen and a hydrogen on the beta-carbon. Detailed results are gathered from infrared chemiluminescence and molecular beam scattering, as well as new kinetics and product yield experiments. The theoretical calculations fully support and characterize the novel reaction mechanism.