Synthesis of hydrofluorocyclopentanes by vapor-phase catalytic hydrodehalogenation

Article abstract of DOI:10.1016/j.jfluchem.2018.06.010

Hydrofluorocyclopentanes (c5-HFCs) were prepared by gas-phase hydrodehalogenation of chlorofluorocyclopentenes (c5-CFOs) over various noble metals catalysts. The activity of the catalysts followed the order Pd > Pt > Rh > Ru, and the halogen atom on the C(sp²) atom exhibited stronger reactivity than the halogen on the C(sp³) atom. Possible mechanisms of the gas-phase hydrodehalogenation of c5-CFOs re proposed herein.

Full text of DOI:10.1016/j.jfluchem.2018.06.010

Accepted Manuscript
Title: Synthesis of hydrofluorocyclopentanes by vapor-phase
catalytic hydrodehalogenation
Authors: Feiyao Qing, Chengping Zhang, Hengdao Quan
PII:
S0022-1139(18)30133-7
DOI:
Reference:
https://doi.org/10.1016/j.jfluchem.2018.06.010
FLUOR 9188
To appear in:
FLUOR
Received date:
Revised date:
Accepted date:
23-3-2018
25-6-2018
28-6-2018
Please cite this article as: Qing F, Zhang C, Quan H, Synthesis of
hydrofluorocyclopentanes by vapor-phase catalytic hydrodehalogenation, Journal of
Fluorine Chemistry (2018), https://doi.org/10.1016/j.jfluchem.2018.06.010
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Synthesis of hydrofluorocyclopentanes by vapor-phase catalytic
hydrodehalogenation
Feiyao Qing,a Chengping Zhang,a Hengdao Quan*b
a Beijing Institute of Technology, 5 South Zhongguancun Street, Haidian District, Beijing,
100081, China
b
National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1
Higashi, Tsukuba, Ibaraki, 305-8565, Japan
* Corresponding author: E-mail: hengdao-quan@aist.go.jp; Tel: 81-298-614196; Fax: 81-
298-614401
Graphical Abstract - Synopsis
Hydrofluorocyclopentanes
(c5-HFCs)
were
prepared
by
gas-phase
hydrodehalogenation of chlorofluorocyclopentenes (c5-CFOs) over various noble metals
catalysts. The activity of the catalysts followed the order Pd > Pt > Rh > Ru, and the
halogen atom on the C(sp2) atom exhibited stronger reactivity than the halogen on the
C(sp3) atom.
Graphical Abstract – Pictogram
F
F
F
ClxF8-x
F
F
H2/Catalyst
R1
R3
H
R2
H
c5-CFOs
c5-HFCs
(x=0, 1, 2 or 3)
R1= H or F
R2= H or F
R3= H or F

Highlights



The synthesis of c5-HFCs by vapor-phase hydrodehalogenation was developed.
The activity of the catalysts followed the order Pd > Pt > Rh > Ru.
The halogen atom on the C(sp2) atom owns stronger reactivity than the C(sp3)
atom.

It was revealed that the possible mechanisms on the C(sp2) atom or the C(sp3)
atom.
Abstract: Hydrofluorocyclopentanes (c5-HFCs) were prepared by gas-phase
hydrodehalogenation of chlorofluorocyclopentenes (c5-CFOs) over various noble metals
catalysts. The activity of the catalysts followed the order Pd > Pt > Rh > Ru, and the
halogen atom on the C(sp2) atom exhibited stronger reactivity than the halogen on the
C(sp3) atom. Possible mechanisms of the gas-phase hydrodehalogenation of c5-CFOs re
proposed herein.
Key words: Hydrofluorocyclopentane, chlorofluorocyclopentene, hydrodehalogenation,
catalysis, green solvent
1. Introduction
To fulfill the Montreal and Kyoto Protocols, which mandated the phasing out of both
ozone depleting substances (ODS) and major greenhouse chlorofluorocarbons (CFCs) [1],
many countries developed CFC alternatives. Cyclic hydrofluorocarbons (c-HFCs) have
zero ozone depleting potential (ODP) and short atmospheric lifetimes, leading to distinct
environmental benefits. Thus, c-HFCs have been considered to be promising alternatives
to hydrochlorofluorocarbons (HCFCs) and HFCs for cleaning applications [2]. For
example, 1,1,2,2,3,3,4-heptafluorocyclopentane (c-HFC-447cccef) has replaced HCFC-
141b and CFC-113 as a next-generation green solvent [3]. With the development of novel
c-HFCs with good performances as cleaning agents, research regarding c-HFCs has
attracted significant interest of researchers in the field of fluorine chemistry.
To date, c-HFCs have been synthesized via the liquid-phase hydrodefluorination of
perfluorocycloolefins (c-PFOs) or direct fluorination of cyclic chlorofluorocarbons (c-
CFCs), in addition to hydrodehalogenation. The liquid-phase hydrodefluorination of c-
PFOs can be performed in the presence of activated hydrogen. Thus, 1,1,2,2,3,3-

hexafluorocyclopentane (c-HFC-456cccff) has been quantitatively synthesized by the
hydrodefluorination of perfluorocyclopentene (c-PFO-1418yyccc) with NaBH4 [4]. In
this method, NaBH4 can absorb moisture from the air, so the operation must be absolutely
anhydrous. This requirement will add to the cost of production of c-HFCs. More
importantly, the reaction requires large amounts of solvent, and it is hard to recycle, which
leads to a significant amount of pollution. In addition, the direct fluorination of c-CFCs
must be activated by fluorination reagents. In a previous study, 1,1,2,2,3,4-
hexafluorocyclobutane (E/Z) was prepared by the fluorination of 1,4,4-
trifluorocyclobutene with F2 or reactive metal fluorides [5]. In this direct fluorination, the
activated fluorination reagents are very dangerous and difficult to prepare. Consequently,
a large amount of fluorinated wastes are be generated. A major product of c-HFC-
447cccff was obtained from the ICH2CF2CF2CF2CH2I with reduced zinc, and a large
amount of solvent was used [6]. In addition, 1,1,2,2,3,3,4,5-octafluorocyclopentane (c-
HFC-438cccee) was synthesized from 1,2-dichloroperfluorocyclopentane and tributyltin
hydride, but the process used would be difficult to industrialize [6]. C-HFC-438cccee
(boiling point of 78 ℃) was also obtained from the hydrodehalogenation of c-PFO-
1418yyccc in the presence of Ru/C, but the by-product c-HFC-447cccef (boiling point of
82.5 ℃) was produced in a 42% yield [7]. The boiling points of the two compounds are
very similar, making them difficult to separate by distillation.
Here,
a
milder and safer method was developed to synthesize
hydrofluorocyclopentanes (c5-HFCs) via vapor-phase catalytic hydrodehalogenation of
chlorofluorocyclopentenes (c5-CFOs). The structures of the c5-HFCs and other
intermediates were confirmed by gas chromatography (GC), gas chromatography-mass
spectrometry (GC-MS),1H nuclear magnetic resonance (NMR), 19F NMR, and 13C NMR.
Furthermore, the activity of the different precious metal catalysts was determined for the
hydrodehalogenation of c5-CFOs for the first time. The reactivity of the halogen atom on
the C(sp2) atom or the C(sp3) atom was also examined. In addition, the mechanisms of
the hydrodehalogenation of c5-CFOs were proposed.
2. Results and discussion
2.1 Synthesis of 1,1,2,2,3-pentafluorocyclopentane (c-HFC-465cceff)
First, 1,2,3-trichloropentafluorocyclopentene (c-CFO-1415xxbcc) was reacted with
hydrogen to generate HFC-465cceff, 3,3,4,4,5-pentafluorocyclopentane (c-HFO-
1445zzecc), 3-chloro-3,4,4,5,5-pentafluorocyclopentene (c-HCFO-1435zzbcc), and 1-
chloro-1,2,2,3,3-pentafluorocyclopentane (c-HCFC-455ccbff) over various noble

catalysts (Table 1).
Table 1. The effect of catalyst on the hydrodehalogenation of c-CFO-1415xxbcc
F F
F F
F F
F F
F F
F
F
F
Cl
F
F
F
F
F
F
F
H2
+
+
+
F
H
F
F
Cl
F
H
F
Cl
Cat.
H
H
H
H
H
H
Cl
Cl
H
H
H
H
H
H
c-CFO-1415xxbcc
c-HCFC-455ccbff
c-HFO-1445zzecc
c-HCFO-1435zzbcc
HFC-465cceff
Yield [%]
Conversion of
c-CFO-
Temperature
Catalysts
c-HFC-
c-HCFC-
455ccbff
[°C]
1415xxbcc [%]
465cceff
1.0%Pd/PAF
1.0%Pd/PAF
1.0%Pt/PAF
1.0%Pt/PAF
1.0%Rh/PAF
1.0%Rh/PAF
1.0%Ru/PAF
1.0%Ru/PAF
150
200
150
200
150
200
150
200
99.4
99.8
95.1
97.8
72.7
85.8
50.8
71.6
42.0
65.6
32.1
46.9
64.5
74.2
30.6
48.8
54.4
30.2
45.7
30.9
7.7
6.5
28.4
22.6
In the hydrodehalogenation of c-CFO-1415xxbcc (Table 1), the activity of the
catalysts followed the order Pd > Pt > Rh > Ru, which is in good agreement with the
literature [8]. These trends can be related to the electronic properties of the respective
metals. The local density of unoccupied states at the Fermi level can be used to
characterize the intrinsic electronic structure of each metal [9]. It measures the number of
quantum states available for bonding reactants and has been previously used to explain
the catalytic activity of group VIII metals [10-13]. As the chemical adsorption ability is
related to the Fermi level, higher Fermi levels in the metal (Pd, Pt, Rh, and Ru) results in
suitable H2 adsorption. Furthermore, higher d band centers result in increased activity of
the metal [14-16]. It is assumed that the organic chlorinated compound is heterolytically

dissociated and adsorbed through the terminal electron-donating chlorine. Thus, higher
density of unoccupied states of the metal result in higher reactivity with the electron-
donor species, and higher activity of the catalyst [17]. When increasing the reaction
temperature, a significant increase of the conversion of c-CFO-1415xxbcc over the
Ru/PAF catalyst was observed. In addition, the yield of c-HFC-465cceff increased with
increasing temperature from 150 to 200 °C in the presence of the same catalyst, while the
yield of c-HCFC-455ccbff decreased with increasing temperature. This became more
significant as the temperature increased, whereas no influence on the supply of hydrogen
to the active centers was observed [18]. The formation of c-HCFC-455ccbff and c-HCFO-
1435zzbcc other than 3H-1,2-dichloropentafluorocyclopentene indicated that
hydrodehalogenation of the chlorine atom at the 1- or 2-position on the C(sp2) atom of c-
CFO-1415xxbcc was easier than that at the 3-position on the C(sp3) atom.
2.2 Synthesis of c-HFC-456cccff
The precursor 1,2-dichlorohexafluorocyclopentene (c-CFO-1416xxccc) was reacted
with hydrogen to produce HFC-456cccff, 4-chloro-1,1,2,2,3,3-hexafluorocyclopentane
(c-HCFC-446dcccf), 1-chloro-3,3,4,4,5,5-hexafluorocyclopentene (c-HCFO-1426xzccc),
and 3,3,4,4,5,5-hexafluorocyclopentene (c-HFO-1436zzccc) over the various catalysts
(Table 2).
Table 2. The effect of catalyst on the hydrodehalogenation of c-CFO-1416xxccc
F F
F F
F F
F F
F F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
H
F
F
H
F
F
Cl
F
F
H
H2
Cat.
+
+
+
Cl
H
Cl Cl
H
H
H
H
H
H
c-HCFO-1426xzccc
c-CFO-1416xxccc
c-HCFC-446dcccf
c-HFO-1436zzccc
HFC-456cccff
Yield [%]
Temper Conver
c-HFO-
c-HFC-
456cccf
f
ature
[°C]
sion
[%]
c-HCFO-
c-HCFC-
Catalysts
1436zzcc
c
1426xzccc
446dcccf
1.0%Pd/PAF 150
1.0%Pd/PAF 200
99.6
99.9
99.3
99.9
0
0
0
0
0
0.5
0
98.9
99.6
90.8
94.2
0
1.0%Pt/PAF
1.0%Pt/PAF
150
200
0.5
0
8.0
4.3

1.0%Rh/PAF 150
1.0%Rh/PAF 200
1.0%Ru/PAF 150
1.0%Ru/PAF 200
81.4
90.8
32.1
43.6
0.3
0
0
0
0
0
0
0
0
0
78.2
87.4
28.6
41.8
0.5
0
In the hydrodehalogenation of c-CFO-1416xxccc (Table 2), the activity of the
catalysts followed the order Pd > Pt > Rh >> Ru. The explanation of the catalytic activity
of the noble metal catalysts in the hydrodehalogenation of c-CFO-1416xxccc is similar
to that of the hydrodehalogenation of c-CFO-1415xxbcc. In addition, when the reaction
temperature was increased, c-CFO-1416xxccc conversion increased, and the yield of c-
HFC-456cccff other than c-HCFC-446dcccf or c-HCFO-1426xzccc also increased. The
formation of c-HFO-1436zzccc and c-HCFO-1426xzccc other than 1,2-dichloro-
1,2,3,4,4,5-hexafluorocyclopentane (c-HCFC-436bbece) or 1,2-dichloro-1,2,3,3,4,5-
hexafluorocyclopentane (c-HCFC-436bbcee) indicated that hydrodehalogenation of the
halogen atom in the 1- or 2-position on the C(sp2) atom of c-CFO-1415xxbcc was easier
than that at the 3- or 4-position on the C(sp3) atom.
2.3 Synthesis of 1,1,2,2,3,4-hexafluorocyclopentane (c-HFC-456cczzf)
A mixture of 1,4-dichlorohexafluorocyclopentene (c-CFO-1416xycbc) and 1,3-
dichlorohexafluorocyclopentene (c-CFO-1416xybcc) was reacted with hydrogen to
produce c-HFC-456cczzf, c-HFC-456cccff, 3-chloro-1,1,2,2,3,4-hexafluorocyclopentane
(c-HCFC-446bccfe), 2-chloro-1,1,2,3,3,4-hexafluorocyclopentane (c-HFC-446bcfec),
1,3,3,4,4,5-hexafluorocyclopentane
(c-HFO-1446yzcce),
1,2,3,3,4,4-
hexafluorocyclopentane (c-HFO-1446yyfcc), and 1,3,3,4,5,5-hexafluorocyclopentane (c-
HFO-1446yzcec) over the various noble metal catalysts (Table 3).
Table 3. The effect of catalyst on the hydrodehalogenation of a mixture of c-CFO-
1416xybcc and c-CFO-1416xybcc
F
F
F
F
F
F
F
F
F
Cl
F
F
F
H
F
H
F
F
F
H
F
F
F
Cl
H2
+
+
+
+
F
F
F
H
F
F
F
F
F
F
F
F
Cat.
H
H
H
H
H
F
F
F
H
H
H
F
Cl
F
Cl
F
c-CFO-1416xycbc
c-CFO-1416xybcc
c-HFO-1446yzcce
c-HFC-456cccff
c-HFC-456cczzf
c-HFO-1446yyfcc
Yield [%]
c-HCFC- c-HFC-
Conversion
[a] [%]
Temperatur
e [°C]
Catalysts
c-HFC-
c-HFC-

446bccfe 446bcfec 456cczzf 456cccff
1.0%Pd/PAF 150
1.0%Pd/PAF 200
99.2
99.8
97.8
98.9
78.2
86.3
24.4
3.2
18.6
4.1
35.7
65.4
29.6
48.3
20.4
26.9
10.7
20.6
8.8
1.0%Pt/PAF
1.0%Pt/PAF
150
200
31.0
10.2
25.4
12.4
20.8
7.1
21.4
7.2
1.0%Rh/PAF 150
1.0%Rh/PAF 200
13.3
8.4
12.5
1.0%Ru/PAF 150
1.0%Ru/PAF 200
46.7
68.3
21.0
13.2
9.6
6.6
8.4
4.9
9.5
15.2
[a] Conversion: Conversion of c-CFO-1416xybcc and c-CFO-1416xybcc.
The results of the hydrodehalogenation of the mixture of c-CFO-1416xycbc and c-
CFO-1416xybcc are listed in Table 3. Temperature significantly increased the conversion
of the c-CFO-1416xycbc and c-CFO-1416xybcc mixture, and the influence of the
catalysts followed the order Pd > Pt > Rh >> Ru. In addition, the yield of HFC-456cczzf
or HFC-456cccff other than c-HCFC-446bccfe or c-HFC-446bcfec increased with
increasing temperature. HFC-456cccff was likely generated due to the isomerization of
c-HFC-456cczzf but could also have been formed due to the hydrodechlorination of c-
CFO-1416xxccc from the isomerizations of c-CFO-1416xycbc and c-CFO-1416xybcc
[19, 20]. On the other hand, HFO-1446yyfcc was likely formed due to the isomerizations
of c-HFO-1446yzcce and c-HFO-1446yzcec [21]. The formation of c-HCFC-446bccfe
and c-HFC-446bcfec other than 2-chloro-1,3,3,4,4,5-hexafluorocyclopentene (c-HCFO-
1426yxcce) or 1-chloro-2,3,3,4,5,5-hexafluorocyclopentene (c-HCFO-1426xycec)
indicated that the hydrodehalogenation of the halogen atom at the 1-position of the C(sp2)
atom of c-CFO-1416xycbc or c-CFO-1416xybcc was easier than that at the 3- or 4-
position of the C(sp3) atom. Considering the difference between hydrodehalogenation of
CFO-1416xxccc and that of the mixture of c-CFO-1416xycbc and c-CFO-1416xybcc, the
conversion in the former was always higher than in the latter case under the same
conditions promoted by Pd, Pt and Rh catalysts (Tables 2 and 3). This indicated that the
hydrodehalogenation of the chlorine from the -CCl=CCl- group is easier than from the -
CCl=CF- group. When the Ru catalyst was used under identical conditions, the

hydrodehalogenation of the chlorine atom from the -CCl=CCl- group is more difficult
than from the -CCl=CF- group.
2.4 Synthesis of HFC-447cccef
The precursor 1-chloroheptafluorocyclopentene (c-CFO-1417xyccc) was reacted
with hydrogen to produce 1,3,3,4,4,5,5-heptafluorocyclopentene (c-HFO-1427yzccc), c-
HFC-447cccef, c-HFC-456cccff, and 1-chloro-2,2,3,3,4,4,5-heptafluorocyclopentane (c-
HCFC-1437dccce) over the different catalysts (Table 4).
Table 4. The effect of the catalysts on the hydrodehalogenation of c-CFO-1417xyccc
F F
F F
F F
F F
F F
F
F
H
F
F
H
F
F
F
F
F
Cl
F
F
F
F
F
F
F
F
F
H
F
F
F
F
H2
Cat.
+
+
+
H
H
H
H
F
H
H
H
F
Cl
c-HCFC-437dccce
c-CFO-1417xyccc
c-HFO-1427yzccc
c-HFC-447cccef
c-HFC-456cccff
Yield [%]
c-HFO-
c-
c-HFC-
c-
HCFC-
Temperatur Conversio
HFC-
Catalysts
e [°C]
n [%]
1427yzcc 447ccce
456ccc 1437dcc
c
f
ff
ce
1.0%Pd/PA
F
150
200
99.9
99.9
1.1
0
92.7
95.2
1.7
3.8
0.4
0.2
1.0%Pd/PA
F
1.0%Pt/PAF 150
1.0%Pt/PAF 200
99.8
99.9
0
0
59.0
64.2
32.3
34.4
8.7
1.2
1.0%Rh/PA
150
96.2
99.8
38.9
0
79.9
85.4
16.6
6.8
7.8
3.4
0.9
F
1.0%Rh/PA
200
0
10.6
1.4
F
1.0%Ru/PA
150
9.7
F

1.0%Ru/PA
F
200
58.4
0
54.5
2.4
0.2
From the results of the hydrodehalogenation of c-CFO-1417xyccc listed in Table 4,
the activity of the catalysts followed the order of Pd > Pt > Rh >> Ru. C-CFO-1417xyccc
exhibited higher conversion at 200 °C compared to 150 °C in the presence of the same
catalyst, while the yield of c-HFC-447cccef or c-HFC-456cccff other than c-HFO-
1427yzccc or ClF7A increased with increasing temperature. The formation of HFO-
1427yzccc other than c-HCFO-1426yxcce, c-HCFO-1426xycec, or 1-chloro-2,3,3,4,4,5-
hexafluorocyclopentene (c-HCFO-1426xycce) indicated that the hydrodehalogenation of
the halogen atom at the 1-position on the C(sp2) atom of c-CFO-1417xyccc was easier
than that at the 3-, 4-, or 5-position on the C(sp3) atom.
2.5 Synthesis of cis-1,1,2,2,3,3,4,5-octafluorocyclopentane (cis-c-HFC-438cccee)
C-PFO-1418yyccc was reacted with hydrogen to produce cis-c-HFC-438cccee and
c-HFC-447cccef over the various catalysts, and the results are listed in Table 5.
Table 5. The effect of catalyst on the hydrogenation of c-PFO-1418yyccc
F F
F F
F F
F F
F
F
F
F
F
F
H
F
F
H
F
F
F
F
F
F
F
F
F
H
H2
Cat.
+
+
F
H
F
F
F
F
H H
c-HFO-1427yzccc
cis-c-HFC-438cccee
c-PFO-1418yyccc
c-HFC-447cccef
Yield [%]
Conversion of
c-PFO-
Temperature
cis-c-HFC-
438cccee
c-HFC-
Catalysts
[°C]
1418yyccc[%]
447cccef
1.0%Pd/PAF
1.0%Pd/PAF
1.0%Pt/PAF
1.0%Pt/PAF
1.0%Rh/PAF
1.0%Rh/PAF
1.0%Ru/PAF
150
200
150
200
150
200
150
83.5
99.8
80.8
95.9
70.2
89.8
48.9
83.1
98.5
64.6
76.4
68.2
86.9
46.7
0.3
0.5
15.4
18.9
1.4
2.3
1.6

1.0%Ru/PAF
200
65.4
63.4
1.9
In the hydrogenation of c-PFO-1418yyccc (Table 5), the activity of the catalysts
under the same reaction conditions followed the order Pd > Pt > Rh >> Ru. In addition,
with increasing reaction temperature, a significant increase of the conversion of c-PFO-
1418yyccc was observed with the same catalyst, and the yield of cis-c-HFC-438cccee or
c-HFC-447cccef also increased. The formation of c-HFO-1427yzccc and c-HFC-
447cccef other than 1,2,3,3,4,4,5-heptafluorocyclopentene (c-HFO-1427yycce) or
1,2,3,3,4,5,5-heptafluorocyclopentene (c-HFO-1427yycec) indicated that the
hydrodehalogenation of the halogen atom at the 1- or 2-position on the C(sp2) atom of
cis-c-HFC-438cccee was easier than at the 3- or 4-position on the C(sp3).
2.6 Reaction mechanism
The hydrodehalogenation of C(sp3)-X (X=Cl or F) can occur via the following
mechanism (Figure 1) [22]: The bond of C(sp3)-X is first attracted by the active metal (M
= Pd, Pt, Ru, or Rh) forming the intermediate complex, then X (Cl or F) was replaced by
a H radical. Consequently, the unstable bond with the metal complex was broken and non-
chloroalkane was produced. Thus, C(sp3)-X was converted into C(sp3)-H via gas-phase
catalytic hydrodehalogenation.
C(sp3)-H
[M]
C(sp3)-[M]-H
HX
C(sp3)-X
M
C(sp3)-[M]-X
H2
2H
Figure 1 The hydrodehalogenation of C(sp3)-X (X=Cl or F)
The hydrodehalogenation of C(sp2)-X (X=Cl or F) can occur via the following
mechanism (Figure 2): First, C(sp2)-X from the -CCl=CF- or -CCl=CCl- group is easily
converted into the olefinic halide -C-=X+ as a stabilized tautomer, and the tautomer -C-
=X+ then reacts with H2 to generate to generate C(sp2)-H via an addition/elimination
mechanism [23]; Second, C(sp2)-H reacts with H2 to produce C(sp3)-H via an addition
reaction.

In the hydrogenation of c-PFO-1418yyccc, the C(sp2)-F group from -CF=CF- cannot
easily form the tautomer -C-=X+ (X=F) in the first step. Meanwhile, the
hydrodehalogenation of C(sp3)-F at the 3- or 4-position cannot occur due to the high
energy of the C-F bond [19]. Thus, the main product is cis-HFC-438cccee originating
from the addition of hydrogen to c-PFO-1418yyccc and the by-product is HFC-447cccef
derived from the hydrodehalogenation of c-PFO-1418yyccc.
HX
C(sp2)-H
H
H
C(sp3)-HX
C(sp3)-H
C(sp2)-X
M
H2
2H
C=X
Figure 2 The hydrodehalogenation of C(sp2)-X (X=Cl or F)
3. Conclusions
In conclusion, a variety of c5-HFCs were synthesized via hydrodehalogenation of
c5-CFOs promoted by various noble metal catalysts with the following order of activity:
Pd > Pt > Rh > Ru. More importantly, the halogen atom on the C(sp2) atom exhibited
stronger reactivity than the halogen on the C(sp3) atom. In addition, possible mechanisms
for the hydrodehalogenation of c5-CFOs on the C(sp2) or C(sp3) atoms were proposed.
The proposed mechanisms explained why the halogen atom on the C(sp2) atom exhibited
stronger reactivity than that on the C(sp3) atom for the hydrodehalogenation of c5-CFOs.
Compared with existing technology, our research provides a milder reaction pathway to
synthesize the c5-HFCs under ambient pressure and relatively low temperatures.
4 Experimental
4.1 Chemicals
The reagents 1-chloro-heptafluorocylopentene (c-CFO-1417xyccc, 99.2%), the
mixture of 1,4-dichlorohexafluorocyclopentene (c-CFO-1416xycbc, 29.7%) and 1,3-
dichlorohexafluorocyclopentene
(c-CFO-1416xybcc,
69.3%),
1,2-
dichlorohexafluorocyclopentene (c-CFO-1416xxccc, 99.5%), 1,2,3-trichloropenta-
fluorocyclopentene (c-CFO-1415xxbcc, 99.2%), and octafluorocyclopentene (c-PFO-

1418yyccc, 99.7%) were synthesized using methods described in the literature [24].
Chloroform-d (CDCl3, 99.8 %), porous AlF3 (PAF, China, Xi’an MCRI), molecular sieve
4A 1/8, PdCl2, PtCl2, RuCl3, and RhCl3 were purchased from J&K Scientific Ltd. (China)
and CCl3F (CFC-11, 99.0+%) was purchased from Synquest Labs, Inc. (USA).
4.2. Instruments
The mass spectrometer used was a GC-MS-QP2010 Ultra (Shimadzu). The column
temperature program used for the GC-MS was: 40 °C for 4 min; 10 °C/min to 230 °C;
hold for 8 min. Both the injection port and thermal conductivity detector were maintained
at 200 °C, and the carrier gas was He introduced at a rate of 10 mL/min.
The gas chromatograph used in this study was a GC-2014S (Shimadzu) with a DB-
VRX capillary column (i.d. 0.32 mm; length 25 m; J & W Scientific Inc.). The column
temperature program was: 40 °C for 4 min; 10 °C/min to 230 °C; hold for 8 min. Both
the injection port and thermal conductivity detector were maintained at 200 °C, and the
carrier gas was He introduced at a rate of 10 mL/min.
19
The F NMR spectra of the intermediates and products during the synthesis were
recorded on a Bruker Avance 400 (400 MHz) NMR with CFC-11 as an internal standard
in CDCl3 at 25 °C. The 13C and 1H NMR spectra of the intermediates and products during
the synthesis were recorded on a Bruker Avance 400 (400 MHz) NMR CDCl3 at 25 °C.
Adistillation tower 1 inch×300 cm, produced by SUS316 was used to rectify various
products and was filled with stainless steel packing.
4.3. Synthetic processes
The synthesis of c5-HFCs was achieved as follows: A reactor tube (3/8 inch×30 cm,
produced by SUS316, hot zone: 10 cm) was filled with 2.5 g of PAF impregnated by a
1.0% palladium solution based on support as a 1.0%Pd/PAF catalyst. Similarly,
1.0%Pt/PAF, 1.0%Ru/PAF, and 1.0%Rh/PAF were prepared [25]. At 150 or 200 °C,
hydrogen at a flow rate of 4 mmol/h and c5-CFOs supplied by a pump at a rate of 4
mmol/h was passed through the reactor for 12 h. The gas from the reaction vessel was
bubbled in water to remove hydrogen chloride. Subsequently, the gas was trapped in a
glass trap soaked in an ethanol/dry ice bath. The product was dried using a 4A molecular
sieve to obtain the organic phase of the product which was then analyzed by GC. The
organic raw material c5-CFO was c-CFO-1415xxbcc, c-CFO-1416xxccc, c-CFO-
1416xycbc and c-CFO-1416xybcc mixture, c-CFO-1417xyccc, and c-PFO-1418yyccc

and the results are shown in Tables 1–5, respectively.
4.4 Analytical results of the raw materials, intermediates, and c5-HFCs
4.4.1 Raw materials
19
13
The GC-MS, F NMR, and C NMR data of the intermediates including c-CFO-
1415xxbcc, c-CFO-1416xxccc, c-CFO-1416xycbc, c-CFO-1416xybcc, c-CFO-
1417xyccc, and c-PFO-1418 were shown in a previous study [25].
4.4.2 Intermediates
1
19
The GC-MS, H NMR, and F NMR data of the intermediates including c-HFO-
1427yzccc, c-HFO-1436zzccc, c-HFO-1446yzecc, c-HFO-1446yzcec, and c-HFO-
1446yyfcc were shown in a previous study [21].
4.4.3 c-HFC-465cceff
F
F
6
F
7
8
4
2
F
10
5
1
F
9
3
H
12
H
11
H
15
H
13
H
14
MS data (m/z): 160 (M+); 159 (M+-H); 139 (M+-HF2); 131 (M+-C2H4); 126(M+-
CH3F); 113 (M+-C2H4F); 100 (M+-C3H5F); 95 (M+-C2H4F2); 69 (M+-C4H5F2); 64 (M+-
C3H4F3); 51 (M+-C4H5F3). 1H NMR data (400 MHz, chloroform-d) δ 2.08 (dm, J = 17.6Hz,
H12, H13, 2H), 2.22 (dm, J = 11.6Hz, H14, H15, 2H), 5.02 (m, H11, 1H). 19F NMR data
(377 MHz, chloroform-d) δ -108.8 (dm, J = 196.04Hz, F9, 1F), -112.2 (dd, J = 248.82Hz,
24.46Hz, F8, 1F), -121.1 (dm, J = 255.98Hz, F6, 1F), -131.1 (dm, J = 254.09Hz, F7, 1F),
-193.1 (m, F10, 1F).
4.4.4 c-HFC-456cccff

F
10
F
12
F
11
5
3
F
9
1
2
F
13
4
H
14
F
8
H
H
6
H
15
7
MS data (m/z): 178 (M+); 159 (M+-F); 139 (M+-HF2); 131 (M+-C2H4F); 126(M+-
CH2F2); 113 (M+-C2H3F2); 108 (M+-CHF3); 95 (M+-C2H2F3); 88 (M+-CH2F4); 77 (M+-
C2HF4); 64 (M+-C3H2F4); 51 (M+-C4H3F4); 39 (M+-C5H3F4); 31 (M+-C4H4F5); 28 (M+-
C3F6); 17 (M+-C4F6). 1H NMR data (400 MHz, chloroform-d) δ 2.39(m, H6, H7, H14 and
H15, 4H). 19F NMR data (377 MHz, chloroform-d) δ -115.09 (s, F8, F9, F12 and F13,
4F), -136.46 (s, F10 and F11, 2F).
4.4.5 c-HFC-456cczzf
F
F
6
F
7
8
4
2
H
10
5
1
F
9
3
H
12
F
11
H
15
H
13
F
14
MS data (m/z): 178 (M+); 159 (M+-F); 139 (M+-HF2); 131 (M+-C2H4F); 126(M+-
CH2F2); 113 (M+-C2H3F2); 100 (M+-C2H4F2); 95 (M+-C2H2F3); 69 (M+-C3H4F3); 64 (M+-
C2H3F4); 51 (M+-C3H4F4). 1H NMR data (400 MHz, chloroform-d) δ 2.53(m, H10, 1H)
2.82(m, H15, 1H), 5.04(m, H12, H13, 2H). 19F NMR data (377 MHz, chloroform-d) δ -
112.7 (dm, J = 154.57Hz, F9, 1F), -116.3 (dd, J = 248.82Hz, 45.24Hz, F8, 1F), -127.2
(dm, J = 105.56Hz, F6, 1F), -133.3 (dm, J = 218.66Hz, F7, 1F), -185.7 (dd, J = 218.66Hz,
34.25Hz, F11, 1F), -209.1 (s, F14 1F).
4.4.6 c-HFC-447cccef
F
F
13
F
14
12
5
3
F
11
1
2
F
15
4
H
6
F
10
F
H
7
H
8
9

MS data (m/z): 196 (M+); 177 (M+-F); 157 (M+-HF2); 131 (M+-C2H3F2); 127(M+-
CF3); 113 (M+-C2H2F3); 100 (M+-C3H3F3); 95 (M+-C2HF4); 82 (M+-C3H2F4); 77 (M+-
C2F5); 64 (M+-C3HF5); 51 (M+-C4H2F5); 46 (M+-C3F6); 31 (M+-C4H3F6); 27 (M+-C3F7);
18 (M+-C5H3F6). 1H NMR data (400 MHz, chloroform-d) δ 2.73 (m, H6, 1H), 2.79 (m,
H7, 1H), 5.06 (dm, J = 50.40 Hz, H8, 1H). 19F NMR data (377 MHz, chloroform-d) δ -
109.32 (dm, J = 247.69 Hz, F15, 1F), -112.55 (dm, J = 249.57 Hz, F14, 1F), -123.70 (dm,
J = 262.39 Hz, F10, 1F), -131.90 (dm, J = 254.48 Hz, F13, 1F), -133.86 (dm, J = 263.52
Hz, F12, 1F), -136.58 (dm, J = 262.51 Hz, F11, 1F), -197.56 (m, F9, 1F). 13C NMR data
(101 MHz, chloroform-d) δ 117.37 (ttm, J = 261.89Hz, 23.94Hz C1, 1C), 114.59 (t-
quartet-m, J = 268.16Hz, 19.12Hz, C4, 1C), 111.83 (t-quintet-m, J = 273.71 Hz, 25.15
Hz, C5, 1C), 85.60 (d-quartet -m, J = 49.09 Hz, 18.99 Hz, C3, 1C), 37.30 (quartet -m, J
= 24.75 Hz, C2, 1C).
4.4.7 cis-c-HFC-438cccee
F
F
10
F
12
11
5
3
F
9
1
2
F
13
4
H
F
6
8
F
15
F
14
H
7
MS data (m/z): 214 (M+); 195 (M+-F); 163 (M+-CHF2); 145 (M+-CF3); 131 (M+-
CH2F3); 118 (M+-HF5); 100 (M+-F6); 95 (M+-C4H2F3); 82 (M+-C3HF5); 69 (M+- M+-CF7);
64 (M+-C3F6); 51 (M+-C4HF6); 44 (M+- C3HF7). 1H NMR data (400 MHz, CDCl3) δ 5.38
(dm, J = 47.2 Hz, H6 and H7, 2H). 19F NMR data (377 MHz, chloroform-d) δ -118.68 (d,
J = 131.0 Hz, F9 and F12, 2F), -130.59 (d, J = 130.8 Hz, F8 and F13, 2F), -129.41 (d, J
13
= 133.46 Hz, F10 and F11, 2F), 223.32 (d, J = 49.01 Hz, F14 and F15, 2F). C NMR
data (101 MHz, CDCl3) δ113.04 (t-quartet-m, J= 261.19Hz, 23.94 Hz, C1 and C4, 2C),
110.76 (t-quintet-m, J = 278.76Hz, 25.25Hz, C5, 1C), 84.70 (d-quintet-m, J = 211.09 Hz,
16.67 Hz, C3, 1C).
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