Place 5.0 g boric acid in a 50-ml distlling flask containing a boiling stone. Using a 50-ml graduated cylinder, add 20 ml of dry n-propanol, and 10 ml of toluene (which forms an azeotrope with water). attach a short piece of Tygon tubing to the side arm, clamping it off at one end. attach a water condenser to the flask. The distlling flask should be mounted at an angle, with the side arm pointing down.
Heat the solution until reflux is achieved. Toluene and water will collect in the side arm, with the denser water moving toward the bottom and the toluene recycling to the distillation pot. Continue reflux until no further water collects in the side arm (~ 30 minutes). It may be necessary to drain the side arm periodically. After the reflux period, drain the side arm.
Remove the condenser, and transfer the remaining solution to a 25 ml round bottom flask containing a boiling stone.Attach a Hickman still fitted with air condenser to the flask with a Keck clip. Clamp a thermometer inside the Hickman still so that its bulb is at the same level as the still's collar
Heat the solution to reflux. Collect any remaining toluene and alcohol in the still's collar. Remove the collected distillate witha Pasteur pipet, collecting the product that distills up to 120º C. Discontinue heating and allow the flask to return to room temperature. the product remains in the flask. Calculate the yield.
Experiment from Microscale Inorganic Chemistry, Szafran, Z.; Pike, R. M.; Singh, M.M. John Wiley and Sons, Inc.: New York, 1991.
© 2004 by Lawrence T. Sein. All rights reserved.
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