Q17-70E - Organic Chemistry (Mcmurry)

Question

Propose a synthesis of bicyclohexylidene, starting from cyclohexanone as the only source of carbon.

Step-by-Step Solution

Answer

A synthesis of bicyclohexylidene from cyclohexanone is,

Step 1: Organic reactions

Organic reactions involve changing one functional group to another by using oxidizing agents or reducing agents depending on the compound we want. For example, a ketone is converted to alcohol using ${\text{LiAlH}}_{\text{4}}$   (a reducing agent).

Step 2: A synthesis of bicyclohexylidene

Starting from cyclohexanone, the ketone group is reduced to secondary alcohol by using a reducing agent ${\text{LiAlH}}_{\text{4}}$, ${\text{H}}_{\text{3}}{\text{O}}^{\text{+}}$. The cyclohexanol formed is now treated with ${\text{PBr}}_{\text{3}}$; it converts alcohol to alkyl bromide, and we get bromocyclohexanol.

On further treating bromocyclohexanol with Mg, ether, we get  ${\text{C}}_{\text{6}}{\text{H}}_{\text{5}}\text{MgBr}$(Grignard reagent). When this Grignard reagent is treated with Cyclohexanone and acid in the water, we get a compound which, further on reaction with ${\text{H}}_2{\text{SO}}_4$, gives the Bicyclohexylidene (desired product).

Synthesis of bicyclohexylidene from cyclohexanone