Synthesis of Isopentyl Acetate (Banana Oil) Using a Fischer Esterification Reaction

1327 Words Oct 24th, 2012 6 Pages
Synthesis of Isopentyl Acetate (Banana Oil) Using a Fischer Esterification Reaction
Zhenshu Wang (Stan)
TA: Aaron League
September 23, 2012

Purpose: The purpose of the experiment was to perform the acid-catalyzed Fischer Esterification of acetic acid and isopentyl alcohol to form isopentyl acetate, or banana oil, which is used in flavor industries. The equilibrium of the reaction was changed by adding an excess amount of acetic acid. The reaction was refluxed and product was purified by extraction and distillation. Isopentyl acetate was analyzed by infrared spectroscopy and 1H NMR spectroscopy.

Reaction Scheme:

Mechanism: Key features of the Fischer Esterification mechanism are: a. protonation of the carbonyl group, b. the
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Doublet peak at 0.899ppm with integration of 11.0 cm indicated six hydrogens in the same environment suggesting that there was an isopentyl group in the product. Based on the observation above, isopentyl acetate was present. There was no peak from 9.7ppm to 12.5ppm indicating that product had no carboxylic acid group which meant the product was pure without acetic acid.
IR spectrum also indicated the presence of isopentyl acetate. Wave number at 1744.4 cm-1 was observed indicating the presence of carbon-oxygen double bond. The presence of carbon-oxygen single bond was confirmed by the wave number at 1244.3 cm-1. Alcohol or carboxylic acid group were not observed since there was no broad peak in the 3200-3500 cm-1 region. This was the evidence indicating that reactants were not in the product. However a wave number of 606.1 cm-1 was observed in infrared spectroscopy indicating a carbon-chlorine bond was in the product. The reason for this could be impurity of CH2Cl2 in final product, an IR spectrum for CH2Cl2 is attached. Dichloromethane was used as cleaning solvent for the sodium chloride plate.
Overall, a successful experiment was performed. Isopentyl acetate (banana oil) was obtained through the reaction between isopentyl alcohol and acetic acid, with a yield rate of 59.8%. Careful analysis using the qualitative techniques of infrared spectroscopy and 1H

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