title: Acidity of M(VI)O2(OH)2for M = Group 6, 16, and U as Central Atoms.
abstract: Gas-phase acidities and aqueous solution pKa's are predicted for MO2(OH)2, where the center atom M is a main Group 6, 16, and U atom using the Feller-Peterson-Dixon approach based on coupled cluster CCSD(T) calculations with additional corrections. The gas-phase acidities of the MO2(OH)2compounds are essentially the same for elements (M) of the same group, 304-310 kcal/mol at 298 K. All of the Group 6 compounds are 5-6 kcal/mol less acidic in the gas phase than H2SO4. The gas-phase acidity of UO2(OH)2is calculated to be up to 338.0 kcal/mol, ∼10% less acidic in the gas phase than the other MO2(OH)2acids. The most acidic molecule in aqueous solution is predicted to be H2SO4. Overall, for the Group 16 compounds, the pKa's increase going down the group, with H2PoO4predicted to be slightly more acidic than nitric acid. H2CrO4is the most acidic of the Group 6 transition metal compounds. The aqueous acidities of H2MoO4and H2WO4are comparable and about 3 pKaunits less acidic than H2CrO4and comparable in acidity to HNO3. H2UO4is not acidic at all in aqueous solution with a pKanear 20 pKaunits and is also not predicted to readily undergo hydrolysis reactions.
authors.affiliation: Department of Chemistry, Washington State University , Pullman, Washington 99164-4630, United States.
authors.forename: Rulin
authors.initials: R
authors.lastname: Feng
authors.affiliation: Department of Chemistry, The University of Alabama , Shelby Hall, Tuscaloosa, Alabama 35487-0336, United States.
authors.forename: Monica
authors.initials: M
authors.lastname: Vasiliu
authors.affiliation: Department of Chemistry, Washington State University , Pullman, Washington 99164-4630, United States.
authors.forename: Kirk A
authors.initials: KA
authors.lastname: Peterson
authors.affiliation: Department of Chemistry, The University of Alabama , Shelby Hall, Tuscaloosa, Alabama 35487-0336, United States.
authors.forename: David A
authors.identifier: http://orcid.org/0000-0002-9492-0056
authors.initials: DA
authors.lastname: Dixon