Ethyl ethanoate can be produced by the reaction of ethanol with ethanoic acid. Both reactants can be synthesized from ethane through a series of reactions, the first of which is shown. \( C_{2}H_{6}(g)+Cl_{2}(g)\rightarrow C_{2}H_{5}Cl(g)+HCl(g) \) The first step in this reaction, initiation, is given by the following equation. \( Cl_{2}\rightarrow 2Cl\cdot \) State an essential condition for this reaction.