Neutral cumulene oxide CCCCO is accessible by one-electron oxidation of [CCCCO]−˙ in the gas phase

Abstract

Calculations at the CCSD(T)/aug-cc-pVDZ//B3LYP/6-31G* level of theory indicate that doublet [CCCCO]⁻˙ is a stable species which should undergo collision-induced Franck–Condon vertical oxidation under neutralisation–reionisation conditions (⁻NR⁺) to produce both triplet CCCCO (ground state) and singlet CCCCO. Some of the neutral CCCCO species formed (particularly the triplet) should be stable for the microsecond duration of the NR experiment, whereas others will be energised (particularly the singlet) and should decompose to C₃ and CO. The [CCCCO]⁻˙ radical anion has been formed in the ion source of the mass spectrometer by the reaction CH₃OCH₂CC–CO–CH(CH₃)₂ + O⁻˙ → [CCCCO]⁻˙ + CH₃O˙ + H₂O + (CH₃)₂CH˙. The ⁻NR⁺ spectrum of [CCCCO]⁻˙ shows a recovery signal at m/z 64 corresponding to ionised CCCCO, together with a pronounced peak at m/z 36 (CCC⁺˙) produced by ionisation of CCC (formed by the reaction CCCCO → CCC + CO). The experimental observations are in agreement with the predictions of the theoretical study.