Q63E - Organic Chemistry (Mcmurry)

Question

Starting from testosterone (Problem 17-62), how would you prepare the following substances?

a.

b.

c.

d.

Step-by-Step Solution

Answer

a. 

b.

c.

d.

Step 1: Oxidizing and Reducing agents

An oxidizing agent in organic chemistry is the formation of C-O at the expense of C-H, and in the case of a reducing agent, the formation of C-H at the expense of C-O occurs. The common oxidizing agents are ${\text{CrO}}_{\text{3}}$ ,  ${\text{KMnO}}_4$ and mCPBA. The common reducing agents are ${\text{LiAlH}}_{\text{4}}$ , ${\text{NaBH}}_{\text{4}}$ and ${\text{H}}_2$ , Pd/C.

Step 2: The preparation of compound (a) from testosterone

a. In testosterone, there is one secondary alcohol present. By looking at the compound we are preparing, only the secondary alcohol group is converted to the ketone group. Here, the jones oxidation occurs when the secondary alcohol is oxidized to ketone by using chromic trioxide (oxidizing agent) and acid in water. Thus, the reagent used for the oxidation of secondary alcohol is  ${\text{CrO}}_{\text{3}}$, ${\text{H}}_{\text{3}}{\text{O}}^{+}$ .   The reaction is as follows,

Preparation of compound (a) from testosterone

Step 3: The preparation of compound (b) from testosterone

b. By looking at the compound (b), only the ketone group is converted to secondary alcohol, and other groups remain as it is. The ketone reduction to secondary alcohol is made by using  ${\text{LiAlH}}_{\text{4}}$(a reducing agent) in the first step and acid in water in the second step. The reaction is as follows,

Preparation of compound (b) from testosterone

Step 4: The preparation of compound (c) from testosterone

c. When we compare the testosterone compound with compound (c), we see the alkene group reduced to an alkane, and the secondary alcohol is converted to a ketone. So, in the first step, the reduction of alkene to alkane is made by using  ${\text{H}}_{\text{2}}$, Pd/C (reducing agent). In the second step, the oxidation of secondary alcohol to a ketone is done using  ${\text{CrO}}_{\text{3}}$, ${\text{H}}_{\text{3}}{\text{O}}^{+}$  (oxidizing agent). Thus, the reaction is as follows,

Preparation of compound (c) from testosterone

Step 5: The preparation of compound (d) from testosterone

d. When we compare the testosterone compound with compound (d), we see the alkene group reduced to an alkane, and the ketone is converted to alcohol. So, in the first step, alkene reduction to alkane is made by using  ${\text{H}}_{\text{2}}$ , Pd/C (reducing agent). In the second step, the reduction of the ketone to alcohol is made by using ${\text{LiAlH}}_{\text{4}}$ (a reducing agent) and acid in water. Thus, the reaction is as follows,

Preparation of compound (d) from testosterone