Diesters from oleic acid: Synthesis, low temperature properties, and oxidation stability

Article abstract of DOI:10.1007/s11746-007-1083-z

Several diesters were prepared from commercially available oleic acid and common organic acids. The key step in the three step synthesis of oleochemical diesters entails a ring opening esterification of alkyl 9,10-epoxyoctadecanoates (alkyl: propyl, isopropyl, octyl, 2-ethylhexyl) using propionic and octanoic acids without the need for either solvent or catalyst. Each synthetic diester was evaluated for both low temperature operability and oxidation stability through measurement of cloud point, pour point, oxidation onset temperature, and signal maximum temperature. It was discovered that increasing chain length of the mid-chain ester and branching in the end-chain ester had a positive influence on the low temperature properties of diesters. Improved oxidation stability is achieved when the chain length of the mid-chain ester is decreased. Additionally, the mid-chain ester plays a larger role in oxidation stability than the end-chain ester. These products may prove useful in the search for bio-based industrial materials, such as lubricants, surfactants, and fuel additives.

Full text of DOI:10.1007/s11746-007-1083-z

J Amer Oil Chem Soc (2007) 84:675–680
DOI 10.1007/s11746-007-1083-z
ORIGINAL PAPER
Diesters from Oleic Acid: Synthesis, Low Temperature Properties,
and Oxidation Stability
Bryan R. Moser Æ Brajendra K. Sharma Æ
Kenneth M. Doll Æ Sevim Z. Erhan
Received: 26 February 2007 / Revised: 3 April 2007 / Accepted: 6 April 2007 / Published online: 30 May 2007
ꢀ AOCS 2007
Abstract Several diesters were prepared from commer-
cially available oleic acid and common organic acids. The
key step in the three step synthesis of oleochemical
diesters entails a ring opening esterification of alkyl 9,10-
epoxyoctadecanoates (alkyl: propyl, isopropyl, octyl, 2-
ethylhexyl) using propionic and octanoic acids without
the need for either solvent or catalyst. Each synthetic
diester was evaluated for both low temperature operability
and oxidation stability through measurement of cloud
point, pour point, oxidation onset temperature, and signal
maximum temperature. It was discovered that increasing
chain length of the mid-chain ester and branching in the
end-chain ester had a positive influence on the low tem-
perature properties of diesters. Improved oxidation sta-
bility is achieved when the chain length of the mid-chain
ester is decreased. Additionally, the mid-chain ester plays
a larger role in oxidation stability than the end-chain
ester. These products may prove useful in the search for
bio-based industrial materials, such as lubricants, surfac-
tants, and fuel additives.
Keywords Additives Á Biodiesel Á Cloud point Á
Diesters Á Oxidative stability Á Pour point
Abbreviations
rt
Room temperature
Stretch
str
vib
sym
Vibration
Symmetrical
asym Asymmetrical
Introduction
Vegetable oils and derivatives thereof are attractive alter-
natives to petroleum-based products because they exhibit
enhanced biodegradability and reduced toxicity and are of
a domestic and renewable origin. Furthermore, vegetable
oil based products have become more cost competitive
with their petroleum derived counterparts as crude petro-
leum oil prices have increased dramatically in recent years
due to a number of geopolitical factors.
Soybean oil (SBO, see Table 1 for list of abbreviations)
is currently the major source of vegetable oil in the United
States for both food and industrial applications. In 2004 the
United States produced about one billion pounds of SBO in
excess of commercial demand, which resulted in lower
prices for both SBO and other agricultural commodities
[1]. At present, the rapid increase in biodiesel (BD) pro-
duction in the United States and elsewhere has reversed the
downward trend in SBO prices. Nevertheless, the devel-
opment of new economically feasible industrial products
from SBO that replace petroleum-derived materials is a
highly desirable goal. The advantages of using SBO and
other oleochemical feedstocks as lubricants are well
Product names are necessary to report factually on available data;
however, the USDA neither guarantees nor warrants the standard of
the product, and the use of the name by USDA implies no approval of
the product to the exclusion of others that may also be suitable.
B. R. Moser (&) Á B. K. Sharma Á K. M. Doll Á
S. Z. Erhan
USDA/ARS/NCAUR, Food and Industrial Oil Research,
1815 N. University St, Peoria, IL 61604, USA
e-mail: Bryan.Moser@ars.usda.gov
B. K. Sharma
Department of Chemical Engineering,
Pennsylvania State University,
University Park, PA 16802, USA
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J Amer Oil Chem Soc (2007) 84:675–680
(10–17) for low temperature operability through cloud
point (CP) and pour point (PP) determination and oxidation
stability through oxidation onset temperature (OT) and
signal maximum temperature (SMT) measurement are also
reported (Table 2). This study may aid in the continued
development of bio-based materials for use as alternatives
to petroleum products in industry and elsewhere.
Table 1 Common abbreviations used throughout this manuscript
Abbreivation
Full description
CP
Cloud point
PP
Pour point
OT
Onset temperature
Signal maximum temperature
Soybean oil
SMT
SBO
SME
BD
Soybean oil methyl esters
Biodiesel
Materials and Methods
PDSC
Pressurized differential scanning
calorimetry
Materials
Mid-chain ester
End-chain ester
Ester group attached at C9 or C10
of fatty acid backbone
Formic acid (88%) was obtained from Fisher Scientific
(Pittsburgh, PA) and oleic acid (99%) from Nu-Chek Prep,
Inc. (Elysian, MN). All other chemicals and reagents were
obtained from Aldrich Chemical (Milwaukee, WI). All
materials were used without further purification. All or-
ganic extracts were dried using anhydrous magnesium
sulfate (Aldrich Chemical).
Ester group attached at C1 of fatty
acid backbone
known. The superior lubricity of BD over that of petro-
diesel, for instance, is one of the major advantages of the
biofuel [2, 3]. However, vegetable oil based materials,
including BD, have inferior oxidation stability [4, 5] and
low temperature operability [6, 7] when compared to
petroleum products. Chemical modification at sites of un-
saturation along the fatty acid backbone of SBO, and other
oleochemicals, can provide materials with improved oxi-
dation stability and/or low temperature properties. Exam-
ples from the literature, though certainly not exhaustive,
include hydrogenation [8], epoxidation [9], metathesis
[10], and alkylation and acylation [11–13]. The reader is
directed elsewhere [14] for a more comprehensive treatise
on the synthesis of fatty acid derivatives.
Characterization
1H- and 13C-NMR spectra were recorded using a Bruker
AV-500 spectrometer (Rheinstetten, Germany) operating at
a frequency of 500.13 and 125.77 MHz, respectively, using
a 5-mm broadband inverse Z-gradient probe in CDCl3
(Cambridge Isotope Laboratories, Andover, MA) as sol-
vent. Each spectrum was Fourier-transformed, phase-cor-
rected, and integrated using MestRe-C 2.3a (Magnetic
Resonance Companion, Santiago de Compostela, Spain)
software. FT-IR spectra were recorded neat on a Thermo
Nicolet Nexus 470 FTIR system (Madison, WI) with a
Smart ARK accessory containing a 45 ZeSe trough in a
scanning range of 650–4,000 cm–1 for 32 scans at a spec-
tral resolution of 4 cm–1.
We report the synthesis and evaluation of a series of
diesters (10–17) derived from oleic acid. Addition of pro-
pionic and octanoic acids to the oxirane moieties of alkyl
9,10-epoxyoctadecanoates (alkyl: propyl, isopropyl, octyl,
2-ethylhexyl) at elevated temperature (100 ꢁC) is the key
step (Fig. 1) in a three-step sequence that includes esteri-
fication and epoxidation. Subsequent evaluation of diesters
Reactions were monitored by GC-MS using a Hewlett
Packard (Loveland, CO) 5870 series II GC equipped with a
6890 series injector and a 5970 series MSD in EI mode. A
Supelco (Bellefonte, PA) SPB-35 (30 m · 320 lm) col-
umn was used with a He flow rate of 0.9 mL/min. The
temperature program started at 150 ꢁC and increased to
290 ꢁC at 10 ꢁC min–1, which was followed by a hold time
of 10 min. The inlet and detector temperatures were set to
250 and 280 ꢁC, respectively, and an injection volume of
1 lL was used with a split ratio of 70:1.
Low Temperature Operability
Cloud point (CP) and pour point (PP) determinations were
made in agreement with ASTM D 5773 [16] and ASTM D
5949 [17], respectively, using a Phase Technology Ana-
lyzer Model PSA-70S (Richmond, BC, Canada). Each
Fig. 1 Synthesis of diesters from oleic acid. Note: R¢ in 10–17
contains a carbonyl group at carbon 1, resulting in an ester;
Pr = propyl; iPr = isopropyl; Oc = octyl; 2-EH = 2-ethylhexyl
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J Amer Oil Chem Soc (2007) 84:675–680
677
trated in vacuo, and placed for 6 h under high vacuum to
afford alkyl oleates (2–5) as clear oils (97 + % typical
yield). Esterifications employing C8 alcohols (2-ethylhex-
anol and octanol) were further dried by Kugelrohr (Buchi
Model B-585, Flawil, Switzerland) distillation at 100–
120 ꢁC and 0.1–0.5 mm Hg to remove excess alcohol.
No further purification was performed. 1H NMR
(500 MHz, CDCl3): d~5.4 (2H, –CH=CH–), ~2.3 (2H,
–CH2CO2R), ~2.0 (4H, –CH2CH=CHCH2–), ~1.6 (2H,
–CH2CH2CO2R), ~1.3 (20H, –CH2–), ~0.9 (3H, –CH3),
13C NMR (126 MHz, CDCl3): d ~174 (–CO2R), ~130
(–CH=CH–), ~35 (–CH2CO2R), ~34 (CH2CH=CHCH2–),
Table 2 Reaction time (h) and percentage yield information for ring-
opening step, and CP (ꢁC), PP (ꢁC), OT (ꢁC), and SMT (ꢁC) of
synthetic diesters
Ra
R¢ Rxn time Yield (%) CPb PPb OTc SMTc
10 Pr
11 Pr
12 iPr
13 iPr
14 Oc
15 Oc
Pr
8
8
8
8
9
9
9
9
93
78
85
72
70
81
70
80
–8
–15 176 246
Oc
Pr
–11 –20 156 214
–13 –18 159 239
–20 –22 155 234
Oc
Pr
6
3
–11 161 232
–15 157 200
Oc
16 2-EH Pr
–26 –35 172 256
–39 –42 163 228
17 2-EH Oc
1
~14 (–CH3). Additional signals in the H and 13C -NMR
a
Pr = propyl; iPr = isopropyl; Oc = octyl; 2-EH = 2-ethylhexyl
spectra vary with head group. FT-IR (neat): ~3,004,
~2,923, ~2,853 cm–1 (CH2 str), ~1,733 (C=O str), ~1,667
(olefin str), ~1,466 (CH2 bending vib), ~1,374 (CH3 sym
bending vib), ~1,249, ~1,179, ~1,108 (C–O str), ~965
(vinyl C–H out of plane bend), ~723 (CH2 rocking vib).
b
c
Means n = 3, SE
Means n = 2, SE
1 ꢁC
1 ꢁC
sample was run in triplicate and average values rounded to
the nearest whole degree are reported in Table 2. For a
greater degree of accuracy, PP measurements were done
with a resolution of 1 ꢁC instead of the specified 3 ꢁC
increment. Generally, materials with lower CP and PP
exhibit improved fluidity at low temperatures than those
with higher CP and PP.
Epoxidation of Alkyl Oleates
To a stirred solution of alkyl oleate (2–5, 10.0 g) and formic
acid (88%, 5.0 mL, 117 mmol) at 4 ꢁC was slowly added
H2O2 (30% in H2O, 8.0 mL, 78 mmol). The reaction pro-
ceeded at rt with vigorous stirring (900+ rpm) until GC-MS
analysis indicated consumption of 2–5 (14–16 h). After
removal of the lower aqueous phase, hexanes (20 mL) were
added to the upper oily phase, which was washed with
NaHCO3 (sat. aq. 2 · 5 mL) and brine (2 · 5 mL), dried,
filtered, concentrated in vacuo, and placed for 6 h under
high vacuum to provide alkyl 9,10-epoxyoctadecanoates
(6–9) as clear oils (95+% overall yield, typically). GC-MS
analysis generally indicated the presence of <5% alkyl
9,10-dihydroxyoctadecanoate. No further purification was
performed. 1H NMR (500 MHz, CDCl3): d ~2.9 (2H,
–CH(O)CH–), ~2.3 (2H, –CH2CO2R), ~1.6 (2H,
–CH2CH2CO2R), ~1.5 (4H, –CH2CH(O)CHCH2–), ~1.3
(20H, –CH2–), ~0.9 (3H, –CH3); 13C NMR (126 MHz,
CDCl3): d ~174 (–CO2R), ~51 (–CH(O)CH–), ~35
(–CH2CO2R), ~14 (–CH3). Additional signals in the 1H and
13C-NMR spectra vary with head group. FT-IR (neat):
~2,923, ~2,853 cm–1 (CH2 str), ~1,733 (C=O str), ~1,466
(CH2 bending vib), ~1,374 (CH3 sym bending vib), ~1249,
~1,179, ~1108 (C–O str), ~723 (CH2 rocking vib), ~1,145
(ether C–O–C sym str), ~896 (C–C asym ring str), ~824
(‘‘12 micron band’’, ref. 15), and a small peak at ~3,500
(OH str) indicative of over-reaction to form alkyl 9,10-di-
hydroxyoctadecanoate in small (<5%) amount.
Oxidation Stability
Pressurized DSC (PDSC) experiments were accomplished
using a DSC 2910 thermal analyzer from TA Instruments
(Newcastle, DE). Typically, a 2-lL sample, resulting in a
film thickness of <1 mm, was placed in an aluminum pan
hermetically sealed with a pinhole lid and oxidized in the
presence of dry air (Gateway Airgas, St Louis, MO), which
was pressurized in the module at a constant pressure of
1,378.95 kPa (200 psi). A 10 ꢁC min–1 heating rate from
50 to 350 ꢁC was used during each experiment. The oxi-
dation onset (OT, ꢁC) and signal maximum temperatures
(SMT, ꢁC) were calculated from a plot of heat flow (W/g)
versus temperature for each experiment. Each sample was
run in duplicate and average values rounded to the nearest
whole degree are reported (Table 2).
Fischer Esterification of Oleic Acid
To a stirred solution of oleic acid (99%, 1, 10.0 g,
35.4 mmol) in ROH (15.0 mL, R = propyl, isopropyl, oc-
tyl, 2-ethylhexyl) was added at rt H2SO4 (conc. 0.10 mL,
5.1 mol%), and the combined reaction was heated at reflux
for 4 h. Upon cooling to rt the alcohol was removed in
vacuo and the resultant oil dissolved in hexanes (10 mL).
After washing with NaHCO3 (sat. aq. 2 · 1 mL) and brine
(2 · 1 mL), the organic phase was dried, filtered, concen-
Synthesis of Diesters
To a solution of alkyl 9,10-epoxyoctadecanoate (6–9, 5.0 g)
in a 7.4-mL (2 dram) vial was added 12 g of either propi-
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J Amer Oil Chem Soc (2007) 84:675–680
onic acid (12.1 mL, 0.16 mol) or octanoic acid (13.2 mL,
0.083 mol). The vial was purged with N2 and sealed with a
septum and was then placed in a Pierce Reacti-vap Model
19780 (Rockford, IL) heating/stirring module with stirring
at 100 ꢁC. Aliquots (20 lL) of each reaction were removed,
diluted in acetone (1 mL), and analyzed by GC-MS until
complete. The reactions were allowed to proceed for 8 h in
the cases of 6 and 7, and 9 h when 8 and 9 were used. The
products resulting from propionic acid (10,12,14,16) were
purified by washing with H2O (3 · 100 mL); however, 11,
13, 15, and 17 were not washed with water due to the low
solubility of octanoic acid. Acid was removed first by rotary
evaporation at 40 ꢁC and then by Kugelrohr distillation at
70 ꢁC and 0.1–0.5 mm Hg to afford diesters 10–17 (70–
93% yield, Table 2), which were stored over molecular
sieves to mitigate potential hydrolysis. 1H NMR (500 MHz,
CDCl3): d ~4.8 (1H, –CH(O2CR¢)-), ~3.6 (1H, –OH), ~2.4
(2H, –CH(O2CCH2–), ~2.3 (2H, –CH2CO2R), ~1.6 (2H,
–CH2CH2CO2R), ~1.5 (2H, –CH2CH(OH)–), ~1.4 (2H,
–CH2CH(CO2R¢)–), ~1.3 (20H, –CH2–), ~0.9 (3H, –CH3);
13C NMR (126 MHz, CDCl3): d ~174–173 (2C, –CO2R,
–CO2R¢), 76–72 (4C, –C9–O · 2, –C10–O · 2), ~35 (1C,
–CH2CO2R), ~14 (–CH3). Additional signals in the 1H- and
13C -NMR spectra vary with ester groups. FT-IR (neat):
~3,500 cm–1 (OH str), ~2,925, ~2,855 (CH2 str), ~1,735
(C=O str), ~1,463 (CH2 bending vib), ~1,371 (CH3 sym
bending vib), ~1,246, ~1,174, ~1,104 (C–O str), ~723 (CH2
rocking vib).
The addition of carboxylic acids to oxiranes 6–9 to
afford diesters 10–17 by ring opening esterification [21, 22]
was accomplished at elevated temperature (100 ꢁC) with-
out need for either catalyst or solvent, as shown in Fig. 2.
The reactant, in this case either propionic or octanoic acid,
served as both reactant and solvent, thus eliminating the
need for a separate solvent. Catalysts were also unneces-
sary since the reaction proceeded to completion at 100 ꢁC.
At reduced temperatures, such as rt, the use of catalyst may
become necessary to avoid either extended reaction times
or no reaction. Ambient temperature reactions were not
investigated here since: (a) use of catalyst would add to
material costs; (b) catalyst removal would complicate
purification; (c) elevated temperature readily provided the
desired products. The reactions were monitored by GC-MS
and terminated when >95% of starting material was con-
sumed (8–9 h). Table 2 contains both yield and time of
reaction data for diesters 10–17.
When carboxylic acids add to oxirane moieties in the
manner described above, diesters result. The additional
mid-chain ester group serves as a point of branching along
an otherwise linear fatty acid backbone. Propionic and
octanoic acids were selected such that a variety of mate-
rials of varying chain length would allow for the study of
branch size on low temperature and oxidation stability
properties discussed below.
No effort to distinguish the regiochemistry (Fig. 2; alkyl
9-alkanoate-10-hydroxy-octadecanoate versus the equally
likely alkyl 10-alkanoate-9-hydroxyoctadecanoate regio-
isomer) or the stereochemistry (R or S at C9 and C10) of
the diesters obtained here was made, due to the laborious
chromatography required and the economics involved at
potentially larger commercial scales. If such materials are
eventually adopted for commercial use, then production
costs relating to synthesis and purification are of paramount
importance. Therefore, the diesters prepared here were
tested for low temperature operability and oxidation sta-
bility behavior without further purification.
Results and Discussion
Synthesis
After the straightforward Fischer esterification [18] of oleic
acid (1) to alkyl oleates 2–5, a modified epoxidation pro-
tocol [12, 13, 19] originally developed by Swern [9] and
later modified for oleochemical use by Bunker and Wool
[20] was employed to provide alkyl 9,10-epoxyoctade-
canoates (6–9, Fig. 1). The reactions were monitored by
GC-MS and terminated when >95% of starting material
was consumed (14–15 h). Further analysis by GC-MS
generally indicated the presence of a small amount (<5%)
of alkyl 9,10-dihydroxyoctadecanoate, demonstrating the
importance of monitoring the epoxidation closely to avoid
unwanted over-reaction. The end-chain esters (R = propyl,
isopropyl, octyl, 2-ethylhexyl) employed here were se-
lected such that relatively short (R = propyl, 2) and long
chain (R = octyl, 4) esters could be compared. Addition-
ally, the effect of branching on low temperature and oxi-
dation properties was also of interest, so isopropyl (3) and
2-ethylhexyl (5) end-chain esters were chosen for com-
parison as well.
Fig. 2 A plausible mechanism for the ring-opening esterification of
oxiranes 6–9 to afford diesters 10–17. Two products, the 9- and 10-
alcohols, are formed in the case of each diester
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J Amer Oil Chem Soc (2007) 84:675–680
Low Temperature Operability
679
Oxidation Stability
The ability of a substance to remain liquid at low tem-
peratures is an important attribute for a number of indus-
trial materials, such as lubricants, surfactants, and fuels.
Therefore, diesters 10–17 were screened for cold flow
performance through determination of both CP and PP. An
improvement in the cold flow behavior of diesters 10–17
(Table 2) was obtained over that of alkyl 9,10-epoxyocta-
decanoate precursors (6–9), SBO, and soybean oil methyl
esters (SME, Table 3). Not surprisingly, as the chain length
of the mid-chain ester is increased, a corresponding
improvement in low temperature behavior was observed.
We hypothesize this is due to the greater ability of the
longer chain esters to more effectively disrupt crystalline
formation at reduced temperatures. For example, compar-
ison of diesters where R (Fig. 1) is held constant reveals an
improvement in CP and PP as the mid-chain ester length
(R¢) was increased, as shown by diester 10 (CP –8 ꢁC; PP
–15 ꢁC, R¢ = propyl; R = propyl) and diester 11 (CP
–11 ꢁC; PP –20 ꢁC, R¢ = octyl; R = propyl). A similar
trend was exhibited when comparing 12 to 13, 14 to 15,
and 16 to 17 (Table 2), which can be expressed as R¢:
propyl > octyl (lower CP and PP) where R is equal. Fur-
thermore, the nature of the end-chain ester group also plays
a role in the cold flow behavior of diesters. Three trends are
apparent from the data where R¢ is held constant: (a)
branching in the end-chain ester lowers CP and PP; (b)
octyl esters exhibit increased CP and PP in comparison to
propyl esters; (c) 2-ethylhexyl esters have the most favor-
able CP and PP. These observations can be expressed as R:
octyl > propyl > isopropyl > 2-ethylhexyl (lower CP and
PP) where R¢ is held constant. Therefore, based on the
trends mentioned above, a material with R = 2-ethylhexyl
and R¢ = octyl should provide the best low temperature
behavior, which is evidenced by 17 (CP –39 ꢁC; PP
–42 ꢁC). Conversely, a material with R = octyl and
R¢ = propyl should correspondingly provide the least
favorable CP and PP, as shown by 14 (CP 6 ꢁC; PP
-11 ꢁC).
The ability of a substance to resist oxidative degradation
is another important attribute for a number of industrial
materials, such as lubricants, surfactants, and fuels.
Therefore, diesters 10–17 were screened for oxidation
stability using PDSC through determination of both OT
and SMT. PDSC is an effective method for measuring
oxidation stability of oleochemicals in an accelerated
mode [5, 23, 24]. The OT is the temperature at which a
rapid increase in the rate of oxidation is observed at a
constant, high pressure (200 psi). A high OT would
suggest high oxidation stability of the material. The SMT
is the temperature at which maximum heat output is noted
from the sample during oxidative degradation. A higher
SMT does not necessarily correlate with improved oxi-
dation stability. Both OT and SMT were calculated from
a plot of heat flow (W/g) versus temperature that was
generated by the sample upon degradation and, by defi-
nition, SMT > OT.
In the present study, as the chain length of the mid-chain
ester is decreased, a corresponding improvement in oxi-
dation stability was observed, which is because longer
chains are more susceptible to oxidative cleavage than
shorter chains. These results are in agreement with other
studies on chemically modified vegetable oils [11] and
synthetic esters [25]. For example, when comparing di-
esters where R is held constant, an improvement in OT was
noticed as the mid-chain ester length (R’) was decreased,
as shown by diester 10 (OT 176 ꢁC, R¢ = propyl;
R = propyl) and diester 11 (OT 156 ꢁC, R¢ = octyl;
R = propyl). A similar trend was exhibited when compar-
ing 12 to 13, 14 to 15, and 16 to 17 (Table 2), which can be
expressed as R¢: propyl > octyl (higher OT) where R is
held constant. The effect of the end-chain ester is less
pronounced. One would gather that, based on the above
conclusions regarding the relationship between mid-chain
ester length and OT, the same trend would apply to the
end-chain ester group. However, R = propyl provided the
highest OT (10) while R = isopropyl (13) gave the lowest.
If the abovementioned trend was still applicable when
considering end-chain ester groups, it would stand to rea-
son that R = octyl (14 or 15) would afford the lowest OT.
The results of 10 and 13 would suggest that branching has a
detrimental effect on OT; however, comparison of
R = octyl (14,15) and R = 2-ethylhexyl (16,17) reveals the
opposite trend, i.e., branching improves OT. It is clear,
based on these results, that the mid-chain ester has a sig-
nificantly higher impact on oxidation stability than the end-
chain ester. Also of note, the trends for CP and PP run
counter to that of OT, i.e., increasing chain length is a
benefit to CP and PP, but a detriment to OT. Future study
will aim to strike a balance between these two opposing
Table 3 CP (ꢁC) and PP (ꢁC) of SBO, SME, and 9,10-epoxyocta-
decanoates
R
CP
PP
SBO
–
–5
0
–9
–2
–5
–7
4
SME
–
6
7
8
9
Pr
4
iPr
Oc
2-EH
–6
8
–3
–13
Refer to Table 2 footnotes
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J Amer Oil Chem Soc (2007) 84:675–680
12. Moser BR, Erhan SZ (2006) Synthesis and evaluation of a series
of a-hydroxy ethers derived from isopropyl oleate. J Am Oil
Chem Soc 83:959–963
properties through investigation of a greater variety of mid-
chain esters and, potentially, end-chain ester groups.
13. Moser BR, Erhan SZ (2007) Preparation and evaluation of a
series of a-hydroxy ethers from 9,10-epoxystearates. Eur J Lip
Sci Technol 109:206–213
Acknowledgments The authors acknowledge Mrs. Donna I.
Thomas for excellent technical assistance.
14. Knothe G, Derksen JTP (eds.) (1999) Recent developments in the
synthesis of fatty acid derivatives. AOCS Press, Champaign
15. Silverstein RM, Webster FX (1998) Spectrometric Identification
of Organic Compounds, 6th Ed. Wiley, New York, p 92
16. ATSM D5773: Standard test method for cloud point of petroleum
products (Constant Cooling Rate Method), in annual book of
ASTM standards, vol 05.03, American Society for Testing and
Materials, Philadelphia, 2003
References
1. Gawrilow I (2004) Vegetable oil usage in lubricants. Inform
15:702–705
2. Knothe G, Van Gerpen JH, Krahl J. (eds.) 2005 The biodiesel
handbook, AOCS Press, Champaign, IL
17. ASTM D5949: Standard test method for pour point of petroleum
products (Automatic Pressure Pulsing Method), in annual book of
ASTM standards, vol 05.03, American Society for Testing and
Materials, Philadelphia, PA, 2003
18. Fischer E, Speier A (1895) Darstellung der Ester. Ber Dtsch
Chem Ges 28:3252–3255
19. Doll KM, Erhan SZ (2005) Synthesis of carbonated fatty methyl
esters using supercritical carbon dioxide. J Agric Food Chem
53:9608–9614
20. Bunker SP, Wool RP (2002) Synthesis and characterization of
monomers and polymers for adhesives from methyl oleate.
J Polym Sci. Part A: Polym Chem 40:451–458
3. Van Gerpen JH, Soylu S, Tat ME (1996) Evaluation of the
lubricity of soybean oil-based additives in diesel fuel, proceed-
ings, annual international meeting of the ASAE, American
Society of Agricultural Engineers, St Joseph, MI, paper no.
996134
4. Coscione AR, Artz WE (2005) Vegetable oil stability at elevated
temperatures in the presence of ferric stearate and ferrous
octanoate. J Agric Food Chem 53:2088–2094
5. Dunn RO (2006) Effect of antioxidants on the oxidative sta-
bility of methyl soyate (Biodiesel). Fuel Pro Technol 86:1071–
1085
6. Hwang HS, Erhan SZ (2001) Modification of epoxidized soy-
bean oil for lubricant formulations with improved oxidative
stability and low pour point. J. Am Oil Chem Soc 78:1179–
1184
7. Li S, Blackmon J, Demange A, Jao TC (2004) Linear sulphonate
detergents as pour point depressants. Lub Sci 16:127–137
8. King JW, Holliday RL, List GR, Snyder JM (2001) Hydrogena-
tion of vegetable oils using mixtures of supercritical carbon
dioxide and hydrogen. J Am Oil Chem Soc 78:107–113
9. Findley TW, Swern D, Scanlan JT (1945) Epoxidation of
unsaturated fatty materials with peracetic acid in glacial acetic
acid solution. J Am Chem Soc 67:412–414
10. Holser RA, Doll KM, Erhan SZ (2006) Metathesis of methyl
soyate with ruthenium catalysts. Fuel 85:393–395
11. Sharma BK, Adhvaryu A, Liu Z, Erhan SZ (2006) Chemical
modification of vegetable oils for lubricant applications. J Am Oil
Chem Soc 83:129–136
21. Campanella A, Baltanas MA (2006) Degradation of the oxirane
ring of epoxidized vegetable oils in liquid-liquid heterogeneous
reaction systems. Chem Eng J 118:141–152
´
22. Campanella A, Baltanas MA (2004) Degradation of the oxirane
ring of epoxidized vegetable oils with solvated acetic acid using
cation-exchange resins. Eur J Lipid Sci Technol 106:524–5301
23. Zhang YY, Ren TH, Wang HD, Yi MR (2004) A comparative
study of phenol-type antioxidants in methyl oleate with quantum
calculations and experiments. Lub Sci 16:385–392
24. Adhvaryu A, Sharma BK, Hwang HS, Erhan SZ (2006) Devel-
opment of biobased synthetic fluids: application of molecular
modeling to structure-physical property relationship. Ind Eng
Chem Res 45:928–933
25. Randals SJ (1999) Esters, in synthetic lubricants and high-per-
formance functional fluids. In: Rudnick LR and Shubkin RL (eds)
Marcel Dekker, New York, pp 63–102
123