Gas-phase organic reactions of the atomic oxygen radical cation

•The atomic oxygen radical cation is abundant in many environments.•Reactivity of O+ with several organic compounds has been studied with a FA-SIFT.•Efficient charge transfer, often with fragmentation, is a dominant mechanism.•Additional reactions include attack on carbonyl and methyl groups.•RRKM and electronic structure calculations provide insight into the reactions.

Reactivity of ground-state oxygen radical cation, O+(4S), has been studied with several organic compounds for the first time. Rate constants and product distributions have been measured for the ion-neutral reactions of O+ with acetaldehyde, acetic acid, acetone, dimethyl ether, methanol, and methyl formate at 300 K in a flowing-afterglow-selected ion flow tube (FA-SIFT). The reactions observed proceed efficiently, occurring above 50% of the collision rate in each case. We observed highly exothermic charge transfer reactions which lead to dissociation in some cases. Other interesting trends in reactivity include attack on methyl groups, and for some reactions, O+ replaces the methyl radical.

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