Download Preparation of Azeleic Acid from Castor Oil Saponification and

Preparation of Azeleic Acid from Castor Oil
Saponification and Oxidation reactions (Please read
Experiment 25.3 on page 569)
This week's reaction: saponification of castor oil
OH
O
O
O
OH
1. KOH, H2O, heat
OH
2. H2SO4
OH
O
O
OH
O
OH
+ 3 HO
OH
O
Triricinoleylglycerol
(castor oil)
glycerol
ricinoleic acid
1. Set up the reaction apparatus inside your hood;
2. Load all reactants and reagents;
3. Heat the flask directly on a hot plate at medium setting;
4. Stirring for two hours;
5. Work up the reaction.
Saponification is a process that produces soap, usually from
fatty esters. In chemistry terms, saponification involves base
(usually NaOH or KOH) hydrolysis of triglycerides, which
are esters of fatty acids, to form the sodium salt of a
carboxylate. In addition to soap, such traditional
saponification processes produces glycerol.
Mechanism of saponification
O
R
O
O
R
O
O
OH-
HO
O
3 NaOH, H2O
+
3 R
heat
OH
ONa
HO
R
glycerol
O
Triglycerides
Next week's reaction:
O
OH
HO
KMnO4
O
HO
ricinoleic acid
O
O
+
+ CO2 + MnO2
OH
azeleic acid
2-octanone
Oxidation and decarboxylation reactions.
O
heat
RH + CO2
R
OH
O
O
gentle heating
O
O
H
O
+ CO2
HO
O
β-ketocarboxylic acid
2-octanone
Decarboxylation is a chemical reaction that releases carbon
dioxide (CO2). Usually, decarboxylation refers to a reaction
of carboxylic acids, removing a carbon atom from a carbon
chain. Decarboxylation is especially easy in βketocarboxylic acids due to the concerted movement of three
pairs of electrons.
Biochemical decarboxylation is common. One example is
pyruvate to acetyl co-A.
CoA +
NAD+
O
OH
CO2 +
NADH
O
S
CoA
O
pyruvate
acetyl-CoA