A combination of DFT calculations and kinetic models is applied to fully elucidate the seemingly complex reactivity of α-cyano arylacetates toward metal-free photoinitiated aromatic perfluoroalkylation. The resulting mechanistic framework rationalizes the observed quantum yield as well as the differences in reactivity and/or selectivity of seemingly similar substrates. The use of a kinetic model for the chemical interpretation of the DFT-computed reaction constants is shown to be critical.