Controlling product composition of metathesized triolein by reaction concentrations

Article abstract of DOI:10.1007/s11746-012-2106-y

Triolein was used as a model material to investigate the effect of concentration on self metathesis of vegetable oils. The metathesis reaction using Grubbs' second generation catalyst (used at a level of 2.5 mol % of triolein) was carried out at 38 °C usi

Full text of DOI:10.1007/s11746-012-2106-y

J Am Oil Chem Soc (2012) 89:2077–2089
DOI 10.1007/s11746-012-2106-y
ORIGINAL PAPER
Controlling Product Composition of Metathesized Triolein
by Reaction Concentrations
•
Shaojun Li Leila Hojabri Suresh S. Narine
•
Received: 20 March 2012 / Revised: 13 June 2012 / Accepted: 19 June 2012 / Published online: 18 July 2012
Ó AOCS 2012
Abstract Triolein was used as a model material to
investigate the effect of concentration on self metathesis of
vegetable oils. The metathesis reaction using Grubbs’
second generation catalyst (used at a level of 2.5 mol % of
triolein) was carried out at 38 °C using dichloromethane as
the solvent. The products from three reaction concentra-
tions were investigated: neat, 10 and 20 mmol/L. The
products from the reactions were separated by column
chromatography and the fractions were characterized by
1H-NMR, 13C-NMR, MS and FTIR. Mono-cyclic and
multi-cyclic triacylglycerol-based compounds and different
level aliphatic triacylglycerol-like oligomers were pro-
duced, but the compositions of the products were found to
be significantly controlled by the reaction concentrations.
Cyclic compounds were favorably produced at lower
reaction concentrations, whereas, linear oligomers were
favorably produced at higher reaction concentrations.
Cyclic compounds were formed mainly from adjacent fatty
acid chains on the glycerol backbone. In the neat reactions,
only linear oligomers were produced. The trans/cis ratios
increased as concentration was increased.
Introduction
The metathesis reaction of triacylglycerols and unsaturated
fatty acid derivatives has been known since van Dam et al.
[1] applied metathesis reactions to fatty acid derivatives in
1972. The olefin metathesis reaction is a process of the
substituent’s exchange between two reacting olefins in an
equilibrium reaction: a transalkylidenation [2]. It involves
two stepwise reactions. First, a catalyst (a transition metal
carbene complex) reacts with an olefin in a [2 ? 2] fashion
to generate an unstable metallacyclobutane intermediate.
Following this, the intermediate either opens to give a new
metal carbene and a new olefin, or it reverts to the starting
material.
The metathesis reaction of renewable raw materials
[3, 4], such as fats and oils, is rapidly becoming an
important reaction to produce safer, less toxic fine chemi-
cals [5] and monomers for the polymer industry [6]. This
approach to petrochemical replacements can contribute to
the development of a sustainable chemistry industry with
concomitant reductions in CO2 emissions. It also can
contribute to the reduction of toxic chemicals by avoiding
by-products and waste [4] through the application of an
efficient catalytic approach in metathesis [7].
Keywords Metathesis Á Triolein Á Grubbs catalysts Á
Reaction concentration Á Cyclic compounds Á Oligomers
In the past, a tungsten-tin catalyst system [1, 8] was
widely used for the metathesis of vegetable oils and
unsaturated fatty acids. However, this catalyst system
presents a number of disadvantages, including the disposal
of solvent and used catalysts, as well as sensitivity to
moisture and oxygen. These complicate the reaction pro-
cess and affect reproducibility [9]. Among the numerous
attempts made to develop improved active and stable cat-
alytic systems, the work of the Grubbs group [7, 10] stands
out; they discovered a series of well-defined, active and
stable ruthenium-based catalysts, in particular the Grubbs’
S. Li Á L. Hojabri Á S. S. Narine (&)
Departments of Physics and Astronomy and Chemistry,
Trent Centre for Biomaterials Research, Trent University,
1600 West Bank Drive, Peterborough, ON K9J 7B8, Canada
e-mail: sureshnarine@trentu.ca
S. Li
e-mail: shaojunli@trentu.ca
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J Am Oil Chem Soc (2012) 89:2077–2089
first and second generation catalysts (see Scheme 1). These
catalysts have been significantly employed in studying
the metathesis of unsaturated fatty acids and vegetable oils
[9, 11].
have not been detected. In our present study we have used
as a model system (pure triolein) and examined the role of
reaction concentration on the products of metathesis reac-
tion. The metathesis reaction was performed using Grubbs’
second generation catalyst and CH2Cl2 as solvent. The
reaction was performed at the highest possible temperature
of 38 1 °C, just below the boiling point of the solvent
(39.6 °C). This study extends the database relating to the
parameters of metathesis and furthers our understanding of
the metathesis of vegetable oils and their derivatives.
Metathesized vegetable oils, such as high-oleic sun-
flower oil [12], soybean oil [8] and the triacylglycerol tri-
olein [9, 11] have been studied. Metathesized soybean oil
and its modified products have been explored as waxes [13]
and additives to improve the drying properties of soybean
oil [8]. Elevance renewable sciences [13] brought these
materials to the forefront on the commercial market. The
metathesis of neat triolein was used as a model system to
study the metathesis reaction of more complicated vege-
table oils [9, 11]. These studies have demonstrated that the
products of metathesized triolein include oligomers, mono
cyclic structures, as well as their cis/trans-configurations.
The predominance of one or more of these classes of
products is important to the final physical properties of the
produced material, and therefore very important in deter-
mining end uses such as lubricants, waxes, or additives.
The reaction conditions (such as catalyst, starting
materials, temperature, etc.) have been shown to have
significant effects on the products of metathesis. For
example, Tian et al. [11] have reported that the metathesis
of triolein and soybean oil performed at relatively high
temperature (55 °C) using Grubbs’ second generation cat-
alyst yield not only linear oligomers and mono cyclic
structures (in both the cis- and trans-configurations) but
also cross-linked rubber materials. The production of these
undesirable cross-linked rubber materials have been avoi-
ded when a lower temperature (room temperature in Tian
et al. report) is used with however, a longer reaction tem-
perature (i.e., 240 h). Biermann et al. [12] reported that at a
temperature of 70 °C, when a Hoveyda–Grubbs’ second
generation catalyst and a chain stopper were used, the
reaction yielded a series of highly branched polyesters
(triacylglycerol-like linear oligomers) and no cross-linked
materials. When Grubbs’ first generation catalyst was used,
even without a chain stopper, the cross-linked materials
Experimental
Materials
Triolein (99 %), Grubbs’ second generation catalyst and
ethyl vinyl ether were purchased from Sigma-Aldrich.
Dichloromethane was dried by distillation over calcium
hydride.
Instruments
Nuclear Magnetic Resonance Spectroscopy
(1H- and 13C-NMR)
1
1
1D H-NMR 1D H spectra were acquired on a Bruker
Avance III 400 spectrometer (m(1H) 400.22 MHz; Bruker
BioSpin MRI GmbH, Karlsruhe, Germany) equipped with
a 5 mm BBO probe. Spectra were acquired at 25 °C over a
16 ppm spectral window with a 1-s recycle delay and 32
transients.
1D 13C-NMR 1D 13C-spectra were acquired on a Bruker
Avance III 400 spectrometer (m(13C) = 100.65 MHz;
Bruker BioSpin MRI GmbH, Karlsruhe, Germany) equip-
ped with a 5 mm BBO probe. Spectra were acquired at
25 °C over a 240 ppm spectral window with a 0.2-s recycle
delay and 2,048 transients.
Mass Spectroscopy (MS)
Electrospray ionization mass spectrometry (ESI–MS)
analyses were performed using a QStar XL quadrupole
time-of-flight mass spectrometer (AB Sciex, Concord, ON,
Canada) equipped with an ionspray source and a modified
HSID interface (Ionics, Bolton, ON, Canada). The ion
source and interface conditions were adjusted as follows:
ionspray voltage (IS = 4,500 V), nebulising gas (GS1 =
45), curtain gas (GS2 = 45), declustering potential
(DP = 60 V) and HSID temperature (T = 200 °C). Mul-
tiple-charged ion signals were reconstructed using the
Scheme 1 Grubbs’ catalysts
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2079
Metathesis of Triolein
BioTools 1.1.5 software package (AB Sciex, Concord,
ON).
A 6-g sample (99 % pure) of triolein dissolved in CH2Cl2
with a concentration of 10 mmol/L (R1), 20 mmol/L (R2),
or neat (R3) was heated to 38 1 °C under a protective N2
atmosphere. Then, 144 mg Grubbs’ second generation
catalyst was added. The reaction mixture was stirred at
38 °C for 6 h. The reaction was quenched with 20 mL
ethyl vinyl ether. This reaction mixture was concentrated
on a rotary evaporator and the residue was re-dissolved in
200 mL hexane. The hexane solution was filtered through a
Celite layer to give a clear yellow solution. After concen-
tration with a rotary evaporator, the samples were purified
by a column chromatography with ethyl acetate and hexane
as the eluent. The structure of these fractions is presented
in Schemes 2 to 4. The following compounds contain
trans- and cis-configurations and positional isomers. The
yield presented is the weight percentage of pure fractions in
the mixtures. The yields of the produced olefins in the
10 mmol/L reaction (R1), 20 mmol/L reaction (R2) and
neat reaction (R3) are 28.3, 26.7 and 21.4 %, respectively.
Fourier Transform Infrared Spectroscopy (FTIR)
FTIR spectra were acquired using a Thermo Scientific
Nicolet 380 FTIR spectrometer (Thermo Electron Scien-
tific Instruments LLC, Fitchburg, WI) fitted with a PIKE
MIRacleTM attenuated total reflectance (ATR) system
(PIKE Technologies, Madison, WI, USA). Solid samples
were placed onto the ATR crystal area and held in place by
a pressure arm. Liquid samples were poured onto the ATR
crystal area for signal acquisition. The signal was acquired
with the following parameters: scanning number = 32;
resolution = 4.000; sample gain = 8.0; mirror velocity =
0.6329; and aperture = 100.
High Performance Liquid Chromatography (HPLC)
HPLC was carried on a Waters Alliance (Milford, MA,
USA) e2695 HPLC system fitted with a Waters ELSD 2424
evaporative light scattering detector. The HPLC system
includes an inline degasser, a pump, and an auto-sampler.
The temperature of the column (C18, 150 9 4.6 mm,
5.0 lm, X-Bridge column, Waters Corporation, MA, USA)
was maintained at 35 °C by a Waters Alliance column
oven. The ELSD nitrogen flow was set at 25 psi with
nebulization and drifting tube maintained at 12 and 55 °C,
respectively. Gain was set at 500. The mobile phase was
chloroform : acetonitrile (50:50)v run for 30 min at a flow
rate of 0.2 mL/min. 1 mg/mL (w/v) solution of sample in
chloroform was filtered through single step filter vial
(Thomson Instrument Company, CA, USA) and 0.5 lL of
sample was passed through the C18 column by reversed-
phase in isocratic mode. All solvents were HPLC grade and
obtained from VWR International (Mississauga, ON,
Canada).
The Structure of Fractions From the Reaction
with 10 mmol/L (R1)
Triolein and its isomers (R1–2)
Yield: 8.1 %
HPLC peak retention time tR(min): 12.6
MS: C57H104O6, Cal. 885, found 603.5, 902.8 [M ?
NH4]?
1H-NMR (in CDCl3, ppm), d = 5.45–5.35 (4H,
m,–CH=CH–), 5.30–5.28 (1H, m,–CH2CH(O)CH2–), 4.34–
4.30 (2H, dd,–CH2CH(O)CH2–), 4.19–4.15 (2H, dd, –CH2CH
(O)CH2–), 2.35–2.31 (6H, t, –C(=O)CH2CH2–), 2.04–1.96
(12H, m,=CHCH2CH2–), 1.65–1.62 (6H, m, –C(=O)
CH2CH2–), 1.32–1.29 (62H, m,–CH2–), 0.92–0.89 (9H, t,
–CH3);
13C-NMR (in CDCl3, ppm), d = 173.48, 173.06,
130.70, 130.39, 130.22, 129.92, 69.09, 62.31, 34.41, 34.25,
32.80, 32.12, 29.87-29.18, 27.40, 25.10, 25.06, 22.90,
14.32;
Gas Chromatography (GC)
The GC analysis was carried out on an Agilent 6890 N
Network System (Palo Alto, CA, USA) equipped with a
flame ionization detector (FID), using a CP-Sil 88 fused
silica capillary column (100 m 9 0.25 mm, 0.2 lm,
Varian, Middelburg, The Netherlands). The carrier gas
was H2. The following column temperature conditions
were employed: initial hold at 45 °C for 4 min, there-
after rising to 175 °C at a rate of 13 °C/min, followed
by a final hold at 175 °C for 27 min. The injector
temperature was 250 °C with a purge flow of 40 mL/min
at 0.1 min.
6, 23-dioxo-1,5-dioxacyclotricos-14-en-3-yl octadec-9-
enoate and/or 5,22-dioxo-1,4-dioxacyclodocos-13-en-2-
yl-methyl octadec-9-enoate and its isomers (R1–3)
Yield: 35.0 %
tR(min): 10.0
MS: C39H68O6, Cal.632.95, found 633.5 [M ? H]?,
650.5 [M ? NH4]?
1H-NMR (in CDCl3, ppm), d = 5.41–5.24 (5H,
m,–CH=CH– and, –CH2CH(O)CH2–), 4.47–4.09 (4H, dd,
–CH2CH(O)CH2–), 2.37–2.31 (6H, m, –C(=O)CH2CH2–),
2.07–1.96 (8H, m, =CHCH2CH2–), 1.65–1.62 (6H, br,
123

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Scheme 2 Structures of
compounds from the reaction
with 10 mmol/L (R1). The
compounds present contain
cis-, trans-configurations, and
positional isomers on glycerol
skeletons
R1-2
R1-3
R1-4
R1-5
R1-6
R1-7
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2081
–C(=O)CH2CH2), 1.37–1.29 (36H, m, –CH2–), 0.92–
0.88(3H, t,–CH3);
13C-NMR (in CDCl3, ppm), d = 173.46, 173.08,
130.96, 130.80, 130.10, 129.92, 69.18, 62.61, 62.38, 61.80,
34.54-34.24, 32.82, 32.35, 32.10, 31.13, 29.91-28.58,
28.23, 27.90, 27.40, 26.77, 25.19-24.83,
13C-NMR (in CDCl3, ppm), d = 173.48, 173.06,
130.97, 130.80, 130.70, 130.38, 130.23, 129.93, 69.11,
68.95, 62.54, 62.47, 62.31, 61.72, 34.55, 34.43,34.43,
34.38, 34.30, 34.25, 32.83, 32.78, 32.36, 32.11, 31.14,
29.99-28.59; 28.24, 27.95, 27.89,27.45, 27.39, 27.07,
26.87,26.78, 25.19, 25.07, 24.95, 24.85,22.90, 14.33;
Bis (1,3-bis(octadec-9-enoyloxy)propan-2-yl) octa-
dec-9-enedioate and its isomers (R1–4)
18-bis
(6,23-dioxo-1,5-dioxacyclotricos-14-en-3-yl)
‘1,1-2(octadec-9-enoyloxy)propane-1,3-diyl dioctadec-9-
enedioate and its isomers (R1–7)
Yield: 5.0 %
tR(min): 10.1
MS: C99H168O18, Cal.1646.38, found 351.2, 645.5,
840.7[M ? 2NH4]2?, 1663.3 [M ? NH4]?
1H-NMR (in CDCl3, ppm), d = 5.40-5.29 (13H, m,
–CH=CH– and –CH2CH(O)CH2–), 4.47–4.14 (12H, m,
–CH2CH(O)CH2–), 2.35–2.31 (18H, m, –C(=O)CH2CH2–),
2.06–1.98 (20H, m, =CHCH2CH2–), 1.63 (18H, br,
–C(=O)CH2CH2–), 1.31–1.26 (84H, m, –CH2–), 0.92–0.88
(3H, t, –CH3);
13C-NMR (in CDCl3, ppm), d = 173.50, 173.05, 130.96-
130.03, 129.92, 69.19, 69.09, 62.61, 62.32, 61.79, 34.54-
34.24, 32.82, 32.12, 31.13, 29.98-28.58, 25.10, 24.84, 22.90,
14.33
Yield: 2.8 %
tR(min): 14.2
MS: C96H172O12, Cal.1518.39, found 351.3, 597.4,
613.4, 1535.4 [M ? NH4]?
1H-NMR (in CDCl3, ppm), d = 5.32-5.26 (10H, m,
–CH=CH–), 5.22–5.17 (2H, m, –CH2CH(O)CH2–), 4.24–
4.20(4H, dd, –CH2CH(O)CH2–), 4.09–4.03 (4H, dd,
–CH2CH(O)CH2–), 2.26–2.22 (12H, m, –C(=O)CH2CH2–),
1.94–1.87 (20H, m, =CHCH2CH2–), 1.54 (12H, br,
–C(=O)CH2CH2–), 1.22–1.19 (96H, m, –CH2–), 0.83–0.79
(12, t, –CH3);
13C-NMR (in CDCl3, ppm), d = 173.40, 172.99,
130.63, 130.30, 69.11, 62.33, 34.43, 34.26, 32.80, 32.13,
29.89-29.20, 27.41, 25.08, 22.91, 14.34
The Structure of Fractions from the Reaction
with 20 mmol/L (R2)
1-(2,3-bis(octadec-9-enoyloxy)propyl) 18-(5,22-dioxo-
1,4-dioxacyclodocos-13-en-2-yl)methyl octadec-9-enedi-
oate and/or 1-(1,3-bis(octadec-9-enoyloxy)propan-2-yl)
18-(6,23-dioxo-1,5-dioxacyclotricos-14-en-3-yl) octadec-
9-enedioate and its isomers (R1–5)
Triolein and its isomers (R2–2)
Yield: 12.8 %
tR(min): 12.6
1
MS, H– and 13C-NMR refer to R1–2
Yield: 7.5 %
6, 23-dioxo-1,5-dioxacyclotricos-14-en-3-yl octadec-9-
enoate and/or 5,22-dioxo-1,4-dioxacyclodocos-13-en-2-
yl-methyl octadec-9-enoate and its isomers (R2–3)
Yield: 31.3 %
tR(min): 11.2
MS: C78H136O12, Cal.1265.91, found 351.2,603.5, 983.8
1283.1 [M ? NH4]?
1H-NMR (in CDCl3, ppm), d = 5.41–5.28 (10H, m,
–CH=CH–), 4.48–4.15 (8H, m, –CH2CH(O)CH2–), 2.36–
2.32 (12H, t, –C(=O)CH2CH2–), 2.04–1.98 (16H, m,
=CHCH2CH2–), 1.64–1.60 (12H, br, –C(=O)CH2CH2–),
1.32–1.29 (72H, m, –CH2–), 0.92–0.89 (6H, t, –CH3)
13C-NMR (in CDCl3, ppm), d = 173.48, 173.07,
130.98-130.24, 69.20, 69.11, 62.55, 62.33, 34.43-34.26,
32.80, 32.12, 29.94-28.85, 28.28, 27.90, 27.46, 25.10,
22.91, 14.34
tR(min): 10.0
1
MS, H– and 13C-NMR refer to R1–3
Bis (1,3-bis(octadec-9-enoyloxy)propan-2-yl) octa-
dec-9-enedioate and its isomers (R2–4)
Yield: 13.1 %
tR(min): 14.2
1
MS, H– and 13C-NMR refer to R1–4
1-(2,3-bis(octadec-9-enoyloxy)propyl) 18-(5,22-dioxo-
1,4-dioxacyclodocos-13-en-2-yl)methyl octadec-9-enedi-
oate and/or 1-(1,3-bis(octadec-9-enoyloxy)propan-2-yl)
18-(6,23-dioxo-1,5-dioxacyclotricos-14-en-3-yl) octadec-
9-enedioate and its isomers (R2–5)
Bis (6,23-dioxo-1,5-dioxacyclotricos-14-en-3-yl) octa-
dec-9-enedioate and its isomers (R1–6)
Yield: 8.8 %,
tR(min): 9.2
MS: C60H100O12, Cal.1013.43, found 351.2, 365.2,
1030.8 [M ? NH4]?
Yield: 9.5 %
tR(min): 11.2
1
MS, H– and 13C-NMR refer to R1–5
1H-NMR (in CDCl3, ppm), d = 5.40–5.30 (8H, m,
–CH=CH– and –CH2CH(O)CH2-), 4.46-4.10 (8H, m, -CH2
CH(O)CH2-), 2.35-2.31 (12H, m, -C(=O)CH2CH2–), 2.06–
1.98 (12H, m, =CHCH2CH2–), 1.64 (12H, br, –C(=O)
CH2CH2–), 1.31 (48H, br, –CH2–);
18-bis (1, 3-bis(octadec-9-enoyloxy)propan-2-yl)
‘1,1-3-(octadec-9-enoyloxy)propane-1,2-diyl dioctadec-
9-enedioate and its isomers (R2–6)
Yield: 2.2 %
tR(min): 15.9
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MS: C135H240O18, Cal.2151.34, found 603.5,
Yield: 8.9 %
1093.5[M ? 2NH4]2?, 1283.1, 2167.9 [M ? NH4]?
1H-NMR (in CDCl3, ppm), d = 5.41–5.36 (14H, m,
–CH=CH–), 5.28 (3H, t, –CH2CH(O)CH2–), 4.33–4.29
(6H, dd, –CH2CH(O)CH2–), 4.19–4.14 (6H, dd,
–CH2CH(O)CH2–), 2.35–2.31 (18H, t, –C(=O)CH2CH2–),
1.99–1.96 (28H, m, =CHCH2CH2–), 1.63 (18H, br,
–C(=O)CH2CH2–), 1.31–1.29 (132H, m, –CH2–), 0.92–0.88
(15H, t, –CH3)
13C-NMR (in CDCl3, ppm), d = 173.40, 172.99,
130.63, 130.30, 69.11, 26.33, 34.43, 34.26, 32.82, 32.13,
31.15, 29.89-29.20, 25.10, 22.91, 14.34
The structure of fractions from the neat reaction
(R3)
tR(min): 24.4
MS: C213H376O30, Cal. 3417.25, found 1725.5[M ?
2NH4]2?, 3433.9 [M ? NH4]?
1H-NMR: (in CD3Cl, ppm): d = 5.36–5.30 (22H, m, –
CH=CH–), 5.25–5.23 (5H, m, –CH2CH(O)CH2–), 4.29–
4.24 (10H,dd, –CH2CH(O)CH2–), 4.14–4.10 (10H, dd,
–CH2CH(O)CH2–), 2.30–2.26 (30H, t, –C(=O)CH2CH2–),
1.99–1.93 (44H, m, =CHCH2CH2–), 1.59 (30H, br,
–C(=O)CH2CH2–), 1.28–1.24 (204H, m, –CH2–),
0.88–0.84 (21H, t, –CH3);
13C-NMR(in CD3Cl, ppm): d = 173.47, 173.06, 130.52,
130.23, 129.93, 69.09, 62.31, 34.41, 34.25, 32.81, 32.13,
29.99-29.28, 27.44, 27.39, 25.11, 25.06, 22.90, 14.33;
Triolein and its isomers (R3–2)
Yield: 21.1 %
Results and Discussion
tR(min): 12.6
1
MS, H– and 13C-NMR refer to R1–2
Metathesis of Triolein
Bis (1,3-bis(octadec-9-enoyloxy)propan-2-yl) octadec-
9-enedioate and its isomers (R3–3)
Yield: 12.4 %
In the metathesis reaction of triolein, there are two reaction
types: intramolecular and intermolecular. Intramolecular
reactions produce macrocyclic structures, whilst intermo-
lecular reactions produce aliphatic oligomers. In theory,
intermolecular or intramolecular reactions can be favoured
by varying reaction conditions, such as the catalyst system,
reaction temperature and reaction concentration. This work
focused only on variations in the reaction concentration.
The structures of the achieved compounds from the
metathesis reaction with different reaction concentrations
[10 mmol/L (R1), 20 mmol/L and a neat reaction (R3)] are
presented in Schemes 2, 3 and 4, respectively. Note that the
olefin, octadec-9-ene, which was also produced in the three
reactionscarriedoutforthisstudy,hasbeenpresented[11]and
is therefore, not presented or discussed further here. Four
different cyclic compounds (R1–3, R1–4, R1–6 and R1–7 in
Scheme 2) and two linear compounds (R1–2 and R1–5 in
Scheme 2) were produced by R1. Two cyclic compounds
(R2–3 and R2–5 in Scheme 3) and three linear oligomer
(R2–2, R2–4 and R2–6 in Scheme 3) were found in the
products of R2 (Scheme 3). Only linear compounds (see
Scheme 4) were found in the neat reaction R3. The weight
percentages of pure fractions obtained from column chroma-
tographywitheluteofmixtureofhexanesand ethylacetateare
presented in Sect. 2.3. The total weight percentages of cyclic
compounds inR1, R2and R3 are 56, 41and 0 %, respectively,
comparing to the percentages of linear compounds (excluding
the olefin) with 11, 28 and 70 %, respectively. Clearly, lower
reaction concentration of triolein favours intramolecular
reactions of substrate and leads to a greater production of
cyclic compounds. As the reaction concentration is increased,
the tendency for intermolecular reactions increases leading to
increased production of linear compounds
tR(min): 14.2
1
MS, H– and 13C-NMR refer to R1–4
18-bis (1, 3-bis (octadec-9-enoyloxy)propan-2-yl)
‘1,1-3-(octadec-9-enoyloxy)propane-1,2-diyl dioctadec-
9-enedioate and its isomers (R3–4)
Yield: 16.3 %
tR(min): 15.9
1
MS, H– and 13C-NMR refer to R2–6
1-(21,43-bis((octadec-9-enoyloxy)methyl)-18,23,40,
45,62,68-hexaoxo-19,22,41,44,63,67-hexaoxapentao-
ctaconta-9,31,53,76-tetraen-65-yl) 18-(1,3-bis(octadec-
9-enoyloxy)propan-2-yl) octadec-9-enedioate and its
isomers (R3–5)
Yield: 11.2 %
tR(min): 19.4
MS: C174H308O24, Cal. 2784.29 found 603.5, 1409.2
[M ? 2NH4]2?, 2801.4 [M ? NH4]?
1H-NMR (in CDCl3, ppm), d = 5.37–5.24 (22H, m,
–CH=CH– and –CH2CH(O)CH2–), 4.28–4.26 (8H, dd,
–CH2CH(O)CH2–), 4.13–4.07 (8H, dd, –CH2CH(O)CH2–),
2.29–2.26 (24H, t, –C(=O)CH2CH2–), 2.02–1.94 (36H, m,
=CHCH2CH2–), 1.85–1.55 (24H, m, –C(=O)CH2CH2–),
1.27–1.24 (168H, m, –CH2–), 0. 84–0.82 (18H, t, –CH3)
13C-NMR (in CDCl3, ppm), d = 173.48, 173.07,
130.72, 130.40, 129.94, 69.11, 62.33, 34.43, 34.27, 32.85,
32.80, 32.13, 29.94-29.21, 25.10, 22.92, 14.35
1-(21,42-bis((octadec-9-enoyloxy)methyl)-18,23,40,45,
62,68-hexaoxo-19,22,41,44,63,67-hexaoxapentaoctaconta-
9,31,53,76-tetraen-65-yl)18-(2-(18-(1,3-bis(octadec-9-
enoyloxy)propan-2-yloxy)-18-oxooctadec-9-enoyloxy)-3-
(octadec-9-enoyloxy)propyl) octadec-9-enedioate and its
isomers (R3–6)
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J Am Oil Chem Soc (2012) 89:2077–2089
2083
Scheme 3 Structures of
compounds from the reaction
with 20 mmol/L (R2). The
compounds present contain
cis-, trans-configurations, and
positional isomers on glycerol
skeletons
R2-2
R2-3
R2-4
R2-5
R2-6
Characterization
1.65 ppm, –CH2– at d 1.32–1.29 ppm, –CH3 at d
0.88 ppm. The ratios of protons corresponding to
–OCH2CHCH2O– and -CH3, as well as the proton of
O=CCH2–, were used to identify the structures of those
compounds and are listed in Table 1. The experimental
values were fully consistent with the theoretical ones.
The differences detected in 1H-NMR between linear
oligomers and cyclic compounds are mainly on the protons
of the glycerol skeleton and double bonds, i.e.,
–CH2CHCH2–, –CH2CHCH2– and –CH=CH–.
Structures shown in Schemes 2–4 were fully confirmed by
NMR and mass spectra.
NMR
1H-NMR In all 1H-NMR spectra, –CH=CH– is present at
d 5.38–5.27 ppm, –C(=O)CH2CH2– at d 2.35–2.31 ppm,
=CHCH2– at d 2.04-1-94 ppm, –C(=O)CH2CH2– at d
123

2084
J Am Oil Chem Soc (2012) 89:2077–2089
Fig. 1 1H-NMR spectra a R1–2
and b R1–3
Typical 1H-NMR spectra of linear and cyclic compounds
are shown in Fig. 1a, b, respectively. As can be seen, the
chemical shift of –CH2CHCH2– in the linear compounds is
presented at 5.25–5.23 ppm and that of –CH2CHCH2– at
4.29–4.25 ppm and 4.14–4.10 ppm. The cyclic compounds
aremixtures of two positional isomers, onewith sn-1 andsn-3
(I) ring structure, a so-called symmetric compound, and the
other with a sn-1 and sn-2 (II) ring, a so-called asymmetric
compound, (i.e., R1–3-I and R1–3-II Fig. 1b, respectively).
The chemical environment of the cyclic compounds is more
complex than that of linear oligomers, as illustrated by the
obvious differences in their 1H-NMR spectra (see Fig. 1a, b).
The chemical shifts at 5.25–5.20 ppm, which originated from
the b-proton located at the sn-2 position (H2 in Fig. 1b), were
observed in the symmetrical cyclic compounds as well as the
linear compounds.
The chemical shifts due to –CH2CHCH2– at positions
sn-1 and sn-3 (H1(3)) in Fig. 1b) in the symmetrical cyclic
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J Am Oil Chem Soc (2012) 89:2077–2089
2085
Fig. 2 13C-NMR spectra of
a R1–2 and b R1–3
compounds are also present at the same range as in the
linear compounds. The chemical shifts are not affected by
the ring structure in the symmetrical cyclic compounds. On
the other hand, the chemical shifts of the b-proton at the
sn-2 position in the asymmetric cyclic compounds (H2 in
Fig. 1b), move to the d 5.37–5.30 ppm range and is par-
tially overlapped by the peaks of the double bond. The
relative amount of asymmetric: symmetric b-protons in the
cyclic compound are found to be close to 3:1. The chemical
shifts in the asymmetric compounds due to the proton at the
position sn-3 which is out of the ring (H3, Fig. 1b) are
presented at 4.42–4.37 ppm and 4.16–4.04 ppm. Note that
they are different from those observed in their linear
counterparts. The proton in the ring at the position sn-1
presented a chemical shift at 4.28–4.10 ppm. The ratio of
the amount of protons at sn-3 in the asymmetric cyclic
compound to the total amount of protons at all the other
sn-1 and sn-3 positions as determined by their respective
123

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J Am Oil Chem Soc (2012) 89:2077–2089
200
bonds in the trans-geometry and cis-geometry, respec-
tively. The relative amount of double bonds in the trans- to
cis-configuration as estimated by the integrals of their
respective chemical shifts is about 4–6. These values have
been confirmed by GC (see Sect. 3.3 below).
R1-2
R1-3
R1-4
R1-5
180
160
140
120
100
80
Cis-Triolein
The protons of double bond in the cyclic compounds
presented three overlapping groups of chemical shifts span-
ning from 5.38 to 5.25 ppm. The chemical shifts at
5.38–5.33 ppm of the first group are similar to those observed
for double bonds of the linear compounds in the trans-con-
figuration. They are therefore assigned to the double bonds in
the trans-configuration which are located in segments out of
the ring (proton I). The second group with chemical shifts at
5.32–5.29 ppm includes the range of chemical shifts which
were observed for the cis-configuration in the linear com-
pounds. Therefore, it probably represents the chemical shifts
from the out of ring double bonds in the cis-configuration.
The very high intensity of the signal in this range, suggests
that the group also includes the signal from the protons at the
ring double bonds in the trans-configuration (proton II). This
assignment is likely because such ringed structures are
reported to contain mainly trans-configuration double bonds
[14]. The higher values of chemical shifts observed for the
60
40
20
4000
3000
2000
1000
Wavenumbers (cm-1)
Fig. 3 FTIR of metathesized triolein products. The structures of
samples are shown in Scheme 3
integrals was found to be 0.57, a value practically equal to
the theoretical value of 0.60 which is consistent with a ratio
of asymmetrical:symmetrical values of 3–1.
The double bonds presented chemical shifts in the range
of 5.38–5.27 ppm. Two groups of chemical shifts are
observed for the linear compounds at 5.38–5.34 ppm and
5.33–5.30 ppm (Fig. 1a). Based on the 1H-NMR of triolein
(100 % cis) and trielaidin (100 % trans) reference mate-
rials, the above chemical shifts are assigned to the double
Scheme 4 Structures of
compounds from neat reaction
(R3). The compounds present
contain cis-, trans-
configurations, and positional
isomers on glycerol skeletons
R3-2
R3-3
R3-4
R3-5
R3-6
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J Am Oil Chem Soc (2012) 89:2077–2089
2087
proton II compared to proton I is probably due to ring-strain
in the cyclic compounds. The third group of shifts at
5.27–5.25 is probably due to proton II with the cis-configu-
ration and b-proton in the asymmetric compounds (H2 in
Fig. 1b).
13C-NMR The main structural differences between the
different compounds manifested in the 13C-NMR chemical
shifts of double bonds and the glycerol skeleton similarly
1
to H-NMR. –CH=CH– is present at d 130.7–129.9 ppm.
The chemical shift at d \ 130.0 ppm is assigned to a cis-
geometry, and at d [ 130.0 ppm to a trans-geometry [11].
The carbon of glycerol skeleton (–CH2CH(O)CH2–) is
present at the range of 69.2–61.6 ppm depending on their
structures. There are two chemical shifts present at
d * 69.09 ppm (–CH2CH(O)CH2–) and *62.31 ppm
(–CH2CH(O)CH2–) in 13C-NMR spectra of linear oligo-
mers, as shown in Fig. 2a. Three more peaks, d = 69.19,
62.54 and 61.80 ppm, are present in13C-NMR spectra
of cyclic compounds (Fig. 2b) are originated from C2 in
R1–3-II, C1in R1–3-II at d * 62. 54 ppm, and C3 in
R1–3-II respectively.
FTIR
The ester carbonyl stretching band (C=O) in the glyceride
skeleton is present at 1744 cm-1 and O–C–C and
C–C(=O)–O stretching bands are present at 1165 and
1110 cm-1, respectively. The stretching bands of CH
groups are present in the region of 3000–2800 cm-1. The
1
Table 1 Ratio of selected protons in H-NMR spectra of fractions
Compounds
R1–2
–OCH2CHCH2O– O=CCH2– –CH3
Theoretical
Experimental
Theoretical
Experimental
Theoretical
Experimental
Theoretical
Experimental
Theoretical
Experimental
Theoretical
Experimental
Theoretical
Experimental
Theoretical
Experimental
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1.5
2.25
2.19
0.75
0.67
1.5
1.52
1.5
R1–3
R1–4
R1–5
R1–6
R1–7
R3–3
R3–4
1.47
1.5
1.46
1.5
1.42
0.75
0.88
0
1.55
1.5
1.46
1.5
0.08
0.25
0.33
1.25
1.23
1.125
1.129
1.48
1.5
1.49
1.5
1.50
The detailed 1H-NMR analyses are presented in the experimental
section. The structures of samples are shown in Schemes 2 and 4
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J Am Oil Chem Soc (2012) 89:2077–2089
infrared absorption at 967 cm-1 in FTIR spectra (see
intermolecular reactions. The former produces macrocyclic
structures; the latter aliphatic oligomers. Products of the
metathesis have been shown to be affected by reaction
concentration, with increased cyclic compounds produced
at lower concentrations, and increased aliphatic oligomers
at higher concentrations. Only aliphatic oligomers were
found in the neat reaction. The cyclic compounds produced
contain positional isomers in the glycerol skeletons: those
with a cyclic structure between positions 1 and 3 in glyc-
erol skeleton (I), and those between positions 1 and 2 (II).
Based on the 1H-NMR spectra, the ratio between I and II is
about 1:3, which demonstrates that intramolecular reac-
tions are three times as likely to occur between the
neighbouring chains than between the sn-1 and sn-3 posi-
tions. Reaction concentration also has an impact on the
trans/cis ratios of double bonds in the products. Our results
show that higher concentration reactions result in an
increase in trans-configurations.
Fig. 3) is assigned to trans-geometry [15]
MS
The mass spectra of the triglyceride compounds were
recorded by electrospray ionization mass spectrometrom-
etry (ESI–MS). The presented compounds are readily
ionized by ammonium. For both cyclic compounds (i.e.,
R1–3, R1–5 and R1–6) and the linear oligomers (i.e., R1–2
and R1–4) with the molecular weight lower than 1600, and
the strong ion signals were observed readily from singly-
ammoniated molecules; whilst, the oligomers with higher
molecular weight in the range *1600–4000 Da (i.e., R1–7
and R2–6, R3–5 and R3–6) were observed as both singly-
and multiply-ammoniated molecules. As seen in Table 2,
the MS data of presented compounds match their corre-
sponding formula weights very well.
Acknowledgments We express our thanks to the Ontario Soybean
Growers/Grain Farmers of Ontario, Elevance Renewable Sciences,
NSERC, GPA-EDC, Industry Canada, and Trent University for their
financial support for the research. We also give our thanks to our
group members, Jiaqing Zuo, Ali Mahdevari, Carolyn Virginia Payne,
and Latifeh Ahmadi for their kind assistance.
trans-/cis-Configuration
Similar to other carbon–carbon coupling reactions, such as
Wittig olefination reaction [16], the metathesis of olefin with
a transition metal catalyst gives a mixture of the two possible
products (trans-isomers and cis-isomers). The trans-isomer
(in both cyclic and linear compounds) is the dominant one
[11, 17] in these reactions. The cis-/trans-configuration pro-
duced from olefin metathesis reaction has been studied
widely. trans-/cis-selectivity can be influenced by reaction
temperature, solvent or substitutions of the substrate, but
mainly by the catalyst system [17, 18] and substrates [14, 19].
Lee and Grubbs [14] found that the ratio of trans/cis was
about 3.6–4.8:1 depending on the substrate when Grubbs’
second generation catalyst was used. Compounds here con-
tain the cis-/trans-configuration. This was confirmed by
FTIR, 1H- and 13C-NMR spectra, as mentioned above.
To investigating the effect of reaction concentration on
the ratio of trans-/cis-configuration, the composition of
R1–2, R2–2 and R3–2, which are representative of linear
compounds produced in R1, R2 and R3 respectively, were
determined by GC. The samples were first methylated
using the method described by Cantellops et al. [20]. The
resultant methyl fatty acids were measured by GC, with the
pure methyl oleate and methyl elaidate as standards. The
ratio of trans/cis in R1–2, R2–2 and R3–2 are 4.6:1, 4.8:1
and 5.8: 1, respectively. This suggests that higher con-
centration produces higher trans-content.
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