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In this experiment, the synthesis and purification of acetaminophen were performed. Initially, crude acetaminophen was obtained with a 58.7% yield through the reaction of p-aminophenol with acetic anhydride. The crude acetaminophen was then decolorized, resulting in purified acetaminophen with a 13.5% yield. The purity of the final product was assessed through qualitative observations of coloration and comparison of melting point ranges with pure acetaminophen. The experiment highlighted the importance of minimizing product loss and impurities in the synthesis and purification process.
Acetaminophen, also known as paracetamol, is a widely used over-the-counter pain reliever and fever reducer.
It can be synthesized from p-aminophenol through a chemical reaction with acetic anhydride. The resulting crude acetaminophen can contain impurities, and the goal of this experiment is to purify the product. This process involves decolorization and crystallization to obtain a purified form of acetaminophen.
Materials:
Methods:
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After complete dissolution of the solid precipitate, heat for an additional 20 minutes.
The percent yield of crude acetaminophen was calculated as follows:
Percent Yield of Crude Acetaminophen = (Weight of Crude Acetaminophen / Weight of p-Aminophenol) x 100
Percent Yield of Crude Acetaminophen = (0.122g / 0.150g) x 100 = 58.7%
The percent yield of the final crystallized acetaminophen was calculated as follows:
Percent Yield of Final Crystallized Acetaminophen = (Weight of Final Crystallized Acetaminophen / Weight of Crude Acetaminophen) x 100
Percent Yield of Final Crystallized Acetaminophen = (0.028g / 0.207g) x 100 = 13.5%
During the experiment, the following observations were made:
The results of the experiments are as follows:
Crude Acetaminophen:
Final Crystallized Acetaminophen:
Through the main reaction between 0.150g of p-aminophenol with acetic anhydride, 0.122g of crude acetaminophen was produced along with some acetic acid.
This indicates a 58.7 percent yield of crude acetaminophen. This is a fair percent yield considering a slight amount of p-aminophenol was lost due to spillage in the transferring process into conical vail and slight amount of crude acetaminophen was lost when trying to remove crystallized crude acetaminophen from conical vial.
Percent yield is 58.7% indicating loss of reactants or spillage of products. There is possible error when performing suction filtration; too much washing of product can cause product to fall through filter ultimately decreasing overall percent yield. also overheating may have caused a loss of product; some of the product may have been splattered out of the reaction vessel when heating. 1005 yield would mean that one has carried out the lab activities perfectly producing the predicted amount of product. Given the 58.7% yield actually obtained, it is evident that experimental procedures be accurately followed for further improvement. It is in the transferring process of p-aminophenol to a 5mL conical vial. Where error is most critical and product can be readily lost.
After decolorization process, 0.060g of decolorized/purified acetaminophen was obtained indicating a significant loss of product. Prior to decolorization process, 0.122g of crude acetaminophen solid was present, meaning half of product was lost in the decolorization process. It is important to note that a significant amount of product was lost due to spillage when transferring crude acetaminophen into conical vial to decolorization. Error may also be present if mixture is overheated and product is evaporated off.
After crystallization process of purified acetaminophen, 0.028g of white final acetaminophen resulted indicating a 13.5% yield. this is a poor percent yield. this indicates slightly less than half of 0.060g of purified acetaminophen was lost. Such a low percent yield can be attributed to the loss of product throughout the crystallization process. It is important o note that a significant amount of product was lost within supernatant after centrifugation, also, product was lost when trying to remove product from Craig tube and plug.
Purity of final product of acetaminophen was tested through qualitative observation of coloration and by comparing obtained melting point ranges of crude and final acetaminophen to the literature melting point range of pure acetaminophen. Because crude solid acetaminophen contains dark impurities carried along with p-aminophenol we can qualitatively compare the level of impurity before and after decolorization. As for the second test for impurity, the melting point range of the crude acetaminophen, 166.8-167.6°C is slightly depressed when compared to the known melting point range of pure acetaminophen 169.5-171°C. Crude acetaminophen melting point range is depressed by 2.7°C. A difference of less than 5°C indicates a good melting point range was obtained for crude acetaminophen this indicating a minimal amount of impurity present. The melting point range of final crystallized acetaminophen, 166.1-169.8°C is slightly depressed and elongated when compared to the known melting point range of pure acetaminophen 169.5-171°C.
It is depressed by 3.4°C and elongated by 2.2°C. A difference of less than 5°C indicates a good melting point range was obtained, though impurities may still be present. When crystals are isolated by filtration from a solvent, it is important to allow complete drying/evaporation of the solvent in order to minimize impurities and get a good melting range. Residual solvent may also function as an impurity and will depress/broaden the melting range for acetaminophen. When two chemicals are mixed, side reactions may take place and produce by-products which can serve as impurities ultimately lowering and elongating the melting point range. For further reference, one must meticulously carry out experimental procedures to ensure that neither reactants nor product is lost and higher percent yield is obtained.
The synthesis and purification of acetaminophen resulted in a crude product with a 58.7% yield and a final crystallized product with a 13.5% yield. The low yields indicate the loss of product during various stages of the experiment, including transfer, heating, and purification steps. The presence of impurities was confirmed through melting point analysis. Further refinement of the experimental procedures is necessary to improve yield and purity.
To enhance the efficiency and yield of the synthesis and purification processes, the following recommendations are made:
Lab Report: Synthesis and Purification of Acetaminophen. (2016, Mar 16). Retrieved from https://studymoose.com/document/isolation-of-crude-acetaminophen
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