Synthesis of a ruthenium complex based on 2,6-bis[1-(pyridin-2-yl)-1H-benzo[d]imidazol-2-yl]pyridine and catalytic oxidation of (1H-benzo[d]-imidazol-2-yl)methanol to 1H-benzo[d]imidazole-2-carbaldehyde with H2O2

Article abstract of DOI:10.3184/174751917X14858862342106

2,6-Bis[1-(pyridin-2-yl)-1H-benzo[d]-imidazol-2-yl]pyridine (bpbp), which has been synthesised by intramolecular thermocyclisation of N²,N⁶-bis[2-(pyridin-2-ylamino)phenyl]pyridine-2,6-dicarboxamide, reacts with sodium pyridine-2,6-dicarboxylate (pydic) and RuCl₃ to give [Ru(bpbp)(pydic)] which can catalyse the oxidation of (1H-benzo[d]imidazol-2-yl)methanol to 1H-benzo[d]imidazole-2-carbaldehyde by H₂O₂. The optimal reaction conditions were: molar ratios of catalyst to substrate to H₂O₂ set at 1 : 1000 : 3000; reaction temperature 50 °C; reaction time 5 h. The yield of (1H-benzo[d]imidazol-2-yl) methanol was 70%.

Full text of DOI:10.3184/174751917X14858862342106

88 RESEARCH PAPER
VOL. 41 FEBRUARY, 88–92
JOURNAL OF CHEMICAL RESEARCH 2017
Synthesis of a ruthenium complex based on 2,6-bis[1-(pyridin-2-yl)-1H-
benzo[d]imidazol-2-yl]pyridine and catalytic oxidation of (1H-benzo[d]-
imidazol-2-yl)methanol to 1H-benzo[d]imidazole-2-carbaldehyde with H O
Shenggui Liu *, Rongkai Pan , Wenyi Su , Guobi Li and Chunlin Ni
2
2
a
a
a
a
b
a
School of Chemistry and Chemical Engineering, Lingnan Normal University, Zhanjiang 524048, P.R. China
College of Materials and Energy, South China Agricultural University, Guangzhou, 510642, P.R. China
b
2
6
2
,6-Bis[1-(pyridin-2-yl)-1H-benzo[d]-imidazol-2-yl]pyridine (bpbp), which has been synthesised by intramolecular thermocyclisation of N ,N -bis[2-
(
pyridin-2-ylamino)phenyl]pyridine-2,6-dicarboxamide, reacts with sodium pyridine-2,6-dicarboxylate (pydic) and RuCl to give [Ru(bpbp)(pydic)] which
3
can catalyse the oxidation of (1H-benzo[d]imidazol-2-yl)methanol to 1H-benzo[d]imidazole-2-carbaldehyde by H O . The optimal reaction conditions were:
2
2
molar ratios of catalyst to substrate to H O set at 1 : 1000 : 3000; reaction temperature 50 °C; reaction time 5 h. The yield of (1H-benzo[d]imidazol-2-yl)
2
2
methanol was 70%.
Keywords: (1H-benzo[d]imidazol-2-yl)methanol, 1H-benzo[d]imidazole-2-carbaldehyde, [Ru(bpbp)(pydic)], hydrogen peroxide, oxidation
catalysis, X-ray structure
1
Benzimidazoles are a common group of heterocyclic compounds
which are widely used in medical, material, agricultural and
dicarbonyl dichloride and N -(pyridin-2-yl)benzene-1,2-diamine
in the presence of triethylamine in CH Cl at room temperature.
2
2
1–8
2
6
industrial fields. Aldehyde is a widely used functional group in
many reactions. 1H-benzo[d]imidazole-2-carbaldehyde is a key
intermediate for the preparation of complicated benzimidazole-
based compounds. Oxidation of (1H-benzo[d]imidazol-2-yl)
methanol to 1H-benzo[d]imidazole-2-carbaldehyde is of
great importance in the synthesis of precursors of a variety of
valuable fine chemicals. Traditionally, 1H-benzo[d]imidazole-
Crystals of N ,N -bis[2-(pyridin-2-ylamino)phenyl]pyridine-2,6-
dicarboxamide and bpbp were obtained by recrystallisation from
ethanol. The ruthenium complex was prepared in two steps from
RuCl . First, the bpbp ligand was treated in ethanol with RuCl to
give a red-brown deposit of [Ru(bpbp)Cl ], then sodium pyridine-
2,6-dicarboxylate was used to substitute the three Cl ions to form
a violet solution of [Ru(bpbp)(pydic)] from which the violet, solid
ruthenium complex was obtained after evaporation of some of
the ethanol. This route is cheaper and more convenient to operate
3
3
3
−
2
-carbaldehyde is produced by oxidation of (1H-benzo[d]
imidazol-2-yl)methanol by KMnO /Al O in the solid phase
4
2
3
9
–12
or by activated MnO2 or SeO or dichromate salts.
In
24
2
than preparation from [Ru(p-cymene)Cl2]2 and the synthesis
these traditional oxidation processes, large amounts of toxic
and volatile organic solvents and metal oxidants are used
extensively, and it is difficult to increase the yield of product.
Hence, developing ‘green’ processes for the selective oxidation
of (1H-benzo[d]imidazol-2-yl)methanol is still a challenging
task in catalysis. Hydrogen peroxide is an environmentally
benign oxidant, which theoretically generates only water as a
by-product. The discovery of new catalysts employing H O
can be carried under air instead of a nitrogen atmosphere.
2
6
Structural analysis of N ,N -bis[2-(pyridin-2-ylamino)phenyl]-
pyridine-2,6-dicarboxamide and (bpbp)
2
6
The structures of N ,N -bis[2-(pyridin-2-ylamino)phenyl]-
pyridine-2,6-dicarboxamide and bpbp are shown in Fig. 2.
The two molecules are not co-planar, and both lie across a
twofold axis of symmetry through the centre of the pyridine
2
2
13–16
2
6
ring. Selected bond lengths and angles for N ,N -bis[2-(pyridin-
2-ylamino)phenyl]-pyridine-2,6-dicarboxamide and bpbp are
listed in Table 1.
as oxidant is gaining considerable attention.
complexes constitute a versatile class of catalysts for important
Ruthenium
17
synthetic transformations in organic chemistry. We have
focused on the synthesis and applications of complexes based
2
6
In the N ,N -bis[2-(pyridin-2-ylamino)phenyl]-pyridine-
2,6-dicarboxamide molecule the average bond length of
N(1)–C(7), N(2)–C(13) is 1.344 Å. Following intramolecular
1
8–21
on the benzimidazole group
attention to the catalytic oxidation properties of ruthenium
and have recently turned our
2
2–23
2
6
complexes based on benzimidazole group ligands.
In this
thermocyclisation
condensation,
N ,N -bis[2-(pyridin-2-
paper, we describe the synthesis of a new benzimidazole-
based ligand, 2,6-bis[1-(pyridin-2-yl)-1H-benzo[d]-imidazol-
ylamino)phenyl]-pyridine-2,6-dicarboxamide is converted to
bpbp. The average bond length of N(5)–C(18), N(2)–C(12) is
2
6
2
-yl]pyridine (bpbp), and its ruthenium complex [Ru(bpbp)
1.313 Å, which is much shorter than in N ,N -bis[2-(pyridin-
2-ylamino)phenyl]pyridine-2,6-dicarboxamide (1.344 Å).
The other C–N bond lengths of imidazoles are all shorter
than those in the amide molecule. Following intramolecular
thermocyclisation condensation the two C–N bonds which link
the substituent pyridine to the imidazoles also became shorter
than those in the amide molecule, their average bond length
being from 1.429 Å to 1.374 Å. The distance in the two crystal
(pydic)] as well as an investigation of the catalytic properties
of this complex in the oxidation of (1H-benzo[d]imidazol-2-yl)
methanol to 1H-benzo[d]imidazole-2-carbaldehyde with H O
2
2
as oxidant.
Results and discussion
Synthesis of 2,6-bis[1-(pyridin-2-yl)-1H-benzo[d]imidazol-2-yl]
pyridine (bpbp) and its ruthenium complex
2
6
molecules suggests that bpbp is more stable than N ,N -bis[2-
(pyridin-2-ylamino)phenyl]pyridine-2,6-dicarboxamide.
The route to synthesising the bpbp ligand and ruthenium complex
[
Ru(bpbp)(pydic)] is shown in Fig. 1. The bpbp ligand was
Characterisation of [Ru(bpbp)(pydic)]
prepared by intramolecular thermocyclisation condensation
2
6
of
N ,N -bis[2-(pyridin-2-ylamino)phenyl]pyridine-2,6-
This complex was characterised by elemental analysis and
1
dicarboxamide which was obtained by reaction of pyridine-2,6-
spectroscopy. The H NMR spectrum of [Ru(bpbp)(pydic)]
*
Correspondent. E-mail: lsgui@sohu.com

JOURNAL OF CHEMICAL RESEARCH 2016 89
+
O
SOCl2
O
HOOC
COOH
N
N
Cl
Cl
O
O
N
N
NH
HN
HN
N
O
NH
O
N
+
2
Cl
Cl
NH
NH2
N
O
O
N
NH
HN
HN
N
heat
N
N
N
N
NH
N
N
N
N
N
N
N
N
alcohol
+
RuCl .nH O
N
N
N
N
3
2
N
N
N
N
N
N
Ru
Cl
Cl
Cl
N
N
N
N
alcohol
N
N
N
+
N
N
N
NaOOC
N
COONa
N
O
N
O
Ru
N
N
N
Ru
Cl
Cl
O
O
Cl
Fig. 1 Synthetic route to ruthenium complex [Ru(bpbp)(pydic)].
2
6
Fig. 2 Molecular structure of N ,N -bis[2-(pyridin-2-ylamino)phenyl]pyridine-2,6-dicarboxamide (A) and bpbp (B) (ORTEP, 30% ellipsoids).

9
0 JOURNAL OF CHEMICAL RESEARCH 2016
Table 1 Selected bond lengths (Å) and bond angles (°)
2
6
N ,N -Bis[2-(pyridin-2-ylamino)phenyl]pyridine-2,6-dicarboxamide
Bond
N(1)–C(7)
Length (Å)
1.341(2)
1.374(2)
Bond
Length (Å)
1.413(2)
1.347(2)
1.374(2)
Degrees (°)
127.23(15)
Bond
N(3)–C(1)
N(2)–C(14)
Length (Å)
1.417(2)
1.409(2)
N(1)–C(6)
N(2)–C(13)
C(20)–N(4)
Angle
N(3)–C(25)
N(4)–C(19)
Angle
C(25)–N(3)–C(1)
C(20)–N(4)–C(19)
1.425(2)
Degrees (°)
126.07(14)
122.46(14)
Angle
C(13)–N(2)–C(14)
Degrees (°)
129.75(15)
C(7)–N(1)–C(6)
2
,6-Bis[1-(pyridin-2-yl)-1H-benzo[d]imidazol-2-yl]pyridine
Bond
N(1)–C(6)
Length (Å)
1.3921(19)
1.3115(19)
1.3928(18)
1.3942(19)
Degrees (°)
105.92(12)
105.28(12)
Bond
Length (Å)
1.4305(18)
1.394(2)
Bond
Length (Å)
1.3877(19)
1.3832(18)
1.3143(18)
N(1)–C(7)
N(2)–C(1)
N(4)–C(19)
N(1)–C(12)
N(4)–C(18)
N(5)–C(18)
N(2)–C(12)
N(4)–C(24)
N(5)–C(29)
Angle
C(12)–N(1)–C(6)
C(18)–N(5)–C(29)
1.4280(17)
Angle
C(12)–N(2)–C(1)
Degrees (°)
104.90(12)
Angle
C(18)–N(4)–C(24)
Degrees (°)
106.47(11)
a
is very similar to the simulation by the Chembio Ultra soft
program. In the IR of the complex the appearance of bands at
Table 2 Optimisation of reaction conditions
b
c
c
Entry
Substrate : H2O2
T (°C)
Conv. (%)
Yield (%)
−1
−
1650 and 1400 cm shows the coordination of COO to the Ru
1
2
3
4
5
6
7
8
9
1 : 3
1 : 3
1 : 3
1 : 1
1 : 2
1 : 4
1 : 3
1 : 3
1 : 3
30
50
80
50
50
50
50
50
50
47
82
>99
58
64
94
45
78
80
56
62
83
2
ion.
Catalytic oxidation of (1H-benzo[d]imidazol-2-yl)methanol to
1
H-benzo[d]imidazole-2-carbaldehyde
In order to explore the preparation method of 1H-benzo[d]
imidazole-2-carbaldehyde we focused on the oxidation reaction
of (1H-benzo[d]imidazol-2-yl)methanol (Fig. 3) by employing
the ruthenium complex [Ru(bpbp)(pydic)] as catalyst and
hydrogen peroxide as oxidant. The effect of different reaction
parameters was examined in water as solvent, as listed in
Table 2. Only a 35% yield of 1H-benzo[d]imidazole-2-
carbaldehyde was obtained when the reaction was conducted at
d
4
e
78
>95
76
82
f
a
Reaction conditions: (1H-benzo[d]imidazol-2-yl)methanol (2 mmol), catalyst
−
3
(2 × 10 mmol), 60 min.
b
Molar ratio.
c
Determined by GC.
3
0 °C, while the selectivity became poor on further increase of
d
In the absence of catalyst.
temperature to 80 °C (entries 1, 2, 3). Therefore, the optimised
temperature was shown to be 50 °C. The yield of 1H-benzo[d]
imidazole-2-carbaldehyde increased with increase in the molar
ratio of H O /(1H-benzo[d]imidazol-2-yl)methanol (entries
e
−4
Catalyst (2 × 10 mmol).
f
−2
Catalyst (2 × 10 mmol).
2
2
The mixture was stirred for 5 h. After filtering, the solution was
evaporation under reduced pressure at 50 °C. Pure 1H-benzo[d]
imidazole-2-carbaldehyde (0.07 mmol, 10.2 g) was obtained with a
2
, 4, 5). A large excess amount of H O could promote over-
2 2
oxidation of (1H-benzo[d]imidazol-2-yl)methanol, which
resulted in a slight decrease in selectivity towards 1H-benzo[d]
imidazole-2-carbaldehyde (entry 6). The reaction almost did
not occur in the absence of catalyst (entry 7). Similarly, the
yield of 1H-benzo[d]imidazole-2-carbaldehyde increased
with increasing amounts of catalyst, while an excess amount
of catalyst caused a decrease in selectivity to 1H-benzo[d]
imidazole-2-carbaldehyde (entries 8, 9).
yield of 70% after recrystallisation from 30% H SO solution. The
2
4
product, 1H-benzo[d]imidazole-2-carbaldehyde, was identified by
1
its H NMR spectrum.
Conclusions
A new ruthenium complex, [Ru(bpbp)(pydic)], has been used as
catalyst for the oxidation of (1H-benzo[d]imidazol-2-yl)methanol
to 1H-benzo[d]imidazole-2-carbaldehyde with H O as oxidant.
The procedure for gram scale oxidation of (1H-benzo[d]
imidazol-2-yl)methanol to 1H-benzo[d]imidazole-2-carbaldehyde
was as follows: (1H-benzo[d]imidazol-2-yl)methanol (0.1 mol,
2
2
The reaction optimal conditions were: molar ratios of catalyst to
substrate to H O of 1 : 1000 : 3000, optimal reaction temperature of
−3
14.8 g) and [Ru(bpbp)(pydic)] (0.001 mmol, 7.32 × 10 g) were
2
2
added into a reactor. The reactor containing this mixture was heated
to 50 °C in an oil bath under vigorous stirring and then 30% H O
50 °C and reaction time of 5 h. The yield of (1H-benzo[d]imidazol-
2-yl)methanol from 1H-benzo[d]imidazole-2-carbaldehyde under
the optimal reaction conditions was 70%.
2
2
(30 mL, 0.3 mol) was slowly dropwise over a period of 30 min.
H
N
H
N
2 2
H O
-Ru(bbp)(pydic)
CHO
N
OH
N
Fig. 3 Reaction scheme of (1H-benzo[d]imidazol-2-yl)methanol to 1H-benzo[d]-imidazole-2-carbaldehyde.

JOURNAL OF CHEMICAL RESEARCH 2016 91
Experimental
Reagents and methods
d6-DMSO): 7.04–7.23(m, 3H), 7.26–7.44 (m, 8H), 7.73–7.80 (m, 4H),
8.09–8.27 (m, 2H), 8.35–8.42 (m, 2H).
All chemicals were of analytical grade and were purchased from J&K
Synthesis of ruthenium complex [Ru(bpbp)(pydic)]; general procedure
1
Company without further purification. N -(pyridin-2-yl)benzene-1,2-
RuCl ·nH O (690 mg, 0.22 mmol) and bpbp (930 mg, 0.2 mmol) were
3
2
2
5
diamine was synthesised according to the literature. Mass spectra
were obtained on a Shimadzu LCMS-2010A instrument. Elemental
analyses were carried out with an Elementar Vario EL Elemental
dissolved in ethanol (60 mL). After the reaction mixture was refluxed for
h at 80 °C to form a red-brown deposit, it was cooled to room temperature
4
and filtered. The red-brown solid was collected (0.672 g, 0.1 mmol) and
sodium pyridine-2,6-dicarboxylate (211 mg, 0.1 mmol), dissolved in
ethanol (20 mL) and water (10 mL), were added to it. The whole reaction
mixture was again refluxed at 80 °C for 4 h to yield a violet solution. After
reaction for a further 3 h the solvent was reduced to 10 mL to give a dark-
violet precipitate, which was filtered off and dried in a vacuum (450 mg,
1
Analyzer. H NMR were recorded on a Bruker AVANCE 400
spectrometer (400 MHz). Chemical shifts are given in ppm and refer to
the residual solvent as the internal standard. IR spectra were recorded
on a Bruker 550 FT-IR spectrometer.
2
6
Synthesis
of
N ,N -bis[2-(pyridin-2-ylamino)phenyl]pyridine-2,6-
0
.61 mmol, yield: 64.01%). Anal. calcd for C H N O Ru: C, 59.09; H,
dicarboxamide; general procedure
36 22 8 4
−1
3.03; N, 15.31; found: C, 59.41; H, 3.09; N, 15.35%; IR (KBr)/cm : 3445,
2
6
N ,N -Bis[2-(pyridin-2-ylamino)phenyl]pyridine-2,6-dicarboxamide
1
1650, 1468, 1444, 1400, 1335, 1261, 1154, 1090, 1020, 911, 747; H NMR
2
6
was synthesised according to a published method.
(
400 MHz, d -DMSO): δ 8.80–8.98 (d, 2H), 8.30–8.78 (q, 3H), 7.77–8.25
6
Pyridine-2,6-dicarboxylic acid (3.34 g, 10 mmo1) was refluxed in
thionyl chloride (10 mL) for 8 h. Excess thionyl chloride was removed
(t, 6H), 7.50–7.73(m, 7H), 7.03–7.47(m, 4H).
1
under vacuum. After cooling to room temperature, N -(pyridin-
X-ray crystallography
2
-yl)benzene-1,2-diamine (7.36 g, 20 mmo1) and triethylamine
Single-crystal structure determinations were performed on a Siemens
Smart-CCD diffractometer equipped with a normal focus, 3 kW sealed
tube X-ray source and graphite monochromated Mo-Ka radiation
(l = 0.71073 Å) at 173 K. The semi-empirical absorption was applied to the
intensity data.
(
6 mL) in 60 mL of CH C1 were added to a solution of the residue in
2
2
CH C1 (30 mL). The mixture was further stirred for 2 h at ambient
2
2
temperature. The white solid product was collected by filtration,
washed with water and dried in a vacuum (yield: 6.50 g, 64.87%).
Anal. calcd for: C H N O : C, 69.4; H, 4.6; N, 19.55; found: C, 69.65;
The structure was solved by direct methods with SHELXS-97 and
2
9
23
7
2
2
H, 4.66; N, 19.51%.
refined by full-matrix least-squares techniques on F with SHELXL-97
program. All non-hydrogen atoms in both structures were refined using
anisotropic displacement parameters. All hydrogen atoms were added
theoretically. Crystallographic data for the structural analysis have been
deposited with the Cambridge Crystallographic Data Centre, CCDC Nos.
Synthesis of 2,6-bis[1-(pyridin-2-yl)-1H-benzo[d]imidazol-2-yl]pyridine
(pdpd); general procedure
2
,6-Bis[1-(pyridin-2-yl)-1H-benzo[d]imidazol-2-yl)]pyridine
was
2
7
synthesised according to a published method.
1499925 and 1499926. Copies of this information may be obtained from
2
6
N ,N -Bis[2-(pyridine-2-ylamino)phenyl]pyridine-2,6-dicarboxamide
The Director, CCDC, 12 Union Road, Cambridge, CB2 1EZ, UK (http://
www.ccdc.cam.ac.uk). The crystal data are summarised in Table 3.
(5.01 g) was heated at 250 °C for 3 h under a nitrogen atmosphere. After
cooling, water (50 mL) was added and the mixture extracted with CH Cl2
2
(50 × 3 mL). The combined organic layers were washed with water. After
Catalytic oxidation of (1H-benzo[d]imidazol-2-yl)methanol; general
filtration the solvent was removed in a vacuum to obtain crude, solid
bpbp which was recrystallised from ethanol (2.78 g, 59.78%). IR (KBr)/
procedure
The catalytic oxidation of (1H-benzo[d]imidazol-2-yl)methanol was
carried out in a magnetically stirred glass reaction tube fitted with a
reflux condenser. A typical procedure was as follows: (1H-benzo[d]
−1
cm : 3425, 3064, 1586, 1438, 1404, 1368, 1329, 1291, 1255, 1200, 1147,
1
1
065, 995, 921, 868, 825, 791, 743, 637, 589, 517, 407; H NMR (400 MHz,
Table 3 Crystal data and structure refinement for the compounds
2
6
Compound
Formula
Formula weight
Crystal system
Space group
a/Å
N ,N -Bis[2-(pyridin-2-ylamino)phen-yl]-pyridine-2,6-dicarboxamide 2,6-Bis[1-(pyridin-2-yl)-1H-benzo[d]-imidazol-2-yl]pyridine
C H N O
C H N7
2
9
23
7
2
29 19
501.54
Monoclinic
P2(1)/n
9.2468(14)
465.51
Monoclinic
P2(1)/n
12.465(2)
b/Å
25.869(4)
14.152(2)
c/Å
11.0007(16)
13.790(2)
β/°
V/Å
µ/mm
Z
Dc/g cm
109.256(3)
2484.2(6)
0.089
4
109.383(2)
2294.9(6)
0.084
4
3
−1
−
3
1.341
1.347
Crystal size
Theta range for data collection/°
Index ranges
0.39 × 0.29 × 0.13
2.11 to 27.05
−10≤ h ≤11, −28≤ k ≤33, −13≤ l ≤7
1048
0.25 × 0.23 × 0.21
1.91 to 25.00
−6≤ h ≤14, −13≤ k ≤16, −16≤ l ≤15
968
F(000)
GOF on F
2
1.048
1.004
Reflections collected/unique
Data/restraints/parameters
R indices (all data)
12562/5374 [R(int) = 0.0198]
5374/0/343
9891/4031 [R(int) = 0.0201]
4031/0/325
R = 0.0650, wR = 0.1441
R = 0.0461, wR = 0.1008
1
2
1
2
Final R indices [I > 2 sigma (I)]
Max. and min. transmission
Largest diff. peak and hole (e A ) 0.456 and −0.428
R = 0.0492, wR = 0.1320
0.988, 0.970
R = 0.0333, wR = 0.0911
0.9826, 0.9793
0.148 and −0.166
1
2
1
2
−
3

9
2 JOURNAL OF CHEMICAL RESEARCH 2016
−
1
imidazol-2-yl)methanol (aqueous solution, 0.1 mol L ), ruthenium
5
B.T. Chen, N. Morlanés, E. Adogla, K. Takanabe and V.O. Rodionov, ACS
Catal., 2016, 6, 4647.
S. Semwal and J. Choudhury, ACS Catal., 2016, 6, 2424.
J. Yellol, S.A. Pérez, A. Buceta, G. Yellol, A. Donaire, P. Szumlas, P.J.
Bednarski, G. Makhloufi, C. Janiak, A. Espinosa and J. Ruiz, J. Med.
Chem., 2015, 58, 7310.
T. Islamoglu, S. Behera, Z. Kahveci, T.D. Tessema, P. Jena and H.M. El-
Kaderi, ACS Appl. Mater. Interfaces, 2016, 8, 14648.
Dubey, K.C. Ravi and B. Balaji, Indian J. Chem., Sect B, 2003, 42, 3128.
−
4
complex catalyst (1 × 10 mmol, 0.01 mol% based substrate) and
inert internal standard (0.2 mmol) were added to a reaction tube which
was heated to a chosen temperature in an oil bath under vigorous
6
7
−1
stirring, and then aqueous hydrogen peroxide (30% H O , 10 mol L )
2
2
was added slowly dropwise. Product samples were drawn at regular
time intervals and analysed by GC and GC-MS. GC analyses were
performed on a Shimadzu GC-2010 plus chromatograph equipped
with an Rtx-5 capillary column (30 m × 0.25 mm × 0.25 µm).
8
9
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a
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(
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Acknowledgements
This work was supported financially by the Natural Science
Foundation of Guangdong Province (No. 2014A030307010).
Special funds for public welfare research and capacity
building in Guangdong Province (Nos. 2015A010105031 and
016A010103042), the National Spark Program Project (No.
015GA780033) and Lingnan Normal University Science
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Received 23 October 2016; accepted 1 January 2017
Paper 1604390 DOI: 10.3184/174751917X14858862342106
Published online: 10 February 2017
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