Preparation, characterization, and theoretical studies of azelaic acid derived from oleic acid by use of a novel ozonolysis method

Article abstract of DOI:10.1007/s11164-011-0406-8

Environmentally friendly manufacture of organic compounds has been intensively reexamined in recent years. Many excellent methods have been devised to produce organic compounds from renewable resources. Azelaic acid has been produced by ozonolysis of oleic acid. The reaction was performed in a Bach bubbling reactor, with fine bubbles, at high temperature (150 °C) without utilizing any catalyst or any solvent. Yield of the reaction was 20% after 2 h. Production of azelaic acid was confirmed by use of FT-IR and ¹H NMR spectroscopic data and high-performance liquid chromatography of both synthesized and reference azelaic acid. A theoretical study was performed to obtain quantum chemical data for azelaic acid and to optimize the molecule's geometry. Springer Science+Business Media B.V. 2011.

Full text of DOI:10.1007/s11164-011-0406-8

Res Chem Intermed (2012) 38:659–668
DOI 10.1007/s11164-011-0406-8
Preparation, characterization, and theoretical studies
of azelaic acid derived from oleic acid by use of a novel
ozonolysis method
•
Abdul Amir H. Kadhum Bilal A. Wasmi
•
•
•
Abu Bakar Mohamad Ahmed A. Al-Amiery
Mohd S. Takriff
Received: 18 August 2011 / Accepted: 12 September 2011 / Published online: 24 September 2011
Ó Springer Science+Business Media B.V. 2011
Abstract Environmentally friendly manufacture of organic compounds has been
intensively reexamined in recent years. Many excellent methods have been devised
to produce organic compounds from renewable resources. Azelaic acid has been
produced by ozonolysis of oleic acid. The reaction was performed in a Bach bub-
bling reactor, with fine bubbles, at high temperature (150 °C) without utilizing any
catalyst or any solvent. Yield of the reaction was 20% after 2 h. Production of
1
azelaic acid was confirmed by use of FT-IR and H NMR spectroscopic data and
high-performance liquid chromatography of both synthesized and reference azelaic
acid. A theoretical study was performed to obtain quantum chemical data for azelaic
acid and to optimize the molecule’s geometry.
Keywords Azelaic acid Á Bubbling Á Dicarboxylic acids Á NMR spectrum Á
Theoretical study
Introduction
Focus on the utilization of renewable resources, for example agricultural material,
as an alternative to planetary resources has increased substantially with the
A. A. H. Kadhum Á B. A. Wasmi (&) Á A. B. Mohamad Á A. A. Al-Amiery Á M. S. Takriff
Department of Chemical and Process Engineering, Faculty of Engineering and Built Environment,
University Kebangsaan Malaysia, 43600 Bangi, UKM, Malaysia
e-mail: Bilal.chem.82@gmail.com
A. A. Al-Amiery
Biotechnology Division, Applied Science Department, University of Technology, Baghdad 10066,
Iraq
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A. A. H. Kadhum et al.
expectation that petroleum reserves will be exhausted during the next few decades
and because of concern about environmental pollution [1].
In this regard, fatty oils have much potential as alternatives to petroleum-based
resources [2]. Efforts are ongoing to utilize the abundantly available fatty oils and
oil-based products for production of mono and dicarboxylic acids which in turn
find major potential application as better substitutes for petroleum-based products
[3, 4]. Among these dicarboxylic acids is azelaic acid, which been used in
industry as an intermediate for many applications, for example production of
polyamides, polyesters, pharmaceuticals, plasticizers, and lubricants or hydraulic
fluids [5, 6]. It is used in the food packaging (e.g., paper, film, and foil laminates),
electronics (e.g., flexible printed circuit board, coil insulation), textile (e.g.,
footwear, interlining for labels, and emblems), and automotive (e.g., coatings,
upholstered car seats, construction of sun visors) industries [7]. It is well known
that azelaic acid can be synthesized by ozonation of oleic acid [6, 8, 9], and the
heterogeneous oleic acid–ozone reaction system has been studied intensively
because of its commercial importance and its implications for atmospheric
chemistry and climate regulation [10]. Unsaturated fatty acids are subjected to a
variety of reactions with several compounds to form a wide range of products.
These reactions may involve either the carboxyl group or the carbon–carbon
double bond in an unsaturated fatty acid [3, 8].The oxidation of unsaturated fatty
acids results in partial or complete cleavage of the carbon–carbon double bond
[4, 11]. Mono and dicarboxylic acids are the main products of the complete
oxidation of unsaturated fatty acids [3–5].
From the perspective of green chemistry, in Malaysia and other countries wealthy
in natural fatty oil products the emphasis is on obtaining synthetic organic
compounds without use of catalyst. In most reported studies on the synthesis of
azelaic acid, catalyst and solvent were used at low temperature [12]. In this study we
have produced azelaic acid by direct ozonation of oleic acid at high temperature in a
bubbling reactor without use of solvent or catalyst.
Materials and methods
Materials
Oleic acid (purity 75%) as starting material was purchased from Sigma Aldrich.
Azelaic acid (purity 95%) as reference compound was purchased from Acros
Organics. The purity of the compounds was checked by thin-layer chromatography
(TLC) on silica gel G plates with benzene–ethyl acetate–methanol 40:30:30
(v/v) or toluene: acetone 75:25 (v/v) as mobile phase; the spots were located under
UV light at 254 and 365 nm. IR spectra were obtained on a Thermo Scientific,
Nicolet 6700 FT-IR spectrometer. 1H NMR spectra were obtained on FT NMR and
NMR systems (600 MHz). The gas bubbling reactor was fabricated by Duru Glass
(Malaysia). Ozone was generated by use of an AC series ozone generator from IN
(USA).
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Preparation, characterization and theoretical studies
661
Methods
Ozonolysis
Oxygen gas at a flow rate of 1 L/min and pressure of 0.03 MPa was fed into the
electric ozone generator to generate ozone gas which was directed as fine bubbles
into the reactor containing oleic acid. The reaction temperature was maintained at
150 °C for 2 h with vigorous stirring. Unreacted ozone was decomposed before
emission of gas to atmosphere.
Separation
Liquid–liquid extraction The product was separated by threefold liquid–liquid
partition between water (polar solvent) and n-hexane (non-polar solvent).
Product separation by HPLC High-performanceliquidchromatography(HPLC)was
performed with an Agilent Technologies series 1100 system equipped with UV–visible
detector (operated at 270 nm) and 15 mm diameter Zorbax Eclipse XDB-C18 column.
The mobile phase was 0.1% aqueous phosphoric acid at a flow rate of 0.8 mL/min.
Theoretical study
Molecular drawings of azelaic acid were plotted using Visualization Materials
Studio 5.5 [13, 14]. All quantum chemical calculations were performed using
density functional theory (DFT) as implemented in the Materials Studio 5.5
software. The DMol3 model was used to obtain quantum chemical data and to
optimize the molecule’s geometry. These calculations used an ab-initio, generalized
gradient approximation (GGA) with the Lee–Yang–Parr (BLYP) correlation
functional and double numerical d-functions (DND) basis set. This approach has
been shown to yield favorable geometry for a wide variety of systems. The quantum
chemical data calculated were the energy of the highest occupied molecular orbital
(HOMO), the energy of the lowest unoccupied molecular orbital (LUMO), and the
molecular dipole moment.
Results and discussion
The ozonation reaction proceeds by the three-step Criegee mechanism [8] which
includes, first, the formation of a primary ozonide (PO), second, the decomposition
of the PO to aldehydes (or ketones) and carbonyl oxides (or Criegee intermediates,
CI) [8], then, finally, recombination of the carbonyl oxide and the aldehyde (or
ketone) to form secondary ozonide (SO). The mechanism suggested in this study is
illustrated in Fig. 1. The ozonolysis process was carried out for 2 h. Ozone was
introduced, as fine bubbles, with vigorous stirring, into the reactor containing oleic
acid at 150 °C. The product was further oxidized for 30 min with hydrogen
peroxide, with a ratio of hydrogen peroxide to ozonolysis product of 10:90 (w/w).
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A. A. H. Kadhum et al.
O+
-O
H
O
O
H
OH
1,3-cycloaddition
O
O
O
O
OH
Retro cycloaddition
O
O
O
O
H
H
OH
H2O2
OH
O
O
O
O
H
H
OH
O
O
O
HO
OH
H
OH
O
O
O
HO
OH
OH
Fig. 1 Suggested mechanism for ozonolysis of oleic acid
Subsequently the product was subjected to liquid–liquid extraction. The upper,
n-hexane, layer was evaporated to dryness and the residue was dried in an oven at
100 °C. The yield of azelaic acid was measured and found to be 20%. The product
1
was analyzed by use of spectroscopic methods (FT-IR and H NMR).
High-performance liquid chromatography
The HPLC results showed that the retention time of the synthesized azelaic acid was
2.683, as illustrated in Fig. 2, whereas the retention time of the reference azelaic acid
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Preparation, characterization and theoretical studies
663
Fig. 2 HPLC of synthesized azelaic acid
was 2.665, as shown in Fig. 3, It can be concluded that the synthesized and authentic
samples have the same retention time, confirming the formation of azelaic acid.
Infrared spectra
Study and comparison of the FT-IR spectra of azelaic acid revealed the main peak was
the dicarboxylic acid peak at 1,695 nm. A substantial negative shift of the (C=O) group
was observed, indicating a decrease in the stretching force-constant of the C=O bond
through the carbonyl-oxygen atom. The carbonyl band for synthesized azelaic acid was
located at 1,695 cm-1 and for the reference azelaic acid it was at 1695.1 cm-1, as
illustrated in Fig. 4. The broad band of the hydroxyl groups was at 3,050 cm-1 for both
the synthesized and reference azelaic acid. The ether bonds (O–C) in-plane and out-of-
plane peakswereat1,097 and1,195 cm-1 forboth thesynthesizedand referenceazelaic
acid. The methylene group (C–H) was located at 2,855 cm-1 for the synthesized
compound and at 2,848 cm-1 for the reference azelaic acid.
1H NMR spectra
The 1H NMR spectra of azelaic acid contained characteristic signals from the O–H
protons at 5.32 ppm. The peaks observed between 1.3 and 1.8 ppm were assigned to
the C–Haliphatic protons of the azelaic acid. The band located at 2.4 ppm may be
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A. A. H. Kadhum et al.
Fig. 3 HPLC of reference azelaic acid
Fig. 4 Comparison of the FTIR spectra of synthesized (a) and reference (b) azelaic acid
assigned to the C–Haliphatic proton near the carboxyl groups, because of the down-
field shift. The spectra obtained from syntesized and reference azelaic acid are
shown in Figs. 5 and 6 respectively:
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665
Fig. 5 1H NMR for synthesized azelaic acid
Fig. 6 1H NMR for reference azelaic acid
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A. A. H. Kadhum et al.
Table 1 The calculated atomic charge for synthesized azelaic acid
Atom
Charges
Atom
Charges
Atom
Charges
[C(1)]
[C(2)]
[C(3)]
[C(4)]
[C(5)]
[C(6)]
[C(7)]
[C(8)]
[C(9)]
[O(10)]
C 0.585
[O(11)]
[O(12)]
[O(13)]
[H(14)]
[H(15)]
[H(16)]
[H(17)]
[H(18)]
[H(19)]
[H(20)]
O -0.125
O -0.661
O -0.121
H 0.053
H 0.053
H 0.028
H 0.028
H 0.028
H 0.028
H 0.028
[H(21)]
[H(22)]
[H(25)]
[H(25)]
[H(25)]
[H(26)]
[H(27)]
[H(28)]
[H(29)]
H 0.028
H 0.028
H 0.028
H 0.028
H 0.028
H 0.052
H 0.052
H 0.194
H 0.194
C -0.112
C -0.046
C -0.057
C -0.055
C -0.057
C -0.045
C -0.112
C 0.586
O -0.657
Fig. 7 3D geometrical structure of azelaic acid
Computational studies
Atomic charges and stabilities
Theoretical studies of azelaic acid revealed that the atomic charges are affected by
the presence of the ring substituent. The minimized geometry is shown in Table 1,
in which calculated atomic charges for the compound are also indicated. It can be
seen from Table 1 that the highest atomic charge is at O(12) (-0.661) and the next
highest charge is at O(11) (-0.125). These results clearly indicate that these two
atoms are the most active sites for reaction and bonding with any electron acceptor.
The calculated bond and twist angles (supplementary file) and 3D geometrical
structure (Fig. 7) indicated that this molecule is not planar.
Density function theory (DFT)
DFT calculations were performed for azelaic acid. The contour plots of the frontier
orbitals for the ground state, including the highest occupied molecular orbital
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Preparation, characterization and theoretical studies
667
Fig. 8 Highest occupied molecular orbital for azelaic acid (HOMO, 12.508 eV)
Fig. 9 Lowest unoccupied molecular orbital for azelaic acid (LUMO, 0.369 eV)
(HOMO) and the lowest unoccupied molecular orbital (LUMO), are shown in
Figs. 8 and 9. It is interesting to see that both orbitals are substantially distributed
over the conjugation plane. It can be seen from Figs. 8 and 9 that the HOMO
orbitals are located on the substituted molecule whereas the LUMO orbitals
resemble those obtained for the unsubstituted molecule and therefore substitution
has an effect on the electron donation ability but only a small effect on electron
acceptance ability.
Conclusion
Ozonolysis of oleic acid was performed at 150 °C without a catalyst and the yield
was 20%. The reaction was performed with very fine gas bubble size. The contact
time between gas and liquid was increased by vigorous stirring to enhance reaction
of ozone with the double bond of oleic acid. The identity of the azelaic acid
produced was confirmed by spectroscopic analysis. It can be concluded that azelaic
acid was successfully prepared directly from oleic acid. Molecular structure
determination was also conducted.
Acknowledgment The authors would like to extend their appreciation to the University Kebangsaan
Malaysia, and to the CRIM for research grant UKM-KK-02-FRGS0196-2010.
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