Synthesis of Ester

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To prepare isopentyl acetate (isoamyl acetate)

2. AIM:

To make an ester referred to as banana oil from acetic acid and isopentyl alcohol


This ester is often referred to as banana oil, since it has the familiar odor of this fruit

CH3 H+ CH3
CH3C OH + CHCH2CH2OH CH3C O CH2CH2CH + H2O CH3 CH3 Acetic acid Isopentyl alcohol Isopentyl acetate (excess) (alcohol) (ester) (vinegar)

Isopentyl acetate is prepared by the direct esterification of acetic acid with isopentyl alcohol. Since the equilibrium does not favor the formation of the ester, it must be shifted to the right, in favor of the product , by using an excess of one of the starting materials. Acetic acid is used in excess because it is less expensive than isopenthyl alcohol and more easily removed from the reaction mixture

In the isolation procedure, much of the excess acid and the remaining isopenthyl alcohol are removed by extraction with water. Any remaining acid is removed by extraction with aqueous sodium bicarbonate. The ester is purified by distillation


1. Isopenthyl alcohol(also called isoamyl alcohol or 3-methyl-1- buthanol) 2. Glacial acetic acid
3. Concentrated sulphuric acid
4. Round bottom flask
5. Reflux apparatus
6. Heating mantle
7. Cold water
8. Conical flask
9. Aqueous sodium bicarbonate
10. Red litmus paper

11. Saturated aqueous sodium chloride
12. Anhydrous magnesium sulphate
13. Distillation apparatus

extreme care must be exercised to avoid contact with concentrated sulphuric acid. It will cause serious burns if it is spilled on the skin. If it comes in contact with skin or clothes, it must be washed off immediately with excess water. In addition, sodium bicarbonate may be used to neutralize the acid. Clean up spills immediately.


6.1 15 ml (12.2g, 0.138mole) of isopenthyl alcohol and 20ml(21g,0.35mole)of glacial acetic acid was poured into a round bottom flask.

6.2 4ml of conc. Sulphric acid was carefully added to the contents of the flask, while swirling. Several boiling stones were then added to the mixture.

6.3 The reflux apparatus was the assembled as shown in the diagram below:


6.4 The mixture was brought to a boil using a heating mantle it was then heated under reflux for 1 hour.

6.5 The heating source was removed and the mixture was allowed to cool to room temperature.

6.6 The cooled mixture was the poured onto a separatory funnel and 55ml of cold water was then added.

6.7 The reaction flask was the rinsed with 10ml of cold water with the rinsings being poured into the separatory funnel.

6.8 A stirring rod was then used to mix the rinsings with the mixture in the funnel.

6.9 A stopper was then placed on the separatory funnel and the funnel was shaked in a swirling motion several times. The funnel was then placed on a holder and allowed to settle.

6.10 The lower aqueous layer was then separated from the upper organic layer (density 0.87 g/ml) .The aqueous layer was the discarded into a waste bottle; it was ensured that the correct layer was saved.

6.11 The crude ester in the organic layer contained some acetic acid, which was removed by extraction with 5% aqueous sodium bicarbonate solution.

6.12 25 ml of the 5% base was carefully added to the organic layer contained in the separatory funnel.

6.13 The separatory funnel was...
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