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Oxidation Lab Report...

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The Oxidation Reaction of 2-ethyl-1,3-hexanediol with Sodium Hypochlorite

Nway Wynn Lab Partner: Kimberly Perez Villagrez TA: Anuja Sharma Lab: Tuesday, 7:30 am

Room #: PSH336

Abstract: The goal of this experiment was to investigate and observe the oxidation reaction of 2-ethyl-1,3-hexanediol using sodium hypochlorite. The purpose of this experiment was to decide whether or not the sodium hypochlorite was selective and what product would form when 2-ethyl-1,3-hexanediol was oxidized with sodium hypochlorite. To purify and isolate the product, an ether and aqueous extraction was performed . The IR spectrum of the starting reactant and product were obtained to characterize the product and used to compare the starting reactant and final product. The final product was determined to be 2-ethyl-1-hydroxy-3-hexanone with a percent yield of 81.63%.

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Introduction. The reason for this experiment was to observe and investigate an oxidation reaction when 2-ethyl-1,3-hexanediol reacts with sodium hypochlorite. Since the reagent, sodium hypochlorite was the oxidizing agent the following reaction was performed with 2-ethyl-1,3-hexanediol:

Figure 1.1 The product side has been left empty because the product would be observed after finishing the experiment.Since a diol with two -OH groups were used to be oxidized by sodium hypochlorite, three different products could have emerged. The reaction could have oxidized the primary alcohol only, the secondary alcohol only or oxidized both alcohol groups. The products that could have occured within the reaction are the following:

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Figure 1.2 In order to test if the reaction was complete, multiple iodine tests were performed to test for the presence of excess sodium hypochlorite. If there was an excess amount of sodium hypochlorite within the reaction, the test strips will turn purple/blue and the reaction will be complete. Afterwards in order to extract and purify the product, an ether and aqueous solution extraction was performed. An IR spectrum of the product was obtained to characterize and to be compared to the starting reactant to be able to determine the final product. Experimental. The procedure that was performed started of with adding 0.46 g (or 0.5 mL) of 2-ethyl-1,3-hexanediol to a pre weighted 25-ml Erlenmeyer flask. 3 ml of glacial acetic acid and a stir bar were added to the 25-ml Erlenmeyer flask. The flask was then placed in a water bath on top of a magnetic stirrer. While the mixture was stirring, 3 mL of 6% aqueous sodium hypochlorite solution was slowly added to the flask. Once the sodium hypochlorite solution was

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added to the flask, a timer started to time the reaction. The temperature of the reaction was maintained below 30 degrees Celsius and was allowed to stir for a total of 15 minutes. After 15 minutes have passed, the first iodine tests were performed by using a glass pipette and placing a drop on an iodine starch test paper. If there was no color change, then another 1 ml of sodium hypochlorite was added to the solution over a 5 minute interval; thus, after adding the 1 ml of sodium hypochlorite, another iodine test was performed to check if there is an excess amount of sodium hypochlorite. If the iodine starch test paper turned blue/purple within the first 15 min, then the reaction is complete, suggesting that there is an excess amount of sodium hypochlorite. Whenever the reaction had obtained a positive test, the reaction end time and overall time was recorded. The reaction mixture was then poured into a beaker containing 10 mL saturated sodium chloride with about 0.5 g of ice. A Pasteur pipet was used to transfer the mixture of the reaction product and ice water into two centrifuge tubes fitted with screw caps equally. The mixtures were shaken and frequently vented to release pressure. The bottom aqueous layer was removed and disposed of in a beaker. The mixtures were then washed with 2 mL of saturated sodium carbonate solution twice. The aqueous layer was discarded each time and this process was repeated with 2 mL of 5% sodium hydroxide solution twice. The organic layer from both centrifuge tubes were then combined. Magnesium sulfate was added to the centrifuge to dry the organic layer. The dried organic layer was transferred to a pre-weighed 30-mL beaker, while the magnesium sulfate was left behind. The beaker was placed in a water bath that was heated on a hot plate, becoming a hot water bath. The final product which was an oil was then weighed and characterized using an IR spectrum. The final product IR spectrum and the starting reactant IR spectrum were compared to determine the final product.

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Results. 0. 49 𝑔 𝑑𝑖𝑜𝑙 ÷ 146. 13

𝑔 𝑚𝑜𝑙

𝑑𝑖𝑜𝑙 = 0. 00335 𝑚𝑜𝑙𝑒𝑠 𝑜𝑓 𝑑𝑖𝑜𝑙

Equation 1: moles of the reactant ( 0. 00335 𝑚𝑜𝑙𝑒𝑠 𝑜𝑓 𝑑𝑖𝑜𝑙 ÷ 0. 00335 𝑚𝑜𝑙𝑒𝑠 𝑜𝑓 𝑑𝑖𝑜𝑙) × 100 = 100% Equation 2: Theoretical yield of reactant 0. 4 𝑔 𝑝𝑟𝑜𝑑𝑢𝑐𝑡 ÷ 146. 13

𝑔 𝑚𝑜𝑙

𝑑𝑖𝑜𝑙 = 0. 00274 𝑚𝑜𝑙𝑒𝑠 𝑜𝑓 𝑝𝑟𝑜𝑑𝑢𝑐𝑡

Equation 3: moles of the product ( 0. 00274 𝑚𝑜𝑙𝑒𝑠 𝑜𝑓 𝑝𝑟𝑜𝑑𝑢𝑐𝑡 ÷ 0. 00335 𝑚𝑜𝑙𝑒𝑠 𝑜𝑓 𝑑𝑖𝑜𝑙) × 100 = 81. 79% Equation 4: Percent yield IR Spectrum of 2-ethyl-1,3-hexanediol

Figure 1.3

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IR Data for 2-ethyl-1,3-hexanediol (Figure 1.3) Frequency

Specific Bond Vibration

Functional Group

3339

O-H

Alcohol

2958

Sp3 C-H

Alkane

2932

Sp3 C-H

Alkane

2874

Sp3 C-H

Alkane

IR Spectrum of 2-ethyl-1-hydroxy-3-hexanone

Figure 1.4 IR Data for 2-ethyl-1-hydroxy-3-hexanone (Figure 1.4) Frequency

Specific Bond Vibration

Functional Group

3339

O-H

Alcohol

2958

Sp3 C-H

Alkane

2932

Sp3 C-H

Alkane

6

2874

Sp3 C-H

Alkane

1704

C=O

Ketone

Since there was only one reactant that was used, which was 2-ethyl-1,3-hexanediol, it is the only limiting reagent. Theoretical yield was found by dividing the starting reactant moles by the limiting reagent moles; thus, multiplying by 100 to get a percentage. The moles of the product were found by dividing the final product by the molecular weight. The percent yield was found by dividing the moles of the product by the moles of the reactant and multiplying it by 100 to get the percentage

Discussion. The goal of this experiment was to observe the oxidation reaction of 2-ethyl-1,3-hexanediol using sodium hypochlorite as the oxidizing agent. An oxidation reaction occurs when a hydrogen atom is added or removed and an oxygen atom is added. The purpose of this experiment was to see if the oxidizing agent was selective or not and what product would be produced from the reaction. Due to the oxidation reaction that occurred 2-ethyl-1,3-hexanediol’s secondary alcohol hydrogen was removed; thus, a C=O carbonyl group had formed. The full reaction time was 32 minutes and 38 seconds and the percent yield was 81.79%. The starch/iodine test was used to determine if there was an excess amount of sodium hypochlorite within the reaction. This is important in determining whether or not the reaction had finished. When the starch/iodine test paper turned blue/purple, it meant that there was an excess of sodium hypochlorite and that the reaction had finished. To purify and isolate the product, an ether and aqueous extraction was performed. The product mixture was combined with diethyl ether to be able to separate the organic layer from the aqueous layer; thus, being able to extract the aqueous 7

layer. The organic layer was then washed with sodium carbonate and sodium hydroxide and the layers were again extracted so the organic layer was by itself. An IR spectrum was done for the starting diol and end product to be able to compare their −1

spectrums. In the IR spectrum for 2-ethyl-1,3-hexanediol, there is a alcohol group at 3339𝑐𝑚

which is also present in the final product. Since an alcohol group is present in the final product, it can be determined that it will not be 2-ethyl-3-oxohexanal. From this information, it can also be determined that sodium hypochlorite is selective and will only oxidize one alcohol group. There are also sp3 alkane peaks present in 2-ethyl-1,3-hexanediol that are also present in the final −1

product. The most important peak is the peak that appears in the final product at 1704𝑐𝑚

that

does not appear in the 2-ethyl-1,3-hexanediol IR spectrum. This peak that is present in the final product shows the presence of a carbonyl group which could be either an aldehyde or a ketone. However it is not an aldehyde because there are no peaks that appear in the final product around −1

2700-2800𝑐𝑚

; thus, it can be determined that it is a ketone group. The final reaction and final

product is as shown:

Figure 1.5 In this experiment I learned what oxidation selectivity was and I witnessed how fickle sodium hypochlorite can be within the 2-ethyl-1,3-hexanediol. Possible errors for this experiment could

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be during the extraction of the aqueous layer. Some of the organic layer could have been extracted and disposed of considering the line that separated them was very thin. While transferring mixtures from the flask, to the tubes, to the beaker, some liquid could have been left and unused.

Conclusion. Since this was an oxidation reaction experiment reacting 2-ethyl-1,3-hexanediol with sodium hypochlorite, to ensure that the 2-ethyl-1,3-hexanediol reacted with all of the sodium hypochlorite, a iodine/starch paper test was done on the mixture to ensure the reaction was finished. The product was purified and isolated by performing an ether and aqueous extraction. In the reaction of oxidizing 2-ethyl-1,3-hexanediol with sodium hypochlorite, a ketone had formed; thus, forming the product 2-ethyl-1-hydroxy-3-hexanone. The percent yield was 81.63%. It was determined that the sodium hypochlorite was a selective oxidizing agent that oxidized the secondary alcohol and left the primary alcohol. Since there was no peak in the IR spectrum that showed an aldehyde, it was determined that a ketone had formed.

References. Arizona State University (2021, October 1 ). Investigating Oxidation Reactions. Retrieved from http://myasucouses.asu.edu University of Texas. Oxidation and Reduction in Organic Chemistry. https://www.utdallas.edu/~scortes/ochem/OChem1_Lecture/Class_Materials/17_redox_states_ca rbon.pdf.

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