The lab smelled like jalapeño peppers. Several of us got worried and started running around, asking everybody who had been working recently if they had been using tin. Most chemists are familiar with the odors of many substances—sweet diethyl ether, garlicky dimethyl sulfoxide, rotting fish amines, etc.—but the scent of organotin is less well known. Organotin (tin atoms with one or more carbon-tin bonds) smell like jalapeño peppers and are very toxic. The day we smelled peppers in the lab was no false alarm. A postdoc had been working with tin compounds. He thought he washed them all away in his hood and that it was safe to use the column chromatography machine that is in the open. The tin was not washed away, however, and he stunk up the lab. He opened the windows and people stayed away from that room for awhile.
Organotin is used in the Stille coupling, a common carbon-carbon bond-forming reaction. Organotin compounds also act as biocides against algae and shellfish that grow on boats. These marine organisms encrust the hull and increase the boat’s water resistance, and subsequently, fuel cost. Much investigation has been done concerning the fate of these compounds in water, sediment, and living things. All organotin is toxic, but the general trend is that longer chains decrease the toxicity. It’s always a good idea to substitute boron for tin (do a Suzuki reaction instead of a Stille) because boron compounds are much less toxic. The postdoc’s tin compounds were tributyl, which is, relatively speaking, not so bad.
When I was a second-year graduate student, I had to make a small tin compound. I had help from a postdoc, but the reaction was arduous and required moving in and out of a glove box. One of the reactants was trimethyltin chloride. I looked up the materials safety data sheet for trimethyltin chloride, and these are some of the ominous things it said:
- Fatal if swallowed, in contact with skin, or if inhaled. Most important symptoms and effects, both acute and delayed: cough, shortness of breath, nausea, vomiting, headache.
- The following applies to organic tin compounds in general: systemic effect: CNS disorders (spasms, narcosis, respiratory paralysis).
Despite all that, I carried around a 5-gram flask of the stuff, trying not to think that if I dropped it, I was dead. The reaction worked, I think, but I destroyed the product while trying to distil it. The project was abandoned, though, and I never had to do that reaction again (that’s the only plus side of a dead-end project). I did not stink up the lab with the tin (if I had, people would be dead), but the postdoc’s column, many months later, forced the group to reevaluate safety procedures for handling tin. These are the rules we try to follow:
- Columns on Stille reactions can only be run on the chromatography machine in the hood.
- Test tubes from the column must be checked and combined in that same hood.
- Those test tubes and other contaminated media cannot be dumped in the usual contaminated glassware bin (because it’s not sealed) but need to be put in Ziploc bags marked “Tin Waste.”
A while later, the lab smelled like jalapeño peppers again. We went from room to room, but nobody had been working with tin. It seemed as though the smell was stronger in the direction of the common area where people eat. We headed there and found a postdoc eating jalapeño-flavored potato chips. He didn’t realize the smell was so strong that it spread through all the labs. We had a good laugh at the false alarm. A few days later, the same thing happened, but we didn’t freak out so much. We quickly checked the common area, where the postdoc was eating the chips again. “Are you trying to scare us on purpose?,” we asked. “No,” he said. “I just can’t finish this big bag in one day.” He had to take the chips home.
Reference: Cima, F.; Harrington, C; Craig, P. J. (Ed.). Organometallic Compounds in the Environment, Wiley, New York, NY, 2003, p. 101.
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