Esterification Lab Report

Experiment 10: Fischer Esterification

Discussion

In this experiment, a Fischer esterification reaction was performed in order to create methyl benzoate from benzoic acid and methanol. Then, a GC was performed to confirm that methyl benzoate had indeed been formed. An ester is an often sweet smelling organic compound which contains a carbonyl carbon bonded to an oxygen connected to another hydrocarbon. Esterification is the process by which esters are synthesized from an alcohol and a carboxylic acid. Fischer Esterification is a type of esterification reaction that was deveoped by Emil Fischer, who was awarded a Nobel Prize in 1902 for sugar and purine synthesis, and was also responsible for the infamous Fischer projections.

The nucleophile

Rarely, phosphoric acid may also be used for this reaction. Another problem with this reaction is that under standard conditions, it only has about a 67% expected yield, instead of the usual 100% expected yield. Keq is described as the concentration of products over reactants, all raised to their stoichiometric coefficients. If the concentration of ester were x, the Keq would be x2/(1-x)2. Due to a Keq of about 4, only about 67% of the reactants form ester, while usually a higher Keq would ensure around 100% yield. To counteract this, product could have been removed from the solution, tilting the equilibrium towards the product side. However, since this would have been impractical and expensive, the reaction was instead shifted to the product side by adding more reactants, when usually only stoichiometric amounts of reactants would be present due to cost constraints.. Either reactant could have been used, but usually the alcohol is used in excess, and also acts as a solvent for the reaction. In this reaction, excess methanol was used not only as a reactant, but also as a solvent for the reaction, hence offsetting some of the costs from using excess reagent. The equation for Keq

The retention time for the product peak, which was the second peak observed on the GC, was 1.420 minutes. This was similar to the peak for methyl benzoate, which according to the supplements, should have occurred at 1.24 minutes. It was hence confirmed that the product formed was indeed methyl benzoate. Another peak with retention time .387 minutes was also observed, which was the peak for the diethyl ether added during the extraction of ester.

The observed retention time, 1.420 min, was slightly different from the expected retention time, 1.24 min. Most of this error most likely occurred due to malfunctioning GCs. The identifying values were also not specifically calibrated to the specific GCs used in lab. Since GC 4 was used for this lab, and was known to have different retention times from other GCs, some error occurred due to lack of specific calibration. The peak observed for methyl benzoate also appeared to be fronting, which means that the slope on the right was close to 90 degrees, giving the peak an appearance resembling that of a right angle triangle. This could have occurred due to overloading of the column by injecting the liquid too quickly. It could also have occurred due to the mismatch of polarity in the sample compound and the stationary