A photoionization study of the COOH species

Abstract

A photoionization mass spectrometric study has been performed on the products of the F+HCOOH, F+DCOOH, and F+HCOOD reactions. Hydrogen/deuterium abstraction on the carbon site yields the COOH/COOD radical which can be photoionized and detected. Abstraction on the oxygen site also occurs, but does not yield a detectable isomeric HCOO/DCOO product. Instead, CO2 is readily observed, implying that HCOO/DCOO is unstable to decomposition under the conditions of this experiment. The detection of COOH is believed to be the first experimental evidence for the stability of this species in the gas phase. An adiabatic ionization potential of 8.486±0.012 eV is obtained. Combined with the recently obtained ΔHf00 (COOH+)=143.2±0.5 kcal/mol, this ionization potential leads to ΔHf00 (COOH)=−52.5±0.6 kcal/mol. Hence, COOH is stable with respect to the lowest energy dissociation products (H+CO2) by 10.2±0.6 kcal/mol.