O Chem Lab report 5

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Feb 20, 2024

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Jade Fuller 11-20-2023 Experiment 5: Preparation of Acetaminophen Introduction and Theory: The molecular structures of many over-the-counter headache medications are comparable. Along with aspirin, acetanilide, phenacetin, and acetaminophen are essential ingredients in many over-the-counter medications because they are mild analgesics (lower fever) and antipyretics (relieve pain). More over-the-counter pain relievers have recently become marketed. It was discovered that phenacetin was a very potent antipyretic and analgesic. An APC tablet, a popular kind of combination pain medication, used to be accessible. Aspirin, phenacetin, and caffeine made up an APC tablet (thus, APC). Commercial pain relievers no longer contain phenacetin. Later research revealed that not all aromatic hydroxyl groups produce harmful chemicals, and acetaminophen, a molecule that was formerly employed in place of phenacetin as an analgesic, is now widely utilized. Salicylamide is another analgesic with some use that shares structural similarities with aspirin. Although its use is decreasing, salicylamide is a component of certain pain relievers. Our theory is acetaminophen is prepared by reacting an amine with an acid anhydride to create an amide. In this instance, the amine p-aminophenol is reacted with acetic anhydride to produce the amide acetaminophen (p-acetamidophenol). Acetaminophen is produced when the purified p-aminophenol goes through the above-described process. The major reasons this product will be impure are the byproducts of different side reactions and the existence of unreacted p-aminophenol. Reactions that happen in addition to the primary reaction of interest are called side reactions. Through recrystallization, the unpurified acetaminophen will be made pure. CAS Numbers 1. Purified p-aminophenol (CAS # 2. Acetic anhydride (CAS #108-24-7) 3. Methanol (CAS #67-56-1) Chemical Reactions: Procedure: Part A: 1 . Put sand in your heating mantle, and plug the mantle into a voltage regulator. 2 . Put 1.52g of toxic p-aminophenol in a 100-mL beaker. Using a graduated cylinder, add 40 mL of water to the flask.With occasional swirling, heat the mixture on a hot plate. Heat until the solid has completely dissolved. Added two scoops of charcoal. Suction filter using a Buchner funnel and filter paper. 3 . Allow the solution to cool slowly to room temperature. Then place the flask in an ice-water bath. 4 . When crystallization is complete after about five minutes, vacuum filter the crystals using a Buchner funnel. Swirl the mixture in the flask and pour about one-third of this mixture into the

funnel. Using your spatula, scrape out as many of the crystals as possible from the flask. Add about 1 mL of ice-cold water to the flask. Swirl the liquid in the flask and then pour the remaining crystals and water into the Buchner funnel. 5. Scrape the crystals onto a watch glass or clay plate for air-drying. Separate the crystals as much as possible with a spatula. The crystals will dry in about 10 minutes. 6 . Weigh the crystals, and calculate the percentage recovery from the crystallization. Observations : ● In part A, the compound was supposed to be a white color, instead it was a yellow-tannish color. ● Substance turned black after adding the activated charcoal. ● Purified p-aminophenol melting point: Range: 160 C - 165 C ● Crude melting point: Range: 160 C - 165 C Part B: 1. Weigh about 0.4g of purified p-aminophenol (M.W. 109.1) and place this in a 5-mL round-bottom flask. 2. Using a pipette, add 20 molar equivalents of water and a 1.5 molar equivalent amount of acetic anhydride. Heat the reaction mixture while gently stirring. 3. After the solid has dissolved, heat the mixture for an additional 10 minutes to complete the reaction. 4. Remove the flask and allow it to cool. When the flask has cooled to the touch, detach the air condenser. 5. Pour the contents into a small flask or beaker and allow it to cool to room temperature. Collect the crystals by vacuum filtration on a Hirsch funnel with filter paper. 6. Rinse the flask with about 1 mL of ice water and transfer this mixture to the Hirsch funnel. Wash the crystals on the funnel with two additional 0.5-mL portions of ice water. Dry the crystals for 5-10 minutes by allowing air to be drawn through them while they remain on the Hirsch funnel. 7. Transfer the product to a watch glass or clay plate and allow the crystals to air dry. 8. Weigh the crude product and set aside a small sample for a melting point determination. Observations :

● Acetic Anhydride has a very strong smell and is a corrosive agent. ● When adding acetic anhydride and the purified p-aminophenol with water in a beaker, the substance turned a dark-brown reddish color and smelled like vinegar. ● After heating the substance for 10 minutes then placing it into an ice bath, the substance’s color lightened. ● Putting the substance through vacuum filtration, the compound on the filter paper looked a pink-creamish color and the liquid at the bottom of the filtration was an orange-brownish color. ● Crude weight = 0.42 grams. Part C: 1. Crystallize the crude acetaminophen from a solvent mixture composed of 50 % water and 50 % methanol by volume using a small test tube. When the solid has dissolved, quickly filter your solution into another test tube while it is still hot and allow the solution to cool at room temperature. 2. When the mixture has cooled to room temperature, place the test tube in an ice-water bath for several minutes to initiate crystallization. Collect the crystals by suction filtration on your Hirsch funnel. Then, collect the crystals on a watch glass or piece of smooth paper. 3. Set the crystals aside to air-dry until the next lab period. Observations : ● Solution in the test tube went from a light, clear, orangish color to a milky white chunky color. ● After adding methanol and water to the compound during vacuum filtration made the compound look cleaner. Part D: 1. Weigh the purified acetaminophen, and calculate the percentage yield. 2. Determine the melting point. Compare the melting point and the color of the final product with that of the crude acetaminophen and the theoretical value. Results and Discussion : In Part A, the melting points discovered are… ● Purified p-aminophenol melting point: 165 C Range: 160 C - 165 C ● Crude melting point: 163 C Range: 160 C - 165 C In Part B, the melting points discovered are…

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● Crude melting weight: 0.42 grams In Part C, the melting points discovered are… ● Crude melting point: 173 C ● Range: 170 C - 173 C Conclusion : The synthesis of acetaminophen involves the acetylation of p-aminophenol, a compound derived from phenol. In a controlled laboratory setting, p-aminophenol is reacted with acetic anhydride, leading to the substitution of a hydroxyl group with an acetyl group. This chemical transformation results in the formation of acetaminophen and acetic acid as byproducts. The reaction necessitates precise temperature control and careful monitoring to achieve optimal yields. Following the synthesis, purification steps, such as crystallization, are employed to obtain a purified form of acetaminophen. Questions : 1. The synthesis of aspirin is similar to the synthesis of acetaminophen. Give a chemical equation showing the synthesis of aspirin using the names of the chemicals and their structures! Salicylic Acid+Acetic Anhydride→Aspirin+Acetic Acid In the reaction, the -OH group of salicylic acid reacts with the acetic anhydride, resulting in the formation of acetylsalicylic acid (c) and acetic acid. + → + 2. Briefly report on two other analgesics not mentioned in the introduction. Draw their structure using ChemDraw and their names. (1) Ibuprofen : Ibuprofen is a nonsteroidal anti-inflammatory drug (NSAID).

Chemical Structure: C13H18O2 Mechanism of Action: The enzymes COX-1 and COX-2, which are involved in the synthesis of prostaglandins, are inhibited by ibuprofen. Ibuprofen has anti-inflammatory, analgesic, and antipyretic properties through lowering prostaglandin levels. Uses: Ibuprofen is frequently used to treat accidents, menstrual cramps, and arthritis-related pain and inflammation. It works well to lower fever as well. (2) Morphine : Morphine is an opioid analgesic derived from the opium poppy plant. Chemical Structure: C17H19NO3. Mechanism of Action:

Morphine acts on specific receptors in the central nervous system known as opioid receptors. It inhibits the transmission of pain signals and alters the perception of pain by binding to these receptors. Uses: Morphine is a potent pain reliever and is often used for severe pain, such as post-surgical pain or pain associated with certain medical conditions. It is also used in the management of pain in palliative care. 3. List any source(s) of errors in the experiment. One error that we had is when we washed the compound in Part A, it was not washed enough and the color of the substance was a tan color instead of white. This error also carried into Part B, instead of the dried compound having a gold color, it had a bronzed-sparkly color since it was not all the way washed. References : Adapted from: Pavia, D. L.; Lampman, G. M.; Kriz, G. S.; Engel, R. G . Introduction to Organic Laboratory Techniques: A Microscale Approach , Fort Worth: Saunders, 1990. PubChem. 2019. Ibuprofen. Nihgov. https://pubchem.ncbi.nlm.nih.gov/compound/Ibuprofen#section=Structures. PubChem. “Morphine.” Pubchem.ncbi.nlm.nih.gov , pubchem.ncbi.nlm.nih.gov/compound/Morphine#section=2D-Structure.

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