1. The active ingredient in Tylenol is acetaminophen. Suppose you had a mixture

Question

1. The active ingredient in Tylenol is acetaminophen. Suppose you had a mixture of acetaminophen and sodium chloride and wanted to separate it. Acetaminophen is soluble in ethyl acetate, CH3COOEt, and slightly soluble in water. Sodium chloride, on the other hand, is water soluble. Let’s assume that the partition coefficient for acetaminophen is KD = 8 between ethyl acetate and water mixture. If we start with a salt acetaminophen mixture that contains 10 g of acetaminophen dissolved in 100 mL of water, how much acetaminophen can we extract with two extractions of ethyl acetate 20 mL each?

Do each extraction separately. Calculate how much do you extract with one extraction first. Then consider how much remains in the aqueous layer and extract again.

Explanation / Answer

Suppose after 1st extraction x gm acetaminophen is extracted into ethylacetate.

Kd = (x/20)/(10-x/100)

or, 8 = x/20 * 100/10-x

or, x = 6.154 gm

amount present in organic layer = 6.154 gm

amount remained in aqueous layer = 10-6.154 = 3.85 gm

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Secons extraction :

Kd = (x/20)/ (3.85-x/100)

or, x = 2.37

amount extracted in organic layer = 2.37 gm

amount left in aqueous layer = 3.85-2.37 = 1.48 gm

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