Catalytic versus stoichiometric reagents as a key concept for Green Chemistry

25 years ago catalysis was highlighted as a main principle of Green Chemistry. Selective catalysis enables an efficient utilisation of resources and the design of benign processes. Waste formation caused by stoichiometric reagents, for instance in reduction or oxidation reactions, can be overcome using suitable catalysts and benign reductants and oxidants, respectively. Solid acidic and basic catalysts prevent prevalent salt formation associated with the use of molecular acids and bases. Catalysts allow us to decrease the activation energy of chemical transformations, enhance the reaction rate, facilitate high selectivity and are crucial to reduce the number of process steps.