Reply to Eugene et al.: Photochemistry of aqueous pyruvic acid

Griffith, Elizabeth C.; Carpenter, Barry K.; Shoemaker, Richard K.; Vaida, Veronica

doi:10.1073/pnas.1316367110

Cited by 11 publications

(19 citation statements)

References 6 publications

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“…Several works have investigated PYA photochemistry in water under highly acidic conditions (pH = 1–2.5). ,− Absorption to the single excited state [ 1 S(n,π*)] is blue-shifted (λ max = 320 nm) with respect to gas phase . The excited singlet then undergoes ISC with the lowest-lying triplet excited state [ 3 T(n,π*)], which becomes the reactive species (see Figure ).…”

Section: Direct Photooxidation Of Organic Speciesmentioning

confidence: 99%

“…This triplet state can react with another PYA or PYT molecule in its ground electronic state through a mechanism that involves either the abstraction of the acidic hydrogen atom via proton-coupled electron transfer or a concerted hydrogen atom abstraction . This initiates a chain of reactions that cause decarboxylation, the formation of oligomers, dimethyltartaric acid, acetoin, acetic and lactic acids, and oxo-C8 and C7 products. ,,, However, controversy exists regarding the entire mechanism and the formation of several products. − As the pH increases, the gem -diol form diminishes, and the pyruvate concentration grows, resulting in an increase in absorption intensity and a moderate blue shift (λ max = 316 nm) . Another mechanism then becomes competitive: the triplet excited state of PYA abstracts one of the hydrogen atoms of the methyl group (instead of the acidic group) from the ground electronic state of another PYA molecule.…”

Section: Direct Photooxidation Of Organic Speciesmentioning

confidence: 99%

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Photoinduced Oxidation Reactions at the Air–Water Interface

et al. 2020

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Chemistry on water is a fascinating area of research. The surface of water and the interfaces between water and air or hydrophobic media represent asymmetric environments with unique properties that lead to unexpected solvation effects on chemical and photochemical processes. Indeed, the features of interfacial reactions differ, often drastically, from those of bulk-phase reactions. In this Perspective, we focus on photoinduced oxidation reactions, which have attracted enormous interest in recent years because of their implications in many areas of chemistry, including atmospheric and environmental chemistry, biology, electrochemistry, and solar energy conversion. We have chosen a few representative examples of photoinduced oxidation reactions to focus on in this Perspective. Although most of these examples are taken from the field of atmospheric chemistry, they were selected because of their broad relevance to other areas. First, we outline a series of processes whose photochemistry generates hydroxyl radicals. These OH precursors include reactive oxygen species, reactive nitrogen species, and sulfur dioxide. Second, we discuss processes involving the photooxidation of organic species, either directly or via photosensitization. The photochemistry of pyruvic acid and fatty acid, two examples that demonstrate the complexity and versatility of this kind of chemistry, is described. Finally, we discuss the physicochemical factors that can be invoked to explain the kinetics and thermodynamics of photoinduced oxidation reactions at aqueous interfaces and analyze a number of challenges that need to be addressed in future studies.

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Section: Direct Photooxidation Of Organic Speciesmentioning

confidence: 99%

Section: Direct Photooxidation Of Organic Speciesmentioning

confidence: 99%

Photoinduced Oxidation Reactions at the Air–Water Interface

et al. 2020

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“…For both sources, these results were consistent with previous studies, which have described the mechanisms of bulk aqueous PA in detail. [83][84][85]93,10492,94,99,102,113 While the observed products are the same for both light sources, the normalized ion intensities of the photoproducts are generally smaller in the LED photolysis than in the Xe lamp photolysis. The lower intensity of the photolysis source and the limited overlap between the LED output and PA absorbance spectrum results in a lower photolysis rate, but these factors do not seem to significantly alter the photoproducts observed and therefore the photochemical pathways of PA.…”

Section: ■ Introductionmentioning

confidence: 92%

“…The mechanisms of aqueous photochemistry of PA proceed through a different pathway than the gas-phase photolysis. − Briefly, diffuse UV radiation can excite a PA molecule to its S 1 state, which then undergoes intersystem crossing to the T 1 state and generates organic radicals, finally resulting in several complex oligomers depending on the specific reaction conditions. The effects of concentration, pH, and O 2 on the reaction mechanism, product yields, and array of products in aqueous phase have all been described. ,,,,− ,− Interpreted using the gas- and aqueous-phase photochemistry of pyruvic acid, the multiphase chemistry of PA has been studied, highlighting the formation of oligomers and consequently the construction of chemical complexity with sunlight . Results from a study of the multiphase chemistry of pyruvic acid indicated that the air–water interface plays a significant role in promoting chemistry not possible in either the gas or bulk aqueous phase .…”

Section: Introductionmentioning

confidence: 99%

Chemistry and Photochemistry of Pyruvic Acid at the Air–Water Interface

et al. 2021

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Interfacial regions are unique chemical reaction environments that can promote chemistry not found elsewhere. The air−water interface is ubiquitous in the natural environment in the form of ocean surfaces and aqueous atmospheric aerosols. Here we investigate the chemistry and photochemistry of pyruvic acid (PA), a common environmental species, at the air−water interface and compare it to its aqueous bulk chemistry using two different experimental setups: (1) a Langmuir−Blodgett trough, which models natural water surfaces and provides a direct comparison between the two reaction environments, and (2) an atmospheric simulation chamber (CESAM) to monitor the chemical processing of nebulized aqueous PA droplets. The results show that surface chemistry leads to substantial oligomer formation. The sequence begins with the condensation of lactic acid (LA), formed at the surface, with itself and with pyruvic acid, and LA + LA − H 2 O and LA + PA − H 2 O are prominent among the products in addition to a series of higher-molecular-weight oligomers of mixed units of PA and LA. In addition, we see zymonic acid at the surface. Actinic radiation enhances the production of the oligomers and produces additional surface-active molecules known from the established aqueous photochemical mechanisms. The presence and formation of complex organic molecules at the air−water interface from a simple precursor like PA in the natural environment is relevant to contemporary atmospheric science and is important in the context of prebiotic chemistry, where abiotic production of complex molecules is necessary for abiogenesis.

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“…Over the past decade, a debate has emerged over the chemical mechanism to explain the aqueous photolysis of pyruvic acid and its photoproducts. − The first steps of the mechanism are generally agreed upon: pyruvic acid absorbs a photon, undergoes intersystem crossing and internal conversion, and then initiates further chemistry from the T 1 surface. From here, the mechanisms in the literature diverge.…”

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confidence: 99%

Comment on “Reactivity of Ketyl and Acetyl Radicals from Direct Solar Actinic Photolysis of Aqueous Pyruvic Acid”

et al. 2017

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Over the past decade, a debate has emerged over the chemical mechanism to explain the aqueous photolysis of pyruvic acid and its photoproducts. 1 − 12 The first steps of the mechanism are generally agreed upon: pyruvic acid absorbs a photon, undergoes intersystem crossing and internal conversion , and then initiates further chemistry from the T1 surface. From here, the mechanisms in the literature diverge. In 2006, Guzmanét al. 6 suggested a ■ AUTHOR INFORMATION

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Reply to Eugene et al.: Photochemistry of aqueous pyruvic acid

Cited by 11 publications

References 6 publications

Photoinduced Oxidation Reactions at the Air–Water Interface

Photoinduced Oxidation Reactions at the Air–Water Interface

Chemistry and Photochemistry of Pyruvic Acid at the Air–Water Interface

Comment on “Reactivity of Ketyl and Acetyl Radicals from Direct Solar Actinic Photolysis of Aqueous Pyruvic Acid”

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