Wetmore, Stacey

Permanent URI for this collection

https://opus.uleth.ca/handle/10133/4547

Browse

Browsing Wetmore, Stacey by Author "Stuart, Daniel"

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Solid-state structure of a protonated ketones and aldehydes
    (Wiley, 2017) Stuart, Daniel; Wetmore, Stacey D.; Gerken, Michael
    Protonated carbonyl compounds have been invoked as intermediates in many acid-catalyzed organic reactions. To gain key structural and electronic data about such intermediates, oxonium salts derived from five representative examples of ketones and aldehydes are synthesized in the solid state, and characterized by X-ray crystallography and Raman spectroscopy for the first time. DFT calculations were carried out on the cations in the gas phase. Whereas an equimolar reaction of the carbonyl compounds, acetone, cyclopentanone, adamantanone, and acetaldehyde, with SbF5 in anhydrous HF yielded mononuclear oxonium cations, the same stoichiometry in a reaction with benzaldehyde resulted in formation of a hemiprotonated, hydrogen-bridged dimeric cation. Hemiprotonated acetaldehyde was obtained when a 2:1 ratio of aldehyde and SbF5 was used. Experimental and NBO analyses quantify the significant increase in electrophilicity of the oxonium cations compared to that of the parent ketones/aldehydes.
  • Thumbnail Image
    Item
    Syntheses, characterization, and computational study of AsF5 adducts with ketones
    (Elsevier, 2019) Stuart, Daniel; Wetmore, Stacey D.; Gerken, Michael
    Lewis acid-base adducts between AsF5 and the ketones, acetone, cyclopentanone, and adamantanone, were synthesized from SO2 and CH2Cl2 solutions. These adducts, which contain O---As pnictogen bonding interactions, were found to be stable in solutions at room temperature. Raman and NMR spectroscopy of the solid adducts showed a characteristic decrease in the C=O stretching frequency, as well as dramatic deshielding of the 13C resonance of the carbonyl group upon adduct formation. Fluorine-19 NMR spectroscopy showed the two fluorine environments of the O–AsF5 moiety. Optimization of the gas-phase geometry using DFT calculations yielded geometries with essentially planar CC=OAs moieties. NBO analyses of the adducts and the free ketones show the polarization of the C=O bond upon adduct formation. The lowering of the LUMO energies upon adduct formation is more dramatic than what was found for protonation of ketones and reflects the substantially enhanced electrophilicity of the adducted ketones.