Catalytic Cycles

Scientists use diagrams called catalytic cycles to show how a catalytic reaction proceeds. Professor Stahl and his students use the following catalytic cycle to describe the Pd2+ catalyzed oxidation of alcohols.

As shown in the scheme, Pd2+ oxidized acetophenol (molecule A) to give acetophenone (molecule B) and two protons. In the process Pd2+ is reduced to Pd0. In order for the catalytic cycle to continue, molecular oxygen (O2) oxidizes Pd0 to Pd2+; the molecular oxygen is reduced to water (H2O).

$$ Quick Reminder $$

Think about the example from before when transition metals were compared to a bank. Pd2+ is a result of withdrawing money (electrons) and Pd0 is a result of depositing money (electrons).