Atmospheric oxidation of furanones by ^•OH and ^•Cl radicals: In situ FTIR rate coefficient determinations, SAR and theoretical studies

Gas-phase kinetics of the overall reactions of ^•OH and ^•Cl radicals with dihydrofuran-3(2H)-one (oxolan-3-one) and dihydro-2-methyl-3(2H)-furanone (2MTHF-3-one) were studied at 298 K and atmospheric pressure. The rate coefficients were determined using the relative method in a 480 L multipass glass reactor coupled to an FT-IR detection system. The rate coefficients found for oxolan 3-one and 2MTHF-one with ^•OH radicals (k₁ and k₂) and with ^•Cl atoms (k₃ and k₄) at 298 K and atmospheric pressure (in cm³ molecule^-1 s^-1) were: k₁ = (1.86 ± 0.29) × 10^-11, k₂ = (2.64 ± 0.47) × 10^-11, k₃= (1.15 ± 0.28) × 10 ^-10, and k₄ = (1.33 ± 0.32) × 10^-10, respectively. Reactivity trends were developed by comparison with other similar structures and Fukui indices employed to determine the reactivity of different sites on the ring. The singularity of the reaction with ^•OH was assessed by computational studies which showed the formation of several stable hydrogen bonded complexes, explaining the difference with the reaction with the ^•Cl atom. SAR estimations of the rate coefficients were calculated and compared to the experimental values.