We present a quantum chemical investigation of benzofuran and cholorobenzofuran formation mechanisms during the combustion of 1,3-dichloropropene. Density functional theory and Gaussian-n thermochemical methods are used to propose detailed mechanistic reaction pathways. These calculations indicate that oxidation of phenylvinyl radical intermediates and subsequent ring closure are key mechanistic pathways in the formation of benzofuran and chlorobenzofuran. Thermochemical and kinetic parameters presented herein will assist in further elucidation of dioxin formation mechanisms from thermolyses of hydrocarbon moieties.