Reference

Electron Photodetachment Spectroscopy of Solvated Anions: RO×HF- or ROH×F-?

Electron Photodetachment Spectroscopy of Solvated Anions: RO×HF- or ROH×F-?. Mihalick, Jennifer E.; Gatev, Geo G.; Brauman, John I. (Department of Chemistry, Stanford University, Stanford, CA 94305-5080, USA). Journal of the American Chemical Society, 118(49), 12424-12431 (English) 1996 American Chemical Society. CODEN: JACSAT. 3970-62-5 and 120686-56-8 are also occured in this study. ISSN: 0002-7863. DOCUMENT TYPE: Journal CA Section: 22 (Physical Organic Chemistry) Electron photodetachment spectra of three alkoxide ions, 2,2-dimethyl-3-pentoxide, 3,3-dimethyl-2-butoxide, trifluoroethoxide, and two complex ions, 3,3-dimethyl-2-butanol/fluoride, 2,2-dimethyl-3-pentanol/fluoride, have been measured using an ion cyclotron spectrometer to generate, trap, and detect the ions. The electron affinities of trifluoroethoxide, 2,2-dimethyl-3-pentoxide, and 3,3-dimethyl-2-butoxide were measured as 58.9 ± 0.1, 47.8 ± 0.3, and 45.7 ± 0.1 kcal mol-1, resp. Using known proton affinities of the three alcs. allows us to det. the O-H bond dissocn. energies. The threshold detachment energies for 2,2-dimethyl-3-pentanol/fluoride and 3,3-dimethyl-2-butanol/fluoride complex ions are 70.3 ± 0.5, and 70.1 ± 0.5 kcal mol-1, resp. The fluoride binding energies are thus on the order of 30 kcal mol-1. The observation or non-observation of photodetachment for alc./fluoride ions depends only on the alc. acidity. In complex ions of the form ROHF-, if ROH is more acidic than HF the structure is RO-×HF, and if ROH is less acidic than HF the structure is ROH×F-. A flat potential energy surface model is consistent with the exptl. results. The exptl. results show no evidence for unusual structural change or stabilization when a hydrogen bond forms between two acids with similar acidities. .