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The undergraduate organic laboratory in the year 2001.

Picture this: It is 1:00 P.m. on a cold winter's day. The year is 2001. You walk into a room that, in many ways, resembles a large office. This morning three calculus classes met here. This afternoon it is the undergraduate organic laboratory. It is eerily quiet. Some students are talking to each other but just a low murmur pervades the room. The floor is carpeted, the students are sitting in comfortable chairs at desks with a laptop computer off to one side.

This day they are going to be carrying out a fractional distillation of a mixture of ethanol and water that they prepared by fermentation during the preceding week. The instructor comes in to talk to them about the experiment. Some sit at their keyboards taking notes, others write in their notebooks. They begin the experiment. Reaching into their desk drawers they put out the 2OmL fermentation mixture that has been bubbling away in a flask in a foamed polystyrene cup (otherwise it might get too cool, because the temperature outside this day is near O'C).

They place 4mL of the mixture in a tiny round-bottomed flask, add a boiling chip and attach a distilling column packed with a scouring sponge. There is no water cooled condenser in this apparatus because at the rate of two drops per minute a short air condenser easily radiates the heat from the vapour as it condenses. The students place the apparatus in a two-inch diameter electric heater, partly filled with sand. The mixture begins to boil within a few seconds. By judiciously moving the sand around the flask, they control the rate of heating so the distillate comes over at the rate of one drop every 30 seconds. This gives them plenty of time to enter the drop number and record the temperature of the distillate. Some do this at their keyboard, others enter the information in their notebooks. Mercury thermometers were eliminated at this university about five years ago; the temperatures are being read from digital thermometers. One enterprising student has made arrangements to interface the output from her digital thermometer directly to her data station so she can devote all of her attention to a slow and steady distillation. As soon as the temperature starts to jump the receiver is changed.

The whole experiment is complete in little more than half an hour; after all, how long can it take to distill the 0.4mL of ethanol out of that mixture? Now the students must determine the purity of their samples. Gas chromatography gives the answer quickly, and an infrared spectrum confirms that ethanol is the product. This university has just installed one of those new flow samplers on their Fourier transform IR instrument, where each sample flows in a Teflon tube through the sample compartment separated by a bubble of air from the sample that precedes and follows it. So now what to do? Some students decide to work on the NMR spectrum of that unknown compound made in the previous week's experiment. They had dissolved the compound in a deuterated solvent, put it in an NMR tube and given it to their lab instructor. He took it down to the analytical laboratory where it was placed in the automatic sample changer and the proton spectrum was run overnight on the old 300MHz spectrometer. The free induction decay was dumped into the department computer system, just as was the raw data from their IR spectra. They work up the data from their infrared and NMR spectra at their desks and enter the final spectrum in the queue for the laser printer located in the corner of the lab. That's also where they plot out their distillation curves and print their lab reports.

The next experiment that day requires the cracking of dicyclopentadiene. The student finds all of the reagents for the experiments on the shelf in front of him in small septum-capped bottles. He removes 0.5mL of dicyclopentadiene with a syringe and over a 10-minute period adds it to a 5mL flask half filled with very hot mineral oil. Each drop of the dimer cracks instantly to the monomer. The receiver is cooled in ice so no odour is detected in the room. But the low-velocity ventilator at the back of his desk, just under the shelf whisks away any vapours that might have escaped. As soon as 0.3ml has collected, he injects it into a septum-capped flash in order to make the cyclopentadienide anion; today's experiment is the synthesis of ferrocene. Two hours later he is subliming about half a gram of his bright orange product. He's been confined to a wheelchair ever since he broke his leg in that spectacular skiing accident at Whistler a few weeks ago.

This scenario is not as far-fetched as it might at first appear. The laptop computer is with us now. At Dartmouth College in New Hampshire every student must own a Macintosh computer. Every student room, faculty office, and most laboratories are connected to the main computer at the college. The organic labs at Wellesley College in Massachusetts have been carpeted for more than a decade. Several universities run undergraduate NMR samples using an automatic sample changer overnight, with off-line workup of the data by each student on the university computer. North Carolina State University will soon be building a lab with ventilation at the back of each lab bench. It costs over $2000/year to run a hood in most parts of Canada because of heat lost in the winter. Digital fever thermometers now cost less than $10 and digital laboratory thermometers with a range of 0 to 150'C can be had for less than $50. Williamson's Macroscale and Microscale Organic Experiments describes the unique microscale cracking of dicyclopentadiene and the use of of inexpensive microscale equipment for refluxing and distillation that does not require water-cooled condensers. And organic chemistry students regularly break their legs skiing. So who makes a flow cell for the FT-infrared spectrometer so that multiple student samples can be run rapidly?
COPYRIGHT 1991 Chemical Institute of Canada
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Copyright 1991 Gale, Cengage Learning. All rights reserved.

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Author:Williamson, Kenneth L.
Publication:Canadian Chemical News
Date:Mar 1, 1991
Words:1011
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