What defines a termination step in a radical substitution reaction?

In a radical substitution reaction, the termination step is characterized by the meeting of two radicals, which results in the formation of a stable covalent bond. This step marks the end of the radical chain reaction because it reduces the number of reactive radicals in the system. When two radicals combine, they effectively deactivate themselves by forming a stable product, thus halting further radical reactions that would lead to more radical generation.

The process of termination is crucial because it helps to stabilize the reaction mixture by reducing the concentration of free radicals. Free radicals are highly reactive and can perpetuate the reaction by initiating further radical formation through chain reactions. By forming a covalent bond, the two radicals lead to the formation of non-radical products, effectively concluding the chain reaction.

Other options indicate processes that do not describe the termination step. The creation of new radicals or the continuous formation of radicals would imply ongoing reactions rather than the cessation of radical activity. Additionally, while products forming without radicals could describe some outcomes of radical reactions, the defining feature of a termination step is the reaction of radicals to cease their reactivity.