Name___________________________
Period______Date_________________
Synthesis of Esters
GROUP _______________
Introduction:
Esters are an important class of organic compounds which are characterized by the following generic
formula.
O
R
C
O
R'
R, R’ = any alkyl group
Low molecular weight esters have pleasant odors and are responsible for many distinctive odors in
fruits and flavorings. Esters can be readily prepared from a carboxylic acid and an alcohol. Generally,
this reaction is catalyzed by a strong acid in order to shift the equilibrium towards the production of the
ester.
O
H
O
H
R
C
OH
+
HO
C
R
H3O+
H
O
C
R + H2O
H3O+
+
butanoic acid
C
H
O
O
OH
R
HO
O
ethanol
ethyl butrate
Pineapple
Figure 1
The structures in Figure 1 will assist in determining which carboxylic acid and alcohol will produce
the ester with the desired flavor.
Purpose:
To determine the smell of the ester produced
Safety:
 Wear protective goggles throughout the laboratory activity.
 Be very careful with the concentrated sulfuric acid. It can cause serious chemical burns.
 Use wafting technique when attempting to identify odors.
Procedure:
1. Heat 75 mL of water in a 100-mL beaker to a gentle boil.
2. Determine the carboxylic acid and alcohol necessary to produce desired ester and odor.
3. In a 10-cm test tube:
A. add 1 drop of the carboxylic acid if it is a solution. Use a tiny amount of acid (tip of scoopula)
for the solid acids.
B. add 3 drops of alcohol
C. add 1 drop of concentrated sulfuric acid
D. add boiling stone to mixture
Group 1:
a. Add 1 drop of acidic acid if it is a solution. Use a tiny amount of acid (tip of scoopula)
for the solid acids.
b. add 3 drops of pentanol
c. add 1 drop of concentrated sulfuric acid
d. add boiling stone to mixture
Group 2:
a. Add 1 drop of Anthranillic acid if it is a solution. Use a tiny amount of acid (tip of
scoopula) for the solid acids.
b. add 3 drops of methanol
c. add 1 drop of concentrated sulfuric acid
d. add boiling stone to mixture
Group 3:
a. Add 1 drop of salicylic acid if it is a solution. Use a tiny amount of acid (tip of
scoopula) for the solid acids.
b. add 3 drops of methanol
c. add 1 drop of concentrated sulfuric acid
d. add boiling stone to mixture
Group 4:
a. Add 1 drop of propinoic acid if it is a solution. Use a tiny amount of acid (tip of
scoopula) for the solid acids.
b. add 3 drops of t-butyalcohol
c. add 1 drop of concentrated sulfuric acid
d. add boiling stone to mixture
Group 5:
a. Add 1 drop of Acetic acid if it is a solution. Use a tiny amount of acid (tip of
scoopula) for the solid acids.
b. add 3 drops of octanol
c. add 1 drop of concentrated sulfuric acid
d. add boiling stone to mixture
Group 6:
a. Add 1 drop of decanoic acid if it is a solution. Use a tiny amount of acid (tip of
scoopula) for the solid acids.
b. add 3 drops of ethanol
c. add 1 drop of concentrated sulfuric acid
d. add boiling stone to mixture
Group 7:
a. Add 1 drop of Acetic acid if it is a solution. Use a tiny amount of acid (tip of
scoopula) for the solid acids.
b. add 3 drops of benzylalcohol
c. add 1 drop of concentrated sulfuric acid
d. add boiling stone to mixture
4. Waft test tube to see if odor is present before heating.
5. Stopper test tube with 1-hole stopper and place in boiling water bath. (Make sure test tube stays
upright)
6. Turn off heat and allow mixture to stand in water bath for 5-10 minutes.
7. Use test tube holder to remove test tube and add pipet full of cold water to test tube. Swirl.
8. Remove small quantity of mixture with pipette:
A. push pipette tip through hole in stopper
B. tip test tube
C. draw up some of the mixture
D. turn test tube upright
E. remove pipette
9. Invert pipette and let mixture flow into the pipet bulb.
10. Carefully force out some of the vapor and waft fumes.
11. Note and record odor of the ester.
Possible problems:
~ If the ester’s smell is overpowering, add more water to dilute the odor.
~ If the ester’s smell is too faint, place the bulb of pipette in warm water.
Circle the Ester you made:
O
O
O
O
O
O
wintergreen
banana
O
grape
NH2
OH
O
O
rum
O
orange
O
O
peach
O
O
broccoli
Key:
1=banana
2=grape
3=wintergreen
4=rum
5=orange
6=broccoli
7=peach