Experiment 5, Preparation of Synthetic Banana Oil

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September 30, 2012
Experiment 5, Preparation of Synthetic Banana Oil

Introduction:

This experiment prepares synthetic banana oil (isopentyl acetate) through the Fisher esterification method by combining isopentyl alcohol with acetic and sulfuric acid then heating the mixture under reflux for an hour. Esterification is a chemical reaction in which two reactants (an alcohol and an acid) form an ester as the reaction product.

Observations and Data:

When the sulfuric acid was combined with the isopentyl alcohol and acetic acid, the mixture turned red (due to residue of another chemical remaining on glassware). During the wash of the organic layer, two distinct layers appeared, a yellow and a clear. The drying process took around 20 minutes through gravity filtration. The distillation process took around 15 to 20 minutes to begin boiling at 137˚ C and stay at 140˚ C for the remainder of distillation. After reaching optimum temperature distillation was complete within ten minutes. After the experiment was completed the final product was 97% ester, 3% alcohol.

Compound| Percent Total|
Isopentyl Acetate (Ester)| 97%|
Isopentyl Alcohol (Alcohol)| 3%|

Results and Discussion

We began with 16.2 mL of isopentyl alcohol and continued through the processes of reaction, separation, and purification until a final product was achieved. There were two peak areas appearing on the gas chromatogram, isopentyl alcohol and isopentyl acetate. The area of isopentyl alcohol (2) is 0.255cm2 where the area of the isopentyl acetate (1) is 8.4cm2. This results in the percentage of isopentyl alcohol (3) in the final product being 3% and the percentage of isopentyl acetate (4) 97%. The percent yield (5)of isopentyl acetate is also 97%. 1

1

1.
1.
8.4 cm2 isopentyl acetate
8.4 cm2 isopentyl acetate
=
=
2

2

(2 cm x 8.4 cm)
(2 cm x 8.4 cm)

=
=
2

2

1

1

2.
2.

0.255 cm2 isopentyl alcohol
0.255 cm2 isopentyl alcohol
(1.7 cm x 0.3 cm)
(1.7 cm x 0.3 cm)

0.255 cm2 isopentyl alcohol

0.255 cm2 isopentyl alcohol

3% isopentyl alcohol
3% isopentyl alcohol
=
=
8.655 cm2 total

8.655 cm2 total

X
X
100%
100%
3.
3.

8.4 cm2 isopentyl acetate

8.4 cm2 isopentyl acetate

8.655 cm2 total

8.655 cm2 total

=
=

97% isopentyl acetate

97% isopentyl acetate

X
X
100%
100%
4.
4.

.97 actual isopentyl acetate

.97 actual isopentyl acetate

=
=
97% yield
97% yield

1.0 theorhetical isopentyl acetate

1.0 theorhetical isopentyl acetate

X
X
100%
100%
5.
5.

The results are not ideal, because the mixture would be 100% isopentyl acetate rather than containing isopentyl alcohol. Errors could have occurred in the beginning when the initial solution turned red, due to improper glassware cleaning. Product could have been lost or improperly filtered during gravity filtration. During the transfer of product from many vials, there may have been contamination. In the drying process, enough time may not have elapsed for the entire drying to occur.

Experimental
Isopentyl alcohol (150mmol) was mixed with acetic acid (17mL) and sulfuric acid (1mL). The solution was then heated under reflux for one hour. The mixture was then transferred into a separatory funnel and washed with 50-mL of water, drained and rewashed twice with 5% sodium bicarbonate. The layers were separated into two containers, one containing the aqueous layers of acetic acid and sulfuric acid in water and one containing the organic layer of isopentyl acetate and isopentyl alcohol. The mixture was then dried with magnesium sulfate. After dry, distillation occurred at 140˚ C to remove isopentyl alcohol leaving a final product of only isopentyl acetate.

Laboratory Notebook Reference

The data from the experiment “Preparation of Synthetic Banana Oil” is located on pages six through nine in the laboratory notebook.
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