Esterification of Banana Oil

Introduction

The purpose of this experiment was to synthesize isopentyl acetate, or banana oil. Esterification is a reversible process but at equilibrium an excess of alcohol or acid will push the reaction to the ester. The esterification process is started by heating a carboxylic acid and an alcohol while removing the water that is being formed, with the help of a catalyst. The alcohol reacts at a very fast rate, the carboxylic acid forms an ester easily and the catalyst is usually a very strong acid. The catalyst is neutralized at the end of the reaction which makes it easier to separate the ester through filtration. When characterizing the ester, there are several tests performed. An IR spectrum helps to determine the components of the compound. This also tests for behavior of the ester. The 13C spectrum determines how many carbons are in the ester and the NMR determines how many hydrogens are present in the ester. A chromic acid test will be positive if an alcohol is present, turning a blue-green color. The Ferric Hydroxylamate test will be positive if the product is an ester, turning a burgundy color.

Reagent Table

Compound Molecular Formula Molecular Structure Boiling Point (oC)

Isopentyl alcohol C5H12O 130

Acetic Acid C2H4O2

118

Sulfuric Acid H2SO4

290

Ethyl ether C4H10O 34.5

Sodium Bicarbonate NaHCO3 851

Sodium chloride NaCl 1461

Chromic Acid H2CrO4

Procedure

First, an ester was made by combining 2.0 mL of glacial acetate and 0.90 mL of isopentyl alcohol in a 5 mL vial containing a spine vane. Six drops of H2SO4 were added. The vial was fit with the proper condenser (water was not circulated). The hot plate was heated until it reached 150 degrees and was then turned down to maintain boiling point. The vial was removed from the heat and cooled in an ice bath.

The solution was extracted first with cold water. The aqueous layer was removed. 1.5 mL of EtO was added to the organic layer and then extracted with cold water again. The aqueous layer was removed. The organic layer was extracted with NaHCO3 and the aqueous layer was removed. More EtO was added to the organic layer and was extracted with saturated NaCl. The aqueous layer was removed.

A drying pipet was prepared from cotton, 2 mm of sand, and 5 mm of Na2SO4. The washed solution was transferred into the pipet and was collected in a 3 mL vial. The drying pipet was washed with 1 mL of ether to collect any solution left in the column. The vial was capped for week 2 of the experiment.

The solution was evaporated on a hot plate at 50-60 degrees. Once evaporation is complete, a distillation was performed. The block temperature was raised to 215 degrees for four minutes and then lowered. The distillate boiling point was recorded and the distillate was transferred into a preweighed vial to determine the amount of oil maintained. An infrared spectrum was run first to characterize the oil. Then a ferric chloride test was performed by heating 1 mL of 0.50 M H2NOH, 0.4 mL (12 drops) 6 M NaOH, and 6 drops of reference / isolate and a boiling stone. The solution was boiled for 4 minutes then cooled and 2 mL of 1 M HCl and 1 drop of FeCl3 was added. The color change was recorded. Then a chromic acid test and a C13 and DEPT test were done.

Results

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