A Hydrolysis Reaction: Hydrolysis of an Anhydride to a
Diacid—cis-Norbornene-5,6-endo-Dicarboxylic Acid
Introduction
As we have seen, anhydrides form by a condensation reaction
between two acid groups. The term anhydride is short for acid anhydride,
meaning two acid groups minus water. When two acid groups are suitably
located in the same molecule, it is possible to form a cyclic anhydride by
pyrolysis of the diacid. For example, maleic anhydride forms by the
pyrolysis of maleic acid. The two acid groups in maleic acid are near enough
to each other, so that water may be eliminated; the trans isomer, fumaric
acid, does not form an anhydride. Figure 1 shows the pyrolysis of maleic
acid to form maleic anhydride. The structure of the anhydride, which
contains an oxygen atom flanked by two carbonyl groups, follows directly
from the loss of water from the two acid groups.
O
O
OH
OH
O
maleic acid

O
+ H2O
O
maleic
anhydride
Figure 1. Formation of a cyclic anhydride.
The reaction shown in Figure 1 is a dehydration reaction, because
water is eliminated from a single molecule. The reaction is not an
equilibrium reaction; it goes to completion. However, the reaction may be
reversed by heating the anhydride in excess water. A reaction, in which
water breaks a carbonyl to oxygen bond, is called a hydrolysis reaction.
The word hydrolysis means cleavage (olysis) by water (hydro). Figure 2
shows the hydrolysis of maleic anhydride.
Lab 03
1
O
O
O

+ H2O
OH
OH
O
O
maleic
anhydride
maleic acid
Figure 2. Hydrolysis of maleic anhydride.
The Experimental Reaction
The product of the Diels-Alder reaction is cis-norbornene-5,6-endodicarboxylic anhydride. It is a cyclic anhydride formed by the cycloaddition
of maleic anhydride to cyclopentadiene. Because it is an anhydride, it may
be hydrolyzed to a diacid. Figure 3 shows the reaction for the hydrolysis.
O
O
+
O
O
cis-norbornene-5,6-endodicarboxylic anhydride
H2O
O
OH
OH
cis-norbornene-5,6-endodicarboxylic acid
Figure 3. Hydrolysis of cis-norbornene-5,6-endo-dicarboxylic anhydride.
Lab 03
2
Procedure
1. Set up a sand bath (metallic heating mantle, sand and rheostat) and set the
rheostat at 85.
2. Weigh your Diels-Alder product on a creased weighing paper and transfer
the solid to a small test tube.
3. Add 1-mL distilled water and a small boiling chip to the test tube.
4. Place the test tube in the hot sand bath and heat the mixture to boiling.
The anhydride may appear to melt and form globules in the test tube.
The anhydride is reacting with water to form the diacid, which is soluble in
hot water.
5. Continue heating until the globules disappear.
6. Remove the test tube from the sand bath and allow its contents to cool to
room temperature.
The diacid is insoluble in cold water.
7. After crystals form, immerse the test tube in an ice-water bath for several
minutes.
8. Collect the cold crystals on a Hirsh funnel.
9. Weigh the dry crystals.
10. Test the crystals with 5% sodium bicarbonate solution and record the
result in your notebook.
11. Pour the hot sand into the designated metal container. Clean and return
glassware to the proper storage location. Check the balance area. Return
chemicals to their original location and turn off all balances.
Lab 03
3
Hydrolysis Questions
1. Define hydrolysis.
2. Write an equation for the preparation of benzoic acid anhydride.
3. Write an equation for the hydrolysis of succinic acid anhydride.
4. The hydrolysis of maleic anhydride in a basic medium produces a salt.
How is the salt converted into the diacid?
5. Circle the structures that undergo hydrolysis.
O
O
CH3OCCH3
O
O O
O
CH3COCCH2CH3
6. Draw the structures of Compound A and B.
CO2CH2CH3
C
O
+
C
H2O
hydrolysis
CO2CH2CH3
A
B
7. Write an equation for the reaction of acetic acid with 5% sodium
bicarbonate solution.
Lab 03
4
8. Explain why fumaric acid, the trans isomer of maleic acid, does not form
an anhydride when pyrolyzed.
9. Write an equation for the hydrolysis of ethyl benzoate in 5% HCl.
10. Write an equation for the hydrolysis of ethyl acetate in 5% NaOH.
Lab 03
5