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

Abstract

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).