COLLISION-INDUCED DISSOCIATION OF THE ISOMERIC IONS H2COOH+ AND HC(OH)(2)(+)

The dissociation of two isomeric forms of the ion CH3O2+ induced by co llisions with the helium buffer gas atoms has been studied in a select ed ion flow drift tube (SIFDT) experiment. When CH2OOH+ is formed via the reaction of O-2(+) with CH4, the product ions From collision induc ed dissociation (CID) are HCO+ (60%) and H3O+ (40%) respectively, inde pendent of the mean relative collision energy E(c) between the buffer gas and the ions, from thermal to 0.2 eV. The Arrhenius activation ene rgy obtained is 24 kcal mol(-1). Protonation of formic acid leads to H C(OH)(2)(+) ions, the CID of which yields 50% HCO+ and 50% H3O+, also independent of E(c). The Arrhenius activation energy is 38.4 kcal mol( -1) When formic acid is protonated in reaction with D3O+ to form CH2DO 2+, the products of CID of this ion are HCO+ and DH2O+ only, showing t hat deuteration occurs on the oxygen alone and not on the carbon. HC(O H): performs fast isotope exchange in collisions with D2O to form HC ( OD): in two consecutive steps and, again, deuteration on the carbon at om is not observed. HC(OH)(2)(+) also rapidly collisionally associates with H2O (k approximate to 10(-27) cm(6) s(-1) at 300 K).