Chemical Synthesis of Carbonates, Esters, and Acetals from Soybean Oil - Green Materials from Plant Oils - page 36

Table 2.3 The physical properties of branched-chain esters including pour point
and oxidation onset temperature.

Sample Oxidation onset/1C Pour Point/1C

Methyl oleate 177 27

Epoxidized methyl oleate 190 0

Propanoic acid branched 175 15

2-Ethylhexanoic acid branched 166 33

Octanoic acid branched 160 24

giving complete conversion in only a few hours at the higher temperatures. 62
Propanoic, octanoic, and 2-ethylhexanoic acids were employed.

2.4.2 Good Lubricant Properties
As mentioned earlier, the epoxides, while showing good oxidation stability,
suffer from high pour points. This new family of compounds shows some
success in the battle between these two properties (Table 2.3). While not
quite up to epoxy material stability, the new compounds are close. Further,
the longer chains even surpass the very favorable pour point of the alkene.
Other lubricant and fuel properties, 63 such as surface tension and friction
reduction, are also favorable, and the versatility and ease of the methods
lend them to building an even larger family of compounds. 22

2.5 Acetals
The final structure discussed in this chapter will be the acetal, also some-
times referred to as a ''ketal'' (Figure 2.1). A vegetable-oil-based acetal was
synthesized from a polyhydroxy compound and acetone, utilizing acid
catalysis. 64 This chemistry is a familiar protecting-group reaction, where
both stable and unstable regions could be envisioned through control of the
acid and base chemistry.

2.5.1 Catalyst Control and the Amazing Levulinic Acid Case
Structures of this same type are even more conveniently available through
the use of an epoxide. Using 2-pentanone and phosphoric acid, acetals
can be conveniently formed at only 50 1C. 65 This temperature regime is
important in a special case, that of using levulinic acid as a ketone.
Levulinic acid is available from biological sources, and is often considered
a platform commodity in the quest to transform cellulose into industrial
chemicals. 66 It is also bi-functional, containing the two reactive groups that
were just discussed earlier in this section and in the previous section.
Because the carboxylic acid reaction does not require a catalyst, but does
require high temperatures, and the acetal reaction requires the opposite, a