The simplest Criegee intermediate CH₂OO reaction with dimethylamine and trimethylamine: kinetics and atmospheric...

We have used the OH laser-induced fluorescence (LIF) method to measure the kinetics of the simplest Criegee intermediate (CH₂OO) reacting with two abundant amines in the atmosphere: dimethylamine ((CH₃)₂NH) and trimethylamine ((CH₃)₃N). Our experiments were conducted under pseudo-first-order approximation conditions. The rate coefficients we report are (2.15 ± 0.28) × 10^-11 cm³ molecule^-1 s^-1 for (CH₃)₂NH at 298 K and 10 Torr, and (1.56 ± 0.23) × 10^-12 cm³ molecule^-1 s^-1 for (CH₃)₃N at 298 K and 25 Torr with Ar as the bath gas. Both reactions exhibit a negative temperature dependence. The activation energy and pre-exponential factors derived from the Arrhenius equation were (-2.03 ± 0.26) kcal mol^-1 and (6.89 ± 0.90) × 10^-13 cm³ molecule^-1 s^-1 for (CH₃)₂NH, and (-1.60 ± 0.24) kcal mol^-1 and (1.06 ± 0.16) × 10^-13 cm³ molecule^-1 s^-1 for (CH₃)₃N. We propose that the electronegativity of the atom in the co-reactant attached to the C atom of CH₂OO, in addition to the dissociation energy of the fragile covalent bonds with H atoms (H-X bond), plays an important role in the 1,2-insertion reactions. Under certain circumstances, the title reactions can contribute to the sink of amines and Criegee intermediates and to the formation of secondary organic aerosol (SOA).