ELECTRON PHOTODETACHMENT SPECTROSCOPY OF SOLVATED ANIONS - RO-CENTER-DOT-HF- OR ROH-CENTER-DOT-F-

Electron photodetachment spectra of three alkoxide ions, 2,2-dimethyl- 3-pentoxide, 3,3-dimethyl-2-butoxide, trifluoroethoxide, and two compl ex ions, 3,3-dimethyl-2-butanol/fluoride, 2,2-dimethyl-3-pentanol/fluo ride, have been measured using an ion cyclotron spectrometer to genera te, trap, and detect the ions. The electron affinities of trifluoroeth oxide, 2,2-dimethyl-3-pentoxide, and 3,3-dimethyl-2-butoxide were meas ured as 58.9+/-0.1, 47.8+/-0.3, and 45.7+/-0.1 kcal mol(-1), respectiv ely. Using known proton affinities of the three alcohols allows us to determine the O-H bond dissociation energies. The threshold detachment energies for 2,2-dimethyl-3-pentanol/fluoride and 3,3-dimethyl-2-buta nol/fluoride complex ions are 70.3+/-0.5, and 70.1+/-0.5 kcal mol(-1), respectively. The fluoride binding energies are thus on the order of 30 kcal mol(-1). We show that the observation or non-observation of ph otodetachment for alcohol/fluoride ions depends only on the alcohol ac idity. In complex ions of the form ROHF(-), if ROH is more acidic than HF the structure is RO(-). HF, and if Roll is less acidic than HF the structure is ROH . F-. A flat potential energy surface model is consi stent with the experimental results. The experimental results show no evidence for unusual structural change or stabilization when a hydroge n bond forms between two acids with similar acidities.