Isopropanol's Effects on Fischer Esterification: A Comparative Study, Lecture notes of Electronics

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Effects of Solvents on the Fischer Esterification

[Student’s Name]

Chemistry 216 Section 423

Group Members: [Student’s Name, Student’s Name, Student’s Name]

Winter 2013

Introduction

The overall purpose of this experiment was to determine if a “bulky” solvent had any effect on the Fischer esterification reaction. Typically, ethanol is used as the solvent and is known to work very well. For this experiment, we ran two reactions with ethanol and two reactions with isopropanol (which served as our “bulky” solvent) in order to ensure we would have at least one working reaction per solvent, as well as to ensure reproducibility. The effect of the “bulky” solvent on the reaction was determined by comparing yields and time to form a precipitate with that of the ethanol reaction. Our hypothesis was that the isopropanol would work just as well as the ethanol. The Fischer esterification is good because it is an important reaction in the synthesis of many anesthetics (such as Benzocaine). Having anesthetics in high yield is important as they have many uses in medicine, be it over-the-counter or prescription. In terms of natural synthesis, an acid-catalyzed esterification reaction is actually what causes the production of esters in wine, giving different wines their different flavors (Braymer). The reaction will utilize reflux prep., vacuum filtration, IR spectroscopy, and melting point analysis to determine if the resulting product matches the intended product, Benzocaine.

Reaction Scheme

2929.71 cm-1, and 2817.17 cm-1 which indicate C-C aromatic stretches as well as sp3- hybridized carbons. Lastly, the presence of sharp, strong peaks at 1680.00 cm- 1 indicates the presence of a C=O ester stretch. These peaks all match with expected peaks of Benzocaine. Additionally, the known IR data for Benzocaine looks very similar to the IR spectrum obtained in the experiment. TLC spotting of the crude solid and the starting material (PABA) was done, as well as a co-spot of both. Results showed an RF value of .35 for the crude product, and RF value of. for the PABA, and two separate spots with RF values of .35 and .16 for the co-spot. The separate RF values indicate that the product is different from the starting material, and the complete separation of spots in the co-spot indicates that the product is pure. When performing melting point analysis, our crude product melted at 88.6 ◦C. This melting point matches the known data for Benzocaine, which has a melting point range of 88-90 ◦C.

Conclusion

Overall, this experiment is important as it the products can be used in medicines to help treat patients who need local anesthetics. Being able to produce these in high yield can help to make sure there is always medicine available for those who need. The results of the reaction that used the ethanol solvent did appear to be successful; however, the results for the isopropanol reaction were unsuccessful. Given the failure of the isopropanol but the success of the ethanol reaction, our hypothesis was incorrect. In order to avoid this in future experiments, I would re-filter any liquid that remained after the initial filtration. When running this experiment, we only filtered once, which may have led to liquid extract mixed with our precipitate.

References

Braymer, Joseph. Chemistry 215 lecture. University of Michigan. 8 February 2013. Reaxsys. 2.13618.7. Elsevier Properties SA, n.d. Web. 13 Feb. 2013. Spectral Database for Organic Compounds SDBS. National Institute of Advanced Industrial Science and Technology (AIST), n.d. Web. 13 Feb. 2013.