Lawrence Berkeley National Laboratory
Changes in Reactivity as Chemistry Becomes Confined to an Interface. the Case of Free Radical Oxidation of C30H62Alkane by OH
- Author(s): Houle, FA
- Wiegel, AA
- Wilson, KR
- et al.
Published Web Locationhttps://doi.org/10.1021/acs.jpclett.8b00172
© 2018 American Chemical Society. We examine in a simple organic aerosol the transition between heterogeneous chemistry under well-mixed conditions to chemistry under interfacial confinement. A single reaction mechanism, shown to reproduce observed OH oxidation chemistry for liquid and semisolid C30H62, is used in reaction-diffusion simulations to explore reactivity over a broad viscosity range. The results show that when internal mixing of the aerosol is fast and the particle interface is enriched in C-H groups, ketone and alcohol products, formed via peroxy radical disproportionation, predominate. As viscosity increases the reactions become confined to a shell at the gas-aerosol interface. The confinement is accompanied by emergence of acyloxy reaction pathways that are particularly active when the shell is 1 nm or less. We quantify this trend using a reaction-diffusion index, allowing the parts of the mechanism that control reactivity as viscosity increases to be identified.