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Derek Lowe The 2002 Model

Dbl%20new%20portrait%20B%26W.png After 10 years of blogging. . .

Derek Lowe, an Arkansan by birth, got his BA from Hendrix College and his PhD in organic chemistry from Duke before spending time in Germany on a Humboldt Fellowship on his post-doc. He's worked for several major pharmaceutical companies since 1989 on drug discovery projects against schizophrenia, Alzheimer's, diabetes, osteoporosis and other diseases. To contact Derek email him directly: Twitter: Dereklowe

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April 21, 2004

Mutter, Mutter, Mutter

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Posted by Derek

I spent my morning wandering through the labs with an inventory sheet in my hand, muttering about what kind of research organization this is if nobody has any triflic anhydride, damn it. For the non-chemists in the audience, this is pretty reactive stuff. It turns alcohols into trifluoromethanesulfonate esters, which nomenclature has been understandably shortened to "triflate" over the years.

We do a lot of these reactions known as nucleophilic substitutions, where one group basically comes in and kicks another one out. Some of them will only work well when you have the most reactive partner you can find, and triflate is God's own leaving group. Once your alcohol has been converted, the sulfonate ester will make way for just about anything you can toss into the flask. In many cases, you don't spend much time purifying or isolating the triflate - just wash the reaction a bit, evaporate the solvent, and roll on to the next step, which is what I was doing today.

Once I found the reagent, that is. Turns out that I was only partially a victim of bad inventory control, though. I was also feeling the effect of not working in the lab as much as I used to. They used to - back in the old days, sonny - package triflic anhydride in glass ampoules. Those are a bit of a pain, because you need to snap them open, which process either works just fine or really not fine at all. The smaller ampoules come pre-scored around their narrowed neck, but the larger ones (say, fifty grams) have to be touched up a bit first with a metal file, unless you're a real buckaroo. (As a side annoyance, this is pretty much the only use most organic chemists have for a triangular metal file, so it can be hard to track one down.)

Once you've opened the thing, you have to find a new container for the leftover reagent. Of course, if there were a good way to store the stuff in a regular container, they wouldn't ship it to you in an ampoule, now would they? Triflic anhydride, and its hydrolysis product, the viciously strong triflic acid, are notorious plastic-eaters and cap-softeners. I'd estimate that a solid majority of the stuff sold every year has gone to waste. People come back in a couple of months and find the stuff looking like used lawnmower oil, so out it goes.

Progress has been scurrying along, though, while I wasn't watching, and it turns out that they now sell the reagent in a regular bottle. The cap is made of some hardy high-density polymer, seemingly impervious to the nastiness it contains. Doubtless I looked right at some of these in the labs where I was searching, not realizing that my mental picture was now out of date. Trifluoromethanesulfonates themselves, though, never go out of style.

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