REACTIONS OF HYDRATED HYDRONIUM IONS AND HYDRATED HYDROXIDE IONS, WITH SOME HYDROCARBONS AND OXYGEN-BEARING ORGANIC-MOLECULES

The rate coefficients and ion products have been determined at 300 K for the reactions of H3O+.(H2O)(0,1,2,3) positive ions and OH-.(H2O)(0,1,2) negative ions with six hydrocarbons and six oxygen-containing organic species using a selected ion flow tube (SIFT) for the positive ions and a flowing afterglow (FA) for the negative ions. This study was initiated in support of a major development program of the SIFT and FA as chemical ionization devices for the analysis of trace gases in air and especially of human breath and the vapors emitted by fruits and food products. The H3O+ and OH- ions mostly react with the molecules, MH, via proton transfer, producing respectively MH(2)(+) and M(-) ions, which is ideal for gas analysis. The hydrated hydronium ions and the hydrated hydroxide ions are largely unreactive with the hydrocarbons included in this study, but they are very reactive with the oxygen-containing organic molecules undergoing ligand switching reactions producing mostly MH(2)(+) and M(-) hydrates. The details of the reactions (e.g. the number of H2O molecules either ejected from the intermediate complexes or remaining associated with the MH(2)(+) and MH(-) ''core ions'') are controlled largely by the reaction energy as far as this can be determined. The utility of the reactions of these hydrated ions as chemical ionization agents in atmospheric trace gas analysis is alluded to. Additionally,new FA data on the three-body association reactions of OH- and OH-. H2O with CO2 are presented.