Preparation of Banana Essence

Preparation of Banana Essence Precious Pattugalan, Pattugalan, Angel Pacheco, Joseph Pacia and Meryl Pagunuran Group 9, 3BIO2, Department of Biological Sciences, University of Santo Tomas, Sampaloc, Manila, Philippines

Abstract A reflux setup was used to investigate the variation of boiling point for a mixture of two immiscible immiscible liquids. Reagents Reagents such as NaHCO 3, NaCl and anhydrous Na 2SO4 were used to recover recover the organic organic layer of the product. product. The catalyst catalyst used used was H 2SO4. The recovered Isoamyl acetate product was a colorless, fruity-smelling liquid. Its percent yield is 42.96%. Introduction An ester is a carboxylic acid derivative in which the --OH is replaced by an --OR group.

[2]

The Fischer reaction, or Fischer esterification, is the acid catalyzed condensation of a carboxylic acid and an alcohol. [3] The ester prepared in this experiment is the Isoamyl acetate. Isoamyl acetate is a fundamental component of banana flavoring.

Figure 1. Molecular Formula of Fischer Reaction

The reflux set-up was used in this experiment to speed up the reaction since esters usually have a slow reaction rate. Reflex refers to the process of boiling while leading the vapor  into a cooling condenser mounted above the flask.

[4]

The separatory funnel was used for the extraction of the organic layer of the solution from the NaHCO 3 and the NaCl layer.

Water out

Condenser

Water in

Figure 2. Reflux Set-Up [4]

Figure 3. Separatory Funnel [4]

The objective of this experiment was to prepare the assigned ester, the Isoamyl acetate, via the Fischer reaction and calculate its percent yield. Results and Discussion The Isoamyl alcohol, or isopentyl alcohol, was the alcohol used for preparing the banana flavoring. Acetic anhydride was used to react with Isoamyl alcohol to give the desired ester  product. Sulfuric acid (H 2SO4) was used as a catalyst in this experiment. Table 1. Results and amounts

Isoamyl Alcohol

2.5 mL

Acetic Anhydride

2.6 mL

Concentrated H 2SO4

5 drops

Isoamyl Acetate Physical State

Liquid

Color

Colorless

Odor

Fruity

Weight

1.28 g

Percent Yield

42. 96 %

The final product Isoamyl acetate was a colorless, fruity-smelling liquid. The percent yield was calculated by using the formula % Yield = Actual YieldTheoretical  Yield . The percent yield was 42.96%. Table 2. Values used to get the percent yield

Amount

Molecular Weight

Density

C5H12O

2.5 mL

88.2 g/mol

0.8092 g/mL

C3H4O4

2.6 mL

102.1 g/mol

1.0820 g/mL

C6H12O2

1.28 g

130.2 g/mol

N/A

Actual Yield: 1.28 g % Yield = 1.281 g 2.982 g 42.96% x 100 =

The relatively low percent yield may be due to the loss of product by technical or  experimental errors. Some of the product may have been left inside the round flask before it was transferred to the separatory funnel or it may have been left inside the separatory funnel when the final product was transferred to the vial. The swirling of the separatory funnel functions in hindering the evolution of carbon dioxide gas inside it. Sodium chloride was used to rinse the organic layer of the solution, instead of  water, because it is aqueous. The aqueous sodium chloride aided the separation of the organic layer and the NaCl layer. [1] Sodium bicarbonate was used to remove, by extraction, the acetic acid in the organic layer. [1]

Anhydrous sodium sulfate (Na 2SO4) was used to rid the product of water.

Experimental At the beginning of the experiment, 2 test tubes were gathered. Test tube A and test tube B were filled with 2.5 mL Isoamyl alcohol and 2.6 mL Acetic anhydride with 5 drops of H 2SO4 respectively. The contents of test tube A was poured inside the flask first. After that, the contents of test tube B were poured slowly inside the flask. The flask was placed in an ice bath because the reaction of the solutions was exothermic. The flask was swirled continuously. The mixture was transferred in a reflux set-up. Before boiling, boiling chips were added to ensure smooth boiling. The mixture was refluxed for 30 minutes, maintaining a temperature of 80°c. After 30 minutes, the mixture has reached equilibrium. Further heating of the mixture will not result in an increase in product yield. [5] After the mixture has been refluxed, the mixture was allowed to cool and then transferred into a separatory funnel. The mixture inside the separatory funnel was was washed with 15 mL of saturated NaHCO3. Two layers were formed in the funnel: the sodium hydrogen carbonate (NaHCO 3) layer and the organic layer. The NaHCO 3 was discarded and the organic layer was washed with 15 mL of NaCl solution. Again, 2 layers were formed: the sodium chloride (NaCl) layer  and the organic layer. The NaCl layer was discarded and the organic layer was dried with anhydrous Na 2SO4. The final product was then placed in a pre-weighed test tube and then weighed.

Conclusion The experiment was successful because isoamyl acetate was recovered from the reaction of isoamyl alcohol and acetic anhydride. The percent yield was also calculated using the values in table 2. Although the percent yield was low, the desired ester product was still recovered from the finished experiment.

References [1] Bailey, P.S., and Bailey, C. A. (2000). Organic chemistry: A brief survey of concepts and applications (6 th ed.). New Jersey: Prentice Hall. [2] Hart, H., Craine, L., Hart, David. and Hadad, C. (2007). Organic chemistry: A short course (12 th ed.). Boston, MA: Houghton Mifflin Company. [3] Kosak, J. R. and Johnson, T. A. (1994). Catalysis of organic reactions. New York City: Marcel Dekker, Inc. [4] Organic Synthesis: Fischer Esterification (2011). Retrieved July 02, 2011 from http://www.scribd.com/doc/27334048/Experiment-5-Organic-Synthesis-FischerEsterification1 [5] MHS  AP Chemistry: Preparation of an Ester (2010). Retrieved July 02, 2011 from http://www.dbooth.net/mhs/ap/isoamylacetate.html Appendices Limiting Reagent: 2.5 mL C5H12O x 0.8092 g ml C5H12O x mol C5H12O88.2 g x mol molC C6H12O2 mol 0.0229 6H12O2 C5H12O = 2.6 mL C3H4O4 x 1.0820 gmL C3H4O4 x mol C3H4O4102.1 g x mol C6H12O2mol C3H4O4 = 0.276 mol C 6H12O2 Theoretical Yield: 0.0229 mol C 6H12O2 x 130.2gmol C6H12O2 = 2.98 g C6H12O2 Actual Yield: 1.28 g % Yield = 1.281 g 2.982 g 42.96% x 100 =