text: The reaction is usually initiated by copper(II) chloride (CuCl), which is the most common catalyst in the production of 1,2-dichloroethane. In some cases, CuCl is supported on silica in presence of KCl, LaCl, or AlCl as cocatalysts. Aside from silica, a variety of supports have also been used including various types of alumina, diatomaceous earth, or pumice. Because this reaction is highly exothermic (238 kJ/mol), the temperature is monitored, to guard against thermal degradation of the catalyst.  The reaction is as follows:
  :CH=CH  +  2 CuCl   →   2 CuCl  +  ClHC-CHCl
  The copper(II) chloride is regenerated by sequential reactions of the cuprous chloride with oxygen and then hydrogen chloride:
  :½ O  +  2 CuCl  →   CuOCuCl
  :2 HCl  +  CuOCuCl    →   2 CuCl  +  HO