Atmospheric breakdown chemistry of the new "green" solvent 2,2,5,5-tetramethyloxolane via gas-phase reactions with OH and Cl radicals

Caterina Mapelli, Juliette V. Schleicher, Alex Hawtin, Conor D. Rankine, Fiona C. Whiting, Fergal Byrne, C. Rob Mcelroy, Claudiu Roman, Cecilia Arsene, Romeo I. Olariu, Iustinian G. Bejan, Terry J. Dillon*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

The atmospheric chemistry of 2,2,5,5-tetramethyloxolane (TMO), a promising "green"solvent replacement for toluene, was investigated in laboratory-based experiments and computational calculations. Results from both absolute and relative rate studies demonstrated that the reaction OH + TMO (Reaction R1) proceeds with a rate coefficient k1(296 K) = (3.1±0.4) ×10-12 cm3 molecule-1 s-1, a factor of 3 smaller than predicted by recent structure-activity relationships. Quantum chemical calculations (CBS-QB3 and G4) demonstrated that the reaction pathway via the lowest-energy transition state was characterised by a hydrogen-bonded pre-reaction complex, leading to thermodynamically less favoured products. Steric hindrance from the four methyl substituents in TMO prevents formation of such H-bonded complexes on the pathways to thermodynamically favoured products, a likely explanation for the anomalous slow rate of Reaction (R1). Further evidence for a complex mechanism was provided by k1(294-502 K), characterised by a local minimum at around T=340 K. An estimated atmospheric lifetime of τ1 ≈3 d was calculated for TMO, approximately 50 % longer than toluene, indicating that any air pollution impacts from TMO emission would be less localised. An estimated photochemical ozone creation potential (POCPE) of 18 was calculated for TMO in north-western Europe conditions, less than half the equivalent value for toluene. Relative rate experiments were used to determine a rate coefficient of k2(296 K) = (1.2±0.1) ×10-10 cm3 molecule-1 s-1 for Cl + TMO (Reaction R2); together with Reaction (R1), which is slow, this may indicate an additional contribution to TMO removal in regions impacted by high levels of atmospheric chlorine. All results from this work indicate that TMO is a less problematic volatile organic compound (VOC) than toluene.

Original languageEnglish
Pages (from-to)14589-14602
JournalAtmospheric Chemistry and Physics
Volume22
Issue number22
DOIs
Publication statusPublished - 17 Nov 2022

Bibliographical note

Funding Information:
This work has received funding from the European Union’s Horizon 2020 Research and Innovation programme through the EUROCHAMP-2020 Infrastructure Activity (grant no. 730997) and the UK Engineering and Physical Sciences Research Council (grant no. EP/M508196/1). Claudiu Roman, Cecilia Arsene, Romeo I. Olariu, and Iustinian G. Bejan acknowledge support from the PN-III-P4-PCE2021-0673 60 UEFISCDI project. Juliette V. Schleicher acknowledges support from the EU ERASMUS programme. Caterina Mapelli and Fiona C. Whiting thank the Department of Chemistry at York for their PhD scholarships.

Funding Information:
This work has received funding from the European Union's Horizon 2020 Research and Innovation programme through the EUROCHAMP-2020 Infrastructure Activity (grant no. 730997) and the UK Engineering and Physical Sciences Research Council (grant no. EP/M508196/1). Claudiu Roman, Cecilia Arsene, Romeo I. Olariu, and Iustinian G. Bejan acknowledge support from the PN-III-P4-PCE2021-0673 60 UEFISCDI project. Juliette V. Schleicher acknowledges support from the EU ERASMUS programme. Caterina Mapelli and Fiona C. Whiting thank the Department of Chemistry at York for their PhD scholarships.

Publisher Copyright:
© Author(s) 2022

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