Gas-phase chemistry of alkylcarbonate anions and radicals

Abstract

Alkylcarbonate anions and radicals ROCOO −/ (R = H, CH 3, C 2H 5, i-C 3H 7, and t-C 4H 9) are investigated in the gas phase by means of mass spectrometry and ab initio calculations. Structural parameters and energies are obtained at the MP2/6-311++G(3df,3pd)//MP2/6-311++G(d,p) level of theory. Standard enthalpies of formation for the anions and radicals are determined via atomization energies and isodesmic reactions using the CBS-Q method. Further, alkylcarbonate anions are probed by metastable ion and collisional activation experiments, and the chemistry of the neutral radicals is investigated by charge-reversal and neutralization-reionization mass spectrometry. Although decarboxylation dominates the unimolecular reactivity of the species for both charge states, some other interesting features are observed, particularly for the anions, such as the formation of the CO 3 − radical anion or the presence of ionic fragments formed via hydrogen atom transfer.