ESTERIFICATION
Introduction:
Esters are a class of organic compounds which, unlike many organics, have pleasant
odors. In fact, many of the "artificial flavors" used in food products are esters - very pure
esters.
Esters occur naturally but can also be synthesized in the lab. To synthesize an ester, you
must start with two other organic compounds - an alcohol and an acid. The ester is
formed when dehydration occurs. The alcohol and acid react to form the ester and a
water molecule.
O
O
OH
H
+
H
+
C+
C
H3C
O
H
H3C
O
H
H+
H2
C
H3C
C
H3C
OH
OH
O+
H
CH 2
H3C
H
H2O +
C
H3C
H
O+
O
O
H3C
H
O
C
C
O
H3C
CH 2
H3C
OH
+
OH
C
H+
H3C
O
O
CH 2
CH 2
CH 2
H3C
H3C
H3C
Some esters that can be synthesized include methyl salicylate (oil of wintergreen),
isoamyl butyrate (pear), isoamyl acetate (banana), ethyl acetate (fruity), and ethyl
salicylate (sweet smell).
Purpose:
The purpose of this experiment is to synthesize and identify four esters.
Equipment/Materials:
hot plate
250 mL beaker
styrofoam cups (4 per group)
Beral pipet (1 per group)
microscale thermometers
labelling tape
OH
Dowex 50 x 2 - 100 ion-exchange resin
glacial acetic acid (20 mL)
salicylic acid (10 g)
isoamyl alcohol (15 mL)
methanol (20 mL)
ethanol (15mL)
Safety:
 Always wear safety glasses and an apron.
 Keep all reactants away from flames.
 Do not smell chemicals by placing your nose at the bottle’s opening; waft the
smell toward your nose with your hand.
 Never eat or drink in the lab.
Procedure:
1. Heat water in a beaker on a hotplate near a wall. Place a microscale thermometer in
the water. Monitor the temperature – it should stay between 70 – 80 oC.
2. Label 4 microscale test tubes A – D at the top with labeling tape. The test tubes may
be placed in microscale Erlenmeyer flasks, which will act as stands for the test tubes.
3. Use the microspatula to place a small amount of ion-exchange resin (about
equal to two garden peas) into the four test tubes.
4. Place the following in the test tube labeled “A”:
10 drops of isoamyl alcohol
10 drops of glacial acetic acid
5. Place the following in the test tube labeled “B”:
10 drops of ethanol
10 drops of glacial acetic acid
6. Place the following in the test tube labeled “C”:
salicylic acid – a similar amount to the resin
enough methanol to dissolve the acid (about 25 drops)
7. Place the following in the test tube labeled “D”:
salicylic acid – a similar amount to the resin
10 drops of ethanol
8. Place all four test tubes in the water bath on the hot plate, and allow them to react for
10 minutes. Be sure that the test tubes are aimed at the wall. (It is not necessary to put
the Erlenmeyer flasks in the water.)
9. After 10 minutes, CAUTIOUSLY smell the odor of each. Remember to waft the smell
towards your nose. What do you smell? Record on the data table.
10. Pour the liquid contents of tube A into a clean styrofoam cup. Swirl the cup one or
two times, then immediately pour the excess reactants into a sink, and rinse with a
small amount of water. Smell the inside of the cup. Record what you smell.
11. Repeat step 10 for the examination of the other three esters.
12. Thoroughly rinse out each of the test tubes and cups.
Data Table:
TUBE
SMELL INITIAL
SMELL AFTER RINSING
A
__________________________
________________________
B
__________________________
________________________
C
__________________________
________________________
D
__________________________
________________________
Questions:
1. Tube A contained the following:
___________________smell
or
___________________ester
or
___________________ester
or
___________________ester
or
___________________ester
2. Tube B contained the following:
___________________smell
3. Tube C contained the following:
___________________smell
4. Tube D contained the following:
___________________smell
5. How did the smell of each ester change after rinsing with water?
6. What name would you give to an orange-smelling ester formed by adding octanol to
acetic acid?
ESTERIFICATION
TEACHER NOTES
STANDARDS MET:
3.4.7.A - Describe concepts about the structure and properties of matter.
 Describe and conduct experiments that identify chemical and physical properties.
3.2.10.C – Apply the elements of scientific inquiry to solve problems.
 Conduct a multiple step experiment.
3.4.10.A – Explain concepts about the structure and properties of matter.
 Explain the formation of compounds and their resulting properties using bonding
theories (ionic and covalent).
 Understand that carbon can form several types of compounds.
3.7.12.A – Apply advanced tools, materials and techniques to answer complex questions.
 Demonstrate the safe use ofcomplex tools and machines within their
specifications.
 Evaluate and use technological resources to solve complex multistep problems.
Lab Time: 45 minutes
Answers to Questions:
1. Tube 1 contained the following:
___banana__________smell
or
__isoamyl acetate____ester
or
__ethyl acetate_____ester
or
_methyl salicylate__ester
or
__ethyl salicylate__ester
2. Tube 2 contained the following:
_____fruity________smell
3. Tube 3 contained the following:
____wintergreen____smell
4. Tube 4 contained the following:
___sweet___________smell
5. How did the smell of each ester change after rinsing with water?
Smell should have become stronger because “harsh” un-reacted chemicals were
washed away.
6. What name would you give to an orange-smelling ester formed by adding octanol to
acetic acid?
octyl acetate
Considerations:
This lab is a version of one developed by Brother Carmen Ciardullo (Micro Action
Chemistry , Flinn Scientific inc., 1990). This book contains a wealth of microscale
experiments and is suggested for any teacher who is considering incorporating microscale
labs into a chemistry class. One change from the original procedure is to rinse the
reactants in a cup and then rinse one time with water. This seems to allow the esters to be
smelled much easier due to the increased surface area and the removal of harsh
“masking” chemicals.
Students will be using concentrated acids so caution must be maintained at all times.
Caution should be taken while heating the tubes. Students can also make other esters
using this equipment but, as with any lab, the instructor should first experiment to
determine if results are acceptable and safety is maintained. The production of the esters
can be verified using gas chromatography (see Verification of Esterification).
Last updated 11-02.