EXPERIMENTAL AND THEORETICAL-STUDY OF CARBON SUBOXIDE C3O2, PROTONATED CARBON SUBOXIDE C3HO2-CENTER-DOT RADICAL IN THE GAS-PHASE( AND C3HO2)

The proton affinity (PA) of carbon suboxide O=C=C=C=O has been determi ned by Fourier transform ion cyclotron resonance as 791 kJ mol(-1). Ab initio calculations at the MP4(SDTQ)/6-31G(*)//6-31G(**) + ZPE(6-31G (*)) level of theory give a proton affinity for C3O2 of 789 kJ mol(-1 ). The gas-phase reactivity of ions a [O=C=CH-C=O](+) and ions b[O=C=C =C-OH](+), generated from various precursors has been studied by mass spectrometry techniques (metastable ion kinetic energy (MIKE), collisi on induced decomposition (CID) and neutralization - reionization (NR) mass spectra). From the experimental and theoretical results it follow s that the gas-phase protonation of carbon suboxide yields ion a. At h igh internal energies these ions show competing losses of H' and CO. T he radical [O=C=CH-C=O]', the neutral counterpart of protonated carbon suboxide, has a lifetime of at least 1 mu s.