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272 results on '"Teruel, Mariano"'

41. Mechanistic study of the complex photooxidation of allyl methyl sulfide (AMS): reaction paths and products of addition under different atmospheric conditionsElectronic supplementary information (ESI) available: Optimized geometries and vibrational frequencies of species considered in the AMS oxidation initiated by OH radicals and thermochemistry tables. See DOI: https://doi.org/10.1039/d3ea00010a

Author

Cardona, Alejandro L., Blanco, María B., Teruel, Mariano A., and Ventura, Oscar N.

Abstract

The addition mechanism of the OH-initiated oxidation of allyl methyl sulfide (AMS) under atmospheric conditions was studied theoretically using both density functional theory (DFT) and the SVECV-f12 composite method. We found that the addition does not occur directly but rather through a pre-reactive complex that serves as a previous stage for addition at both the C1 and C2 positions. However, based on thermodynamics the addition at C2 possibly occurs by branching of the C1 addition mechanism. Once the addition proceeds, the reaction with O2under atmospheric conditions produces RO2radicals that can decompose in multiple ways. Complex mechanisms of intramolecular rearrangement and decomposition both in the absence and presence of NOxhave been examined. The thermodynamically most favourable decomposition paths produce 2-hydroxy-acetaldehyde, 2-methyl-thio-acetaldehyde, formaldehyde, and the methyl thiomethyl peroxy (MSP) intermediate. This latter species is proposed as the main source of sulfur dioxide (SO2), which is the product found in the highest yield during the experimental determinations.

Published
2023
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45. Degradation mechanism of 2-fluoropropene by Cl atoms: experimental and theoretical products distribution studies.

Author

Rivela, Cynthia B., L. Cardona, Alejandro, Blanco, María B., Barnes, Ian, Kieninger, Martina, Ventura, Oscar N., and Teruel, Mariano A.

Abstract

The gas-phase reaction products of 2-fluoropropene (2FP) with Cl atoms have been determined for the first time at 298 K and atmospheric pressure using a 1080 L quartz-glass photoreactor coupled with in situ FTIR spectroscopy to monitor reactants and products. Acetyl fluoride and formyl chloride were observed as the main products with yields of (106 ± 10)% and (100 ± 11)%, respectively. Electronic structure calculations of reactants, intermediates, products and transition states on a detailed mechanism of the reaction were performed by DFT procedures (BMK, M06, M062X/D3), as well as accurate composite methods on both the addition and abstraction reaction channels. From the joint experimental and theoretical studies, we concluded that the reaction occurs primarily via addition to the Cα carbon, with a smaller participation of the addition on the Cβ carbon, which is not produced directly from the separated reactants but from the CH3CFCH2Cl intermediate radical through a submerged transition state. The abstraction channel occurs at larger energies than the addition ones, and also presents a submerged transition state, with a lower barrier. No products arising from this channel are expected. The proposed mechanism explains also why formaldehyde, predicted as a product by former theoretical studies, is not found among the experimental products. The atmospheric implications of the reaction products are assessed. [ABSTRACT FROM AUTHOR]

Published
2022
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