Acetaminophen decolorization

The decolorized acetaminophen is collected on a Hirsch funnel. It is further purified by crystallization from a methanol/water mixture. There are two procedures given in this experiment. Experiment llA involves crystallization using a Craig tube, whereas Experiment IIB is a larger-scale reaction involving an Erlenmeyer flask and Hirsch funnel for crystallization. 

Weigh the crystallized acetaminophen (MW = 151.2) and calculate the percentage yield. This calculation should be based on the number of moles of the limiting reagent used at the beginning of this procedure. Determine the melting point of the product. Compare the melting point of the final product with that of the crude acetaminophen. Also compare the colors of the crude, decolorized, and pure acetaminophen. Pure acetaminophen melts at 169.5-171°C. Place your product in a properly labeled vial and submit it to your instructor. 

Dissolve 0.5 g of sodium dithionite (sodium hydrosulfite) in 4.0 mL of water in a small Erlenmeyer flask. Add your crude acetaminophen to the flask. Heat the mixture at about 100°C for 15 minutes, with occasional swirling. Some of the acetaminophen will dissolve during the decolorization process. Cool the mixture thoroughly in an ice-water bath for about 10 minutes to reprecipitate the decolorized acetaminophen (scratch the inside of the flask, if necessary, to induce crystallization). Collect the purified material by vacuum filtration on a Hirsch funnel using small portions (about 1.0 mL total) of ice-cold water to aid the transfer. Dry the crystals for 5-10 minutes by allowing air to be drawn through them while they remain on the Hirsch funnel. You may go on to the next step before the material is totally dry. Weigh the purified acetaminophen and compare the color of the purified material to that obtained earlier. 

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