Which substances frighten even seasoned chemists?

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Which substances frighten even seasoned chemists?

Thioacetone.

Sounds somehow remotely like nail polish remover or bad breath.

But it is a horror substance that could well be used as a chemical weapon.

The people of Freiburg in Germany could certainly tell you something about it, although the last time Freiburg came into contact with it was 150 years ago.

Thioacetone does not explode and is not toxic.

But it is the smelliest substance in the world.

And Freiburg tried to manufacture it in 1889.

The manufacturing process is not simple. The compound (CH3)2CS remains liquid only when the temperature is below -20 degrees Celsius.

When it warms up, it clumps together to form a solid - trithioacetone - which also smells awfully.

The stench could be perceived even half a kilometer away from the factory. And it spread throughout the city. Siue had to be evacuated.

People vomited and fainted from it.

Quote from Wikipedia:

[...] our attempts in this direction failed, however, due to the fact that this substance has a terrible odor, which spreads in an astonishingly short time and contaminates whole parts of the city.[...] The intensity of the odor of this substance exceeds, according to our perceptions, everything that has become known in this respect from strong-smelling substances."

- Baumann, E. & Fromm, E., p. 2593

To illustrate the intensity of the odor, the authors describe an attempt to produce thioacetone from 100 grams of acetone. The experiment took place in Freiburg, Germany. In doing so:

"[...] the odor spread in a short time to distances of 3/4 kilometer to far-flung parts of the city. Inhabitants of the streets adjacent to the laboratory complained that the smelling substance had caused fainting fits, nausea and vomiting in some persons.[...] Extremely small quantities of the sulfurous body are thus sufficient to pollute millions of cubic meters of air."

- Baumann, E. & Fromm, E., p. 2594

That should have been enough experience.

But in 1967, chemists at an Esso station near Oxford decided to try again.

A bottle of the substance was not well capped, and the entire lab now had itself "an odor problem beyond our worst expectations."

The chemists replaced the cap, , but this "led to an immediate complaint of nausea and sickness from colleagues working in a building two hundred meters away."

In addition, thioacetone produces the kind of odor that sticks.

Two chemists who had made tiny amounts of the thioacetone could no longer go into restaurants because they smelled so bad that waitresses sprayed the air around them with scented spray.

The Esso people abandoned the project for obvious reasons.

But before they did, they had to realize how bad thioacetone stinks.

They were the ones who found out that the smell of thioacetone had a range of half a kilometer.

But also that even one drop of a solvent with thioacetone in it, dripped onto a glass plate in a closed work area with its own exhaust air, could immediately still be smelled several hundred meters away.

The odor also could not be rinsed off or diluted. Clothing that has come into contact with this high-performance stink can therefore be disposed of, since the fibers can never be completely freed of it.

However, if the skin is also affected, it can take months for the odor to recede completely. Fortunately, the chemoreceptors in one's own nose get used to these odors relatively quickly, so at least one will be happy with it alone.

And the person who is in a room with this drop can kiss any social contact goodbye for the next few weeks.

Is it a coincidence that people react to such thio compounds in even the smallest amounts with such terrible disgust?

No.

Because evolution has taught us to immediately move away from inedible substances.

These thiols are also formed in the process of decomposition, when the amino acid cysteine is broken down into thiols.

And what is a truly unbelievably disgusting smell to us?

Decomposing meat.