Issue 41, 2022

Role of hydrogen bonding in bulk aqueous phase decomposition, complexation, and covalent hydration of pyruvic acid

Abstract

Pyruvic acid (PA) is a model for amphiphilic oxygenated organic compounds, and together with its hydrogen-bonded (H-bonded) water complexes, their presence can alter atmospheric aerosol formation. However, the fundamental understanding of PA reaction mechanisms in different environments is still being debated. Here, the role of H-bonding on PA's degradation, complexation, and covalent hydration in bulk aqueous phase is investigated theoretically. Using CCSD(T)-F12/aug-cc-pVDZ-F12 on B2PLYP-D3BJ structures with solvation model based on density, we revealed the stabilization by intramolecular H-bonding of an intermediate, PA hydrogen-transferred tautomer, altered the PA degradation mechanisms compared to gas phase. We also found that the intramolecular H-bonding in the most stable gas phase conformer (Tc) is weakened due to bulk solvation, leading to slower acetaldehyde production rate. Natural bond orbital analysis characterized the primary intermolecular H-bond in PA–water complexes as electron donation of an Owater lone pair (p) to the σ* orbital of the OH group of PA. Stronger H-bonding is correlated to p to σ* interaction, wider OH–O angles, and larger differences in the H-bond lengths between phases. The less charge difference between phases on H-bonded atoms also indicates aggressive competition of H-bonding with solvation. Water's cooperative behavior was observed by lowering the water-complexed 2,2-dihydroxypropanoic acid (DHPA–H2O) barrier from PA–water complexes compared to DHPA in both phases, stabilizing the transition state and product with intermolecular H-bonding. PA is vital in atmospheric keto-acid chemistry; thus, changes in PA reaction mechanisms in different environments due to H-bond behavior will affect aerosol formation.

Graphical abstract: Role of hydrogen bonding in bulk aqueous phase decomposition, complexation, and covalent hydration of pyruvic acid

Supplementary files

Article information

Article type
Paper
Submitted
03 Aug 2022
Accepted
05 Oct 2022
First published
06 Oct 2022

Phys. Chem. Chem. Phys., 2022,24, 25151-25170

Role of hydrogen bonding in bulk aqueous phase decomposition, complexation, and covalent hydration of pyruvic acid

M. D. P. Barquilla and M. L. Mayes, Phys. Chem. Chem. Phys., 2022, 24, 25151 DOI: 10.1039/D2CP03579K

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