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October 10, 2006
Five Things I Haven't Used in Years
1. A Soxhlet extractor. It's not that I don't like them, it's just that I haven't had the need for one. We used to use one to wash polar products out of all the gunked-up salts from big lithium aluminum hydride reactions, and I once used one to slowly wash a more soluble impurity out of a powdery mixture of isomers. I think some of my younger colleagues have hardly ever seen one, which I find vaguely depressing.
2. For that matter, a liquid-liquid extractor. I had one of these built for me back in grad school that came up to my waist if I set it up on the floor. A week's worth of ethyl acetate washing did wonders for my crude material, which was about as crude as it's possible to get, since it was obtained by destructive vacuum distillation of corn starch. I'll have to go into that story in detail some time.
3. An infrared spectrometer. Last time I put something into an IR, I swear, it must have been nearly seventeen years ago. It's a perfectly good, perfectly reasonable analytical technique that's just been totally swamped by NMR and LC/mass spec technology. It still does some things very well (like tell you if you have a nitrile or not), bu as far as I can tell, no one cares.
4. A polarimeter. I've narrowly dodged this one over the years, but I think I haven't had to get an optical rotation since about 1996. You want to avoid chiral centers if you're making pharmaceuticals, and if you have chirality, you want to buy it in your starting material. And if you have doubts about your enantiomeric purity, you want to use something like chiral HPLC and not trust the specific rotation. Tiny bits of impurity with huge rotations can totally throw the number off. Stick with techniques where the error terms are linear and don't have exponents in them.
5. Cyclic voltammetry. One of my first projects in grad school bid fair to wander off into physical organic chemistry, at least until we found that the effect we were trying to explain didn't exist in the first place. I tried all kinds of odd techniques to get a handle on the (nonexistent) anomaly, and that included wandering down to the electrochemists in the other hallway. It didn't hurt that the grad student who ran the apparatus was really cute. But cute electrochemists are thin on the ground, in my data set, anyway.
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