The World's Smelliest Molecule

It was with some trepidation that I carried my highly potent sample of the world’s smelliest molecule out to the end of the (appropriately named) perfume garden. I needed to open the bottle and doing so in my lab was simply too risky – the slightest nudge that resulted in a spill would render the place unusable. I was actually opening grapefruit mercaptan, or for the more technically minded, para-Menthen-8-thiol. It is found in - surprise surprise – grapefruit, and it smells like.. well.. grapefruit.

Do I use this is perfume? No. It is for academic interest only and I have to say that on that front it packs a pretty punch. The detection threshold is 0.1 ppt (parts per trillion). Coffee has some fairly smelly components in it too, but nothing to compare with this – wow!

But why is it that we are so sensitive to some molecules and not to others? It’s a good question and again we find ourselves coming back to the old problem of how the nose works to find an explanation. Luca Turin (the vibrationist) will tell you that it is zinc at the receptor sites that controls threshold values. Any other ideas?

Mercaptans in general are of course used in others areas due to their low threshold values. They are added to natural gas for example to allow us to detect even small leaks.

Anyway my smelly sample is now stored on my shelf in the relatively safe concentration of 0.00000001% in ethanol. Even at this level I treat it with some considerable respect.