My recent entries in this category have, for the most part, been hazardous in a direct (not to say crude, or even vulgar) manner. These are compounds that explode with bizarre violence even in laughably small amounts, leaving ruined equipment and shattered nerves in their wake. No, I will not work with such.

But today’s compound makes no noise and leaves no wreckage. It merely stinks. But it does so relentlessly and unbearably. It makes innocent downwind pedestrians stagger, clutch their stomachs, and flee in terror. It reeks to a degree that makes people suspect evil supernatural forces. It is thioacetone.

Or something close to it, anyway. All we know for sure is that thioacetone doesn’t like to exist as a free compound – it’s usually tied up in a cyclic thioketal trimer, when it’s around at all. Attempts to crack this to thioacetone monomer itself have been made – ah, but that’s when people start diving out of windows and vomiting into wastebaskets, so the quality of the data starts to deteriorate. No one’s quite sure what the actual odorant is (perhaps the gem-dimercaptan?) And no one seems to have much desire to find out, either.

There are sound historical reasons for this reluctance. The canonical example (Chemische Berichte 1889, 2593) is the early work in the German city of Freiburg in 1889 (see page 4 of this textbook), which quotes the first-hand report. This reaction produced“an offensive smell which spread rapidly over a great area of the town causing fainting, vomiting and a panic evacuation.”. An 1890 report from the Whitehall Soap Works in Leeds refers to the odor as “fearful”, and if you could smell anything through the ambient conditions in a Leeds soap factory in 1890, it must have been.

The compound shows up sporadically in the literature until the mid-1960s, when several groups looked into thioketones as sources of new polymers. The most in-depth analysis took place at the Esso Research Station in Abingdon, UK, where Victor Burnop and Kenneth Latham got to experience the Freiburg Horror for themselves:

“Recently we found ourselves with an odour problem beyond our worst expectations. During early experiments, a stopper jumped from a bottle of residues, and, although replaced at once, resulted in an immediate complaint of nausea and sickness from colleagues working in a building two hundred yards away. Two of our chemists who had done no more than investigate the cracking of minute amounts of trithioacetone found themselves the object of hostile stares in a restaurant and suffered the humiliation of having a waitress spray the area around them with a deodorant. The odours defied the expected effects of dilution since workers in the laboratory did not find the odours intolerable … and genuinely denied responsibility since they were working in closed systems. To convince them otherwise, they were dispersed with other observers around the laboratory, at distances up to a quarter of a mile, and one drop of either acetone gem-dithiol or the mother liquors from crude trithioacetone crystallisations were placed on a watch glass in a fume cupboard. The odour was detected downwind in seconds.”

Now that’s a compound to be taken seriously. How do you work with something that smells like hell’s dumpster? Like this:

“The offensive odors released by cracking trithioacetone to prepare linear poly(thioacetone) are confined and eliminated by working in a large glove box with an alkaline permanganate seal, decontaminating all apparatus with alkaline permanganate, eliminating obnoxious vapors with nitrous fumes generated by a few grams of Cu in HNO3, and destroying all residues by running them into the center of a wood fire in a brazier.”

So there you have it – just install a fireplace next to your hood (what every lab needs, for sure) and remember that, in a thioacetone situation, fogging the area with brown nitrogen oxide fumes will actually improve the air. (This is from Chemistry and Industry, 1967, p. 1430, if you need more details, and I hope you don’t).

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