Fischer Esterification - Lab Report Discussion

In order to successfully run the reaction of Fischer esterification, the application of Le Châtelier’s principle was used. This meant that the acid, acetic acid, needed to be in excess, in order to shift the equilibrium to the right. This is why 1.5 mL of alcohol and 3 mL of glacial acetic acid were used. Several drops of sulfuric acid were then added to the mixture in order to serve as a catalyst for the reaction, meaning the reaction rate would speed up as the transition state would be easier to reach and go over. The solution was then assembled to form a reflux apparatus and heated for about one hour. This step was done to ensure that the component with the lowest boiling point in the mixture, which happened to be the solvent, was able to boil and recondense into a liquid in the reflux apparatus.

Once heating was completed, in order to extract the final product, 3 mL of 5% sodium bicarbonate was added into the mixture, so that it could react with the excess acetic acid, thus neutralizing the acid and forming a salt. The salt that is formed is very soluble in water, and not at all soluble in the organic phase. This causes the acetic acid to be removed from the organic phase, leaving only alcohol, the reaction products, and impurities in the organic phase. This step of the extraction process is done three times in order to ensure that all of the acetic acid is removed from the organic phase and as much as the organic phase is collected as possible. With the extraction, some water is still left in the centrifuge tube, therefore sodium sulfate is used to help remove the water as it is a drying agent. A distillation apparatus with a Hickman stillhead is then heated to 180°C in order to purify the ester that is being formed, by allowing the vapors to condense and be recollected in the stillhead by pipetting the solution out from the stillhead’s side arm.

The percent yield was calculated by taking the original amount of the alcohol and using stoichiometry to figure out the theoretical amount of the product (1,3-dimethylbutyl) acetate, being 1.417g. Dividing that number by the actual yield of 0.307g and multiplying by 100% resulted in a percent yield of 21.67%. This number isn’t very high, and this could be due to incomplete extraction of the final product after distillation or extracting some of the needed aqueous layer with the organic layer.

The purity of the product can be deduced by looking at the observed boiling point