title: Gas phase structures of peroxides: experiments and computational problems.
abstract: Gas-phase structures of several organic and inorganic peroxides X-O-O-X and X-O-O-X', which have been determined experimentally by gas electron diffraction and/or microwave spectroscopy, are discussed. The OO bond length in these peroxides varies from 1.481(8) Å in Me3 SiOOSiMe3 to 1.214(2) Å in FOOF and the dihedral angle ϕ(XO-OX) between 0° in HC(O)O-OH and near 180° in Bu(t) O-OBu(t) . Some of the peroxides cause problems for quantum chemistry, since several computational methods fail to reproduce the experimental structures. Extreme examples are MeO-OMe and FO-OF. In the case of MeO-OMe only about half of the more than 100 computational methods reported in the literature reproduce the experimentally determined double-minimum shape of the torsional potential around the OO bond correctly. For FO-OF only a small number of close to 200 computational methods reproduce the OO and OF bond lengths better than ±0.02 Å.
authors.affiliation: Institut für Physikalische und Theoretische Chemie, Universität Tübingen, Auf der Morgenstelle 8, Tübingen (Germany). heinz.oberhammer@uni-tuebingen.de.
authors.forename: Heinz
authors.initials: H
authors.lastname: Oberhammer
mesh_terms: D005740:Gases / Q000737:chemistry*; D008958:Models, Molecular; D010100:Oxygen / Q000737:chemistry; D010545:Peroxides / Q000737:chemistry*; D011789:Quantum Theory; D013816:Thermodynamics
chemical_list: D005740:Gases; D010545:Peroxides; D010100:Oxygen
keywords: conformational analysis; gas electron diffraction; microwave spectroscopy; peroxides; quantum chemical calculations