Question

Epoxidation of cholesterol with mCPBA yeilds 5,6α-epoxy-5α-cholestan-3β-ol as the major product and 3-chlorobenzoic acid as a side product. What is the theoretical yeild of the products if 0.04 grams (40 mg) of mCPBA and 0.065 g (65 mg) of cholesterol were used? Include balance equation and show work.

Answer 1

Molar mass of cholesterol = 386.65 g/mol

Mass of cholesterol used = 0.065 g

Moles of cholesterol used = 0.065/386.65 = 1.68 x 10^-4 mol

Molar mass of mCPBA = 172.57

Mass of mCPBA used = 0.040 g

Moles of mCPBA used = 0.040/172.57 = 2.32 x 10^-4 mol

Moles of cholesterol used < Moles of mCPBA used

Hence, cholesterol is the limiting reagent here.

Theoretically, 1 mole of cholesterol would produce 1 mole of epoxidation product.

Therefore, 1.68 x 10^-4 mol of cholesterol would produce 1.68 x 10^-4 mole of epoxidation product.

Molar mass of the epoxidation product (5,6α-epoxy-5α-cholestan-3β-ol) = 402.65 g/mol

Therefore the theoretical yield of the product = 402.65 x 1.68 x 10^-4 = 0.068 g