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

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