Looking at the Bigger Picture: Photoproducts of Pyruvic Acid

Abstract:

Pyruvic Acid (PA), CH₃C(O)COOH, is the prototypical alpha-keto carboxylic acid. It is present in the troposphere in urban areas, above forests, and in marine environments. Previous research has examined the long-time photochemical products resulting from photodissociation and subsequent chemical reactions. We have used the complementary methods of velocity-map imaging and multiplexed photoionization mass spectrometry to gain a broad understanding of the primary dissociation events following photoexcitation at 193 and 351 nm. Using these two techniques we observe the major products of PA photodissociation, including CO₂, CO, H, OH, HCO, CH₂CO, CH₃CO, and CH₃, and place constraints on the photodissociation dynamics. In addition, we have observed production of three isomers of C₂H₄O, namely acetaldehyde, vinyl alcohol, and the proposed, but never-before observed methylhydroxy carbene. Using multivariate analysis we provide a description of the photoinitiated chemistry of PA with necessary simplifications caused by the complexity of the dissociation. These experiments offer the first comprehensive description of the dissociation pathways of PA excited to the S₃ state (following 193 nm excitation) and the S₂ state (351 nm).

This research used resources of the Advanced Light Source, which is a DOE Office of Science User Facility under contract no. DE-ACO2-05CH11231. HR gratefully acknowledges support by the U.S. Department of Energy, Basic Energy Sciences, Grant No. DE-FG02-05ER15629. This material is based upon work supported by the Division of Chemical Sciences, Geosciences and Biosciences, Office of Basic Energy Sciences (BES), US Department of Energy (USDOE). Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International, Inc., for the USDOE’s National Nuclear Security Administration under contract DE-NA0003525. This work describes objective technical results and analysis. Any subjective views or opinions that might be expressed do not necessarily represent the views of the USDOE or the US Government.