Question

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

Short answer

Reduce cyclohexanone to cyclohexanol, dehydrate to cyclohexene, then dimerize to bicyclohexylidene.

Step-by-step solution

Understand the Target Molecule

Bicyclohexylidene is a compound consisting of two cyclohexyl groups connected by a double bond. Therefore, our goal is to build this structure.

Introduction to the Starting Material

We start with cyclohexanone, which has a ketone group. This functional group will need to be modified to form the desired double bond in bicyclohexylidene.

Formation of Cyclohexanol

Convert cyclohexanone to cyclohexanol through a reduction reaction. This can be accomplished using a reducing agent like sodium borohydride ( NH_4BH_4 ).

Dehydration to Form Cyclohexene

Dehydrate cyclohexanol to form cyclohexene. This can be done using an acid catalyst such as concentrated sulfuric acid ( H_2SO_4 ), which will eliminate water and form a double bond.

Dimerization of Cyclohexene

Cyclohexene can undergo a dimerization reaction in the presence of a catalyst like palladium on carbon ( Pd/C ) under hydrogen gas to form bicyclohexylidene by coupling two cyclohexene molecules.

Final Product - Bicyclohexylidene

Verify the formation of bicyclohexylidene, which composes two cyclohexane rings joined by a double bond, ensuring the synthesis is successful.

Key concepts

Cyclohexanone

Cyclohexanone is a fundamental starting material in organic synthesis. It belongs to a class of compounds known as ketones, characterized by the carbonyl functional group, \(-C=O\). Cyclohexanone has a six-carbon ring structure, making it a convenient building block for synthesizing complex organic molecules.
Its utility in synthesis stems from the presence of the carbonyl group, which is highly reactive and can undergo various chemical transformations. This property is what enables cyclohexanone to act as a carbon source in the synthesis of bicyclohexylidene.

• Acts as a key intermediate in many synthetic routes
• Highly reactive due to its carbonyl group
• Essential for creating complex structures like bicyclohexylidene

Reduction Reaction

A reduction reaction in organic chemistry involves the addition of hydrogen or the removal of oxygen from a molecule. In the case of cyclohexanone, to create cyclohexanol, we use a reduction process.
This is typically done using reducing agents such as sodium borohydride \((NaBH_4)\), which facilitate the addition of hydrogen to the carbonyl group, transforming the ketone into an alcohol. This conversion is crucial as it leads to the next steps in synthesizing bicyclohexylidene.

• Involves the gain of hydrogen atoms
• Sodium borohydride is a common reducing agent used here
• Transforms cyclohexanone into cyclohexanol

Dehydration Reaction

The dehydration reaction is the next step in the synthesis, where cyclohexanol is converted into cyclohexene. Dehydration involves the removal of water \((H_2O)\) from a molecule, which in this case forms a double bond.
This process typically uses an acid catalyst, such as concentrated sulfuric acid \((H_2SO_4)\), which promotes the elimination of a hydroxyl group \((-OH)\) and a hydrogen atom \((-H)\) from adjacent carbon atoms, resulting in the formation of a double bond.

• Essential for introducing a double bond into the structure
• Uses acid catalysts to facilitate the reaction
• Leads to the formation of cyclohexene from cyclohexanol

Dimerization Reaction

Dimerization is a reaction where two molecules combine to form a single dimer molecule. In the synthesis of bicyclohexylidene, cyclohexene undergoes a dimerization reaction.
This is facilitated by using a catalyst such as palladium on carbon \((Pd/C)\) under hydrogen gas conditions. The catalyst helps in aligning the cyclohexene molecules so that they can form bonds between them, resulting in the formation of bicyclohexylidene.
This step is critical as it couples the two cyclohexene units into the desired structure.

• Involves coupling two identical molecules
• Facilitated by metal catalysts
• Crucial for forming the bicyclohexylidene structure

Organic Synthesis Methods

Organic synthesis is a methodology used to construct organic compounds from simpler substances through chemical reactions. The synthesis of bicyclohexylidene from cyclohexanone is a classic example.
It involves multiple reaction types: reduction, dehydration, and dimerization, showcasing the versatility of organic synthesis methods.
These methods allow chemists to tailor reactions specifically to achieve desired molecular architectures, considering factors like reaction conditions, catalysts, and reagents.

• Combination of various reaction types
• Focuses on achieving specific molecular structures
• Outside-the-box problem-solving in designing synthesis pathways