Controlling the action of chlorine radical: from lab to environment

The strength of Bz-Cl-center dot complexation has been explored using density functional theory (DFT) calculations, including dispersion-corrected (DFT-D) calculations. Of the methods tested, the omega B97X-D method seems the best performing, along with the previously tested MPW1K method. The effect of substituent (X = NO2, F, Cl, Br, H, CH3, OCH3, OH, NH2 and N(CH3)(2)) on the stabilities of the Ar-Cl-center dot p-like intermediates show a good correlation with the linear free energy relationships used experimentally, but this is not the case for Ar-Cl-center dot sigma-complexes, suggesting the transition state of abstraction as being pi-like in nature. The role of PAH and lignin derivatives in mediating chlorination reactions in nature is explored. Stable pi-complexes were identified for lignin derivatives, indicating humic substances may mediate chlorine atom reactivity at the marine boundary layer, in addition to forming chlorolignins.