The Dangerous Stink of the World’s Smelliest Chemical

In the early 1960s, Professor Roland Mayer at Dresden University of Technology went on a hunt. His mission? Discover new practical methods of producing a group of aromatic sulfur-containing chemical compounds called thioketones. He was well aware of the dangers involved. “Some schools have been forced to abandon work they had started because of the foul and penetrating odour of these compounds,” he wrote. But where others failed, he prevailed. Mayer and his colleagues produced a host of thioketones, stink and all. Amongst the created chemicals, one especially stood out. “We have recently isolated monomeric thioacetone itself for the first time by a different method…” Mayer wrote. “The smell of this unstable red oil is indeed almost indescribable.” The dry, scientific manner in which Mayer wrote of thioacetone might suggest that he handled his encounter with the chemical in stoic fashion, but that’s highly unlikely. According to blogger and medicinal chemist Derek Lowe, what Mayer sniffed that day is one of the most offensive odours known to humanity. “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.” That’s not hyperbole. In 1889, a factory in Freiberg, Germany attempted to make thioacetone. Their “success” produced “an offensive smell which spread rapidly over a great area of the town, causing fainting, vomiting and a panic evacuation.” In 1967, when British researchers Victor Burnop and Kenneth Latham attempted to use thioketones to create new polymers, they accidentally unleashed a similar horror at the Esso Research Station. “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.” Thioacetone is often ephemeral. Above -4 degrees Fahrenheit, it readily converts to a trimer (essentially a complex composed of three of itself). The trimer sports its own stench, but it’s not nearly as harsh as thioacetone’s. The reason for thioacetone’s horrid odour remains somewhat of a mystery. But for the sulphur attached to its chemical structure, one would scarcely be clued in to its noxious nature. Indeed, an image of thioacetone seems positively benign. To be sure, the sulphur is almost certainly the culprit. Organic sulphur compounds are notoriously putrid, but why thioacetone is so much worse than the others is still up for debate. However, this may be one mystery that chemists are content leaving unsolved.

Real Clear Science, 31 July 2017 ;