The stability and reactivity of the neutral species CNCCO generated by one electron oxidation of the anion [CNCCO]− have been investigated by a combination of theoretical calculations (carried out at the CCSD(T)/aug-cc-pVDZ//B3LYP/6-31G(d) level of theory) and tandem mass spectrometric experiments. Some of the neutrals formed in this way are stable for the microsecond duration of the experiment, but others are energised. The neutrals which are energised may either (i) dissociate [CNCCO → CNC + CO (+92 kJ mol−1)], and/or (ii), undergo the isonitrile to nitrile rearrangement to yield NCCCO energised neutrals (barrier 133 kJ mol−1, reaction exothermic by 105 kJ mol−1). Some of these rearranged neutrals NCCCO have excess energies as high as 238 kJ mol−1 and will dissociate [NCCCO → NCC + CO (+203 kJ mol−1)].
