This stoichiometric reaction can be converted into a catalytic process if a redox system is also present which regenerates the pd2 I '; from Pd". Cu(1l)-salts are generally used for this purpose. In analogy to the oxidation of ethylene to acetaldehyde (cf Section 7.3.1 .l), Cu''.: can readily oxidize the zerovalent palla dium to Pd2 The copper cation, which is reduced to the monovalent state, is regenerated with air to Cu"". The multi- step reaction can be summarized in the net equation