Schlenk Line and Schlenk Flask: General Tips
1. Familiarize yourself with the technique by reading one of the recommended references below. The books by Shriver and the last chapter in Brown's book are especially recommended since they should give an overview of almost all the techniques one would have to learn. The other articles are somewhat supplementary and pertain to specific types of equipment. One reading is undoubtedly not enough. The best thing is to periodically read while actually gaining hands-on experience.
2. When attempting the first few experiments ask someone to demonstrate basic skills and manipulations. Try to "rehearse" the actual experiment in your mind especially when you feel you lack the experience. Train yourself to ask at which points during the manipulation can things go wrong. Also, mentally devise ways to minimize exposure to moisture or oxygen. Develop an intuitive sense for foreseeing events during the experiment. Experience, trial and error (hopefully minor) are the best teachers in attaining expertise.
3. Compounds which are sensitive to less than 10 ppm oxygen are normally best handled in a glovebox.1,2 A practical thing to think about when doing an experiment is to decide which parts of the experiment can be done in and out of the glovebox. In this way, the two methods complement one another. A cardinal rule to keep in mind is that there are many things that one cannot place in the glovebox (halocarbons, volatile phosphines, etc) in view of their undesirable qualities. To supplement this need one can resort to using a polyethylene glovebag.
4. When performing any vacuum technique that requires the use of a liquid N2 dewar, always take care to make sure the line is under vacuum before putting the dewar over the trap in order to avoid liquefying oxygen. Also, when the liquid N2 dewar is no longer needed, remove it from the trap, stop the vacuum pump, and vent the vacuum so that any liquid caught in the trap can thaw and be disposed of properly. NEVER leave the dewar on the trap after the pump is turned off!
5. A two-way manifold, usually consisting of three or four gas inlet/outlet stopcocks provides the most basic equipment for Schlenk work. The vacuum/nitrogen cycle is the heart of minimizing the amount of oxygen in a Schlenk vessel and should be done at least three times. Try to maintain a steady N2 flow through the manifold, particularly when opening vessels to the atmosphere. (This is best monitored by watching the flow of N2 gas through a bubbler.) When maintaining a positive flow, attempt to maintain "laminar" flow of gas.1 Try to moderate changes between vacuum and N2 gas cycles; avoid sudden large changes in pressure. Do not rush!
6. If a part to the Schlenk line breaks, in most cases it should be taken to the glassblower for repair as many of the parts are expensive and hard to replace. There are several spare parts around the lab, and this should be the status quo as keeping the Schlenk lines in working order is of utmost importance to much of our research.
7. Expand your knowledge by reading relevant portions of the experimental sections in published papers. These are especially useful for learning new short cuts and ideas.
References:
1. Shriver, D. F. "The Manipulation of Air Sensitive Compounds"; McGraw-Hill: New York, 1969. Chapter 7 is a good place to start reading.
2. Shriver, D. F., Drezdzon, M. A. "The Manipulation of Air Sensitive Compounds"; 2nd ed., Wiley: New York, 1986.
3. Kramer, G. W.; Levy, A. B.; Midland, M. M. In Organic Synthesis via Boranes; Brown, H. C., Ed.; Wiley-Interscience: New York, 1975.
4. Gill, G. B.; Whiting, D. A. Aldrichimica Acta 1986, 19, 31.
5. Burlitch, J. "How to use Ace No-Air Glassware", Bulletin 3841, Ace Glass Inc.
6. Wayda, A. L.; Dye, J. L. J. Chem. Educ. 1985, 62, 356.