Temperature dependence of the reaction of anti-CH₃CHOO with water vapor

Abstract

The kinetics of the reaction of anti-CHCHOO with water vapor were investigated using transient UV absorption spectroscopy at temperatures from 288 to 328 K and 500 Torr. We found that both the water monomer and the water dimer react with anti-CHCHOO. The rate coefficients of the reaction of the water monomer and dimer with anti-CHCHOO at 298 K were determined to be (1.31 ± 0.26) × 10 cm s and (4.40 ± 0.29) × 10 cm s, respectively. Furthermore, for the water dimer reaction, we observed very large negative temperature dependence with an activation energy of -12.17 ± 0.66 kcal mol. On the other hand, the monomer reaction showed minimal temperature dependence with nearly zero activation energy. At atmospherically relevant humidity, in opposition to previous experiments conducted for CHOO in which water dimer reaction predominates at room temperature, for anti-CHCHOO, the water monomer reaction can contribute significantly (∼30% of the reaction with water vapor at relative humidity RH = 40% and 298 K). These results show that substitution of an alkyl group can greatly affect the reaction of Criegee intermediates with water vapor, especially changing the contributions of water monomer and dimer reactions.

Unimolecular decomposition rates of a methyl-substituted Criegee intermediate syn-CH3CHOO

“…22,23 Removing the contribution of anti-CH 3 CHOO Fig. 1 20 we may separate their signals by tting the time traces with two exponential functions (eqn (1)).…”

“…In this work, we used water vapor to scavenge anti-CH 3 -CHOO 20 and directly monitored the kinetics of syn-CH 3 CHOO via its strong UV absorption in real time. 21 The unimolecular rates were determined at atmospherically relevant temperatures and pressures.…”

“…Creative Commons Attribution 3.0 Unported Licence.that of anti-CH 3 CHOO 12,13,20,25. More kinetic investigation on the reaction of syn-CH 3 CHOO with H 2 O will be discussed later in this paper.Effect of bimolecular reactions of syn-CH 3 CHOO with radical byproductsFig.…”

The atmospheric impacts of monoterpene ozonolysis on global stabilised Criegee intermediate budgets and SO<sub>2</sub> oxidation: experiment, theory and modelling

“…To date, the effects of the water dimer, (H 2 O) 2 on SCI removal have only been determined experimentally for CH 2 OO (Berndt et al, 2014;Chao et al, 2015;Lewis et al, 2015;Newland et al, 2015a;Sheps et al, 2017;Liu et al, 2017) and anti-CH 3 CHOO (Lin et al, 2016b). Theoretical calculations have predicted the ratio of the SCI + (H 2 O) 2 : SCI + H 2 O rate constants, k 5 /k 3 , of larger and more substituted SCI to be of a similar order of magnitude as for CH 2 OO (i.e.…”

Implementation of a chemical background method for atmospheric OH measurements by laser-induced fluorescence: characterisation and observations from the UK and China

“…CC BY 4.0 License. 10 −14 cm 3 molecule −1 s −1 for anti-CH3CHOO (Taatjes et al, 2013;Sheps et al, 2014;Lin et al, 2016)), respectively. Reaction with the water vapour monomer was also shown to be relatively fast (k ~ 1.2 × 10 −15 cm 3 molecule −1 s −1 , kloss ~ 300 s −1 at ~1% H2O) for the ensemble of SCIs, including the C1 SCI, generated 470 from isoprene ozonolysis (Newland et al, 2015).…”