Green Oxidation of Cyclohexanol Experiment Part 2, Reaction, Workup, and Characterization

Summary

In this video, Brent Kadrowski demonstrates the green oxidation of cyclohexanol in an organic chemistry lab experiment. The process includes weighing cyclohexanol, adding a bleach solution as the oxidant, and controlling the reaction temperature. After completing the reaction, he tests for excess hypochlorous acid and quashes it with sodium bisulfite. The product, cyclohexanone, is then isolated through steam distillation, followed by an extraction with ether. Finally, the cyclohexanone is characterized using IR spectroscopy and gas chromatography to confirm the reaction's success.

Takeaways

• 😀 The experiment demonstrates a green oxidation of cyclohexanol to cyclohexanone.
• 😀 Cyclohexanol is measured at 1.50 grams and mixed with glacial acetic acid as a catalyst.
• 😀 Bleach, a sodium hypochlorite solution (8.25% concentration), is used as the oxidant in this reaction.
• 😀 The reaction occurs in two layers, and the temperature should be kept below 50°C to prevent decomposition of the oxidant.
• 😀 After the reaction is complete, a potassium iodide starch paper test is used to check for any residual hypochlorous acid.
• 😀 If hypochlorous acid remains, a saturated sodium bisulfite solution is added to quench it.
• 😀 Sodium hydroxide (NaOH) is added to deprotonate acetic acid and prevent co-distillation.
• 😀 Steam distillation is used to isolate the product, cyclohexanone, from the reaction mixture.
• 😀 Sodium chloride is added to the distillate to separate the cyclohexanone from the water layer and aid in phase separation.
• 😀 The organic layer is extracted using ether, and drying is achieved with anhydrous magnesium sulfate before filtration and evaporation of ether.
• 😀 The final product is characterized using IR spectroscopy and gas chromatography to confirm the successful conversion of cyclohexanol to cyclohexanone.

Q & A

What is the purpose of adding glacial acetic acid in the green oxidation of cyclohexanol experiment?

Glacial acetic acid acts as a catalyst in the reaction, facilitating the oxidation of cyclohexanol to cyclohexanone without being consumed in the reaction.

Why is it important to monitor the temperature while adding bleach to the reaction mixture?

The reaction is exothermic, meaning it releases heat. If the temperature exceeds 50°C, it could cause the hypochlorous acid to decompose, potentially affecting the reaction's outcome. Hence, careful temperature monitoring ensures the reaction proceeds properly.

What is the role of sodium bisulfite in the experiment?

Sodium bisulfite is used to quench any remaining hypochlorous acid after the oxidation. It reacts with the hypochlorous acid, neutralizing it and converting it into harmless sodium chloride.

Why is sodium hydroxide added to the reaction mixture?

Sodium hydroxide is added to deprotonate the acetic acid catalyst, converting it into a non-volatile salt. This prevents the acetic acid from co-distilling during the subsequent distillation process.

What is the purpose of steam distillation in this experiment?

Steam distillation is used to separate cyclohexanone (the organic product) from the reaction mixture. Since cyclohexanone is volatile and water-insoluble, it can be separated from the aqueous phase by distillation.

What is the significance of adding sodium chloride to the distillate?

Adding sodium chloride to the distillate increases the density of the water layer, aiding in the separation of the aqueous phase from the cyclohexanone. It also reduces the solubility of cyclohexanone in the water, helping retain more of the product in the organic phase.

How is the organic layer separated from the aqueous layer during the extraction process?

The organic and aqueous layers are separated by using a pointed-bottom centrifuge tube, where the denser aqueous layer is removed first. A water droplet test confirms the identity of the organic layer by showing that water sinks through it.

What is the purpose of drying the organic layer with anhydrous magnesium sulfate?

Anhydrous magnesium sulfate is used to remove any residual water from the organic layer. It forms a thin layer at the bottom of the vial and absorbs the water, leaving behind a dry cyclohexanone product.

Why is ether evaporated during the workup procedure?

Ether is evaporated to isolate the cyclohexanone product. Since ether is volatile, it can be easily removed through evaporation, leaving behind the desired organic product.

How can IR spectroscopy be used to confirm the success of the reaction?

IR spectroscopy can detect functional group changes in the product. In this case, the conversion of the hydroxyl group in cyclohexanol to a carbonyl group in cyclohexanone is observed, confirming the successful oxidation.