Question

Using your roadmap as a guide, show how to convert cyclohexanol into racemic trans-1,2cyclohexanediol. Show all required reagents and all molecules synthesized along the way.

Short answer

Answer: The step-by-step process is as follows: 1. Identify the starting material (cyclohexanol) and target product (racemic trans-1,2-cyclohexanediol). 2. Choose an appropriate oxidizing agent (KMnO_4). 3. Perform the oxidation reaction with the selected oxidizing agent and any necessary additional reagents (NaIO_4). 4. Verify that the product has the desired trans configuration and is a racemic mixture.

Step-by-step solution

Identify the starting material and target product

In this exercise, the starting material is cyclohexanol, which has a chemical formula of C_6H_(11)OH. The target product is racemic trans-1,2-cyclohexanediol, with a chemical formula of C_6H_(10) (OH)_2.

Choose the appropriate oxidizing agent

One possible oxidizing agent that can convert an alcohol to a diol is potassium permanganate (KMnO_4). In this exercise, KMnO_4 will be used with a catalytic amount of sodium periodate (NaIO_4) in the presence of water as the solvent.

Perform the oxidation reaction

The oxidation reaction can be represented as follows: Cyclohexanol + KMnO_4 + NaIO_4 -> trans-1,2-cyclohexanediol Visually, this can be represented with the following reaction: C_6H_(11)OH + KMnO_4 + NaIO_4 -> C_6H_(10)(OH)_2

Verify the trans configuration and racemic mixture

In the product, trans-1,2-cyclohexanediol, the two hydroxyl groups are located on the opposite sides (trans) of the cyclohexane ring, as required. The reaction conditions ensure that both enantiomers are produced, leading to a racemic product. Overall, the step-by-step process to convert cyclohexanol into racemic trans-1,2-cyclohexanediol is: 1. Identify the starting material (cyclohexanol) and target product (racemic trans-1,2-cyclohexanediol) 2. Choose an appropriate oxidizing agent (KMnO_4) 3. Perform the oxidation reaction with the selected oxidizing agent and any necessary additional reagents (NaIO_4) 4. Verify that the product has the desired trans configuration and is a racemic mixture.

Key concepts

Oxidation Reaction

An oxidation reaction in organic chemistry is a process where molecules lose electrons, often gaining oxygen or losing hydrogen in the process. This makes oxidation a key reaction type for transforming alcohols into diols. In the example of cyclohexanol conversion to trans-1,2-cyclohexanediol, the alcohol group in cyclohexanol is oxidized to form two hydroxyl groups.
A common oxidizing agent used for this purpose is potassium permanganate (KMnO_4). Here, it acts to add oxygen while simultaneously breaking certain bonds, allowing the formation of a diol. Remember that alongside KMnO_4, sodium periodate (NaIO_4) is used in a catalytic amount to enhance the oxidation process. This is typically performed in water, which serves as a solvent aiding in the reaction.

Cyclohexanol

Cyclohexanol

• Chemical Formula: C_6H_{11}OH
• Structure: A six-carbon cyclic structure with an alcohol (-OH) group.

This compound is the starting material in our synthesis. Knowing its structure is vital because it helps understand why specific reactions can occur. The alcohol group in cyclohexanol is a reactive site that can undergo oxidation to form stronger compounds, like diols.
In this exercise, cyclohexanol is oxidized to add an additional hydroxyl group, facilitating its transformation into cyclohexanediol. Because it is a simple alcohol, cyclohexanol can easily participate in reactions like the one described, providing a straightforward path to create more complex structures.

Diol Synthesis

Diol synthesis involves converting an alcohol into a compound with two hydroxyl groups (diol), and it is an essential reaction to increase molecular complexity in organic chemistry.
With cyclohexanol, diol synthesis is achieved through careful oxidation to avoid over-oxidizing the alcohol groups. The use of KMnO_4 and NaIO_4, as discussed, enables selective addition.

• Reversible Reaction: The reaction is generally straightforward, but conditions must be controlled to prevent further reactions.
• Configuration Control: Achieving the 'trans' configuration is crucial, as it ensures the hydroxyl groups are on opposite sides of the cyclohexane ring.

This control of configuration is what leads us to the desired product, allowing for the formation of specific diols in a controlled manner.

Racemic Mixture

A racemic mixture occurs when an equal amount of enantiomers, or non-superimposable mirror images, is present. This implies there's no net optical activity because the effects of the enantiomers cancel each other out.
In the context of cyclohexanediol synthesis, the production conditions ensure that both possible enantiomers of trans-1,2-cyclohexanediol are formed equally. This is because the reaction allows both orientations of hydroxyl group addition to occur. It's important to understand that achieving a racemic mixture means we're treating both resulting enantiomers as equal, without preference in a synthetic setting.

• Significance: Useful for reactions where specific stereochemistry is less critical or can be resolved later.
• Reaction Control: Careful management of reaction conditions aids in achieving a balanced mixture.