Synthesis and characterization of novel diol, diacid and Di-isocyanate from oleic acid

Article abstract of DOI:10.1007/s11746-013-2376-z

Novel linear diol 2, diacid 3, and diisocyanate 4 with functional groups located at each end of the chain have been produced from oleic acid via a diester precursor. All the compounds were fully characterized by IR, ¹H NMR, ¹³C NMR and Mass Spectrometry. These unbranched terminally-functionalized compounds are important monomers for the manufacture of biodegradable thermoplastic polyurethanes and polyesters. The general synthetic scheme should also prove useful for the syntheses of diols, diacids and diisocyanates from any unsaturated fatty acid.

Full text of DOI:10.1007/s11746-013-2376-z

J Am Oil Chem Soc (2014) 91:349–356
DOI 10.1007/s11746-013-2376-z
ORIGINAL PAPER
Synthesis and Characterization of Novel Diol,
Diacid and Di-isocyanate from Oleic Acid
•
Latchmi Raghunanan Jin Yue Suresh S. Narine
•
Received: 9 September 2013 / Revised: 23 October 2013 / Accepted: 23 October 2013 / Published online: 6 November 2013
Ó AOCS 2013
Abstract Novel linear diol 2, diacid 3, and diisocyanate 4
with functional groups located at each end of the chain
have been produced from oleic acid via a diester precursor.
All the compounds were fully characterized by IR,
1H NMR, 13C NMR and Mass Spectrometry. These
unbranched terminally-functionalized compounds are
important monomers for the manufacture of biodegradable
thermoplastic polyurethanes and polyesters. The general
synthetic scheme should also prove useful for the syntheses
of diols, diacids and diisocyanates from any unsaturated
fatty acid.
bio-degraded, but are amongst the most versatile of poly-
mers due to their wide range of applications in areas such
as coatings, adhesives, sealants, thermoplastics, foams and
elastomers [1]. Furthermore, recent work within the Trent
Centre for Biomaterials Research (TCBR) has shown that
the introduction of ester groups of varying lengths into
polymers such as thermoplastic polyurethanes [2] and
polyamides [3] can be used to manipulate crystal properties
and polymer strength while introducing some biodegrad-
ability into the finished material.
Polyurethanes are formed by reacting monomers con-
taining at least two hydroxyl groups (polyols) with diiso-
cyanates. Triolein [4], soybean oil [5], canola oil [6] and
other bio-based oils [7] have all been used as vegetable oil
feedstocks for the syntheses of functional polyols. All of
these polyols, however, contain more than two hydroxyl
groups per molecule which limits their applications to the
syntheses of crosslinked polyurethanes. On the other hand,
thermoplastic polyurethanes (TPUs) derived from vege-
table oil have scarcely been reported in the literature:
Palaskar et al. [8] synthesized TPUs from oleic acid and
ricinoleic acid derivatives via the self-condensation of
azido alcohol monomers, and from monoester- and dies-
ter-containing diol monomers of sunflower and ricin oils
[9]; Xu and coworkers [10] synthesized TPU films from a
polyricinoleate diol derived from ricinoleic acid; and
Bueno-Ferrer et al. [11] synthesized TPUs from dimeric
fatty acids derived from rapeseed oil. The dangling chains
present on these monomer units, however, sterically
affected crystal packing within the polymers, and hence
resulted in TPUs with reduced thermal and mechanical
properties. To the best of our knowledge, unbranched
terminally-functionalized diisocyanates derived from
vegetable oil for the syntheses of TPUs have yet to be
reported.
Keywords Diester ꢀ Diol ꢀ Diacid ꢀ Diisocyanate ꢀ
Polyurethane ꢀ Thermoplastic ꢀ Biobased ꢀ
Biodegradable ꢀ Functional polymers
Introduction
Increasing environmental and sustainability concerns are
driving research efforts to develop high-performance non-
toxic biodegradable polymers from renewable sources to
replace petroleum-derived ones [1]. To this end, polymers
which contain the ester functional group are sought after
for their biodegradable properties. On the other hand,
known biodegradable polyesters possess physical proper-
ties which are inferior for use in many applications.
Alternately, polymers such as polyurethanes and polya-
mides are generally not inherently biodegradable or easily
L. Raghunanan ꢀ J. Yue ꢀ S. S. Narine (&)
Departments of Physics and Astronomy and Chemistry, Trent
Centre for Biomaterials Research, Trent University,
Peterborough, ON K9J 7B8, Canada
e-mail: sureshnarine@trentu.ca
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J Am Oil Chem Soc (2014) 91:349–356
Synthesis of Diester 2b from Oleic Acid
This work reports on the syntheses of novel monomers
for thermoplastic poly(ester-urethanes) from vegetable oils.
These monomers may be tailored so that the ester-chain
segments in the respective polymers are conveniently
manipulated. Furthermore, all of the molecules described
herein are terminally functionalized, free of dangling
chains, and contain a high density of ester linkages per
polymer unit; i.e., they are expected to form polymers with
good thermal stabilities and mechanical properties with a
large degree of biodegradability per polymer unit.
A mixture of oleic acid (100 g, 90 % purity, 0.35 mol),
1,3-propanediol (12.2 g, 0.16 mol) and sulfuric acid
(3 mL, 98 %) were reacted under vacuum (10 mmHg) at
100 °C for 24 h. The resulting mixture was dissolved in
400 mL of ethyl acetate and washed with saturated sodium
bicarbonate solution (100 mL), saturated sodium carbonate
solution (2 9 100 mL) and brine (50 mL) before being
dried over anhydrous sodium sulfate. The solvent was
evaporated under reduced pressure and the residue purified
by flash chromatography (silica gel; hexane/EtOAc 30:1)
to afford diester 2b as a pale yellow oil.
Materials and Methods
Synthesis of Diester-Diol 7 from Diester 2
Materials
A solution of diester 2 (40.0 g, 67 mmol) in anhydrous
ethanol (400 mL) was ozonized at 0 °C until completion as
determined by TLC (hexane:ethyl acetate = 5:1). This
mixture was then hydrogenated at 70 °C and 100 psi for
2.5 h following the addition of another 700 mL of ethyl
acetate and 10.0 g of Raney nickel catalyst. The resulting
mixture was finally filtered to remove the catalyst and the
solvent evaporated under reduced pressure to give the
crude product. Purification of this crude material by flash
chromatography (silica gel; hexane/EtOAc 4:1, 2:1, 1:1,
1:4) yielded the pure diester-diol 7 as a white solid.
Ethyl chloroformate and sodium azide were obtained from
BDH Ltd and Fluka, respectively. Raney nickel 2800
(slurry in water), oleic acid (90 %), oleoyl chloride (85 %),
1,2-ethanediol (99.8 %), 1,3-propanediol (99 %), 1,4-
butanediol ([99 %), 1,6-hexanediol (99 %), 1,9-nonane-
diol (98 %), 1,10-decanediol (98 %), pyridine (99.8 %),
anhydrous sodium sulfate (99.4 %) and calcium hydride
(95 %) were purchased from Sigma-Aldrich Co., USA.
Acetone, chloroform, ethyl acetate, hexanes, and concen-
trated hydrochloric acid (HCl) were purchased from ACP
Chemical Int. (Montreal, Quebec, Canada). Ozone was
produced in an ozone generator (Azcozon Model RMV16-
16 from Azco Industries Ltd, Canada) with oxygen as the
feed gas. Silica gel (230–400 mesh) was obtained from
Rose Scientific Ltd, AB, Canada. TLC plate (250 lm) was
obtained from Silicycle Chemistry Division, QC, Canada.
Synthesis of Diester-Diacid 8 from Diester 2
A solution of diester 2 (5.0 g, 8.3 mmol) in ethyl acetate
(250 mL) was ozonized at room temperature until com-
pleted as determined by TLC (hexane:ethyl acetate = 2:1).
Hydrogen peroxide (2.6 mL, 34 %, 26 mmol) was then
added and the reaction mixture heated under reflux over-
night. The resulting mixture was washed with brine
(2 9 50 mL) and dried over anhydrous sodium sulfate
before solvent removal under reduced pressure to give the
crude product. Purification by flash chromatography (silica
gel; hexane/EtOAc 5:1, 4:1, 2:1, 1:1) afforded diester-
diacid 8 as a white solid.
Preparation of Diester-Containing Monomers
Syntheses of Diesters 1–6 from Oleoyl Chloride
Oleoyl chloride (20 g, 66.6 mmol) was dissolved in
anhydrous chloroform (150 mL) and added dropwise to a
stirred solution of the respective diol (30 mmol) and
pyridine (7.3 mL, 90 mmol) in anhydrous chloroform
(50 mL) under an atmosphere of nitrogen. The reactions
were allowed to complete overnight with continuous
stirring at room temperature. The reaction mixtures were
then washed with water (200 mL), 5 % aq. HCl (200 mL),
and water again (2 9 200 mL) before being dried over
anhydrous sodium sulfate. Crude diesters were obtained
after removal of the solvent (CHCl3) under reduced
pressure, and the pure diesters obtained as colourless
liquids at room temperature following clean-up of the
crude material on silica-gel chromatographic columns
using as the eluting solvent suitable volume ratios of ethyl
acetate-hexanes.
Synthesis of Diester-Diisocyanate 9 from Diacid 8
To a suspension of pure compound 8 (0.42 g, 1 mmol) and
triethylamine (0.34 mL, 2.4 mmol) in THF (5 mL) at 0 °C
was added ethyl chloroformate (0.21 mL, 2.2 mmol) in a
dropwise manner. The resulting mixture was stirred for 2 h
at 0 °C. This mixture was then added dropwise to a solu-
tion of sodium azide (1.04 g, 16 mmol) in water (28 mL)
at 0 °C. After stirring for 2 h at 0 °C, the reaction mixture
was extracted with diethylether (3 9 50 ml). The com-
bined organic layers were dried over anhydrous sodium
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J Am Oil Chem Soc (2014) 91:349–356
351
sulfate and the solvent removed under reduced pressure.
THF (10 mL) was then added to the flask and the resulting
solution heated under reflux for 2 h before solvent removal
again under reduced pressure to afford the diester-diiso-
cyanate 9 as a yellow oil.
calibration curve method. Calibration curves, in turn, were
obtained from a plot of standard concentrations against the
response factor, Rf, calculated as shown below.
ðStandard sample AreaꢁInternal Standard ConcentrationÞ
Rf ¼
ðInternal Standard Area ꢁStandard sample ConcentrationÞ
Chemical Characterization
Standard Sample Area and Internal Standard Areas refer
to the areas under the HPLC curve obtained from HPLC
analyses of sample standards (0.25–2.00 mg/mL)
containing tristearin as an internal standard (1 mg/mL).
All calibration curves were prepared in duplicate.
1H Nuclear Magnetic Resonance
Samples were dissolved in approximately 2 mL CDCl3 for
1D 1H NMR on
a Varian V NMR spectrometer
[t(1H) = 399.75 MHz; Varian Inc., Walnut Creek, USA]
equipped with a 5 mm PRF auto switchable H probe. All
1
Fourier Transform Infra-Red Spectroscopy
spectra were obtained at 25 °C over a 30,000 Hz spectral
window with a 1 s recycle delay, 32 K complex points, and
16 transients.
FTIR spectra were obtained using a Thermo Scientific
Nicolet 380 FT-IR spectrometer (Thermo Electron Scien-
tific Instruments, LLC, USA) equipped with a PIKE
MIRacleTM attenuated total reflectance (ATR) system
(PIKE Technologies, Madison, WI, USA).
Mass Spectroscopy
Electrospray ionization mass spectrometry (ESI–MS) ana-
lysis was performed using a QStar XL quadrupole time-of-
flight mass spectrometer (AB Sciex, Concord, ON, Canada)
equipped with an ionspray source and a modified hot source-
induced desolvation (HSID) interface (Ionics, Bolton, ON).
The ion source and interface conditions were adjusted as
follows: ionspray voltage (IS = 4,500 V), nebulizing gas
(GS1 = 45), curtain gas (GS2 = 45), declustering potential
(DP = 60 V) and HSID temperature (T = 200 °C). Multi-
ply-charged ion signals were reconstructed using the Bio-
Tools 1.1.5 software package (AB Sciex, Concord, ON).
Liquid samples were loaded onto the ATR crystal area,
and sample spectra were acquired over a scanning range of
400–4,000 cm-1 for 64 repeated scans at a spectral reso-
lution of 1 cm-1
.
Results
Diesters
1
The obtained H-NMR chemical shifts, mass spectra peak
mass-to-charge ratios, and FTIR peak wavenumbers of the
synthesized diesters are given below. These are all con-
sistent with the structures targeted: (1) from the mass spec
data, it was determined that the experimental molecular
masses were as calculated—evidence that the synthesized
molecules possessed the desired molecular composition as
those of the target compounds; (2) the presence of the
characteristic O=C(O) (1,737–1,742 cm-1) and (O)C–O–C
(1,160–1,170 cm-1) ester peaks on the FTIR spectra were
confirmations that the ester moieties were incorporated into
the synthesized molecules [12]; the presence of C=CH
stretching peaks (3,003–3,006 cm-1 for cis bonds) also
confirmed that the synthesized molecules retained the un-
saturation of the parent molecules [12]; and (3) all protons
of the synthesized molecules were accounted for on the 1H-
NMR spectra with respect to the expected chemical shifts
of the target compounds based on tabulated empirical data
and the ratios of the expected numbers of protons per peak
to the area under the respective peaks; expected proton
chemical shifts from most de-shielded to least:
C=CH [ O–CH [ O=CCH=C=CCH [ CH2 [ CH3 [13].
Combined, these data were sufficient to confirm that the
High Performance Liquid Chromatography
HPLC measurements were carried out on a Waters Alliance
(Milford, MA) e2695 HPLC system fitted with a Waters
ELSD 2424 evaporative light scattering detector. This sys-
tem included an inline degasser, a pump, and an auto-sam-
pler. The Waters Empower Version 2 software was used for
data collection and data analysis. A 150 9 4.6 mm XBridge
C18 (5 lm particle size) column (Waters XBridge, Missis-
sauga, ON) was used in the reverse-phase isocratic mode.
The temperature of the column was maintained at 35 °C by a
Waters Alliance column oven. The ELSD nitrogen pressure
was set at 25 psi and the nebulizer set to cooling mode. The
drift tube temperature was maintained at 55 °C. Gain was set
at 500. The mobile phase was chloroform:acetonitrile
(40:60)v run for 30 min at a flow rate of 0.5 ml/min. Sol-
vents were HPLC grade and were obtained from VWR
International, Mississauga, ON.
Samples were prepared by dissolving in chloroform
(1 mg/mL). Sample size per experiment was 2 lL. The
purities of the eluted samples were determined using the
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J Am Oil Chem Soc (2014) 91:349–356
structures synthesized were in fact the molecules that we
had set about to make.
C=CH), 3.99–4.03 (4, t, O–CH), 2.22–2.26 (4, t, O=CCH),
1.95–1.97 (8, m, C=CCH), 1.55–1.60 (8, m, O–CCH,
O=CCCH), 1.21–1.35 (44, m, C–CH2), 0.82–0.85 (6, t, C–
CH3). MS (ESI): calculated for C42H78O4 646, found m/
z 664 ([M ? NH4]?).
2-[(Z)-Octadec-9-enoyl]oxyethyl-(Z)-octadec-9-enoate, 1
Colourless oil (14.3 g, 81 %); IR (ATR): 1,742 (C=O) cm-1
;
1H NMR in CDCl3 d (ppm): 5.27–5.36 (4, m, C=CH), 4.24
(4, s, O–CH), 2.27–2.31 (4, t, O=CCH), 1.96–2.00 (8, m,
C=CCH), 1.58–1.61 (4, m, O=CCCH), 1.24–1.28 (40, m, C–
CH2), 0.84–0.87 (6, t, C–CH3). MS (ESI): calculated for
C38H70O4 590, found m/z 608 ([M ? NH4]?).
9-[(Z)-Octadec-9-enoyl]oxynonyl-(Z)-octadec-9-enoate, 5
Colourless oil (18.6 g, 90 %); IR (ATR): 1,737 (C=O)
cm-1 1H NMR in CDCl3 d (ppm): 5.31–5.33 (4, m,
;
C=CH), 4.01–4.05 (4, t, O–CH), 2.24–2.26 (4, t, O=CCH),
1.96–2.01 (8, m, C=CCH), 1.56–1.61 (8, m, O–CCH,
O=CCCH), 1.24–1.29 (50, m, C–CH2), 0.84–0.87 (6, t, C–
CH3). MS (ES): calculated for C45H84O4 688, found m/
z 706 ([M ? NH4]?).
3-[(Z)-Octadec-9-enoyl]oxypropyl-(Z)-octadec-9-enoate,
2a
Colourless oil (16.9 g, 93 %); IR (ATR): 1,739 (C=O)
cm-1
;
1H NMR in CDCl3 d (ppm): 5.28–5.36 (4, m,
10-[(Z)-Octadec-9-enoyl]oxydecyl-(Z)-octadec-9-enoate
C=CH), 4.11–4.14 (4, t, O–CH), 2.25–2.29 (4, m,
O=CCH), 1.94–2.03 (8H, m, C=CCH), 1.91–1.92 (2H, m,
O–CCH), 1.55–1.63 (4H, m, O=CCCH), 1.20–1.35 (40, m,
C–CH2), 0.83–0.88 (6, t, C–CH3). MS (ESI): calculated for
C39H72O4 = 604, found m/z 622 ([M ? NH4]?).
Colourless oil (13.7 g, 65 %); IR (ATR): 1,737 (C=O) cm-1
;
1H NMR in CDCl3 d (ppm): 5.27–5.35 (4, m, C=CH),
4.00–4.04 (4, t, O–CH), 2.23–2.27 (4, t, O=CCH), 1.95–2.00
(8, m, C=CCH), 1.55–1.60 (8, m, O–CCH, O=CCCH),
1.24–1.27(52, m, C–CH2), 0.83–0.87(6, t, C–CH3). MS (ESI):
calculated for C46H86O4 702, found m/z 720 ([M ? NH4]?).
3-[(E)-Octadec-9-enoyl]oxypropyl-(E)-octadec-9-enoate,
2b
Diol from Diester 2
Pale yellow oil (83.3 g, 86 %); IR (thin film) 1,741 (C=O)
cm-1; 1H NMR (CDCl3, 500 MHz) d (ppm): 5.33 (m, 4H,
CH=CH), 4.14 (t, J = 6.3 Hz, 4H, CH2O), 2.29 (t,
J = 7.5 Hz, 4H, CH2CO), 2.00 (m, 8H, CH2CH=CH), 1.95
(quintet, J = 6.3 Hz, 2H, OCH2CH2CH2O), 1.61 (quintet,
J = 7.0 Hz, 4H, CH2CH2CO), 1.25–1.34 (m, 44H, CH2),
0.87 (t, J = 7.0 Hz, 6H, CH3); 13C NMR (CDCl3
125 MHz): d 173.620 (C=O), 129.943 (CH=), 129.684
(CH=), 60.784 (CH2OCO), 34.215, 31.891, 29.753, 29.674,
29.508, 29.304, 29.147, 29.114, 29.083, 28.053, 27.202,
27.147, 24.919, 22.659, 14.068 (CH3); LRMS (ESI) cal-
culated for C39H72O4Na ([M ? Na]?) 627.6, found 627.6.
White solid (18.2 g, 70 %); IR (thin film) 3,214 (OH),
1,724 (C=O) cm-1; 1H NMR (CDCl3, 500 MHz) d 4.10 (t,
J = 6.5 Hz, 4H, CH2O), 3.57 (t, J = 6.8 Hz, 4H, CH2OH),
2.26 (t, J = 7.8 Hz, 4H, CH2CO), 1.92 (quintet,
J = 6.3 Hz, 2H, OCH2CH2CH2O), 1.57 (quintet,
J = 7.0 Hz, 4H, CH2CH2CO), 1.51 (quintet, J = 7.0 Hz,
4H, CH2CH2OH), 1.27–1.31 (m, 16H, CH2); 13C NMR
(CDCl3 125 MHz): d 173.805 (C=O), 62.777 (CH2OH),
60.827 (CH2OCO), 34.191, 32.659, 29.147, 28.983,
27.949, 25.628, 24.853; LRMS (ESI) calculated for
C21H40O6Na ([M ? Na]?) 411.3, found 411.3.
4-[(Z)-Octadec-9-enoyl]oxybutyl-(Z)-octadec-9-enoate, 3
Diacid from Diester 2
Colourless oil (16.5 g, 89 %); IR (ATR): 1,738 (C=O)
1
White solid (3.4 g, 35 %); IR (thin film) 2,600–3,300
(OH), 1,737 (C=O, ester), 1,710 (C=O, carboxylic acid)
cm-1; H NMR in CDCl3 d (ppm): 5.32 (4, m, C=CH),
4.07 (4, t, O–CH), 2.25–2.29 (4, t, O=CCH), 1.96–2.01 (8,
m, C=CCH), 1.66–1.69 (4, m, O–CCH)), 1.56–1.61 (4, m,
O=CCCH), 1.24–1.28 (40, m, C–CH2), 0.84–0.87 (6, t, C–
CH3). MS (ESI): calculated for C40H74O4 618, found m/
z 636 ([M ? NH4]?).
cm-1 1H NMR (CDCl3, 500 MHz) d 10.40 (br s, 2H,
;
COOH), 4.14 (t, J = 6.3 Hz, 4H, CH2O), 2.34 (t,
J = 7.3 Hz, 4H, CH2COO), 2.29 (t, J = 7.3 Hz, 4H,
CH2COOH), 1.96 (quintet, J = 6.3 Hz, 2H, OCH2CH2-
CH2O),
1.58–1.63
(m,
8H,
CH2CH2COO,
CH2CH2COOH), 1.32–1.38 (m, 12H, CH2); 13C NMR
(CDCl3 125 MHz): d 180.043 (COOH), 173.797 (CO),
60.891 (CH2OCO), 34.178, 34.005, 28.857, 28.807,
27.987, 24.800, 24.555; LRMS (ESI) calculated for
C21H35O8 ([M-H]-) 415.2, found 415.2.
6-[(Z)-Octadec-9-enoyl]oxyhexyl-(Z)-octadec-9-enoate, 4
Colourless oil (18.4 g, 95 %); IR (ATR): 1,737 (C=O)
cm-1 1H NMR in CDCl3 d (ppm): 5.25–5.33 (4, m,
;
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J Am Oil Chem Soc (2014) 91:349–356
353
Di-isocyanate from Diester 2
used. The role of pyridine in these esterification reactions
was twofold. In the first instance it acts catalytically to
improve the electrophilic nature of the acyl reagent so that
the latter becomes more susceptible to the nucleophilic
attack of the alcohol reagent [16]. The second function of
pyridine in the esterification reaction of acyl chlorides and
alcohols is makes use of its basic properties to neutralize
the acid by-product (hydrogen chloride) generated during
the esterification reaction, thereby maintaining a facile
reaction environment. This means that the use of pyridine
in these reactions is stoichiometric, and for every one
molecule of hydrogen chloride expected to be formed in
the reaction, an equivalent molecule of pyridine is required.
A small excess in the amount of 3:1 pyridine-to-diol (molar
ratio) was used in these reactions. All diesters synthesized
by this method were obtained in yields between 80 and
95 % and purities C97 %.
Yellow oil (0.34 g, 80 %) was obtained: IR (thin film)
2,274 (N=C=O), 1,736 (C=O) cm-1 1H NMR (CDCl3,
;
500 MHz) d 4.14 (t, J = 6.5 Hz, 4H, CH2O), 3.28 (t,
J = 6.8 Hz, 4H, CH2N), 2.30 (t, J = 7.5, 4H, CH2COO),
1.96 (quintet, J = 6.5 Hz, 2H, OCH2CH2CH2O),
1.59–1.63 (m, 8H, CH2CH2N, CH2CH2COO), 1.31–1.34
(m, 12H, CH2); 13C NMR (CDCl3 125 MHz): 173.536
(COO), 121.900 (NCO), 60.774 (CH2O), 42.860, 34.062,
31.117, 28.862, 28.515, 27.953, 26.271, 24.709; LRMS
(EI) calculated for C21H34O6N2 410.1, found m/z 410.1.
Discussion
cis-Diesters were synthesized (Scheme 1) using a modified
version of a method previously used within the TCBR for
the preparation of linear monoesters [14]; these esters
could be conveniently prepared from the reaction of car-
boxylic acids and alcohols (Steglich esterification) or via
the reaction of acyl chlorides (activated carboxylic acid
derivative) with alcohols The latter was selected based only
on the availability of the raw materials for the reactions.
This reaction is known to proceed via a nucleophilic
addition–elimination mechanism [15]. In the first step, the
nucleophilic O-head on the alcohol attacks the electrophilic
C-center on the acyl chloride, and in the second step
hydrogen chloride is eliminated to give the ester. In the
syntheses of these aliphatic diesters, every one molecule of
the diol requires two molecules of the oleoyl chloride for
complete reaction. To ensure optimal yields of the diesters
by these reactions, an excess of the oleoyl chloride to each
diol (the limiting reagent) in the amount of 2.2:1 (mol) was
An alternative method of preparing diesters from oleic
acid (Scheme 1) was also investigated to determine if
‘greener’ reactions might be more practical. In the solvent-
free state, oleic acid was reacted with 1,3-propanediol
under the influence of temperature and catalyzed by trace
amounts of sulfuric acid. These direct condensation reac-
tions of acids and alcohols are generally limited by the
formation of equilibrium systems, hence the removal of
water under vacuum was employed as a technique to
manipulate the equilibrium and therefore improve the
reaction yield. As compared to the acylation method used
to synthesize similar diesters (above), this method did not
require the use of solvents. However, and unlike the first
method, this reaction is temperature dependent. In fact,
increasing the temperature from 80 to 100 °C resulted in a
significant improvement in the product yield from 66 to
86 %. Since the product yield of this reaction was similar
O
O
N
O
H
2
N
2
HO
OH
(a)
(b)
Cl
2
O
O
n
Cl
y
n
x
y
y
x
x
Diol
Fatty acid acyl chloride
Diester 1-6
O
O
O
H+;
2 H2O
2
HO
OH2
O
O
n
OH
y
n
x
y
y
x
x
Diol
Diester 1-6
Fatty acid
x=y=7 (fatty acid = oleic acid); n=2, 3, 4, 6, 9, 10
Scheme 1 Synthesis of diesters from oleic acid via a the acylation reaction of the acid derivative and alcohol, or b the solvent-free condensation
reaction
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J Am Oil Chem Soc (2014) 91:349–356
to those obtained via the acylation reaction, and since the
diester synthesized by this method proved to be more dif-
ficult to purify than the former (owing to the presence of
the fatty acid in the crude product) this method was not
pursued further for the purposes of this study.
Compound 7 was obtained from 2 by a simple ozonol-
ysis of the carbon–carbon double bond followed by
hydrogenation with Raney nickel as the catalyst
(Scheme 2). Like its precursor (diester 2), the diester-diol 7
has also previously been synthesized within our labs [3]. In
the latter instance, the reduction of the ozonide interme-
diate (aldehyde) into the desired diol was facilitated
through the use of sodium borohydride [3]. The yields of
both reactions were similar; the use of one method over the
other would, therefore, be only a matter of preference or
convenience. Ethanol was selected as the solvent for this
reaction since it has been shown that protic solvents min-
imize the side reactions during ozonolysis which result in
the formation of carboxylic acid by-products [20].
It is also noteworthy to point out that the diesters syn-
thesized via the acylation reaction are geo-isomerically pure
compounds—they possess only the cis configuration around
the unsaturated carbon–carbon double bonds. On the other
hand, the diester(s) synthesized via the optimized solvent-
free condensation reaction described herein would be iso-
merically impure, containing mixtures of both the cis and the
trans geo-isomers. This latter observation can be attributed
to the aggressive reaction conditions of both vacuum and
relatively high temperatures—conditions known to facilitate
cis/trans interconversion [17]—under which the reaction
was run. For the applications discussed in this paper, the
formation of geo-isomers is of little consequence since—and
as shown in Scheme 2—the double bonds will in fact be
functionalized and cleaved at a later stage to form derivative
monomers containing terminally reactive sites.
Like compound 7, compound 8—a diester-containing
diacid—was obtained via a 2-step reaction in which the
diester precursor 2 was first ozonized to give the aldehyde
intermediate (Scheme 2). Unlike the ozonolysis reaction of
compound 7, however, the formation of the acid by-pro-
ducts were in fact desired. Hence, the aprotic solvent ethyl
acetate was selected over ethanol as the reaction media
[20]. In the second step, the aldehyde groups were oxidized
with hydrogen peroxide to give the diacid ester derivative.
The overall reaction was a facile one, and the diacid was
obtained in good yields. The synthesis of this diester-con-
taining diacid is being reported for the first time.
With the exception of diester compound 2, all of the
base diesters (1, 3–6) reported herein are novel; their
syntheses and characterization are being presented for the
first time within the reported literature. Diester 2, on the
other hand, is a known compound which has been previ-
ously extracted from rice bran [18] and synthesized via the
esterification of oleic acid and 1,3-propanediol [3, 19].
Compound 9, also a novel molecule, was synthesized
from compound 8 by reacting with sodium azide and
O
O
O
O
2: Diester
1. O3, ethanol solvent
2. H2/ Raney Ni
1. O3, ethyl acetate solvent
2. H2O2
O
O
O
O
HOOC
O
HO
O
O
COOH
O
OH
6
6
6
6
8: Diacid
7: Diol
1. Et3N, ethylchloroformate
2. NaN3
3. heat
O
O
OCN
O
O
NCO
6
6
9: Diisocyanate
Scheme 2 Synthesis of diol, diacid and diisocyanate from unsaturated diester
123

J Am Oil Chem Soc (2014) 91:349–356
355
Scheme 3 Synthesis of
diisocyanate via the Curtius
rearrangement reaction
O
O
HOOC
O
O
COOH
6
6
NEt3
Ethyl chloroformate
HNEt3Cl
O
O
EtO
O
O
OEt
O
O
6
6
O
O
O
O
NaN3
NaOCOOEt
N
O
O
N
N
N
N
N
O
O
6
6
O
O
N2
O
O
O
O
C
C
N
O
O
N
6
6
subsequent Curtius rearrangement under heat (Scheme 3).
This method was reported by Cate and coworkers [21] for the
synthesis of 2,6-diisocyanatoheptane from 2,6-dimethyl-
heptanedioic acid, and has previously been used within our
own group to synthesize novel diisocyanates from fatty acids
[22]. In Cate et al.’s [21] report, in the 13C NMR of the
diisocyanate, a peak around 120 ppm corresponding to the
isocyanate carbon was missing. This indicated that the signal
of the isocyanate carbon is very weak; the same was found
for our isocyanate compound 9, with the peak at 121.9 ppm
appearing only when the 13C NMR was run long enough. In
the IR spectrum, a strong absorption band at 2,274 cm-1
designating the stretch of N=C=O confirmed the existence of
isocyanate. The mass spectrum was obtained by electron
ionization and the molecular ion peak (410.1) showed up
with small intensity.
can be extended to the use of different fatty acids and/or dif-
ferent diol components of the general form given in Scheme 1
to synthesize a variety of novel functionalized terminal dies-
ter-diols, diester-diacids, and diester-diisocyanates.
Conclusions
In conclusion, we have reported a general strategy for the
syntheses of novel diols, diacids and diisocyanates from
oleic acid via novel linear diesters. This general synthetic
scheme should prove useful for the synthesis of a series of
diols, diacids or di-isocyanates from any unsaturated fatty
acid. These ester-containing monomers are useful for the
production of bio-based biodegradable thermoplastic
polyurethanes and polyesters whose physical properties
may be manipulated by varying the length of the ester
group segments.
Whileonlythemonomericderivativesoftheonediester(2)
were described in this report, it is expected that these reactions
123

356
J Am Oil Chem Soc (2014) 91:349–356
´
11. Bueno-Ferrer C, Hablot E, Perrin-Sarazin F, Garrigos MC,
´
Acknowledgments The authors wish to acknowledge the financial
support of Elevance Renewable Sciences, NSERC, Grain Farmers of
Ontario, GPA-EDC, Industry Canada, and Trent University.
Jimenez A, Averous L (2012) Structure and morphology of new
bio-based thermoplastic polyurethanes obtained from dimeric
fatty acids. Macromol Mater Eng 297:777–784
12. Guillen MD, Cabo N (1997) Infrared spectroscopy in the study of
edible oils and fats. J Sci Food Agric 75:1–11
13. Robinson JW, Frame EMS, Frame II GM (2004) Undergraduate
instrumental analysis, CRC
14. Bouzidi L, Li S, Di Biase S, Rizvi SQ, Narine SS (2012)
Lubricating and waxy esters, I. synthesis, crystallization, and melt
behavior of linear monoesters. Chem Phys Lipids 165:38–50
15. Elomari SA, Miller SJ, Zhou Z (2012) Synthesis of biolubricant
esters from unsaturated fatty acid derivatives. US Patent
20,120,283,160
References
´
1. Petrovic ZS (2008) Polyurethanes from vegetable oils. Polym
Rev 48:109–155
2. Hojabri L, Jose J, Leao AL, Bouzidi L, Narine SS (2012) Syn-
thesis and physical properties of lipid-based poly(ester-ure-
thane)s, I: effect of varying polyester segment length. Polymer
53:3762–3771
3. Zuo J, Li S, Bouzidi L, Narine SS (2011) Thermoplastic polyester
amides derived from oleic acid. Polymer 52:4503–4516
4. Zlatanic A, Petrovic ZS, Dusek K (2002) Structure and properties
of triolein-based polyurethane networks. Biomacromolecules
3:1048–1056
5. Guo A, Javni I, Petrovic ZS (2004) Preparation and character-
ization of soy-based polyols. Abstr Pap Am Chem Soc
227:U280–U280
16. Fersht AR, Jencks WP (1970) Reactions of nucleophilic reagents
with acylating agents of extreme reactivity and unreactivity.
correlation of beta values for attacking and leaving group varia-
tion. J Am Chem Soc 92:5442–5452
17. Sun Q, Li Z, Lan Z, Pfisterer C, Doerr M, Fischer S, Smith SC,
Thiel W (2012) Isomerization mechanism of the HcRed fluo-
rescent protein chromophore. Phys Chem Chem Phys
14:11413–11424
6. Narine SS, Yue J, Kong XH (2007) Production of polyols from
canola oil and their chemical identification and physical proper-
ties. J Am Oil Chem Soc 84:173–179
7. Benecke HP, Garbark DB, Vijayendran BR (2012) Methods for
production of polyols from oils and their use in the production of
polyesters and polyurethanes. EP 1(883):690
8. Palaskar DV, Boyer Al, Cloutet E, Alfos C, Cramail H (2010)
Synthesis of Biobased Polyurethane from Oleic and Ricinoleic
Acids as the Renewable Resources Via the AB-Type Self-Con-
densation Approach. Biomacromolecules 11:1202–1211
9. Palaskar DV, Boyer A, Cloutet E, Le Meins J-F, Gadenne B,
Alfos C, Farcet C, Cramail H (2012) Original diols from sun-
flower and ricin oils: synthesis, characterization, and use as
polyurethane building blocks. J Polym Sci Part A Polym Chem
50:1766–1782
18. Chaudhari SNK, Nair VM, Lamture JB, Venkataramani S,
Bhaskaran S, Menon KKG (1986) Diol Esters—a Family of
Potential Plant-Growth Regulators, Proceedings of the Indian
Academy of Sciences-Plant Sciences 96:393–400
19. Liao D-z, Wang S-q, Zhang T-m, He J-y, Mao L-x (2007) Syn-
thesis of 1,3-propanediol dioleate. Hecheng Huaxue 15:477–479
20. Omonov TS, Kharraz E, Curtis JM (2011) Ozonolysis of canola
oil: a study of product yields and ozonolysis kinetics in different
solvent systems. J Am Oil Chem Soc 88:689–705
21. Cate AT, Dankers PYW, Kooijman H, Spek AL, Sijbesma RP,
Meijer EW (2003) Enantioselective cyclization of racemic
supramolecular polymers. J Am Chem Soc 125:6860–6861
22. Hojabri L, Kong X, Narine SS (2010) Novel long chain unsatu-
rated diisocyanate from fatty acid: synthesis, characterization,
and application in bio-based polyurethane. J Polym Sci Part A
Polym Chem 48:3302–3310
10. Xu YJ, Petrovic Z, Das S, Wilkes GL (2008) Morphology and
properties of thermoplastic polyurethanes with dangling chains in
ricinoleate-based soft segments. Polymer 49:4248–4258
123