A lot of chemicals out there will end your life in ways that are so beyond the imagination, they could only be real.
Then there are chemicals that can’t technically harm you. They’ll just waft under your nose and make you plead for death.
Today’s Moment of Science… Thioacetone, the smell that can clear a town.
Smell being a qualitative measure, pinning down the worst smell according to science is tricky. No matter how unambiguous it seems that a particular smell is the son of distilled turd nuggets, there’s always gonna be that one chemist who insists “but I like the rotten-egg-cabbage-farts test tube.” Sulfur-containing compounds, notably several in the group known as mercaptans, are amongst those most likely to make you think getting your sense of smell back after covid was a mistake.
The Guinness Book of utterly absurd things to keep track of awarded the title of ‘biggest stinker’ to ethanethiol, aka ethyl mercaptan. Closely related to the methyl mercaptan– the additive in otherwise odorless natural gas that gives it that smell– it’s also what attracts turkey vultures to carrion. These devil birds can even be employed to sniff out the source of a gas leak. Like chemicals given such on-the-nose names as cadaverine and putrescine, ethyl mercaptan is one of life’s more malodorous chemicals associated with decaying flesh.
Indeed, Mother Nature’s wettest farts can land with a thwack to our olfactory receptors. But it takes a chemist to really peel wallpaper.
Thioacetone was first discovered in 1889 as a byproduct of trithioacetone synthesis, and started causing trouble with all due haste. The molecule is quite similar to acetone. But where oxygen is double bonded to the species’ central carbon atom, it’s been replaced with a more festive accessory: sulfur. Keep it very cold and thermally stable, lest it randomly polymerizes into trithioacetone (likewise a stinker). To break down the polymer into three molecules of something-goddamn-died-in-here, it needs to be heated to 500°C. Which I’m sure smells fine.
When this little gem was discovered in Germany, chemists attempted to conduct experiments on the stuff. We’re a masochistic bunch.
Without an isolated molecule, lab notes reflected that Baumann and Fromm’s early experiments on the stuff likely had some mixture that included thioacetone, trithioacetone, and two minor leaguers to be named later. Their reaction started with 100g of acetone, so even if every molecule was converted to thioacetone, that’s less than half a soda can (anything to avoid metric, really).
It certainly isn’t an amount that sounds like it could cause harm to people a distance away based solely on the smell. It didn’t even spill. But it was distilled with steam and, just a hunch, nineteenth century fume hoods weren’t spectacular.
Up to half a mile away, the lab’s neighbors reported nausea, vomiting, and fainting. In another experiment because we are not fast learners, they used 30g but this time they distilled it under vacuum to hopefully not release a cloud of fuck into the Freiburg air. There wasn’t any visible loss of product, but this was no ordinary smell. Residents in surrounding streets had similar reactions as they did to Baumann and Fromm’s previous experiment.
Those early attempts to isolate the molecule were ultimately abandoned when every single experiment resulted in threats of lawsuits.
Thioacetone was resurrected for research in Oxford, UK in the 1960s. A stopper accidentally came out of a bottle of the reek for just a moment. No sooner was the bottle closed again when, from a building 200 yards away, there were widespread reports of nausea and vomiting. A follow-up experiment revealed that, in just seconds, a mere drop of it was detectable a quarter of a mile downwinds.
Having a life while working with it was damn near impossible because the chemists were so acclimated to these ripe odors. So when thioacetone clung to them like the smell of a three day old sun baked diaper, they didn’t notice. Everyone else did. Working with it under vacuum wasn’t much help. Diluting it, counterintuitively, somehow only made it worse.
Other than when a chemist-cum-youtuber decides to cook up a batch because they just have to smell the indescribable, it serves very few purposes. I’ve worked with nerve agents and I’m leaving this one on a shelf, tightly sealed, preferably on another continent.
This has been your Moment of Science, asking you to go ahead and… smell this.
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