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Kakati UP, Dowerah D, Deka RC, Gour NK, Paul S. Oxidation pathways and kinetics of the 1,1,2,3-tetrafluoropropene (CF 2CF-CH 2F) reaction with Cl-atoms and subsequent aerial degradation of its product radicals in the presence of NO. ENVIRONMENTAL SCIENCE. PROCESSES & IMPACTS 2024; 26:734-750. [PMID: 38426396 DOI: 10.1039/d3em00545c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/02/2024]
Abstract
To give a comprehensive account of the environmental acceptability of 1,1,2,3-tetrafluoropropene (CF2CF-CH2F) in the troposphere, we have examined the oxidation reaction pathways and kinetics of CF2CF-CH2F initiated by Cl-atoms using the second-order Møller-Plesset perturbation (MP2) theory along with the 6-31+G(d,p) basis set. We also performed single-point energy calculations to further refine the energies at the CCSD(T) level along with the basis sets 6-31+G(d,p) and 6-311++G(d,p). The estimation of the relative energies and thermodynamic parameters of the CF2CF-CH2F + Cl reaction clearly shows that Cl-atom addition reaction pathways are more dominant compared to H-abstraction reaction pathways. The value of the rate coefficient for each reaction channel is calculated using the conventional transition state theory (TST) over the temperature range of 200-1000 K at 1 atm. The estimated overall rate coefficients for the title reaction are found to be 1.10 × 10-12, 1.21 × 10-10, and 1.13 × 10-8 cm3 per molecule per s via the respective calculation methods viz. MP2/6-31+G(d,p), CCSD(T)//MP2/6-31+G(d,p), and CCSD(T)/6-311++G(d,p)//MP2/6-31+G(d,p), at 298.15 K. Moreover, the calculated rate coefficients and percentage branching ratio values suggest that the Cl-atom addition reaction at the β-carbon atom is more preferable to that of the α-carbon addition to CF2CF-CH2F. Based on the rate coefficient values calculated by the three different methods, the atmospheric lifetime for the title reaction at 298.15 K is estimated. The radiative efficiency (RE) and Global Warming Potential (GWP) results of the title molecule show that its GWP would be negligible. Further, we have explored the degradation of its product radicals in the presence of O2 and NO. From the degradation results, we have found that CF2(Cl)COF, FCOCH2F, FCFO and FCOCl are formed as stable end products along with various radicals such as ˙CF2Cl and ˙CH2F. Therefore, these findings of kinetic and mechanistic data can be applied to the development and implementation of a novel CFC replacement.
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Affiliation(s)
| | - Dikshita Dowerah
- Department of Chemical Sciences, Tezpur University, Tezpur-784028, Assam, India.
| | - Ramesh Chandra Deka
- Department of Chemical Sciences, Tezpur University, Tezpur-784028, Assam, India.
| | - Nand Kishor Gour
- Department of Chemical Sciences, Tezpur University, Tezpur-784028, Assam, India.
| | - Subrata Paul
- Department of Chemistry, Assam University, Silchar-788011, Assam, India
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Manonmani G, Sandhiya L, Senthilkumar K. A Computational Perspective on the Chemical Reaction of HFO-1234zc with the OH Radical in the Gas Phase and in the Presence of Mineral Dust. J Phys Chem A 2022; 126:9564-9576. [PMID: 36534504 DOI: 10.1021/acs.jpca.2c03229] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The gas phase and heterogeneous reaction on mineral dust aerosols of trace gases could significantly affect the tropospheric oxidation capacity and aerosol composition of the atmosphere. In this work, the OH radical-initiated oxidation of a hydrofluoroolefin, HFO-1234zc, and subsequent reaction of favorable intermediates with other reactive species, such as O2, HO2, and NOx (x = 1-2) radicals, were studied, and the role of mineral dust in the form of silicate clusters on the reaction mechanism and rate constant was studied. In the gas phase, OH radical addition to HFO-1234zc is kinetically more favorable than the H-atom abstraction reaction. The calculated reaction energy barrier and thermochemical parameters show that both the initial reactions are more feasible on silicate clusters. Thus, silicates can act as chemical sinks for trapping of hydrofluoroolefins (HFOs). It is found that both gas-phase and heterogeneous reactions are responsible for the transformation of HFOs into fluorinated compounds in the atmosphere. Further, the results show that the ozone creation potential of HFO-1234zc is low, and few of the products are harmful to aquatic organisms. This study provides new insights on the formation of toxic pollutants from the oxidation of HFO-1234zc, which may have significant implications in the troposphere.
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Affiliation(s)
- G Manonmani
- Department of Physics, Bharathiar University, Coimbatore641 046, India
| | - L Sandhiya
- CSIR-National Institute of Science Communication and Policy Research, New Delhi110012, India
| | - K Senthilkumar
- Department of Physics, Bharathiar University, Coimbatore641 046, India
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Rivela CB, L Cardona A, Blanco MB, Barnes I, Kieninger M, Ventura ON, Teruel MA. Degradation mechanism of 2-fluoropropene by Cl atoms: experimental and theoretical products distribution studies. Phys Chem Chem Phys 2022; 24:5094-5108. [PMID: 35147616 DOI: 10.1039/d1cp03214c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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.
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Affiliation(s)
- Cynthia B Rivela
- Laboratorio Universitario de Química y Contaminación del Aire (L.U.Q.C.A.), Instituto de Investigaciones en Fisicoquímica de Córdoba (I.N.F.I.Q.C.), CONICET, Dpto. de Fisicoquímica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Ciudad Universitaria, 5000 Córdoba, Argentina.
| | - Alejandro L Cardona
- Laboratorio Universitario de Química y Contaminación del Aire (L.U.Q.C.A.), Instituto de Investigaciones en Fisicoquímica de Córdoba (I.N.F.I.Q.C.), CONICET, Dpto. de Fisicoquímica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Ciudad Universitaria, 5000 Córdoba, Argentina.
| | - María B Blanco
- Laboratorio Universitario de Química y Contaminación del Aire (L.U.Q.C.A.), Instituto de Investigaciones en Fisicoquímica de Córdoba (I.N.F.I.Q.C.), CONICET, Dpto. de Fisicoquímica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Ciudad Universitaria, 5000 Córdoba, Argentina.
| | - Ian Barnes
- Physikalische Chemie/FBC, Bergische Universitaet Wuppertal, Wuppertal, Germany
| | - Martina Kieninger
- CCBG-Detema, Facultad de Química, Universidad de la República, 11200 Montevideo, Uruguay.
| | - Oscar N Ventura
- CCBG-Detema, Facultad de Química, Universidad de la República, 11200 Montevideo, Uruguay.
| | - Mariano A Teruel
- Laboratorio Universitario de Química y Contaminación del Aire (L.U.Q.C.A.), Instituto de Investigaciones en Fisicoquímica de Córdoba (I.N.F.I.Q.C.), CONICET, Dpto. de Fisicoquímica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Ciudad Universitaria, 5000 Córdoba, Argentina.
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