Catalyst Poisoning To Enhance Selectivity
Usually, catalyst poisoning is undesirable as it leads to a loss of usefulness of expensive noble metals or their complexes. However, poisoning of catalysts can be used to improve selectivities of reactions.
In the classical "Rosenmund reduction" of acyl chlorides to aldehydes, the palladium catalyst (over barium sulfate or calcium carbonate) is poisoned by the addition of sulfur or quinoline. This system reduces triple bonds faster than double bonds allowing for an especially selective reduction. Lindlar's catalyst is another example — palladium poisoned with lead salts.
Read more about this topic: Catalyst Poisoning
Famous quotes containing the words poisoning and/or enhance:
“It is beyond a doubt that during the sixteenth century, and the years immediately preceding and following it, poisoning had been brought to a pitch of perfection which remains unknown to modern chemistry, but which is indisputably proved by history. Italy, the cradle of modern science, was at that time, the inventor and mistress of these secrets, many of which are lost.”
—Honoré De Balzac (1799–1850)
“Art and science coincide insofar as both aim to improve the lives of men and women. The latter normally concerns itself with profit, the former with pleasure. In the coming age, art will fashion our entertainment out of new means of productivity in ways that will simultaneously enhance our profit and maximize our pleasure.”
—Bertolt Brecht (1898–1956)