For experiment 10, the oxidation of 2-octanol to 2-octanone took place using 10.0 mL of sodium hypochlorite (NaOCl) as the oxidizing agent along with 0.500 mL of glacial acetic acid and 5.0 mL of acetone. Adding the sodium hypochlorite to the solution caused the temperature to increase, indicating that this was an exothermic reaction. Adding 10% NaOH was necessary in order to confirm that the product was basic before adding diethyl ether to extract the solution. This was done twice and then the solution was dried using MgSO4 before being placed in the rotovap. The remaining product was weighed and then analyzed using infrared spectroscopy. The calculated percent yield for this reaction was 44.9%, with 0.29 grams of product remaining. Introduction: Household bleach, or sodium hypochlorite, is a common oxidizing agent that is used in organic chemistry due to it being cheap and easy to obtain. It has a molecular weight of 74.44 grams/mol and has a pKa of 7.53 when it is combined with an acid, and is also called hypochlorus acid (HClO).4 2-octanol is a fatty alcohol that is commonly used as a flavoring agent in food and is soluble in organic solvents such as diethyl ether and acetic acid.3 It is colorless and has a boiling point of 179°C and its molecular weight is 130.231 grams/mol. When alcohols undergo oxidization, an aldehyde or ketone is produced, depending on the structure. Secondary alcohols, such as 2-octanol, will produce a ketone when oxidized, and primary alcohols will produce aldehydes.2 When an oxidizing agent such as household bleach (sodium hypochlorite) interacts with an alcohol, a hydrogen atom is removed in the process. It is important to note that an acid must be present in order for oxidation to occur in alcohols because the acid increases the concentration of the oxidizing agent so that the reaction may proceed.1 The oxidation of 2-octanol to 2-octanone was demonstrated in lab by combining the solvents 2-octanol (0.800 mL) and acetone (5.0 mL) with acetic acid (0.500 mL) and then slowly adding bleach (sodium hypochlorite). The mechanism for this experiment can be seen in equation 1 where 2-octanol is being oxidized by sodium hypochlorite to produce 2-octanone. The line reaction for equation 2 better explains how this reaction took place to form a ketone. (1) (2) Experimental Methods: An apparatus was assembled using a 100-mL 3-neck flask with a separatory funnel on the middle neck. A thermometer was then placed in a side neck and a rubber stopper was placed in the other. This apparatus was held together with a clamp on a ring stand and was set directly on a hot plate. 2-octanol (0.800 mL), glacial acetic acid (0.500 mL) and acetone (5.0 mL) was added to the 3-neck flask along with a stirring bar. Bleach (10.0 mL) was then added to the separatory funnel to begin the reaction. The stirring mechanism on the hot plate was set to 2 before adding the bleach to the solution one drop at a time. The thermometer was checked periodically to make sure that the temperature did not exceed 40°C and remained around 35°C. After approximately 20 minutes, the bleach was completely added to the mixture and was left to stir for an additional 15 minutes. Once the mixture was close to 25°C, the stirring mechanism on the hot plate was turned off and the pH was obtained. Bleach (2 mL) was added to neutralize the mixture and then 10% NaOH (~2 mL) was also added to confirm basicity. As shown in equation 3, the loss of the hydrogen atom on the acetic acid was necessary in order for it to be neutralized so that the product could be extracted in the next step. (3) To extract the solution, diethyl ether (10 mL) was added twice along with saturated NaCl. The extracted solution was added to a 50 mL Erlenmeyer flask and was dried over MgSO4. The flask was placed in an ice bath until crystals began to form. The product was then placed in the rotovap. After doing so, the percent yield was calculated and the product was analyzed using infrared spectroscopy. Results and Discussion: The oxidation of 2-octanol to 2-octanone took place for this experiment by using sodium hypochlorite as the oxidizing agent. The temperature of the solution was monitored carefully once the sodium hypochlorite was added slowly to the 3-neck flask composed of 0.800 mL of 2-octanol, .500 mL glacial acetic acid and 5.0 mL of acetone. The starting temperature was 25°C and increased to 27°C after 10 minutes and then to 30°C after 15 minutes. Once the temperature began to drop, the stirring mechanism on the hot plate was turned off and the final temperature was recorded at 28°C. The solution had a yellow tint, but this was possibly due to there being leftover product from a previous experiment. This did not affect the results. The pH obtained immediately after the reaction completed was 6, so 2.0 mL of sodium hypochlorite was added to make the product less acidic. 10% NaOH was then added to confirm the basicity of the solution before proceeding with the extraction. The pH was at 9 and then the aqueous layer of the product was drained twice using diethyl ether and saturated NaCl. The product was added to a 50 mL Erlenmeyer flask and was dried using MgSO4. Placing the product into the ice bath assisted with the formation of crystals so that the rotovap could be used to extract the remaining product shortly after. The weight of the product was 0.29 grams and then it was analyzed using IR spectroscopy. As seen in Figure 1.1, there were peaks around 3000, indicating that there was a C-H stretch and the ketone functional group can be seen around 1750. The “blob” around 3300 shows that there was still starting material present, which was an alcohol. Overall, the IR spectroscopy for the product that was obtained in lab is comparable to the expected peaks that would be seen for 2-octanone. Figure 1.1: The IR spectroscopy of 2-octanone after completing the experiment. The calculated percent yield for the remaining product was 44.9%, which was fairly low. Some of the product may have been lost when extraction took place to separate the aqueous layer from the organic layer. The stopcock on the separatory funnel may not have been closed quickly enough to prevent the organic product from being extracted with the aqueous (ether) product. 0.800 mL of 2?octanol ×0.821 grams1 mL=0.657 grams of 2?octanol 0.657 grams of 2?octanol×1 mole 2?octanol130 grams 2?octanol ×128 grams 2?octanone1 mole 2?octanone=0.64689 grams 2?octanone % yield = ActualTheoretical=0.290 grams 2?octanone 0.64689 grams 2?octanone=44.9% Conclusions: Based on the results obtained from this experiment, it can be concluded that the oxidation of 2-octanol to 2-octanone was a success. Despite there being a low percent yield, the IR spectra for the product produced in lab was similar to the expected peaks for 2-octanone. This suggests that sodium hypochlorite was an effective oxidizing agent for 2-octanol with the help of acetic acid and acetone. To prevent the loss of product in the future, it might be helpful to take more time to carefully extract each layer from the separatory funnel so that organic product is not lost with the aqueous layer. Being more precise in the observations section of the laboratory manual would also be beneficial for better understanding why there may have been errors in the experiment that would account for a low percent yield.
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