04 Jul 2022
04 Jul 2022
Status: this preprint is currently under review for the journal ACP.

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

Caterina Mapelli1, Juliette V. Schleicher1,a, Alex Hawtin1, Conor D. Rankine1,2, Fiona C. Whiting1, Fergal Byrne1,5, Con Rob McElroy1, Claudiu Roman3,4, Cecilia Arsene3,4, Romeo I. Olariu3,4, Iustinian G. Bejan3,4, and Terry J. Dillon1 Caterina Mapelli et al.
  • 1Department of Chemistry, University of York, York, YO10 5DD, UK
  • 2Department of Chemistry, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK
  • 3Faculty of Chemistry, “Alexandru Ioan Cuza” University of Iasi, Iasi, 11th Carol I, 700506, Romania
  • 4Integrated Center of Environmental Science Studies in the North Eastern Region – CERNESIM, “Alexandru Ioan Cuza” University of Iasi, Iasi, 11th Carol I, 700506, Romania
  • 5Department of Chemistry, Maynooth University, Maynooth, Co. Kildare, W23 F2H6, Ireland
  • anow at: École Polytechnique Fédérale de Lausanne, 1015 Switzerland

Abstract. The atmospheric chemistry of 2,2,5,5-tetramethyloxolane (TMO), a promising ‘green’ solvent replacement for toluene, was investigated in laboratory and computational experiments. Results from both absolute and relative rate studies demonstrated that the reaction OH + TMO (R1) proceeds with a rate coefficient k1(296 K) = (3.1 ± 0.4) × 10−12 cm3 molecule−1 s−1, a factor of three smaller than predicted by recent structure activity relationships. Quantum chemical calculations (CBSQB3-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 prevent formation of such H-bonded complexes on the pathways to thermodynamically favoured products, a likely explanation for the anomalous slow rate of (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 ≈ 3 days was calculated for TMO, approximately 50 % longer than toluene, indicating that any air pollution impacts from TMO emission would be less localised. Relative rate experiments were used to determine a rate coefficient, k2(296 K) = (1.2 ± 0.1) × 10−10 cm3 molecule−1 s−1 for Cl + TMO (R2); together with the slow (R1) this may indicate an additional contribution to TMO removal in regions impacted by high levels of atmospheric chlorine. All results indicate that TMO is a less problematic volatile organic compound (VOC) than toluene.

Caterina Mapelli et al.

Status: open (until 15 Aug 2022)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2022-446', Anonymous Referee #1, 12 Jul 2022 reply
  • RC2: 'Comment on acp-2022-446', Anonymous Referee #2, 20 Jul 2022 reply

Caterina Mapelli et al.

Caterina Mapelli et al.


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Short summary
Solvents represent an important source of pollution from the chemical industry. New ‘green’ solvents aim to replace toxic solvents with new molecules made from renewable sources and designed to be less harmful. Whilst these new molecules are selected according to toxicity and other characteristics, no consideration has yet been included on air quality. Studying the solvent breakdown in air, we found that TMO has a lower impact on air quality than traditional solvents with similar properties.