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Abstract The mechanism of isomerization of hydroxyacetone to 2‐hydroxypropanal is studied within the framework of reaction force analysis at the M06‐2X/6‐311++G(d,p) level of theory. Three unique pathways are considered: (a) a step‐wise mechanism that proceeds through the formation of the Z‐isomer of their shared enediol intermediate, (b) a step‐wise mechanism that forms the E‐isomer of the enediol, and (c) a concerted pathway that bypasses the enediol intermediate. Energy calculations show that the concerted pathway has the lowest activation energy barrier at 45.7 kcal mol−1. The reaction force, chemical potential, and reaction electronic flux are calculated for each reaction to characterize electronic changes throughout the mechanism. The reaction force constant is calculated in order to investigate the synchronous/asynchronous nature of the concerted intramolecular proton transfers involved. Additional characterization of synchronicity is provided by calculating the bond fragility spectrum for each mechanism.
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This content will become publicly available on January 22, 2026
A theoretical study on the environmental oxidation of fenpyrazamine fungicide initiated by hydroxyl radicals in the aqueous phase
Fenpyrazamine (FPA) is a widely used fungicide in agriculture to control fungal diseases, but its environmental degradation by oxidants and the formation of potential degradation products remain unexplored. This study investigates the oxidation of FPA by hydroxyl radicals (HO˙) using density functional theory (DFT) calculations at the M06-2X/6-311++G(3df,3pd)//M06-2X/6-31+G(d,p) level of theory. Three standard oxidation mechanisms, including formal hydrogen transfer (FHT), radical adduct formation (RAF), and single electron transfer (SET), were evaluated in the aqueous phase, with reaction kinetics analyzed over a temperature range of 283–333 K. As a result, the reactivity order of the mechanisms was determined to be RAF > FHT > SET. At 298 K, the calculated total rate constants for FHT and RAF reactions were competitive, being 6.09 × 109 and 8.21 × 109 M−1 s−1, respectively, while that for SET was slightly lower at 2.35 × 109 M−1 s−1. The overall rate constant was estimated to be 1.67 × 1010 M−1 s−1. The most favourable RAF reaction occurred at the C38[double bond, length as m-dash]C39 double bond, while the predominant FHT reactions involved the H15 and H13 hydrogen atoms of the methyl C8 group. The lifetime of FPA in natural water with respect to HO˙ oxidation was predicted to range from 10.84 hours to 2.62 years, depending on environmental conditions. Furthermore, the toxicity assessments revealed that while FPA is neither bioaccumulative nor mutagenic, it poses developmental toxicity and is harmful to aquatic organisms, including fish, daphnia, and green algae.
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- Award ID(s):
- 2045025
- PAR ID:
- 10596749
- Publisher / Repository:
- Royal Society of Chemistry
- Date Published:
- Journal Name:
- Environmental Science: Processes & Impacts
- Volume:
- 27
- Issue:
- 1
- ISSN:
- 2050-7887
- Page Range / eLocation ID:
- 211 to 224
- Subject(s) / Keyword(s):
- fenpyrazamine oxidation fungicide
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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