Accelerated Chlorination at the Surface of Organic Aerosol

An interface is a distinct chemical environment where reactivity can proceed differently than the bulk. Although organic interfaces are ubiquitous in nature, they have received comparably less attention than their aqueous counterparts. Here we examine the uptake dynamics of chlorine gas at the air/squalene interface to better interpret the anomalous reaction kinetics observed in previous aerosol experiments. Utilizing molecular dynamics simulations and coarse-grained kinetic models, we find evidence that chlorine addition to squalene carbon double bonds at the interface occurs over an order of magnitude faster than in the bulk. This acceleration is due to enhanced probability and frequency of encounter between a chlorine molecule and a double bond at the air-oil interface.