Whew. This one's a little embarassing. One of my favorite things about organic chemistry is just how much it's like Lego. Molecules that seem like indecipherable structures to the uninitiated start looking more and more like a bunch of building blocks. It's been said that organic chemistry is the chemistry of functional groups, and it's quite true. Chemists have to worry about the whole molecule, but any one operation is likely to work on one or two bits or pieces of the molecule at a time. This kind of thinking can be a bit dangerous, since sometimes a building block you dream up - especially if you're a naive summer undergrad at the time - turns out to be strikingly similar to a chemical weapon.
In retrospect, I should have realized it. I was trying to make phenacyl bromide, which is just the bromine analogue of phenacyl chloride. This is now indelibly burned in my brain as the structure of the chemical found in CN gas, "mace," or "tear gas":
The instructions in Organic Syntheses (link isn't working, sorry) note that it is a lachrymator - a compound that irritates the mucous membranes, especially the eyes. Dutifully, I made it in the fume hood. The compound is a solid ("tear gas" is actually a suspension of phenacyl chloride in organic solvent, dispersed as an aerosol), and it was to be purified by recrystallization - a technique involving dissolving the compound in the minimum amount of hot solvent necessary, allowing it to cool, and harvesting purer crystals of your compound. I had a bit too much solvent, so I took it out of the hood to put it on the rotavap to remove some.
Mistake. Apparently, even though it was a solid, and in solution, the small amount that was volatile was enough to lachrymate, and quite well. So well that everyone in the lab was out of there in about 10 seconds, and I was left to figure out just what to do with the stuff.
In crystal-clear hindsight, of course, I should have probably guessed this stuff would bite: benzyl bromide, a closely related structure, is also a potent lachrymator (and another war gas!).
Of course, you only live one life, and you make all your mistakes, and learn what not to do, and that's the end of you. - Richard Feynman
See you tomorrow.
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Ahhh, benzyl bromide. Responsible for many lab hours of peace and quiet during my PhD. I think because I worked with it and the p-Br form I didn't get affected by it, my supervisor did. Whenever I used it he would run out of the lab in tears. Eventually we posted a note on the door and he couldn't come in, even when we weren't using it. I wonder if it would work in my current lab...?
Ah, Organic Chemistry. Truly the most "chemical" of all the chemistry sub-domains. Not physics in disguise, nor biology under cover. :)
In "An Anecdotal History of Air Pollution" (in one of the "Advances in Environmental Science and Technology" books), J. P. Lodge describes a situation that would occasionally occur in post-WWI Los Angeles, when (as I recall) a plant that emitted a certain amount of bromine would line up downwind of a styrene plant. Benzyl bromide was the result and the smog was particularly um, interesting on those days.
I thought these compounds worked by hitting the vanilloid receptor -- is this wrong? It looks like the kind of molecule which would just add to stuff and cause general irritation.
Benzyl chloride, benzyl bromide and benzoyl chloride make for irritating labs.
My organometallics lecturer at some unknown point in the past went a few notches up from mace and now has a lovely story about how he made lewisite accidentally. :S
I am also working with phenacyl bromide, and I had no idea it was tear-gassish. I was just working in my lab one day and all of a sudden it got me. I bought the phenacylbromide commercially (it's not that expensive)- do you think there was a little of the chloride left over, or was it just the good old bromide doing it's work?
Almost certainly just the bromide. I synthesised phenacyl bromide by the ancient literature prep of acetophenone+dibromine with catalytic aluminum chloride. I am wondering why I made it when Aldrich sells it; the homebrew stuff decayed after a few days to a week, even when recrystallized and held dry over drierite or P2O5 in an evacuated dessicator. Presumably I just wanted to use neat bromine in a reaction.
phenacyl chloride indeed is lachrymatory . I have some p chloro phenacyl bromide from second crop.