asprin.docx - Bryanna Tanase John Torres Geoffrey Gray...

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Bryanna Tanase John Torres Geoffrey Gray Synthesis of Acetylsalicylic Acid
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Introduction Aspirin is one of the most well-known pharmaceuticals in history that is still prevalent today. It is given as a prescription for treatment of rheumatoid arthritis, systemic lupus, and other conditions where the immune system attacks parts of the body 2 . It is also available over the counter to reduce fever, relieve headaches, colds, and tooth and muscle aches 2 . Aspirin is synthesized most readily by combining salicylic acid with acetic anhydride, a sulfuric acid catalyst, and heat which create aspirin (acetylsalicylic acid) when reacted 3 (see figure 1). Water is added to stop the reaction and cause aspirin crystals to form 3 . Acetylsalicylic acid is composed of a carboxylic acid and ester functional group, and it is a member of the ester group of organic compounds 4 . Figure 1: Aspirin synthesis reaction 3 Esters can be synthesized through many different methods. The method of choice is esterification, which reacts an alcohol with a carboxylic acid in the presence of an acid catalyst 1 . The general chemical equation for the reaction is shown in Figure 2, and the R groups on the ester and alcohol can be the same of different 5 . A more specific example of an esterification reaction is when ethyl ethanoate is prepared by reacting ethanoic acid and ethanol in an acid catalyst (Figure 2) 5 .
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Figure 2: General and specific esterification examples 5 The second method of synthesizing esters is by adding an acid chloride to an alcohol, this works with phenols but better results are received when the phenol is converted into something more reactive 5 . An example of this type of ester formation is when liquid enthanoyl chloride is reacted with ethanol, producing a burst of hydrogen chloride along with the ester, ethyl ethanoate 5 . The equation for this reaction is pictured below 5 . Figure 3: Equation for ethyl ethanoate preparation 5 . Esters can also be made from alcohols and phenols using acid anhydrides. These reactions are slower than the former acid chloride, and the reaction mixture is usually warmed 5 . A typical example of this reaction involves mixing ethanol with ethanoic anhydride 5. The reaction is slow until heated and a mixture of ethanoic acid and ethyl ethanoate is formed 5 . The equation for this reaction is shown below. Figure 4: Preparing ethyl ethanoate using an acid chloride Spectroscopic techniques can be helpful in determining whether or not aspirin is prepared in that an IR spectrometer will show a broad peak at 3300 for the alcohol attached to the benzene ring, a broad fuzzy peak at 2500 for the carbonyl group of the ester, and a sharp peak at 1690 for the alcohol group attached to the right side of the ester 1 .
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The goal of this experiment is to synthesize acetylsalicylic acid from salicylic acid and acetic anhydride. In the first step of the reaction, acetic anhydride is protonated, and then the lone pair electrons on the alcohol oxygen in salicylic acid attack the protonated acetic to form (R)-2-(1-acetoxy-1-hydroxyethoxy) benzoic acid. The final step is that phosphoric acid in
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