Preparing Isopentyl Acetate Worksheet

Dr. Irina SmoliakovaChem 340L, Survey of Organic Chemistry Lab
Experiment 9
Preparing Isopentyl Acetate by the Fischer Esterification
The following are the major steps of Experiment 9:
Read and understand the experiment description on pages 139–147 (the
experiment background and the description of the semi-microscale Fischer
esterification) of the lab textbook.
(ii) Watch two YouTube videos by clicking on the following links:
https://www.youtube.com/watch?v=eTLV3i70c3w (Banana Oil, Synthesis
of Asoamyl Acetate, Part I) and
https://www.youtube.com/watch?v=9UbOr3_-G-E (Banana Oil, Synthesis of
Asoamyl Acetate, Part II). Note that the procedures described in the
textbook and used in the recorded videos are similar, yet not the same.
(iii) Write Report 9 (see the guidelines below) and upload your report in
Blackboard by the deadline.
(iv) Take Lab Quiz 9 on Bb.
If you have questions, contact Dr. Smoliakova or your TA.
(i)
Guidelines for Lab Quiz 9 (a total of 10 pts)
(Use these guidelines for your preparation for the final exam to answer the
questions related to Experiment 9.)
1. Fischer esterification. Reversibility of this reaction. Le Chatelier principle.
Catalysts that can be used in Fischer esterification.
2. Reaction equation for the preparation of isopentyl acetate from isopentyl
alcohol and acetic acid. The catalyst used in the experiment.
3. Names (IUPAC and common), structures, roles (reactants, products, catalysts,
drying agents, solvents, etc.), physical properties (liquid or solid, characteristic
odor, solubility and miscibility in water, density compared to water, etc.), and
hazards of all organic and inorganic compounds used in the experiment.
4. Functional groups in all organic compounds used or obtained in the
experiments.
5. Equipment, apparatus and glassware used in the experiment.
6. Review distillation and extraction techniques.
7. Main steps of the procedure used in the experiment shown in the two videos.
8. Acid-base reactions of sulfuric and acetic acids with NaHCO3.
* This document was prepared by Dr. Smoliakova and used with her permission
1
Dr. Irina Smoliakova
Chem 340L, Survey of Organic Chemistry Lab
Guidelines for Report 9 (a total of 30 pts)
1. Introductory Section (10 pts):
a) (1 pt) Write your name, course number, lab section number, and the number
and title of the experiment.
b) (1 pt) Write the objectives of this experiment.
c) (8 pts) Draw and complete the Table of Properties. For “Solubility or
Miscibility in Water,” write (i) numerical values for the solubility of solids
and (ii) either “miscible” or “immiscible” for liquids.
Table of Properties
Compound
Name
Compound
Structure
(not
formula!)
Physical
State
and
Appearance
Solubility
or
Miscibility
in Water
acetic acid
isopentyl
alcohol
isopentyl
acetate
sulfuric
acid
sodium
hydrogen
carbonate
(sodium
bicarbonate)
sodium
sulfate
Amount
Taken either
in g (for
solids)
or
mL
(for
liquids)
32.0 mL
20.0 mL
Density,
g/mL
(for
liquids)
calculate
and
write
down
the
theoretical
yield in g
n/a
report the
phys. state
and
appearance
of the pure
compound,
not those of
their
aqueous
solutions
same
as
above
Amount
Taken in
Moles
Hazards
calculate
the
theoret.
yield in
moles
4.0 mL
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
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Dr. Irina Smoliakova
Chem 340L, Survey of Organic Chemistry Lab
2. Observation Section (10 pts)
a) (7 pts) Describe everything that the student did during the experiment shown
in the two videos. You should use the past tense. Write complete sentences. Be
concise (limit your writing to 1 page). Be sure to use the correct names of all pieces
of equipment and all steps of the experiment.
b) (2 pts) The boiling point of isopentyl acetate is 142 oC. However, in the recorded
video, the ester distilled at a significantly lower temperature. Why?
b) (1 pt) What color and smell does isopentyl acetate have?
3. Results/Conclusion Section (10 pts)
a) (2 pts) Calculate the percent yield of isopentyl acetate assuming that
someone isolated 19.0 mL of the ester using the amounts of acetic acid and
isopentyl alcohol indicated in the Table of Properties on page 2 of this
document (the values are highlighted in yellow). Show your calculations.
b) (2 pts) Write the equation of the reaction performed in the video. Draw the
Lewis structures of all reactants, products, and the catalyst in this equation.
Below each structure (except H2O), indicate the class of the compound (e.g.,
an alkene, an amine, an acetal, etc.).
c) (1 pt) Write the equation of the acid-base reaction between NaHCO3 and acetic
acid. Indicate the pKa values of two acids and the position (left or right) of the
acid-base equilibrium.
d) (1 pt) Write the equation of the acid-base reaction between NaHCO3 and
sulfuric acid. Indicate the pKa values of two acids and the position (left or
right) of the acid-base equilibrium.
e) (1 pt) What does “glacial” mean when chemists say “glacial acetic acid”?
f) (1 pt) What gas was formed during the washing of the organic layer with an
aqueous solution of NaHCO3 in a separatory funnel?
g) (1 pt) What was the purpose of using anhydrous Na2SO4 in the experiment?
h) (1 pt) Why was a beaker placed underneath the separatory funnel during the
extraction step of the experiment?
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12/25/21
Experiment 9
Preparing Isopentyl Acetate by
the Fischer Esterification
Pages 139-147 and two YouTube videos:
https://www.youtube.com/watch?v=eTLV3i70c3w and

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Purpose of the Experiment
• The purpose of Experiment 9 is to prepare isopentyl acetate
(also known as isoamyl acetate) from isopentyl alcohol and
acetic acid by the Fischer esterification.
O
H3C
+
OH
acetic acid
(a carboxylic acid)
H2SO4 (catalyst)
HO
isopentanol
(an alcohol)
reflux
O
H3C
O
+
H2O
isopentyl acetate
(an ester)
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Fischer Esterification
• The Fischer esterification is the ester synthesis from a carboxylic acid and
an alcohol using H2SO4 or another acid as a catalyst.
R1
O
+
HO R2
OH
H2SO4 (cat.)
O
reflux
a carboxylic
acid
an alcohol
O
R1
+ H2O
R2
an ester
• This is a reversible reaction. In reversible transformations, products can
react to furnish starting compounds. In the Fischer esterification, the
ester produced in the reaction is capable of reacting with water to yield
the starting carboxylic acid and alcohol.
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Le Chatelier Principle
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• To govern reversible reactions, chemists use the Le Chatelier principle. To
increase the yield of compound C, we can either use an excess amount of
one of the two reagents (either A or B) or remove one of the products
(either C or D) from the reaction mixture.
A + B
C + D
• We will use excess acetic acid (A) to get a higher yield of the ester (C).
• In industry, either excess carboxylic acid (A) or excess alcohol (B) is used
along with removal of water (D), which is a by-product of the esterification
reaction.
• Note: catalysts do not affect the equilibrium position. They increase the
rate of both direct and reverse reactions. Increasing the reaction
temperature also does not affect the equilibrium position.
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Procedure USED IN THE TEXTBOOK and Apparatus 5
Part 1. Refluxing the Reaction Mixture
• Be sure to use metal utility clamps,
not plastic. Figure 2 on page 145
shows only one clamp. You must use
two. The second clamp is to support
the condenser.
• Be especially careful while working
with concentrated sulfuric acid.
• Do not forget to add a few boiling
chips into the cold reaction mixture.
• Reflux the mixture for 1 hour.
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Procedure USED IN THE TEXTBOOK and Apparatus
Part 2. Separating and Washing the Product Layer
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• In the second step, you will separate the ester from the reactants and water using a
separatory funnel. Note: (1) the density of the ester is lower than that of water; (2)
solubility of isopentanol in water is 28 g/L. Acetic acid is miscible with water.)
A
B/C
D
organic layer
(contains your product
and a little bit of
isopropanol)
organic layer
(contains your
product)
organic layer
(contains your
product)
aqueous layer
(contains H2SO4,
acetic acid and a
little bit of isopropanol)
aqueous layer
(contains ionic
Na salts formed
during
extraction)
aqueous layer
(contains H2O
and NaCl)
A. Shake the reaction B and C. Add a NaHCO3 solution to the
mixture and 20 mL of organic layer. It will react with traces of
H2O. Drain the
acetic and sulfuric acids. Shake the
aqueous layer.
mixture. Drain the aqueous layer. Repeat.
D. Wash the organic layer using a NaCl aqueous
solution to remove other compounds from the
organic layer. Drain the aqueous layer. Pour the
product (the top layer) into an Erlenmeyer flask.
Dry the compound over Na2SO4.
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Procedure USED IN THE TEXTBOOK and Apparatus
Part 3. Distilling the Product
• Assemble a simple distillation apparatus (see page 38, Figure
3).
• Add a few boiling chips to the crude product before you start
distillation.
• Tare a 10-mL round-bottom flask. Use this flask as a receiving
flask. Attach the flask to the condenser adapter using a Keck
plastic clamp.
• Collect the fraction with b.p. 134-143 oC in the tared receiving
flask. Weigh the flask with the compound. Determine the
product yield in grams.
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