Why do pennies and other coins smell that way? Oct-1-En-3-One (also 1-octen-3-one) is the chemical responsible for the dull, metallic smell we associate with money. It is actually a by-product of the reaction of certain chemicals in human sweat that break down in the presence of iron (Fe²+) ions. In other words, it’s not the coin that smells, but your sweat (in the presence of money) that smells. A similar reaction occurs in the presence of blood, which is probably the evolutionary reason why only a little oct-1-en-3-one is necessary to cross the smell threshold.
Chemical formula: C8H14O, or CH2=CHC(=O)(CH2)4CH3
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