Fischer Esterification Formal Report

The Extraction of Isoamyl Acetate (banana flavor) and the Calculation of its Percent Yield by means of Fischer Esterification

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Department of Biological Sciences, College of Science

University of Santo Tomas

Abstract

The experiment was conducted to extract isoamyl acetate using Fischer Esterification. The objective of this paper is to prepare the banana flavor and to calculate its percent yield. In the experiment, the mixture was refluxed for 30 minutes at 80° and the organic layer was then extracted to remove the aqueous layer. The percent yield obtained was 56.86%.

I. Introduction

Isoamyl Acetate, a chemical compound producing banana flavor, is one of the additive components used in the food industry today. The fruity taste and odor produced is due to a group of organic compounds called Esters which are derived from carboxylic acids. Simple esters generally tend to possess pleasant odors such as peach, apple, and banana. The most common way to generate simple esters is through a process called Fischer Esterfication. This Fischer reaction happens when a carboxylic acid and an alcohol is mixed with a small amount of acid. In order to separate the products formed by the reaction, a process called Reflux is to be done, wherein heat is applied without losing any liquid to evaporation. The experiment performed aimed to prepare banana flavor through Fischer Esterification and to calculate its percent yield.

II. Methodology

First, set up the cold mixture by preparing two test tubes in an ice bath. Place 2.5 Isoamyl Alcohol in test tube A, then combine 2.6 mL Acetic Anhydride and 5 drops of concentrated H2SO4 in test tube B. Transfer drop by drop the contents of test tube B to A and keep in the ice bath while mixing the sample. Next, allow the water bath to reach 80° then reflux for 30 minutes before transferring into a 50 mL beaker containing one cube of ice. Transfer the mixture in a separatory funnel with saturated NaHCO3. Wait until the bubbling ceases then extract the mixture by separating the lower layer of liquid from the upper layer. Lastly, dry the upper layer with Anhydrous Na2SO4. Weigh the mixtures then calculate for the percent yield.

III. Results and Discussion

Limiting reagent: Isoamyl alcohol

Theoretical yield: [pic 1]

% excess acetic anhydride:  [pic 2]

Percent yield: [pic 3]

In the performed experiment, the reaction mixture must undergo reflux so that any escaping vapor when heating is condensed and returned back to liquid. This reflux set up is significant since the reaction becomes thermally accelerated by performing it at an elevated temperature. After transferring contents to the separatory funnel, the apparatus was swirled gently in order to obtain the organic contents of the mixture. The vigorous bubbling seen at the end is an emulsion which occurs whenever a liquid is dissolved in another liquid. After the solution has rested, the separation of the organic layer from water could be seen. Several chemicals were used in the experiment including saturated NaCl solution which was used to wash the organic layer. NaCl was used instead of water since salt water helps pull water from the organic layer to the water layer. On the other hand, sodium bicarbonate was used since it is known to be effective in removing acids from solutions. Lastly, anhydrous sodium was used because of its abilities as a “drying agent,” which removes water from the mixture.