A Disposable, Slow-Addition Funnel for Small-Scale Preparative Reactions Standard eauioment (ex.. motor-driven micrometer devices. slow-addition dnxminz . . ~ solution to a reaction .. funnelsi f&slowaddition of small volumes of reaeent t l s k h a s w ~ w a drawhark< l s u c h as h i ~ hn x t , dilfieultw tntuunting tlogyln~ ~.alr#llnr) t ~ t I etc. ~ 1 I Want 10 report 8" efficient and in?xpenslhe s111utim11, thi' problem using two disposable pipets (Pasteur-type) and asmall piece of latex tubing according to the figure. Procedure. Seal one of the pipets ( A ) in such a way as to make the sealed end easily breakable. Add the reagent solution and mount the latex tubing. Draw a hair capillary on the other pipet ( B )and seal the end. Heat pipet R and mount i t upside down in the latex tubing. Let the pipet coal to room temperature and break the outlet end of pipet A. Air (or nitrogen, if the pipet is broken in a nitrogen-flushed flask) will be sucked in until the pressure difference is equilibrated, thus preventing the solution from emerging. Mount the "funnel" on the reaction flask (e.g., through an open stopcock) and break the hair capillary near the top. (The equipment indicated in the figure is usually superior to two-necked flask arrangements for m a t operations). The reagent solution now will add dropwise a t a slow rate. If faster addition is needed, break the capillary a t a lower point. A dropping rate as low as one dropevery 20 sec is easily abtained even with low-viscosity solvents such as ether. The dropping is interrupted easily hy sealing the hair capillary. If the reaeent solution is air- andlor moisture-sensitive. the funnel can be flushed
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be immersed in a flask flushed with nitrogen. 'Permanent address: Organic Chemistry 2, Chemical Center, The Lund Institute of Technology, 5-220 07 Lund 7, Sweden.
Rice University Houston. TX 77001
410 1 Journal of Chemical Education
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