A novel anion rearrangement. The conversion of [CC(O)(CN)](-) to [NCCCO](-) in the gas phase: a joint experimental and theoretical study

The neutral radical (NCCCO)-C-13 has been made by charge stripping of anion [(NCCCO)-C-13](-) in a collision cell of a ZAB 2HF mass spectrometer. The precursor anion is formed in the ion source of the mass spectrometer by the loss of the elements of MeOH from the anion (NC)-C-13--CHCO2Me. Neutral (N CCCO)-C-13 can, in turn, be charge stripped to the corresponding cation [(N CCCO)-C-13](+) which then decomposes by competitive losses of CO and (NC.)- C-13. No losses of (CO)-C-13 or NC. are observed in this spectrum: thus, th e neutral (NCCCO)-C-13 does not scramble the carbons in the carbon chain du ring the lifetime (ca. 10(-6) s) of the neutral. An attempt to form the neu tral radical CC(O)(CN) (which is isomeric with NCCCO) from the precursor an ion [CC(O)(CN)](-) was unsuccessful, since on formation, [CC(O)(CN)](-) und ergoes facile rearrangement to the more stable [NCCCO](-). A theoretical in vestigation at the B3LYP/aug-cc-pVDZ//B3LYP/6-31G(d) level of theory indica tes that (i) there are singlet and triplet forms of [CC(O)CN](-) which are only 7 kJ mol(-1) different in energy, and (ii) both of these ions undergo facile rearrangement to form the respective singlet and triplet forms of [N CCCO](-) in strongly exothermic reactions.