Zirconia-supported Keggin phosphomolybdovanadate nanocomposite: A heterogeneous and reusable catalyst for alkene epoxidation under thermal and ultrasonic irradiation conditions

Article abstract of DOI:10.1016/j.crci.2011.03.003

Keggin phosphomolybdovanadate, PVMo, was supported on a zirconia matrix by the wet impregnation method. The phase and chemical structure, optical absorption, surface physicochemical properties and morphology of PVMo-ZrO ₂ composite were studied by X-ray diffraction (XRD) technique, FT-IR and diffuse reflectance UV-vis spectroscopic (DR UV-vis) methods, and scanning electron microscopy (SEM), which indicated that the primary Keggin structure has remained intact after formation of the composite. Moreover, the obtained nanocomposite was used as an efficient catalyst of olefins under reflux and ultrasonic irradiation conditions. The catalyst was reused several times, without observable loss of activity and selectivity. Indeed, the catalytic activity of the PVMo-ZrO₂ was compared with pure Keggin phosphomolybdovanadate.

Full text of DOI:10.1016/j.crci.2011.03.003

C. R. Chimie 14 (2011) 588–596
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´
Full paper/Memoire
Zirconia-supported Keggin phosphomolybdovanadate nanocomposite:
A heterogeneous and reusable catalyst for alkene epoxidation under
thermal and ultrasonic irradiation conditions
b
b
b
Hossein Salavati a, , Shahram Tangestaninejad , Majid Moghadam , Valiollah Mirkhani ,
*
Iraj Mohammadpoor-Baltork b
a Department of Chemistry, Payame Noor University (PNU), Tehran 19395-4697, Islamic Republic of Iran
b Department of Chemistry, Catalysis Division, University of Isfahan, Isfahan 81746-73441, Islamic Republic of Iran
A B S T R A C T
A R T I C L E I N F O
Article history:
Keggin phosphomolybdovanadate, PVMo, was supported on a zirconia matrix by the wet
impregnation method. The phase and chemical structure, optical absorption, surface
physicochemical properties and morphology of PVMo–ZrO2 composite were studied by X-
ray diffraction (XRD) technique, FT-IR and diffuse reflectance UV–vis spectroscopic (DR
UV–vis) methods, and scanning electron microscopy (SEM), which indicated that the
primary Keggin structure has remained intact after formation of the composite. Moreover,
the obtained nanocomposite was used as an efficient catalyst of olefins under reflux and
ultrasonic irradiation conditions. The catalyst was reused several times, without
observable loss of activity and selectivity. Indeed, the catalytic activity of the PVMo–
ZrO2 was compared with pure Keggin phosphomolybdovanadate.
Received 25 February 2010
Accepted after revision 14 March 2011
Available online 12 May 2011
Keywords:
Phosphomolybdovanadate
Ultrasonic irradiation
Zirconia
Nanocomposite
Epoxidation
´
ß 2011 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved.
1. Introduction
the catalytic properties of the catalyst. Although explana-
tion of the true role of the supports is not clear, however, it
Polyoxoanions, as transition metal–oxygen–anion clus-
ters, have attracted a great interest as homogeneous
catalysts because of their acid-base and redox properties.
Therefore, it is important to understand their catalytic role
in different chemical reactions in which they are
employed. They exhibit great advantages because their
catalytic properties can be tuned by changing the identity
of charge-compensating counteractions, heteroatoms, and
framework metal atoms [1,2].
For various reasons, such as higher efficiency, better
accessibility of the active sites, the environmentally
friendly nature and lower cost supporting of a catalyst
on a support is currently favored. The support does not
always play merely a mechanical role; it can also modify
appears that the nature of the support and the amount of
the deposit may influence the catalytic properties of
supported catalysts [3–6]. The sites influence the catalytic
activity and selectivity of the catalysts in the epoxidation
reactions. In recent years, zirconia has attracted much
attention both as a catalyst and catalyst support because of
its high thermal stability, amphoteric character and
oxidizing and reducing properties [7–13].
Polyoxometalates can be used either directly as a bulk
material or in supported form. The supported form is
preferable because of its high surface area compared with
the bulk material (5–8 m2 gꢀ1) and better accessibility of
reactants to the active sites. Owing to very low surface area
and high solubility of these compounds in polar solvents,
the development of supported and heterogeneously active
forms of POM catalysts is in demand. POMs have been
supported on different inorganic solids such as silica,
mesoporous molecular sieve MCM-41 or MCM-48, NaY
* Corresponding author.
E-mail address: hosseinsalavati@pnu.ac.ir (H. Salavati).
1631-0748/$ – see front matter ß 2011 Acade´mie des sciences. Published by Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.crci.2011.03.003

H. Salavati et al. / C. R. Chimie 14 (2011) 588–596
589
zeolite, activated carbons, layered double hydroxide,
amorphous or anatase TiO2, montmorillonite and carbon
nanotubes [14–37].
were performed on a Shimadzu GC-16A instrument using a
2 m column packed with silicon DC-200 or Carbowax 20 m.
In all experiments, n-decane was used as internal standard.
1H NMR spectra were recorded on a Bruker-Avance AQS
300 MHz using CDCl3 as solvent and TMS as an internal
reference. Conversions and yields were obtained by GC
experiments and the products were identified after
isolation and purification.
The main effect of ultrasound in liquids is cavitation
phenomenon, which produces numerous tiny gas bubbles
called cavitation bubbles. The collapse of these bubbles
generates high temperatures and pressures are generated
at the centre of the bubbles. These local effects produce a
variety of radicals and highly active intermediates, which
initiate other secondary chemical reactions in the bulk
liquid. These radicals can react with contaminants to form
by products.
2.1. Preparation and characterization of PVMo–ZrO2
composite
The most successful applications of ultrasound have
been found in the field of heterogeneous chemistry
involving solids and metals. This is due to the
mechanical impact of ultrasound on solid surfaces. In
conventional chemistry there are several problems
associated with reactions involving solids or metals:
small surface area of the solid/metal may lead to
excessive reactivity, penetration of reactants into deeper
areas is not possible, oxide layers or impurities can cover
the surface, reactants/products have to diffuse onto and
from the surface and reaction products can act as deposit
on the surface and prevent further reactions. The
mechanical effects of ultrasound offer an opportunity
to overcome the following types of problem associated
with conventional solid/metal reactions: break-up of the
surface structure allows penetration of reactants and/or
release of materials from the surface, degradation of
large solid particles due to shear forces induced by shock
waves and microstreaming leads to reduction of particle
size and increase of surface area and accelerated
motion of suspended particles leads to better mass
transfer [38].
Recently, we reported the sonocatalytic oxidation of
organic compounds catalyzed by vanadium containing
polyphosphomolybdate supported on MCM-41, TiO2
nanoparticles, montmorillonite and carbon nanotubes
[25,26]. In this paper, we wish to report the sonocatalytic
oxidation of alkenes with H2O2 catalyzed by Na5PV2-
Mo10O40 (PVMo) supported on ZrO2. The effect of
ultrasonic irradiation on the catalytic activity of this
catalyst was also investigated.
The Na5[PV2Mo10O40].14H2O (PVMo) was prepared as
described in the literature [39]. The typical procedure for
preparation of PVMo–ZrO2 nanoparticles is as following:
PVMo (0.1 g) and ZrO2 (0.4 g) were mixed and put into an
agate mortar. The mixture was thoroughly ground for
20 min, washed in a supersonic washing machine using
absolute alcohol as dispersant, and centrifuged. The
washing and centrifuging processes were repeated five
times. The wet nanoparticles of PVMo–ZrO2 were obtained
and dried in vacuum for 5 h (60–80 8C).
2.2. General procedure for oxidation reactions with H2O2
under reflux conditions
All reactions were carried out in a 50 mL thermostated
glass reactor equipped with a magnetic stirrer. Tempera-
tures were controlled with an accuracy of ꢁ2 K. In a typical
experiment, the reaction vessel was loaded with the
supported catalyst (containing 2.86 mmol of PVMo), alkene
(1 mmol) in acetonitrile (5 mL) and H2O2 (1 mL, 30%), and the
mixture was refluxed. The progress of the reaction was
monitored by GC. At the end of the reaction, the mixture was
diluted with Et2O (20 mL) and filtered. The catalyst was
thoroughly washed with Et2O and combined washings and
filtrates were purified on a silica gel plate or a silica gel
column. IR and 1HNMR spectral data confirmed the identities
of the products.
2.3. General procedure for oxidation reactions with H2O2
under ultrasonic irradiation
A UP 400S ultrasonic processor equipped with a 3 mm
wide and 140 mm long probe, which was immersed
directly into the reaction mixture, was used for sonication.
The operating frequency was 24 kHz and the output power
was 0–400 W through manual adjustment. The final
volume of solution was 6 ml. The temperature of the
solution reached 60 8C during sonication.
2. Experimental
All chemicals were of analytical grade and were used
without further purification. Elemental analyses were
performed on a Perkin-Elmer 2400 instrument. Atomic
Absorption analyses were carried out on a Shimadzu 120
spectrophotometer. Compositional and elemental investi-
gations were performed by backscattered electrons and
EDX analysis, respectively. Diffuse reflectance spectra
were recorded on a Shimadzu UV-265 instrument using
optical grade BaSO4 as reference. FT-IR spectra were
obtained as potassium bromide pellets in the range 400–
4000 cmꢀ1 with
Scanning electron micrographs of the catalyst and support
were taken on SEM Philips XL 30. Powder X-ray diffraction
data were obtained on a D8 Advanced Bruker using Cu K
radiation (25–708). Gas chromatography experiments (GC)
To a mixture of alkene (1 mmol) and the supported
catalyst (containing 2.86 mmol of PVMo) in acetonitrile
(5 mL) was added hydrogen peroxide (1 mL, 30%) and the
mixture was exposed to ultrasonic irradiation. The
reaction progress was monitored by GC. After the reaction
was completed, the reaction mixture was diluted with Et2O
(20 mL) and filtered. The catalyst was thoroughly washed
with Et2O and combined washings and filtrates were
purified on a silica gel plates or a silica gel column. IR and
1HNMR spectral data confirmed the identities of the
products.
a Nicollet-Impact 400D instrument.
a

[)(TD$FIG]
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H. Salavati et al. / C. R. Chimie 14 (2011) 588–596
3. Results and discussion
3.1. Preparation and characterization of PVMo–ZrO2
composite
Since phosphomolybdovanadate of the Keggin struc-
˚
ture have molecular diameters of ꢂ12 A, it is feasible to
support phosphomolybdovanadate on ZrO2. The XRD
patterns of zirconia and the PVMo–ZrO2 composite are
shown in Fig. 1A and B, respectively. In the XRD of ZrO2, the
diffraction peaks at 2u = 28.68, 31.58 34.58, 50.58 and 60.18
correspond to the tetragonal zirconia phase. Fig. 1B shows
that the Keggin unit has been dispersed homogeneously
into the ZrO2 framework. The sizes of these nanoparticles,
calculated from the data of XRD peak broadening according
to the Scherer equation: D = 0.89l/bcosu [40,41], was
Fig. 1. XRD patterns of: (A) ZrO2 (B) PVMo–ZrO2 nanocomposite.
obtained as 35 nm.
Fig.
2 shows SEM images of nanoparticles. The
morphologies and microstructure of the nanoparticles
are approximately spherical. It is well-known that the
catalytic activity of composites is strongly dependent on
the shape, size and size distribution of the particles.
Therefore, it is important to characterize the microstruc-
ture of the composite. Fig. 2b shows the SEM images of the
PVMo-ZrO2 powder. SEM image reveals that the powder is
composed of aggregated fine particles and the average
particle sizes is about 40 nm which is consistent with the
average size obtained from the peak broadening in X-ray
diffraction studies.
FT-IR spectrum of the prepared catalyst showed
absorption bands at 1072, 959, 866 and 787 cmꢀ1
,
corresponding to the four typical skeletal vibrations of
the Keggin polyoxoanions, which indicated that PVMo has
been supported on zirconia (Fig. 3). These peaks could be
attributed to
n(P = Oa), n(Mo = Ot), n(Mo-Ob-Mo) and n(Mo-
Oc-Mo), respectively (Ot = terminal oxygen, Ob = bridged
[()TD$FIG]
Fig. 2. SEM images of: (A) ZrO2 and (B) PVMo–ZrO2 nanocomposite.

[
[()TD$FIG]
H. Salavati et al. / C. R. Chimie 14 (2011) 588–596
591
Fig. 4. UV-Vis DR spectra of: (a) ZrO2 (b) PVMo, and (c) PVMo–ZrO2
nanocomposite.
been introduced into the nanostructure framework
(Fig. 4).
It is evident that the electronic spectrum of nanocom-
posite (Fig. 4c), with a broad and strong absorption peak in
200-400 nm, is different from pure ZrO2 (Fig. 4a) and pure
PVMo (Fig. 4b). As shown in Fig. 4, after formation of PVMo-
ZrO2 nanocomposite, the O!Mo charge transfer peak of
PVMo (266 nm) and O!Zr charge transfer peak of ZrO2
(247 nm) disappear, and a broad absorption peak appears.
The PVMo-ZrO2 nanocomposite containing 20 wt% of
POM was prepared through entrapment of catalyst into
zirconia matrix via the wet impregnation method. (The ratio
of PVMo to ZrO2 was also checked by elemental analysis of
the supported catalyst. In this manner, the amounts of Mo
and ZrweredeterminedbyNeutron Activation Analysis. The
obtained results confirmed that the amount of PVMo is
about 20 wt%). In this process, POM-ZrO2 nanocomposite is
formed via electrostatic interaction and hydrogen bonding.
This interaction also exists in H3PW12O40-SiO2 and
H4SiW12O40-SiO2 composites; their preparation has been
reportedpreviously[36]. Thehydrogenbondingisformed in
the nanocomposite between the oxygen atoms of the PVMo
and the BZr–OH groups of the zirconia network, which can
be expressed in the forms of Mo = OtꢃꢃꢃHO–ZrB and Mo–
ObꢃꢃꢃHO–ZrB, where Ot and Ob refer to the terminal and the
bridge oxygen atoms in the PVMo unit, respectively. These
two interactions confirm the fixation of the Keggin unit into
the ZrO2 support firmly, so that the leaching of PVMo in
liquid phase reactions may be decreased [46,47].
Fig. 3. FT-IR spectra of: (A) PVMo; (B) PVMo–ZrO2, and (C) Recovered
PVMo–ZrO2 nanocomposite.
oxygen of two octahedral sharing a corner and Oc = bridged
oxygen sharing an edge). The IR spectra indicated that the
structure of the polyoxoanion has been retained upon
impregnation. Therefore, it is confirmed that a strong
chemical interaction, not simple physical absorption,
exists between the polyanion and the zirconia surface.
The broad and strong band at about 600 cmꢀ1 is attributed
to the Zr–O stretching vibration of tetragonal ZrO2 [42–45].
The UV-Vis spectra of PVMo in CH3CN displayed
absorption peaks at 266 and 308 nm, which are
associated with octahedrally coordinated Mo6+ and arise
due to the Mo-O and V-O charge-transfer absorptions in
the heteropoly cage. These two absorption peaks
appeared in the solid-state UV-vis spectra of the catalyst,
since pure ZrO2 shows no UV absorption peak; therefore,
these results indicated that primary Keggin structure has
3.2. Catalytic activity
Since heterogeneous catalysts are recoverable, hence,
heterogenization of homogenous catalysts is of great
interest. Therefore, we decided to immobilize PVMo on
zirconia nanoparticles, and investigate its catalytic activity
in the epoxidation of alkenes with H2O2 under agitation
with magnetic stirring (MS) and under ultrasonic irradia-
tion (US).

592
H. Salavati et al. / C. R. Chimie 14 (2011) 588–596
Table 1
Epoxidation of olefins with H2O2 catalyzed by PVMo–ZrO2 under reflux conditions.a
Entry Substrate
Products
Time Conversion Epoxide
TOF
(h)
(%)b,c
Selectivity (%)b (hꢀ1
)
[
[TD$INLE]
OH
OH
1
2
10
70
80
73
24.5
22.7
O
]
[TD$INLE]
OH
10
65
O
O
[
[TD$INLE]
O
3
10
48
59
16.8
O
[
[TD$INLE]
85d
31.5
O
4
10
90
O
H
[
[TD$INLE]
85e
30.8
O
5
10
88
O
CH3
[
[TD$INLE]
42f
15.8
O
6
10
45
O
OH
[
[TD$INLE]
O
7
8
10
10
28
58
45g
46h
9.8
OH
]
[TD$INLE]
O
20.3
OH
a
b
c
d
e
f
Reaction conditions: olefin (1 mmol), catalyst (2.86
Based on the starting olefin.
mmol), H2O2 (1 mL), CH3CN (5 mL).
GC yield.
13.5% benzaldehyde was produced.
13% acetophenone was detected as by product.
16% verbenone and 10% verbenol were produced.
12% alcohol was produced.
g
h
31% alcohol was detected.
3.2.1. Alkene epoxidation with H2O2 catalyzed by PVMo–ZrO2
under reflux conditions
further progress was observed (Table 1). The results
showed that the conversion was 70% with 80% epoxide
selectivity. Epoxidation of cyclohexene showed 65%
conversion and the epoxide selectivity was 73%, and allylic
oxidation products (cyclohexene-1-one and cyclohexene-
First, the ability of the prepared catalyst, PVMo-ZrO2,
was investigated in the epoxidation of cyclooctene with
H2O2 in acetonitrile. The reactions were continued until no

H. Salavati et al. / C. R. Chimie 14 (2011) 588–596
593
Table 2
Epoxidation of olefins with H2O2 catalyzed by PVMo–ZrO2 under ultrasonic irradiation.a
Entry Substrate
Products
Time
Conversion Epoxide
TOF
(min) (%)b,c
Selectivity (%)b (hꢀ1
)
[
[TD$INLE]
OH
OH
1
2
40
40
93
97
98
493
530
O
]
[TD$INLE]
OH
100
O
O
[
[TD$INLE]
O
3
40
75
78
397
O
[
[TD$INLE]
90d
530
O
4
40
100
O
H
[
[TD$INLE]
89e
530
O
5
40
100
O
CH3
[
[TD$INLE]
75f
424
O
6
40
80
O
OH
[
[TD$INLE]
O
7
8
40
40
50
85
58g
82h
265
450
OH
]
[TD$INLE]
O
OH
a
b
c
d
e
f
Reaction conditions: olefin (1 mmol), catalyst (2.86
Based on the starting olefin.
mmol), H2O2 (1 mL), CH3CN (5 mL).
GC yield.
10% benzaldehyde was produced.
11% acetophenone was detected as by product.
20% verbenone and 11% verbenol were produced.
21% alcohol was produced.
g
h
15% alcohol was detected.
1-ol) were detected in the reaction mixture. In the case of
indene, styrene and -methyl styrene, the corresponding
epoxides were obtained in 48, 90 and 88% epoxide
selectivity. In the oxidation of -pinene, the major product
was -pineneoxide, while verbenone and verbenol were
produced as minor products. Oxidation of linear alkenes
such as 1-octene and 1-dodecene was accompanied by
allylic oxidation. A blank experiment in the absence of the
catalyst showed only small amounts of products in the
oxidation of cyclooctene with H2O2.
a
a
a

594
H. Salavati et al. / C. R. Chimie 14 (2011) 588–596
Table 3
Epoxidation of olefins with H2O2 (30%) catalyzed by homogeneous PVMo under reflux conditions.a
Entry Substrate
Products
Time Conversion Epoxide Selectivity TOF
(h)
(%)b,c
(%)b
(hꢀ1
)
[
[TD$INLE]
OH
OH
1
2
20
55
95
9.6
O
]
[TD$INLE]
OH
20
44
85
7.7
O
O
[
[TD$INLE]
O
3
20
35
49
6.1
O
[
[TD$INLE]
O
4
20
43
29
7.5
O
H
[
[TD$INLE]
O
5
20
27
42
4.7
O
CH3
[
[TD$INLE]
O
6
20
20
52
3.3
O
OH
[
[TD$INLE]
O
7
8
20
20
26
30
58
31
4.5
5.2
OH
]
[TD$INLE]
O
OH
a
Reaction conditions: olefin (1 mmol), catalyst (2.86
GC yield based on the starting olefin.
mmol), H2O2 (1 mL), CH3CN (5 mL).
b
3.2.2. Alkene epoxidation with H2O2 catalyzed by PVMo–ZrO2
under ultrasonic irradiation
times and improved the yields and products selectivities.
The system under ultrasonic irradiation showed a good
catalytic activity in the oxidation of linear alkenes such as
1-octene and 1-dodecene.
The power of ultrasound is a very important parameter
and also has a great influence on the phenomena of
acoustic cavitation and efficiency of ultrasound treatment.
Fig. 5 shows the effect of irradiation power on the
epoxidation of cyclooctene, which indicates that increas-
As mentioned in the previous works, ultrasonic
irradiation can be used as an efficient tool to influence
the product yield and selectivity [10,11]. Therefore, we
decided to investigate the effect of ultrasonic waves on the
epoxidation of different alkenes with H2O2 catalyzed by
PVMo–ZrO2. As shown in Table 2, application of ultrasonic
waves in this catalytic system has reduced the reaction

[
[()TD$FIG]
H. Salavati et al. / C. R. Chimie 14 (2011) 588–596
595
100
90
80
70
60
50
40
30
20
10
0
Epoxide Selectivity (%)
Conversion (%)
20
40
60
80
100
Fig. 6. Comparison of Ultrasonic irradiation and magnetic agitation in the
Ultrasound intensity
oxidation of cyclooctene with H2O2 catalyzed by PVMo–ZrO2.
Fig. 5. The effect of ultrasonic irradiation intensity on the oxidation of
cyclooctene with H2O2 catalyzed by PVMo–ZrO2.
the reaction can be also accelerated under ultrasonic
irradiation.
ing of ultrasound power will improve the extent of
oxidation and the highest conversion, was observed at a
power of 400 W.
Fig. 6 comprises systems under ultrasonic irradiation
and under agitation with magnetic stirring, which
indicates that the catalytic activity of PVMo–ZrO2 catalyst
has been enhanced by ultrasonic irradiation.
The blank experiments in the absence of catalyst
showed that ultrasonic irradiation has poor ability to
epoxidize the alkenes with hydrogen peroxide.
In order to show the effect of ultrasonic irradiation on
the catalytic activity enhancement, the particle size
distribution of the catalysts was determined before and
after sonication. The results showed that the catalyst
agglomerates break-up during the sonication process. It
seems that a part of ultrasonic irradiation effect is due to
this phenomenon. To stress this point, the catalytic activity
In order to show the effect of support on the catalytic
activity, all reactions were repeated in the presence of
homogeneous PVMo catalyst and under the same reaction
conditions. It is clear from Tables 1 and 3 that the catalytic
activity of PVMo–ZrO2 was much higher than that of
unsupported heteropolyanion. The conversions, selectiv-
ities and TOFs are higher for heterogeneous PVMo–ZrO2 in
comparison with the homogeneous one. Therefore, the
catalytic activity increases by dispersing of the catalyst on
the ZrO2. On the other hand, the ability of ZrO2, as catalyst,
was checked in the oxidation of cyclooctene with H2O2.
The obtained results showed that ZrO2 has poor ability to
catalyze the epoxidation of cyclooctene and the amount of
epoxide was less than 3%.
3.2.3. Catalyst reuse and stability
The stability of the supported catalyst was monitored
using multiple sequential oxidation of cyclooctene with
hydrogen peroxide under reflux or ultrasonic irradiation.
For each of the repeated reactions, the catalyst was
recovered, washed thoroughly with acetonitrile and 1,2-
dichloroethane, successively, and dried before being used
with fresh cyclooctene and hydrogen peroxide. In both
cases, the catalysts were consecutively reused four
consecutive times (Table 4). Addition of fresh alkene and
oxidant to the filtrates showed that the amount of epoxide
is comparable to the blank experiments. These results are
in accordance with the leaching data. The nature of the
of
a sonicated sample catalyst was studied in the
epoxidation of cyclooctene under conventional mechanical
stirring. It was found that the reaction time reduced from
10 h to 6.5 h for epoxidation of cyclooctene. These results
show that in addition to break-up of the agglomerates,
other factors such as thorough mixing of the reactants and
producing of hot spots are the main reasons for catalytic
enhancement by ultrasonic irradiation. On the other hand,
collapse of the produced bubbles results in generation of
high temperatures. As the reaction under mechanical
stirring requires a temperature of about 80 8C, therefore,
Table 4
The results obtained from catalyst reuse and stability in the oxidation of cyclooctene with magnetic stirring (MS) and under ultrasonic irradiation (US).a
Run
Time
Conversion (%)b
Epoxide Selectivity
(%)
V leaching (%)c
MS (h)
US (min)
MS
US
MS
US
MS
US
1
2
3
4
10
10
10
10
40
40
40
40
70
68
68
68
93
92
91
90
80
80
80
80
97
97
97
97
1.0
0.8
0.4
0.0
1.0
0.7
0.5
0.0
a
Reaction conditions: olefin (1 mmol), catalyst (2.86
GC yield based on the starting olefin.
Determined by ICP.
mmol), H2O2 (1 mL), CH3CN (10 mL).
b
c

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