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Octenone (Why metal smells)

By moleculeoftheday on September 9, 2008.

Yesterday, I discussed octenol, a lipid degradation product that's all over your skin. Ever wonder why a cut on your hand smells "like metal," or your hands smell "like metal" after handling some?

i-a6dfb9e25e95fbbbe8631105b712e299-octenone.png

Metal ions are great at shuttling electrons around, and that's just what they're doing here. The iron ions in blood (or metal oxides on the metal surface) catalyze the oxidation of the same lipids that degrade to octenol to something a little more oxidized (that is, octenone) - the oxidizing equivalents just come from the air. Octenone is where that metal smell comes from!

Of course, you need skin lipids to get the octenone smell. If you've ever bled a lot (and you have a rigorous scientific disposition, giving you sufficient presence of mind to note the odor), you might have noticed that there was not much smell. A paper cut or nosebleed (or the scabs on your knees you used to pick off as a kid), however, has gobs of octenone aroma. This is because the blood needs to hang out on the surface of the skin to do the catalysis.

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