Incandescent copper cent

The cheapest catalyst on the market: a Euro 2-cent to oxidise acetone!

Catalysis is a crucial process for a myriad of chemical reactions, whereby the catalyst, without being consumed, lowers the activation energy required for the reaction to occur. This increases the proportion of molecules with kinetic energy equal to or greater than the activation energy, and therefore considerably speeds up the reaction. Without catalysts (such as enzymes), this article would never have been written, as most probably humanity wouldn’t even exist.

Today, we’ll be catalysing the oxidation of acetone (CH₃COCH₃) with a Euro 2-cent coin, which is made of copper-coated steel.

Crank up the heat!

The procedure is as straightforward as possible. First, a borosilicate beaker was filled with approximately 20 mL of pure acetone. Then, a 2-cent coin was tied to a copper wire and activated by heating it over a Bunsen burner flame (far away from the acetone). Once the coin was red hot, the wire was tied to a spatula so that the coin hung a few centimetres above the acetone. The magic starts immediately. The reactions involved are the following:

First, a coating of copper oxide (CuO) is formed when the coin comes into contact with air after being heated with the Bunsen burner.

Cu(s) + ½O₂(g) → CuO(s)

Then, the copper oxide reacts with the acetone vapours to give ketene, methane, oxygen and copper, regenerating our initial catalyst. Acetone’s oxidation is highly exothermic, causing the coin to glow red-hot and catalyse even more acetone. This process can continue as long as there is sufficient acetone.

CuO(s) + CH₃COCH₃(g) → 2CH₂CO(g) + 2CH₄(g) + Cu(s) + ½O₂(g)

To appreciate the beauty and simplicity of the reaction, I actively encourage you to watch the following videos!

Watch the dancing glow

Yikes, it’s hot!

Leidenfrost effect

The Leidenfrost effect occurs when a water droplet is close to a solid surface that is hotter than its boiling point (100ºC at sea level), such as our copper coin, causing an insulating vapour to form and preventing the droplet from actually touching the surface.

Beautiful colours

The surface structure of the oxide layers on this copper wire, which we also used to catalyse the oxidation of acetone, gives rise to beautiful colours.