Experiment 8

Experiment 8 - Experiment 8: Williamson Ether Synthesis of...

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16 Experiment 8: Williamson Ether Synthesis of Phenacetin The process of displacement of a halide (RX where X = Cl, Br, I) by an alkoxide anion (RO-) to form an ether is called a Williamson ether synthesis. The principal start- ing material of this reaction is N-(4-hydroxyphenyl)- acetamide, a compound also known as acetaminophen. It is an analgesic (a medication that reduces or elimi- nates pain) and antipyretic (a medication that reduces fever) and is found in many over-the-counter drugs. For example, it is the active ingre- dient of many Tylenol® products. The principal product phenacetin was once the active ingredient of several analgesic and antipyretic Excedrin® medications. Interestingly, phenacetin is converted in the human body to acetaminophen, which is the active agent. The phenol of acetaminophen is a relatively poor nucleophile. However, the presence of the base (potassium carbonate) causes the generation of the conjugate base of aceta- minophen. This new species is called a phenoxide anion, and it serves as a more potent nucleophile than the starting alcohol. The phenoxide anion then displaces iodide via backside attack in a one-step process involving a negatively charged pentavalent inter- mediate. The rate of the reaction depends on the concentration of both the phenoxide anion and the iodoethane; so the reaction is described as S N 2 (substitution nucleophilic bimolecular). please regenerate this completed table in part 1 of your notebook rea- gents Phenol potassium carbonate MEK ethyl iodide ethylated phenol phena- cetin formu- la equiv 1 1.16 1.5 eq 1 MW 151.16 mg/mmol 138.21 mg/mmol 155.97 mg/mmol 179.22 mg/mmol den 1950 mg/mL vol 1.0 mL 0.08 mL (4 drops) mass 100 mg 180 mg 156 mg 118.56 mg mmol. 0.66 mmol 1.30 mmol 1.0 mmol 0.66 mmol mp H N OH O H N O O EtI K 2 CO 3 Now you know… The quarter is almost over and now is a good time to start making a study plan for the final exam. We have covered a lot of material and
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This note was uploaded on 04/09/2010 for the course CHEM 6a taught by Professor Pettus during the Winter '07 term at UCSB.

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Experiment 8 - Experiment 8: Williamson Ether Synthesis of...

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