Hydrogen peroxide and di(hydroperoxy)alkane adducts of phosphine oxides, Hilliard adducts (R3PO●H2O2)2, and Ahn adducts R3PO●(HOO)2CR2, are safe and solid materials. They can easily be synthesized selectively, are very efficient oxidizers, highly soluble in organic solvents, and they have long shelf lives. The stoichiometric composition of the bulk materials can be easily confirmed by 31P NMR titration with Ph3P. The structures of the adducts are known from single crystal X-ray analyses. They assume consistently a chair-type conformation for Hilliard adducts, and a twist boat for Ahn adducts. However, the dimeric nature of the Hilliard adducts, for example, might not persist in solution, since the hydrogen bonds between the P=O groups and the two H2O2 molecules in their core might not persist in the presence of a solvent. Therefore, 31P DOSY NMR experiments were performed on a variety of adducts to determine the integrity of the hydrogen-bonded assemblies in different solvents. The majority of Hilliard adducts have Stokes diameters in solution that are consistent with the monomeric species R3PO●H2O2. Due to the high solubilities of Hilliard and Ahn adducts, natural abundance 17O NMR spectra could be recorded. The spectra provide well-resolved signals for all different 17O nuclei in P=O, H2O2, and (HOO)2CR2 groups. IR and 31P NMR spectroscopy indicate hydrogen bonding in the solid state and in solution. The Raman bands ν(O-O) confirm the presence of intact peroxide groups and their hydrogen bonding. In combination with other analytics, these results suggest that Hilliard adducts are dimeric in the crystal lattice, but with one exception they are monomeric in most solvents. Surprisingly, the Ahn adducts are much more capricious, as will be discussed in this presentation.

Structure elucidation of peroxide adducts in solution and in the solid state

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.