Esterification (n-Butyl Acetate)
In a 5-mL short-necked, round-bottomed flask, place 0.2 g of Dowex 50x2-100 ion-exchange resin, 0.60 g (0.58 mL; 0.01 mol) of acetic acid, 0.74 g (0.91 mL; 0.01 mol) of 1-butanol, and a stirring bar. Attach the addition port with the sidearm corked and an empty distilling column, as shown in Figure 40.1, and clamp the apparatus at the angle shown. Heat the flask while stirring on a hot sand bath and bring the reaction mixture to a boil. Stirring the mixture prevents it from bubbling. As an option, you might hold a thermometer just above the boiling fluid and note a temperature of about 91°C. Remove the thermometer and allow reaction mixture to reflux in a manner such that the vapors condense about on third of the way up the empty distilling column, which is functioning as a condenser. Note that the material that condenses is not homogeneous, as drop of water begin to collect in the upper part of the apparatus. As the sidearm with condensate, it is cloudy at first and then two layers separate. When the amount of the lower aqueous layer does not appear to increase, the reaction is over. This will take about 20-30 min. Carefully remove the apparatus from the heat, low it to cool, and then tip the apparatus very carefully to allow all the upper la in the sidearm to run back into the reaction flask. Disconnect the apparatus,
Remove the product from the reaction flask with a Pasteur pipette, determined weight and boiling point, and assess its purity by thin-layer chromatographic (TLC analysis and infrared (IR) spectroscopy. The product can be analyzed by gas chromatography on a 10-ft (3-m) Carbowax column. At 152°C, the 1-butanol has at retention time of 2.1 min, the n-butyl acetate 2.5 min, and the acetic acid 7.5 min. Look for the presence of hydroxyl and carboxyl absorption bands in the IR spectrum, the product can easily be purified by simple distillation (see Figure 5.7 on page 97).