If 3b-cholestanol is an impurity in Cholesterol, why doesn’t it also react with Br2? What happens to it after bromination of Cholesterol takes place?
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Cholesterol has a double bond the bromine can add to, cholestanol does not have the double bond and therefore does not react. Using the increased mol. weight of the brominated cholesterol, separation can be done by chromatography or crystallization. The purified dibromocholesterol can then be debrominated to form cholesterol free for cholestanol.