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

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  • October 13, 2012
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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 formation of the tetrahedral intermediate, and c. regeneration of acid to show its role of catalyst in the reaction.

Procedure: The procedure followed was as described in the Wissinger Manual.1 Modifications of the procedure included: The drying agent took 25 minutes, as opposed to the suggested 10-15 minutes. The voltage for the heating mantle was changed from 70 volts, in the manual, to 80 volts.

Reagent/Product Table
| Acetic Acid| Isopentyl Alcohol| Con H2SO4(95-98%)| Isopentyl Acetate| H2O| Mol Wt.| 60.05| 88.15| 98.079| 130.19| 18.02|
Grams| 8.9| 5.0| 2.2| X| X|
moles| 0.148| 0.0567| 0.0225| X| X|
mL| 8.5| 6.2| 1.2| X| X|
Density 2g/mL| 1.049| 0.813| 1.84| 0.876| 1.00|
bpt/mpt, oC 2| 118| 130.5| 337| 142| 100|
Solubility 2| Miscible with water| Slightly sol in water| Miscible with water| Slightly sol in water| N/A| Hazards 3| irritant| Avoid breathing vapors| corrosive, irritant| Flammable, avoid skin contact| No hazards|

Results and Observations:
Observations: When concentrated sulfuric acid was added to the acetic acid and isopentyl alcohol, an exotherm was observed. The reflux was performed as described in the manual; however, the mixture was...