Oxidation of Allylic Alcohols and Allylic Alcohols in Conjugated Carbon SystemsAlejandra Gamon1, Stephanie Doria1, and Lawrence Callan2

Science Undergraduate Research Group Experience College of the Sequoias

Abstract

Objectives

Methods and Materials

Results

Summary and Conclusion

Investigate if primary allylic alcohols, such as 2-buten-1-ol, can be oxidized through atypical Jones’s reaction into carboxylic acids or if they will be oxidized into aldehydes orif instead the double bonds will undergo hydrolysis.

Investigate if alcohols in conjugated systems, such as 2,4-Hexadien-1-ol, can be oxidizedinto carboxylic acids through a Jones’s reagent reaction or if the conjugated system willacquire a more stable form and prevent the formation of a carboxylic acid.

Oxidation of Crotyl Alcohol to Crotonic Acid

Figure 5: Infrared Spectrum Results of Crude Product

B) Standard IR spectrum of Crotyl Alcohol

A) IR spectrum of crude product

C) Percent match of crude product to Crotyl Alcohol

Figure 6: IR Spectrum results of Purified Product

A) IR Spectrum of purified product

B) Standard IR spectrum of Crotyl Alcohol

C) Percent match of purified product to Crotyl alcohol

Oxidation of Crotyl Alcohol with chromic acid resulted in a 92.8 percent match ofthe crude product to Crotonic Acid (Figure 5C). After purification, a 96.1 percentmatch to crotonic acid was obtained (Figure 6C).

Oxidation of Sorbic Alcohol to Sorbic Acid

Figure 7: Infrared Spectrum Results of Crude Product

A) IR spectrum of crude product

B) Standard IR spectrum of Sorbic Acid

C) Percent match of crude product to standard IR spectrum of Crotyl Alcohol

Oxidation of Sorbic alcohol with Jones’s reagent resulted in a 90.0 percentmatch of the crude product to sorbic acid (Figure 7A). Further purification ofthe product was not possible due to the small amount of product obtained.

The Jones’ reagent was discovered by Ewart Jones and is comprised of a solution ofchromium trioxide and dilute sulfuric acid. The reagent is commonly used to oxidizeprimary and secondary alcohols to carboxylic acids and ketones. However, there havebeen no studies done as to whether or not the reagent can be used to oxidize primaryallylic alcohols. We experimented on two different compounds, 2-buten-1-ol (crotonylalcohol) and 2,4-hexadien-1-ol (sorbic alcohol), using the Jones’ reagent to see ifoxidation of allylic alcohols was possible. One of the main questions we had waswhether or not the reaction would produce products with a carboxylic acid or if thereaction would produce an aldehyde instead. We also wanted to test allylic alcohols andconjugated systems to find out if the double bonds would be oxidized during the processof titration. Using a typical Jones’ reagent procedure, we titrated the alcohols in an icebath over time and used separation and purification techniques to isolate the products.We were able to isolate both 2-butenoic acid (crotonic acid) and 2,4-hexadienoic acid(sorbic acid) in multiple trials using the separate compounds. Therefore, we found that itis possible to oxidize allylic alcohols to carboxylic acids without oxidizing the double bondor compromising the conjugated system.

We measured out a 0.050 mole sample of our reactant and added a proportional amount of acetone assolvent. We placed the solution in a beaker with a thermometer and suspended it in an ice bath to preventthe temperature from increasing and decomposing the products. Slowly, we began titrating the solutionwith the Jones’ reagent. The titration is complete when the solution remains orange for at least 20 minutesto signify an excess of chromic acid. After the titration there are green salts in the solution that must be leftbehind; to remove the green salts we decanted the liquid into a new beaker and rinsed the salts withacetone. Now, to remove excess chromic acid we added a minimum amount of isopropyl alcohol until thesolution became light blue. A small portion of sodium bicarbonate is added to neutralize the pH of thesolution which clears the solution of the blue coloring. Then we filtered the solution and rinsed the solutioncake with acetone. We heated the remaining solution over a water bath until there was a small amount ofacetone left and allowed the solution to dry overnight. This rendered crude products for both compounds.We purified the crude crotyl alcohol by dissolving it in acetone and heating it over a hot water bath. Therewas too little crude sorbic alcohol to obtain a purified product.

Through experimentation with both chemicals we found that not only will the Jones’ reagent oxidize primary allylic alcohols to carboxylic acids but it will have no effect on the C=C double bond. Our results from the IR spectrum show that the molecules did not undergo hydrolysis or cleavage during the reaction. We also found that conjugated systems remain unaffected during this titration as well.

Step 1:

Step 2:

Figure 1: Step 1 Illustrates the mechanism of the Jones’ reagent during aldehyde formation. Step 2illustrates the mechanism of the Jones’ reagent that oxidizes the aldehyde from step 1 into acarboxylic acid.

A)

B)

Figure 2 (Above): Figure 2A depicts the general reaction of crotyl alcohol into crotonic acid and figure 2B depicts the general reaction of sorbic alcohol into sorbic acid.

Figure 3 (Left): This image shows the Jones’ Reagent which was utilized for the experiment.

Figure 4: These pictures illustrate the various color changes that occur during the reaction with the Jones’ reagent.