Synthesis of Isopentyl (Amyl) Acetate Ester
(Banana Oil)
Resources
Pavia:
697
p. 84 – 91; 686 – 688; 693 –
Lab Website: http://classweb.gmu.edu/chemlab
Schornick:
3/12/2016
http://classweb.gmu.edu/
jschorni/chem318
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Synthesis of Isopentyl (Amyl) Acetate Ester
(Banana Oil)

Overview

Synthesis – Acid (H2SO4) catalyzed Fischer Esterification
reaction of a Carboxylic Acid (Acetic Acid) with the
Hydroxyl group of an Alcohol (Isopentyl [Amyl] Alcohol)
This is a Condensation reaction where the molecules
become joined through the intermolecular elimination of
water
3/12/2016

Refluxing - Reagents will be Refluxed for about 60 minutes.

Liquid/Liquid Extraction - The product will be washed
several times with Water, Sodium Bicarbonate, Sodium
Chloride

Dry Sample

Refractive Index (with temperature correction)

Infrared Spectrum
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Synthesis of Isopentyl (Amyl) Acetate Ester
(Banana Oil)

3/12/2016
The Laboratory Report:
 Synthesis Experiment
 Mass, Moles, Molar Ratio, Limiting Reagent,
Theoretical Yield
 Procedures
 Title – Concise: Simple Distillation, Dry Sample, IR
Spectrum, etc.
 Materials & Equipment (2 Columns in list (bullet)
form)
Note: include all reagents & principal equipment
used, including details of distillation setup
 Description:
 Use list (bullet) form
 Concise, but complete description
 Use your own words – Don’t copy book!!
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Synthesis of Isopentyl (Amyl) Acetate Ester
(Banana Oil)

3/12/2016
The Laboratory Report: (Con’t)
 Results – Neat, logically designed template to present
results
 Summary – experimental results, including
Theoretical Yield results, in paragraph form
 Analysis & Conclusions
 Limiting reagent
 Discuss reaction mechanism in the context of your
experimental results
 Verification of product
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Synthesis of Isopentyl (Amyl) Acetate Ester
(Banana Oil)
3/12/2016
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Synthesis of Isopentyl (Amyl) Acetate Ester
(Banana Oil)
Reagents
Acetic Acid
Mol Wgt
- 60.05 g/mole
Density
- 1.049 g/mL
Boiling Point - 117.9oC
% Acid
- 100%
Isopentyl (amyl) Alcohol
Mol Wgt
- 88.15 g/mole
Density
- 0.809 g/mL
Boiling Point - 130.0oC
Sulfuric Acid
Mol Wgt
- 98.08 g/mole
Density
- 1.84 g/mL
% Acid
- 96.5 %
Molarity
- 36 moles/Liter
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Product
Isopentyl (amyl) Acetate
Mol Wgt
- 130.19 g/mole
Density
- 0.876
Boiling Pnt - 142oC
Ref. Index - 1.4040
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Synthesis of Isopentyl (Amyl) Acetate Ester
(Banana Oil)

Heating Under Reflux

The reaction mixture is heated in a “reflux apparatus” consisting
of a 25 or 50 mL round bottom flask attached to a vertical watercooled condenser set in a heating mantle.
Liquid/Liquid Extraction
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Synthesis of Isopentyl (Amyl) Acetate Ester
(Banana Oil)

Elements of the Experiment

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Equilibrium

Reaction equilibrium does not favor
formation of the ester

Therefore, an excess of one of the reagents
(Acetic Acid – Cheap!!!) is used to force the
equilibrium to product side, i.e., to the right
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Synthesis of Isopentyl (Amyl) Acetate Ester
(Banana Oil)

Elements of the Experiment (Con’t)

3/12/2016
Liquid/Liquid Extraction

The reaction mixture is mixed with Distilled Water
and placed in a separatory funnel where the phases
separate into two layers – Aqueous (higher density)
layer on bottom and the Organic layer on top.
Separate the Aqueous phase into a waste beaker

Extract Organic phase twice with 5% Sodium
Bicarbonate to remove excess acid. Discard
Aqueous phase into waste beaker

Extract Organic phase twice with Saturated Sodium
Chloride to remove excess water. Discard Aqueous
phase into waster beaker
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Synthesis of Isopentyl (Amyl) Acetate Ester
(Banana Oil)

3/12/2016
Elements of the Experiment (Con’t)

Dry Product – Dry crude ester (organic layer) with
Anhydrous Sodium Sulfate (less than 1 gram)

Mass of Product

Percent (%) Yield

Refractive Index corrected for temperature

Infrared (IR) Spectrum
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Synthesis of Isopentyl (Amyl) Acetate Ester
(Banana Oil)

3/12/2016
Procedure

Measure out ~10 mL of Glacial Acetic Acid to the
nearest 0.1 mL and compute the mass from the
volume and density

Weigh the Isopentyl Alcohol in the vial to the nearest
0.001 g

Mix the reagents in a Beaker, swirling gently to ensure
complete solution

If necessary, heat gently to help dissolution of
reactants

Carefully add 1.0 mL concentrated Sulfuric Acid to the
mixture mixing (swirling) quickly
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Synthesis of Isopentyl (Amyl) Acetate Ester
(Banana Oil)

3/12/2016
Procedure (Con’t)
 Set up a “Reflux” Apparatus using a 50 mL round
bottom flask
 Add a “Corundum” or “Teflon” (not calcium carbonate)
boiling chip and heat the mixture under “Gentle”
reflux for 50 – 60 minutes
 Cool the mixture to Room Temperature
 Liquid/Liquid Extraction
 Pretest the Separatory Funnel to ensure that the
stopper and the stopcock assembly do not leak
 Add about 50 mL distilled water to the funnel
 Shake vigorously for about 10 seconds
 Adjust stopper or stopcock as necessary and repeat
 Drain water from funnel
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Synthesis of Isopentyl (Amyl) Acetate Ester
(Banana Oil)

Procedure

3/12/2016
Liquid/Liquid Extraction (con’t)

Transfer the reaction mixture to the Separatory
Funnel using a short neck stem funnel

Note: Do not transfer boiling chip to funnel

Rinse reaction vessel with 10 mL Distilled Water
and add to mixture in separatory funnel

Mix phases by shaking and venting

Remove the lower aqueous layer and put it aside
for later disposal
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Synthesis of Isopentyl (Amyl) Acetate Ester
(Banana Oil)

Procedure (Con’t)

Liquid/Liquid Extraction (Con’t)

Extract the upper organic layer with 10 mL aqueous
Sodium Bicarbonate (NaHCO3) to remove excess
Acid.
Note: The reaction between any residual acid and
Sodium Bicarbonate produces CO2 gas and
could be under considerable pressure in the
separatory funnel.
Hold the stopper firmly, invert the funnel, and
release the stopcock very slowly so the venting
of the gas is controlled
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Synthesis of Isopentyl (Amyl) Acetate Ester
(Banana Oil)

Procedure (Con’t)

3/12/2016
Liquid/Liquid Extreaction (Con’t)

Remove the lower aqueous layer and add to
previous waste aqueous solution

Repeat the NaHCO3 extraction a second time

Perform a third extraction of the upper organic
layer in the Separatory Funnel with 10 mL of
saturated Sodium Chloride to remove excess water

Remove the lower aqueous layer and add to
previous waste aqueous solution
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Synthesis of Isopentyl (Amyl) Acetate Ester
(Banana Oil)

Procedure (Con’t)

Liquid/Liquid Extraction (Con’t)

Repeat the Sodium Chloride extraction a second
time

Transfer the organic layer containing the crude ester
to a small, clean, Erlenmeyer flask

Instructor will add 1.0 g of Anhydrous Sodium
Sulfate
Note: If mixture does not appear to dry (drying
agent will clump), add a little more Sodium
Sulfate
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Synthesis of Isopentyl (Amyl) Acetate Ester
(Banana Oil)

3/12/2016
Procedure (Con’t)

Allow the mixture to settle

Decant the dried sample into a pre-weighed 100 mL
beaker, leaving all solid material in the flask

Reweigh the beaker and determine the mass of
product

Determine percentage yield

Measure the Refractive Index and correct for
temperature

Obtain the IR Spectrum
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