The two neutral radicals NCCCCO and CCC(O)CN have been made by collision-induced vertical one-electron reduction and oxidation (respectively) of the charged species NCCCCO+ and (-) CCC(O)CN. The two charged precursors were prepared by the following reactions: (a) [NC-Cequivalent toC-CO-CH3](+.) --> NCCCO+ + CH3. and (b) (CH3)(3)Si-Cequivalent toC-CO-CN + F- --> -CCC(O)CN + (CH3)(3)SiF. Neutral NCCCCO is a stable species, but when energized decomposes by loss of CO to form the radical CCCN [process endothermic by 38.5 kcal mol(-1): calculations at the CCSD(T)/aug-cc-pVDZ//B3LYP/6-31G(d) level of theory]. Neutral CCC(O)CN is 46.8 kcal mol(-1) more positive in energy than the isomer NCCCCO. When energized, CCC(O)CN decomposes by loss of NC- to form CCCO (process endothermic by 28.1 kcal mol(-1)), but also undergoes a rearrangement process to produce NCCCCO, which is formed with excess energy and may decompose by loss of CO.