Radicals in the bulk liquid can originate via inter-tray convective flow, vapor-liquid mass transfer, or they can be generated via chain initiation reactions, as shown in Fig. . The relative significance of these sources varies with location within the distillation column. In hotter regions with low dissolved oxygen concentrations, such as the reboiler and trays near it, the dominant source of radicals remains consistent with the base case scenario studied in our previous work: 6 reverse disproportionation reactions between species with loosely bonded hydrogens (allylic hydrogens and bisallylic hydrogens) and conjugated dienes produce allylic radicals and bisallylic radicals, maintaining a relatively high radical concentration, as shown in Fig. (a) and (d). Many of these radicals have low molecular weight, and the elevated temperature in the reboiler facilitates their evaporation. They are carried upward by the convective flow of vapor to the condenser, where the temperature is low enough that they condense back into the liquid.