Hexanal, once commonly called caproic aldehyde, is a six-carbon straight-chain aldehyde. It is a clear liquid with an atmospheric-pressure boiling point of 131 ºC. P. Bagard published the first synthesis of hexanal in 1907. It is found in foods ranging from olive oil to pears to Hass avocados. Its fruity flavor makes it a useful additive in the flavor industry.
In 2014, Y. Takeuchi and co-workers at the University of Tokyo studied hexanal in another context: They discovered that it and its isomer 4-methylpentanal act as pheromones in rats. They found that exposing rats to these chemicals in combination causes the rodents to display increasingly anxious behavior. Neither compound alone produces similar results.
Stressed-out rats also release the aldehyde mixture. In so doing, they increase the anxiety levels of other rats.
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