Arp, Fabian Felix (2020-12). Peroxides Stabilized by Phosphine Oxides: Synthesis, Characterization, and Applications. Doctoral Dissertation.
A large variety of Hilliard adducts with the general motif (R3PO?H2O2)2 and Ahn adducts with the composition R3PO?(HOO)2CR'R" have been synthesized and fully characterized. Their single crystal X-ray structures have been determined and analyzed. The IR and 31P NMR data are in accordance with strong hydrogen bonding of hydrogen peroxide and di(hydroperoxy)alkanes, respectively. The bonding nature of the adduct assemblies has been investigated by DOSY NMR experiments. Raman spectroscopy of the symmetric Hilliard adducts and the ?(O-O) stretching bands confirm the presence of hydrogen-bonded hydrogen peroxide in the solid materials. The solubilities in organic solvents have been quantified to be very high for Hilliard adducts and high for Ahn adducts. Due to these high solubilities in organic solvents their 17O NMR spectra could be recorded in natural abundance, providing well-resolved signals for the P=O and O-O groups. In the case of Ahn adducts, the 17O NMR spectra allow for the full resolution of both signals for the C-O-O-H group. Reaction of bis(dicyclohexylphosphino)ethane dioxide with hydrogen peroxide leads to an extended crystalline network based on the formation of hydrogen bonds with the P=O groups of the diphosphine dioxide. The structural motif of the network is characterized by X-ray diffraction. A new selective synthesis for an industrially important MEKPO (methyl ethyl ketone peroxide) dimer is described. The dimer is created by reaction of dppe (bis(diphenylphosphino)ethane) dioxide with butanone and hydrogen peroxide. This peroxide is stabilized by forming strong hydrogen bonds to the phosphine oxide groups within an extended network. Competition experiments between Ahn adducts and their respective phosphine oxides allowed to rank the affinities of the di(hydroperoxy)cycloalkanes for the different phosphine oxide carriers. Based on variable temperature 31P NMR investigations the Gibbs energies of activation ?G? for the adduct dissociation processes at different temperatures, as well as the enthalpy ?H? and entropy ?S? of activation have been determined.