Experimental evidence that halogen bonding catalyzes the heterogeneous chlorination of alkenes in submicron liquid droplets

Abstract

A key challenge in predicting the multiphase chemistry of aerosols and droplets is connecting reaction probabilities, observed in an experiment, with the kinetics of individual elementary steps that control the...

Catalytic Coupling of Free Radical Oxidation and Electrophilic Chlorine Addition by Phase-Transfer Intermediates in Liquid Aerosols

“…For example, although 2-decyl-1-tetradecanol (C 24 OH, C 24 H 50 O, a branched alcohol) did not alter the distribution of reaction products, its presence inside the aerosol accelerated (up to ∼20×) the electrophilic addition of Cl 2 to the alkene, as shown in Figure S1 in the Supporting Information. Prior literature on the surface partitioning of oxygenated molecules in organic solvents and additional experimental evidence presented in ref suggest that the presence of oxygenates enhances the aerosol capture of Cl 2 gas, likely by prolonging its lifetime at the gas–aerosol interface. This in turn promoted faster solvation and electrophilic Cl 2 addition to the alkene.…”

“…To our knowledge, this is a unique example of a gl-PTC operating at room temperature. This builds upon our previous work where we focused solely on how the Cl 2 heterogeneous addition rate is altered by the presence of molecules doped into alkene droplets.…”

“…Although further theoretical support is needed, we hypothesized that weak interfacial halogen-bonds between adsorbed Cl 2 and the oxygenated additives were responsible for the enhanced capture of Cl 2 by the aerosols. These previous observations motivated us to explore, using aerosols, the coupling of free radical oxidation with electrophilic addition, because free radical oxidation produces many of the same kinds of oxygenated reaction products (i.e., ketones and alcohols) that we previously found to be effective gl-PTCs for the electrophilic Cl 2 addition to olefins.…”

“…Previously, we showed that the rate of heterogeneous addition of gas-phase Cl 2 to liquid squalene (Sqe, C 30 H 50 , a branched alkene), in submicron aerosol particles, could be catalytically enhanced by the addition of oxygenated molecules to the liquid or gas phases . For example, although 2-decyl-1-tetradecanol (C 24 OH, C 24 H 50 O, a branched alcohol) did not alter the distribution of reaction products, its presence inside the aerosol accelerated (up to ∼20×) the electrophilic addition of Cl 2 to the alkene, as shown in Figure S1 in the Supporting Information.…”

A Kinetic Model for Predicting Trace Gas Uptake and Reaction

“…The framework on which these derivations are based was recently implemented 48 in a stochastic reaction-diffusion simulation to explain the multiphase reaction rate of O3 with aqueous droplets containing aconitic acid, 48 maleic acid 49 and nitrite. 50 The framework expresses the Henry's law constant as a product of two equilibria 17,21,26,51 and explicitly includes diffusion and the coupling of surface and bulk processes, which are neglected in resistor-type models. This paper is organized as follows.…”