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March 30, 2005
More on Question Four
Posted by Derek
I thought I'd briefly explain one of my "Ten Questions" from the other day. The old-fashioned qualitative organic tests that I mentioned in #4 are things that were used in the 1960s and before to identify classes of compounds. Various brews can give you color indicators for the presence of double bonds, methyl ketones, aldehydes and the like. Some of them are quite dramatic - Tollens reagent, for example, suddenly deposits a silver mirror layer (scroll down on that link to see it) on the inside of the flask when it goes right.
But no one uses this stuff any more. No one at all, at least not if they can help it. Modern methods like NMR and routine HPLC/mass spectrometry have completely destroyed the usefulness of the old chemical tests, because you can now find out far more about your compound with little or no destruction of the sample.
Some undergraduate courses apparently still have these reactions in their curricula, and the only reason I can see is inertia. I've heard rationalizations about using them to teach reaction mechanisms and so on, but you can do that just as easily with reactions that real chemists actually run in the real world. And why wouldn't you? If you're a student that's been asked to run a battery of qualitative organic tests, you should ask for a refund of your tuition. You're being had.
Comments (4)
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1. Grady on March 31, 2005 2:47 PM writes...
I took classes where we were required to do qualitative tests, and I later served as a TA in classes where people were we required students to do those tests. It pissed me off both times.
The "look at the pretty colors" effect does help keep the short-attention span crowd interested in "chem for non-majors" classes, so they can't be totally discounted, but I think you're spot on that that there's no place for this in modern chemistry curriculum. The people making up the curriculum aren't connected to the industry, in most cases. In one case I remember, the faculty member was actually a little bitter about not being able to make it in industry, and everything in their lab had to be done "old-school" out of a sort of romanticism. It's always going to be that way until people like yourself, Derek, get involved in designing curriculum, instead of leaving it up to departmental deadwood for whom the qualitative tests were relevant. It's like this in many fields, especially education(what a sorry situation that is), but a notable exception is computer science. I remember taking a fortran class. The guy actually worked in the industry, and, yes, came right out and told us that we were basically wasting our time learning fortran if we wanted to get work as programmers. The fact that graduate degrees were rare in CS helped make the classes more relevant, I think, because you didn't have people who never worked in the industry a day in their life as the major source of teachers, but rather profs who were either retired, or still worked in the industry.
Permalink to Comment2. Dawn B. on March 31, 2005 3:07 PM writes...
I had to do a simple battery for ketone/aldehyde once in O Chem. I think it is worth doing, once. It lets the students learn how things used to be, highlights a mechanism, and does the "pretty colors" effect mentioned above. As long as the teacher also notes other methods that could be used and that are used, I think doing something once is worthwhile. I also think this type of testing is quicker than having each student run an NMR on a sample [30 people at once doing a 5 min reaction versus 30 people in line to 5 min reactions]. It is also probably cheaper to buy the reagents for the testing in bulk than to pay someone to help setup & run the NMRs and/or buy an automatic NMR sampler for the university or to worry about students "breaking" diagnostic equipment.
Permalink to Comment3. charles on April 5, 2005 5:29 AM writes...
As of 2002, and probably still, the OSD lab for chemistry majors at my alma mater wa a combination of the old and new techniques.
We had six unknowns; the first two were done by the old methods, the remaining four used NMR, IR, and GC/MS with one test from the old battery for "final confirmation" of the functional group we thought we had. They aren't terribly efficient anymore, but the old ways are interesting to at least look at in passing.
Permalink to Comment4. steve on April 6, 2005 6:30 PM writes...
I agree with Derek's point that obsolete methods are probably not a good use of scarce learning time, but part of me always thinks of those post-apocalypse scenarios where someone saves the day by knowing the old-fashioned methods when all the fancy gear has been destroyed. It's silly, of course, but read Lucifer's Hammer (especially the part about the chemist who becomes the "wizard" because he knows how to make stuff) and see if you don't get the same feeling.
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