Lab Report Exp19

Lab Report Exp19 - Ryan Cohen 5/25/09 Synthesis of Aspirin...

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Ryan Cohen 5/25/09 Synthesis of Aspirin and Oil of Wintergreen The purpose of this lab was to introduce key concepts in the synthesis of organic molecules, most notably, the importance of purifying a synthesized compound. The lab synthesized two very practical organic compounds, Aspirin and Oil of Wintergreen. The synthesis of these compounds introduced significant analytical techniques for identifying, measuring and eliminating impurities in synthesized organic compounds. Moreover, it demonstrated how functional groups within an organic compound, specifically in esterification reactions, interact to construct a desired product. The first part of the lab synthesized a crude sample of Acetylsalicylic Acid, commonly known as Aspirin, revealing how functional groups react to create such useful organic products as Aspirin. The synthesis of Aspirin follows a general trend in organic chemical reactions known as esterification reactions. Essentially, a compound containing a hydroxyl group reacts with a compound containing a carboxylic acid group, producing an ester molecule and water as a product. In the case of Aspirin production, salicylic acid (containing a hydroxyl group) reacts with acetic acid (containing a carboxylic acid group) producing Aspirin (an ester) and water. However, since this reaction is relatively slow, the lab used acetic anhydride instead of acetic acid to drive the reaction to completion. As a result, acetic acid was produced as a product rather than water. The chemical formula that describes this reaction goes as follows: C 7 H 6 O 3 (s) + C 4 H 6 O 3 (l) H+ C 4 H 8 O 4 (s) + C 2 H 4 O 2 (l) The mass of Aspirin produced was 2.695g giving a slightly high percent yield of 114%. This can be easily explained by the inevitable presence of impurities in the aspirin sample. Un-reacted
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salicylic acid and acetic acid were added to the product, producing a slightly inflated % yield. Ultimately, the data revealed the importance in understanding functional groups in the synthesis of organic compounds. Moreover, it demonstrated the significant effect in % yield impurities can have in a product. The second part of the lab performed a purity test on the produced Aspirin sample by isolating specific chemical characteristics of the un-wanted impurity. Referring to the chemical reaction to produce Aspirin, un-reacted salicylic acid and acetic acid can manifest as impurities in the final product. However, since acetic acid is water soluble, the elimination of acetic acid can be accomplished by simply rinsing the product. The second part of the lab tests for the presence of salicylic acid as an impurity. FeCl 3 solution was added to a sample of the produced aspirin as well as a sample of salicylic acid. Recognizing that the salicylic acid coordinates to the iron(III) in FeCl 3 , similar color in the two samples suggested the presence of salicylic acid in
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Lab Report Exp19 - Ryan Cohen 5/25/09 Synthesis of Aspirin...

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