Infrared Spectroscopic Study of the Mechanism of Reaction of Zinc Acetylacetonate with Ozone Using Matrix Isolation and Theoretical Calculations

The reaction of zinc acetylacetonate, Zn(C5H7O2)2, with O3 is reported using matrix isolation, infrared spectroscopy, and theoretical calculations to identify reaction products and provide inferences about the reaction mechanism. A new "flow over" deposition technique is also reported that was used along with twin-jet and merged-jet deposition to explore this reaction under different conditions. Oxygen isotopic labeling with 18O was used to help confirm product identities. The primary observed reaction products include methyl glyoxal, formic acetic anhydride, acetyl hydroperoxide, and acetic acid. Additional weak products, including formaldehyde, were formed as well. The reaction appears to occur through the initial formation of a zinc-bound primary ozonide that can release methyl glyoxal and acetic acid or rearrange to a zinc-bound secondary ozonide, followed by product release of formic acetic anhydride and acetic acid or acetyl hydroperoxide from the zinc-bound species.