Chemistry Reference
In-Depth Information
Table 2.1 Physical properties of methyl oleate and methyl linoleate and their
corresponding epoxides. Oxidation onset temperature, pour point, and
kinematic viscosity are reported.
Oxidation
onset/1C
Kinematic viscosity
at 40 1C/mm s
1
Pour
Point/1C
Sample
Soybean oil
155
B
32
9
Methyl oleate
177
3.7
27
Methyl linoleate
138
3.2
48
Epoxidized soybean oil
199
175
3
Epoxidized methyl oleate
190
8.0
0
Epoxidized methyl linoleate
180
145
2
stability make them effective as plasticizers and in grease applications.
However, their high pour point and viscosity open the door for further
chemical modifications.
2.3 Carbonates
Carbonates are materials that contain a carbon double bonded to an oxygen,
and with single bonding to two other oxygen atoms (Figure 2.1). If these
atoms are linked by a carbon chain, forming a ring, then it is a special case
called a ''cyclic carbonate''. These cyclic carbonates have found industrial
uses as solvents, dielectric fluids, and diluents for many decades.
45
They can
be reacted with amines, alcohols, or thiols to form polyurethanes and
polycarbonates of varying physical properties. Ethylene carbonate, propylene
carbonate, and glycerol carbonate are three of the common organic
carbonates that are well known for their bio-degradability, low toxicities, and
high flash points.
Cyclic carbonates are generally synthesized by either the reaction of a
chlorohydrin, the reaction of a diol with phosgene or, most promisingly,
the insertion of carbon dioxide into an epoxide.
46
Early examples of
thephosgenemethod
47,48
were used on methyl hydroxy stearates,
and the chlorohydrin method has also been shown to produce satisfactory
products.
49
However, following the principles of green chemistry, avoid-
ance of chlorinated intermediates can be accomplished by the use of
epoxides, easily produced as described in the previous section.
2.3.1 Previous Syntheses at Lower Pressure
There have been several reports on the transformation of oils into
cyclic carbonates including epoxidized soybean oil,
50,51
vernonia oil,
52
and
epoxidized cottonseed oil.
53
One interesting report also produced a
carbonated bio-diesel by first subjecting epoxidized soybean oil to an
esterification reaction, then performing the carbonation.
54
These reports all
have a couple of things in common. Firstly, they utilize a ring-opening
