Question 31.38 - Organic Chemistry

Question

Draw the products formed when cholesterol is treated with each reagent. Indicate the stereochemistry around any stereogenic centers in the product.

1. ${\mathbf{CH}}_{\mathbf{3}}\mathbf{COCl}$
   
2. ${\mathbf{H}}_{\mathbf{2}}\mathbf{,}\mathbf{ }\mathbf{Pd}\mathbf{-}\mathbf{C}$
3. PCC
4. $\mathbf{oleic}\mathbf{ }\mathbf{acid}\mathbf{,}\mathbf{ }{\mathbf{H}}^{\mathbf{+}}$
5. $\left[1\right]{\mathbf{BH}}_{\mathbf{3}}\mathbf{·}\mathbf{THF}\mathbf{;}\left[2\right]{\mathbf{H}}_{\mathbf{2}}{\mathbf{O}}_{\mathbf{2}}\mathbf{,}\mathbf{-}\mathbf{OH}$
   

Step-by-Step Solution

Answer

Answer

a. 

           The product formed when cholesterol treated with ${\mathrm{CH}}_3\mathrm{COCl}$

b. 

           The product formed when cholesterol treated with ${\text{H}}_2$, Pd-C

c. 

The product formed when cholesterol treated with PCC

d. 

             The product formed when cholesterol treated with oleic acid, ${\text{H}}^{+}$

e. 

       The product formed when cholesterol treated with $\left[1\right]{\mathrm{BH}}_3·\mathrm{THF} {\mathrm{H}}^{+}; \left[2\right]{\mathrm{H}}_2{\mathrm{O}}_2,{\mathrm{OH}}^{-}$

Step 1: About cholesterol

The yellowish crystalline-colored solid present in animal cell membranes is cholesterol. This is a class of lipid biosynthesized by animal cells. It is the principal sterol synthesized by almost all animals.

Step 2: Reaction of cholesterol with acetyl chloride

When cholesterol reacts with acetyl chloride, the hydroxyl group of cholesterol gets replaced by the $C{H}_{3}COO$ group. The reaction is shown below.

                       The reaction of cholesterol with  ${\mathrm{CH}}_3\mathrm{COCl}$

Step 3: Reaction of cholesterol with hydrogen and palladium

The reaction of cholesterol with ${\mathrm{H}}_2, \mathrm{Pd}-\mathrm{C}$ will result in the formation of a product in which the double bond of the cyclohexane ring gets converted to a single bond. The reaction is shown below.

The reaction of cholesterol with ${\mathrm{H}}_2, \mathrm{Pd}-\mathrm{C}$

Step 4: Reaction of cholesterol with PCC

The reaction of cholesterol with PCC will give a ketone. The OH group of cholesterol becomes the ketonic group. The reaction is shown below.

The reaction of cholesterol with PCC

Step 5: Reaction of cholesterol with oleic acid

The reaction of cholesterol with oleic acid will result in the formation of a product in which the OH group is replaced by the oleic acid group through an oxygen atom. The reaction is shown below.

                        The reaction of cholesterol with  $\mathrm{oleic} \mathrm{acid}, {\mathrm{H}}^{+}$

Step 6: Reaction of cholesterol with borane and tetrahydrofuran

The reaction of cholesterol with borane and tetrahydrofuran will result in the formation of a product in which the double bond of a cyclohexane ring gets converted into a single bond, and the OH group will get attached. 

The reaction is shown below.

The reaction of cholesterol with $\left[1\right]{\mathrm{BH}}_3·\mathrm{THF};\left[2\right]{\mathrm{H}}_2{\mathrm{O}}_2,-\mathrm{OH}$