Oxidation-Reduction Experiment

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Questions and Answers

What should be done if borneol does not dissolve completely after stirring?

Add an additional 0.5 mL of acetone (correct)

Wait for a longer period before checking

Increase the temperature of the water bath

Add more glacial acetic acid

What is the primary purpose of adding sodium hypochlorite solution to the borneol mixture?

To dissolve the borneol completely

To extract the organic layer

To adjust the pH of the mixture

To convert borneol into isoborneol (correct)

What is the purpose of using a separatory funnel in the procedure?

To heat the mixture evenly

To separate the organic and aqueous layers (correct)

To measure the temperature accurately

To stir the reaction mixture effectively

How long should the sodium hypochlorite solution be added dropwise?

40 minutes Signup and view all the answers

What is the correct ratio of sodium hypochlorite solution used in the procedure?

10-14% Signup and view all the answers

During the extraction process, what should be done after adding methylene chloride to the reaction mixture?

Shake gently to avoid an emulsion Signup and view all the answers

What initial temperature should the water bath be set to for the procedure?

50 °C Signup and view all the answers

What is a possible consequence if the sodium hypochlorite solution is added too quickly?

An emulsion may form Signup and view all the answers

What is the main purpose of using sodium hypochlorite in the oxidation of borneol?

It is safer and avoids hazards of chromate solutions. Signup and view all the answers

What is the significance of using a large excess of sodium hypochlorite during the oxidation process?

It ensures complete oxidation occurs. Signup and view all the answers

Which compound is formed from the oxidation of borneol?

Camphor Signup and view all the answers

What role does sodium borohydride play in the second part of the experiment?

It reduces camphor to isoborneol. Signup and view all the answers

Why is sodium borohydride preferred over lithium aluminum hydride in this experiment?

It is more stable and easier to handle. Signup and view all the answers

In the reduction of camphor, from which side does the hydride approach the molecule?

Bottom side due to steric repulsion. Signup and view all the answers

What is the likely minor product formed during the reduction of camphor?

Borneol Signup and view all the answers

Which component is crucial for generating hypochlorous acid in the oxidation process?

Acetic acid Signup and view all the answers

What is the purpose of washing the combined methylene chloride layers with saturated sodium bicarbonate solution?

To remove carbon dioxide from the solution Signup and view all the answers

After drying the organic layer with anhydrous sodium sulfate, what is the next step?

Evaporate the solvent in a fume hood Signup and view all the answers

During the alternate procedure, what is the primary function of Oxone in the reaction?

To oxidize borneol to camphor Signup and view all the answers

What should be done if the initial camphor sample is less than 0.2 g?

Add stock camphor to increase the mass Signup and view all the answers

What is the purpose of taking an IR spectrum of the isolated camphor?

To verify the oxidation was successful Signup and view all the answers

Why is sodium borohydride added in excess during the reduction of camphor?

To ensure complete reduction Signup and view all the answers

What is an appropriate way to verify that the product is not contaminated?

Through melting point determination and IR spectrum analysis Signup and view all the answers

How long should the solution be stirred after adding water to dissolve the salts during the alternate procedure?

10 minutes Signup and view all the answers

What is the purpose of integrating the two peaks in the NMR spectrum?

To determine the relative percent of isobomeol and bomeol obtained. Signup and view all the answers

Why might the instructor direct a TLC run of the product against samples of camphor, bomeol, and isobomeol?

To confirm the absence of starting material (camphor) and the predominant isomer. Signup and view all the answers

In which region should you focus when analyzing the NMR spectrum for the signal responsible for one of the isomers?

3.5-4.0 ppm Signup and view all the answers

What is the primary objective of referring to the NMR spectra for the two isomers?

To identify which peak corresponds to each isomer. Signup and view all the answers

What should be done if the NMR spectrum indicates a mixture of both isomers?

Integrate the peaks to assess the ratio of the isomers. Signup and view all the answers

What is the primary reason for ensuring that the reagents are in solution during the reaction?

To allow for a successful chemical reaction Signup and view all the answers

What should be added if the mixture begins to dry out during the warming process?

Further methanol Signup and view all the answers

Why is anhydrous sodium sulfate used in the process?

To dry the methylene chloride solution Signup and view all the answers

What method is suggested to recover isobomeol after NMR analysis?

Evaporating the NMR solvent Signup and view all the answers

What is a necessary condition for the melting point, IR, and NMR analyses to verify successful reduction?

The sample must be completely dry Signup and view all the answers

What is the appropriate way to ensure the sample is at the correct height in the NMR tube?

Add more NMR solvent as necessary Signup and view all the answers

What volume of ice-cold water should be added to the mixture after it cools?

5.0 mL Signup and view all the answers

Which analytical technique is specifically mentioned to determine the isomer produced?

Nuclear magnetic resonance (NMR) Signup and view all the answers

Study Notes

The Oxidation-Reduction Scheme

This experiment consists of two parts: Oxidation of Borneol to Camphor (part A) and Reduction of Camphor (part B).
You need to complete both parts for this experiment and submit a single lab report.

Oxidation of Borneol to Camphor

Uses a less common and safer hypochlorous acid oxidation method.
This method avoids hazardous and expensive chromium-based solutions.
Bleach (sodium hypochlorite) is used to generate the hypochlorous acid.
To ensure complete oxidation, a large excess of sodium hypochlorite is used.
The experiment uses a 50-mL round bottom flask.
0.360 g of racemic borneol, 1.0 mL of acetone, and 1.0 mL of glacial acetic acid are added to the flask.
The mixture is stirred until the borneol dissolves.
20 mL of 10%-14% sodium hypochlorite solution is added dropwise over 40 minutes.
The solution is stirred and heated in a warm water bath (50 °C).
After the reaction, the mixture is transferred to a separatory funnel and extracted with methylene chloride.
The organic layer is washed with saturated sodium bicarbonate (to remove excess acid), 5% aqueous sodium bisulfite (to remove any remaining hypochlorite), and water.
The organic layer is dried with anhydrous sodium sulfate.
The solvent is evaporated and the product (camphor) is weighed and analyzed by IR spectroscopy.
An alternate procedure using Oxone and sodium chloride can be used.

Reduction of Camphor

Sodium borohydride is used to reduce camphor to isoborneol.
It is preferred over lithium aluminum hydride because it is easier to handle.
The reduction is stereospecific, with the hydride attacking from the bottom side (endo approach) due to steric hindrance.
The experiment starts with a sample of camphor from part A and a minimum of 0.2 g is used.
4.0 mL of methanol is added to dissolve the camphor.
0.4 g of sodium borohydride is added, which is a large excess but results in better outcome.
The mixture is heated on a warm hot plate for 2 minutes, adding more methanol if needed.
5.0 mL of ice-cold water is added.
The white solid (isoborneol) is collected by vacuum filtration.
The solid is dissolved in methylene chloride and dried with anhydrous sodium sulfate.
The solvent is evaporated and the product is weighed and analyzed by melting point analysis, IR spectroscopy, and NMR spectroscopy.
NMR spectroscopy helps determine the ratio of isoborneol to borneol in the product.
A TLC can be used to compare the product with reference standards of camphor, borneol, and isoborneol.

Important Information

The lab report is graded and should include both parts of the experiment.
Keep the camphor product in a tightly stoppered vial.
NMR analysis requires dissolving the entire sample in CDCl3.

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Description

This quiz covers the two-part oxidation-reduction experiment focused on the conversion of borneol to camphor and the subsequent reduction of camphor. Participants will explore the methods used, specifically the hypochlorous acid oxidation using sodium hypochlorite, offering a safer alternative to chromium-based solutions. Test your knowledge on the experimental procedures and chemical reactions involved.