disclosed is a process for the synthesis of 1 , 1 , 2 , 3 - tetrachloropropene using 1 , 1 , 3 - trichloropropene and / or 3 , 3 , 3 - trichloropropene and cl 2 gas as the reactants , wherein the process takes place in a single reactor system . before this invention , hcc - 1230xa was made in a two - step process using hcc - 1240za / hcc - 1240zf and cl 2 gas , and the processing was conducted using two separate reactors .