Chapter 20 Bromination/Debromination of Cholesterol

Purpose This reaction involves nucleophilic attack by the alkene on bromine, forming a tertiary carbocation with bromonium ion character. This ion is attacked from the backside by bromide ion to form dibromocholesterol in the trans and diaxial configuration. This reaction is employed in the practical purpose of purifying cholesterol.

(Moles Product / Moles Starting Material) x 100 = % Yield Comments Follow p. 360, 362 (microscale). Follow the lab handout for all experimental procedures. Wearing rubber gloves is necessary during this lab. You will work with toxic and corrosive compounds. Calculate yield. Moderate to good yields should be achieved. (Moles Product / Moles Starting Material) x 100 = % Yield Answer question 2, p. 364.

Safety Avoid getting the acetic acid and bromine solution on skin. Be gentle when stirring in a test tube as it is easy to punch a stirring rod through the bottom of the test tube. Filtrate (liquid waste) contains halogenated material and must be placed into the halogenated waste container.