Five different anionic [C-3,H-4,O](.-) isomers, i.e., the radical anions of acrolein, acetyl carbene, formyl methyl carbene, methoxy vinylidene, and oxyallyl are generated in an ion beam mass spectrometer and subjected to neutralization-reionization (NR) mass spectrometric experiments including neutral and ion decomposition difference (NIDD) mass spectrometry; the latter allows for the examination of the neutrals' unimolecular reactivity. Further, the anionic, the singlet and triplet neutral, and the cationic [C-3,H-4,O](.-/0/.+) potential-energy surfaces are calculated at the B3LYP/6-311++G(d,p) level of theory. For some species, notably the singlet state of oxyallyl, the theoretical treatment is complemented by G2, CASSCF and MR-CI calculations. Theory and experiment are in good agreement in that at the neutral stage (i) acrolein does not react within the mu sec timescale, (ii) acetyl and formyl methyl carbenes isomerize to methyl ketene, (iii) methoxy vinylidene rearranges to methoxy acetylene, (iv) singlet (1)A(1) oxyallyl undergoes ring closure to cyclopropanone, and (v) triplet B-3(2) oxyallyl may have a Lifetime sufficient to survive a NR experiment.