Chem 353-40

Chem 353-40 - Two-Step Synthesis of Aspirin from...

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Two-Step Synthesis of Aspirin from Wintergreen Oil Aspirin was the first characterized nonsteroidal anti-inflammatory drug (NSAID) shown to inhibit the cyclooxygenase-1 and 2 (COX 1 and 2) isoenzymes and remains one of the most widely used medications in the world. COX 1 and 2 enzymes are involved in prostaglandin synthesis. Because prostaglandins play a role in inflammation, compounds that inhibit their synthesis by inhibiting the COX enzymes are often effective anti- inflammatory medications. Because aspirin causes stomach ulcers, bleeding, and other problems for some people, other NSAIDs have been developed that do not have these side effects. Ibuprofen is possibly the most common NSAID alternative to aspirin, although acetaminophen is also classified as a NSAID, despite its lack of anti-inflammatory activity. Specific COX-2 inhibitors more dramatically reduce the risk of peptic ulceration. Dan Simmons from Brigham Young University discovered the COX-2 enzyme. This discovery lead to the development of COX-2 specific NSAIDs such as Celebrex and Vioxx. Vioxx has been removed from the market due to safety concerns, but Celebrex continues to be sold as a “super-aspirin”. In this experiment, you will complete a two-step reaction , where you purify, characterize, and use the intermediate in your ultimate synthesis of aspirin. The first reaction is called saponification, because soap is made by basic hydrolysis of fatty esters. In this reaction, methyl salicylate, or wintergreen oil, is refluxed with aqueous sodium hydroxide and worked up under acidic conditions to give the ester hydrolysis product, salicylic acid. As early as 5 B.C., Hippocrates recorded the analgesic (pain reduction) and antipyretic (fever reduction) properties of salicylic acid extracted from the inside of white willow bark. Salicylic acid is commonly used in skin care products for treatment of acne and warts.
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To add to your arsenal of carbonyl reactions completed in the laboratory, in the second reaction, you will be reacting acetic anhydride with salicylic acid to form acetylsalicylic acid, otherwise known as aspirin. Whereas salicylic acid and acetylsalicylic acid have similar analgesic, antipyretic, and anti-inflammatory properties, salicylic acid is acetylated to form a compound with reduced acidity, and thus this acetylation reaction marks the first attempt to make a NSAID that was less irritating to the stomach. salicylic acid acetylsalicylic acid (aspirin) OH O OH OO O 85% H 3 PO 4 O O OH O Compound MW Wt/Vol mmol mp bp Density n D STEP 1: Methyl salicylate 1 152.15 0.30 mL 2.31 223 1.17 1.536 25% Sodium Hydroxide 2 40.00 3 mL ~23 Hydrochloric Acid (3M) 2 36.46 STEP 2: Salicylic Acid 1 138.12 0.225 g 1.63 160 Acetic Anhydride 3 102.09 0.50 mL 5.29 139 1.08 Phosphoric Acid (85%)
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This note was uploaded on 04/06/2011 for the course CHEM 353 taught by Professor Bronson during the Winter '11 term at BYU.

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Chem 353-40 - Two-Step Synthesis of Aspirin from...

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