Synthesis of 1,1,2,2,3,3,4-heptafluorocyclopentane as a new generation of green solvent

Article abstract of DOI:10.1016/j.jfluchem.2015.10.012

1,1,2,2,3,3,4-Heptafluorocyclopentane is a new generation of green solvent. It was synthesized by the liquid-phase fluorination reactions from hexachlorocyclopentadiene to 1-chloroheptafluoro-cyclopentene in the presence of KF in DMF and by the vapor-phase hydrogenation reaction from 1-chloroheptafluorocyclopentene to 1,1,2,2,3,3,4-heptafluorocyclopentane in the presence of Pd-based hydrogenation catalyst. Quantum chemical calculations for the isomers energies using Gaussian09 were conducted to verify the chemical equilibriums between isomers of trichloropentafluorocyclopentene or dichlorohexafluorocyclopentene in the fluorination reactions. Possible mechanisms for 1,1,2,2,3,3,4-heptafluorocyclopentane synthesis were proposed.

Full text of DOI:10.1016/j.jfluchem.2015.10.012

Journal of Fluorine Chemistry 181 (2016) 11–16
Contents lists available at ScienceDirect
Journal of Fluorine Chemistry
journal homepage: www.elsevier.com/locate/fluor
Synthesis of 1,1,2,2,3,3,4-heptafluorocyclopentane
as a new generation of green solvent
b
Chengping Zhang a, Feiyao Qing a, Hengdao Quan b, , Akira Sekiya
*
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 305-8565, Ibaraki, Japan
A R T I C L E I N F O
A B S T R A C T
Article history:
1,1,2,2,3,3,4-Heptafluorocyclopentane is a new generation of green solvent. It was synthesized by the
liquid-phase fluorination reactions from hexachlorocyclopentadiene to 1-chloroheptafluoro-cyclopen-
tene in the presence of KF in DMF and by the vapor-phase hydrogenation reaction from 1-
chloroheptafluorocyclopentene to 1,1,2,2,3,3,4-heptafluorocyclopentane in the presence of Pd-based
hydrogenation catalyst. Quantum chemical calculations for the isomers energies using Gaussian09
were conducted to verify the chemical equilibriums between isomers of trichloropentafluorocyclo-
pentene or dichlorohexafluorocyclopentene in the fluorination reactions. Possible mechanisms for
1,1,2,2,3,3,4-heptafluorocyclopentane synthesis were proposed.
Received 13 August 2015
Received in revised form 20 October 2015
Accepted 23 October 2015
Available online 28 October 2015
Keywords:
1,1,2,2,3,3,4,4,5-Heptafluorocyclopentane
1-Chloroheptafluorocyclopentene
Green solvent
ß 2015 Published by Elsevier B.V.
Fluorination
Hydrogenation
1. Introduction
as follows: short atmospheric lifetime and minimal GWP; non-
flammability, chemical and thermal stability; higher cleaning
In order to fulfill the Montreal Protocol and the Kyoto Protocol,
which try to eliminate the usage of ozone depleting substances
(ODS), 1,1,2-trifluoro-1,2,2-trichloroethane (CFC-113), 1,1,1-
trichloroethane and 1,1-dichloro-1-fluoroethane (HCFC-141b) in
the field of cleaning agent, many countries have promoted
upgrades of substitutes of the solvents. Acceptable alternatives
with zero ozone depletion potential (ODP) value, such as 1,1,1,3,3-
pentafluorobutane (HFC-365mfc), 1,1,1,2,2,3,4,5,5,5-decafluoro-
pentane (HFC-4310mee) and 1,1,1,2,2,3,3,4,4-nonafluoro-4-
methoxybutane (HFE-449s1) have been found for many applica-
tions (Table 1). However, these alternatives have resulted in
greenhouse effect due to large global warming potential (GWP)
and due to long atmospheric life time [1]. Therefore, search for
other suitable alternatives continues.
Ideal substitutes for ODS solvents should have beneficial safety
and excellent properties such as non-flammability, acceptable
toxicity, adequate solvency and high stability. Furthermore, they
should have minimal environmental impact [3]. 1,1,2,2,3,3,4-
heptafluorocyclopentane (F7A) is an alternative that is zero
ozone depleting and possesses many of these desirable attributes
capacity than HFC-4310mee and HFE-449s1; easy-to-use boiling
point (82.5 8C) and higher recyclability; low toxicity [1]. Therefore,
F7A is an ideal substitute for ODS solvents. It has been accepted as a
substitute for HCFC-141b and 1,3-dichloro-1,1,2,2,3-pentafluor-
oethane (HCFC-225cb) in metals, precision and electronics
cleaning [4]. F7A is an environmentally friendly new generation
of green solvent [1].
F7A was synthesized by liquid-phase fluorination reaction and
gas-phase hydrogenation reaction from the starting material like
hexachlorocylopentadiene (HCCPD) or octachlorocyclopentene as
follows: Firstly, HCCPD or octachlorocyclopentene reacted with
the fluorination reagents to generate the intermediate 1,2-
dichlorohexaflurocyclopentene (F6-12). The fluorination reagents
were SbF5 [5,6], SbF3Cl2 [7], SbFxCl5ꢀx (0 < x < 5) [8], a mixture of
SbF3 and SbF3Cl2 [9] or anhydrous hydrogen fluoride in the
presence of chlorine and fluorination catalysts like SbCl5 [10–12],
or catalysts containing bismuth and iron [13]. Secondly, F6-12 was
fluorinated with KF to produce the intermediate 1-chloro-
heptafluorocylopentene (F7-1) [14]. Thirdly, F7-1 was hydroge-
nated to synthesize F7A in the presence of Pd-based hydrogenation
catalyst via gaseous phase [15–18].
The above studies concentrated on how the technical
process could be developed and optimized but neglected the
intermediates such as 1,4,4-trichloropentafluorocyclopentene
*
Corresponding author.
E-mail address: hengdao-quan@aist.go.jp (H. Quan).
http://dx.doi.org/10.1016/j.jfluchem.2015.10.012
0022-1139/ß 2015 Published by Elsevier B.V.

12
C. Zhang et al. / Journal of Fluorine Chemistry 181 (2016) 11–16
Table 1
chlorine was arranged in order from stronger to weaker in the
liquid-phase fluorination of perhalogenated cyclopentene as
follows: –CCl55CCl– > –CClF– > –CCl2– > –CCl55CF–. Quantum
chemical calculations for the isomers energies using Gaussian09
were conducted to verify the chemical equilibriums between the
isomers of intermediates in the fluorination reactions. Based on the
results of our experiments, the mechanisms of the fluorination
reactions from HCCPD to F7-1 in liquid-phase and the hydrogena-
tion reaction from F7-1 to F7A in vapor phase were proposed.
Environmental impact of various acceptable alternatives.
Compound
HFC-365mfc HFC-4310mee HFE-449s1 HCFC-225cb F7A
ODP
0
0
0
4.7b
0.03
5.9b
0
3.4a
Lifetime/year
GWP
8.7b
804b
16.1b
1650b
421b
525b
195a
(100 year)
a
The data is derived from [1].
The data is derived from [2].
b
(F5-144), 1,3,3-trichloropentafluorocyclopentene (F5-133), 1,2,3-
trichloropenta-fluorocyclopentene (F5-123), 1,2,4-trichloropenta-
fluorocyclopentene (F5-124), 1,4-dichlorohexafluorocyclopentene
(F6-14) and 1,3-dichlorohexafluorocyclopentene (F6-13). Until
2008, Yamada reported that a mixture of tetrachlorotetrafluor-
ocyclopentene, F5-124 and F6-12 was fluorinated to give by-
products F6-14 and F6-13, which were treated as wastes to be
removed from crude products [13]. Especially, these literatures
could not provide distinctly the structures of the intermediates.
More importantly, no literature has reported extensively the
synthesis of F7A from HCCPD via multi-step reactions.
Here, we reported comprehensively for the first time the
synthesis of F7A from starting material HCCPD by multi-step
reactions, which were comprised of the liquid-phase fluorination
from HCCPD to F7-1 in the presence of KF in N,N-dimethylmetha-
namide (DMF) and the vapor-phase hydrogenation from F7-1 to
F7A in the presence of Pd-based hydrogenation catalyst
(Scheme 1). We confirmed that the structures of intermediates
by GC, GC–MS, 19F NMR, 13C NMR, etc. The reactivity of various
2. Results and discussion
HCCPD reacted with KF in DMF to produce F5-144, F5-133, F5-
123 and F5-124 at various temperatures. The results are listed in
Table 2.
In the fluorination of HCCPD, the yield of F5-144 decreased with
increasing temperature in the range of 100–150 8C, while the yield
of F5-133 increased with increasing temperature. In addition, the
yield of F5-123 and F5-124 first increased and then decreased with
increasing temperature in the range of 100–150 8C, which was
attributed to that F5-123 and F5-124 transferred into F6-14 and
F6-13 in the advanced fluorination. In addition, the total yield of
F5-144 and F5-133 was far larger than the one of F5-123 and F5-
124, which indicated that the chlorine from –CClF– owned
stronger reactivity than the one from –CCl2– in the fluorination
of HCCPD.
F5-144, F5-133, or mixture of F5-123 and F5-124 reacted with
KF in DMF solution to produce F6-14, F6-13 and F6-12,
respectively, the results are listed in Table 3.
F5-144 reacted with KF in DMF to generate main products such
as F5-133, F6-14 and F6-13. The yield of F5-133 decreased with
increasing temperature ranged 90–130 8C. In the fluorination
process, the existence of F6-14 other than 4,4-dicholrohexafluor-
ocyclopentene showed that the reactivity of sp3-Cl from –CCl2–
was stronger than the one of sp2-Cl from –CCl55CF–. In addition, F5-
133 was formed in the fluorination of F5-144 with KF in the solvent
DMF (seen Table 2), which displayed the isomerization from F5-
144 to F5-133 occurred in the fluorination of HCCPD. And in a
sense, the yield of F5-144 decreased with increasing temperature
in the fluorination of HCCPD due to the isomerization from F5-144
to F5-133 at a higher reaction rate. The mixture of F5-123 and F5-
124 was further fluorinated to produce F6-14, F6-13 and F6-12, the
yield of F6-13 was around two times of that of F6-14.
Cl
Cl
Cl
Cl
Cl
Cl
HCCPD
F
M
D
/
F
K
F
Cl
F
F
F
F
F
F
F
Cl
Cl
F
F
F
F
F
F
F
F
F
F
F
Cl
Cl
F
F
F
Cl
Cl
Cl
Cl
Cl
Cl
F
Cl
F5-144
F5-133
F5-123
F5-124
F5-133 reacted with KF in DMF to generate main products such
as F5-144, F6-14 and F6-13. The yield of F5-144 decreased with
increasing temperature ranged 90–130 8C. The existence of F6-14
other than 4,4-dicholrohexafluorocyclopentene unfolded that the
reactivity of the chlorine from –CCl2– was stronger than the one
from –CCl55CF–. The formation of F5-133 and F5-124 at the
temperature of 90 8C reflected the isomerization from F5-133 to
F5-144, F5-123 and F5-124 in the fluorination process of F5-133.
However, the products F5-123 and F5-124 reacted easily with KF to
be exhausted with increasing temperature. The yield of F6-12
F
F
F
F
F
F
F
F
Cl
F
F
F
F
F
F
F
F
F
F
Cl
Cl
Cl
Cl
Cl
F
F
F6-13
KF/DMF
F6-12
F6-14
K
F
/
D
M
F
F
F
F
F
F
F
Cl
Table 2
F
Temperature impact in the fluorination of hexachlorocyclopentadiene.
F7-1
H2 Pd/C
Temperature [8C]
Yield of
F5-144 [%]a
Yield of
F5-133 [%]a
Yield of F5-123 and
F5-124 [%]a
F
F
F
100
110
120
130
140
150
49.2
16.3
0.4
8.1
18.1
32.0
50.1
67.8
80.8
0.3
2.8
9.6
2.3
2.2
0.6
F
F
F
H
0.0
H
H
F
0.0
F7A
Scheme 1. Synthesis of 1,1,2,2,3,3,4-heptafluorocyclopentane.
0.0
Yield was determined by GC and 19F NMR versus a calibrated internal standard.
a

C. Zhang et al. / Journal of Fluorine Chemistry 181 (2016) 11–16
13
Table 3
Temperature impact in the fluorination of different isomers of trichloropentafluorocyclopentene.
Material
Temperature [8C]
Amount of
F5-144 [%]a
Amount of
F5-133 [%]a
Amount of
F5-123 + F5-124 [%]a
Yield of
F6-14 [%]a
Yield of
F6-13 [%]a
Yield of
F6-12 [%]a
F5-144
90
110
130
90
12.5
10.6
9.1
84.1
67.2
58.9
80.6
7.9
3.4
0.0
0.0
4.3
0.0
9.6
0.0
0.0
F5-144
F5-144
0.0
5.9
12.7
1.7
0.0
F5-133
13.0
9.7
1.9
0.8
0.0
F5-133
110
130
90
0.0
2.1
4.5
0.1
71.2
0.6
2.5
2.0
F5-133
0.0
0.0
80.0
46.1
12.8
0.0
2.3
5.2
F5-123 + F5-124b
F5-123 + F5-124b
F5-123 + F5-124b
0.0
0.0
4.2
9.0
110
130
0.0
0.0
10.7
16.9
22.8
36.5
0.0
0.0
a
Amount and yield were determined by 19F NMR versus a calibrated internal standard, respectively.
F5-123 + F5-124 was comprised of F5-123 (70%) and F5-124 (30%) by 19F NMR.
b
Table 4
Temperature impact in the fluorination of various isomers of dichlorohexafluorocyclopentene.
Material
Temperature [8C]
Amount of F6-14 [%]a
Amount of F6-13 [%]a
Amount of F6-12 [%]a
Yield of F7-1 [%]a
Yield of F8Eb [%]a
F6-14
F6-14
F6-14
F6-13
F6-13
F6-13
F6-12
F6-12
50
80
29.1
30.8
28.6
29.1
30.6
22.3
0.0
66.1
67.4
34.4
70.5
68.6
51.4
0.0
3.8
0.0
0.9
1.1
0.1
0.7
110
50
0.0
4.5
32.5
0.1
0.0
0.3
80
0.0
0.4
0.4
110
50
0.0
4.7
21.6
0.0
98.7
19.7
1.3
110
0.0
0.0
78.8
1.7
a
Amount and yield were determined by 19F NMR versus a calibrated internal standard, respectively.
F8E represented octafluorocyclopentene.
b
increased sharply to 71.2% with the increasing temperature in the
range 90–130 8C.
favorable in the preparation of F7-1. In order to increase the
availability of the starting material HCCPD, fluorination conditions
should be hold in such a way as to produce more F5-133 and F6-12
and to decrease the productions of by-products F8E. According to
the results from our experiment, the fluorination of HCCPD, F5-133
and F6-12 can be controlled at the temperature of, 150 8C, 130 8C
and 110 8C, respectively, which could achieve our purpose
effectively.
The mixture of F5-123 and F5-124 reacted with KF in DMF to
generate main products such as F6-14, F6-13 and F7-1. The yield of
F6-13 increased with increasing temperature ranged 90–130 8C,
which was greater than F6-12 possibly due to the stronger activity
of the chlorine from –CCl55CCl– group compared with the one from
–CClF– group.
F6-14, F6-13 or F6-12 reacted with KF in DMF solution to
produce F7-1 and octafluorocyclopentene (F8E). The results are
listed in Table 4.
F7-1 reacted with hydrogen in the presence of Pd-based catalyst
at different temperatures to produce our target compound F7A as
well as by-products such as 1-chloro-2,2,3,3,4,4,5-heptafluorocy-
clopentane (F7A-1), 1,3,3,4,4,5,5-heptafluorocyclopentene (F7E)
and 1,1,2,2,3,3-hexafluorocyclopentane (F6A) [15].
The quantum chemical calculations for the compounds F5-144,
F5-133, F5-123, F5-124, F6-14, F6-13 and F6-12 using Gaussian09
were conducted. Geometry optimizations were performed at the
RB3LYP/6-311+G(2d, p) level, and the optimized structures were
used for the subsequent calculations of molecular properties. GIAO
nuclear magnetic shielding values were calculated at all atomic
positions at the closed-shell restricted RB3LYP levels of theory
using the 6-311+G(2d, p) basis set. The energies of the compounds
F5-144, F5-133, F5-123, F5-124, F6-14, F6-13 and F6-12 were
obtained under the reaction conditions (KF/DMF, 110 8C), respec-
tively (Table 5).
In the fluorination of F6-14, the yield of F7-1 increased gently
from 0.9% to 4.5% with increasing temperature in the range of 50–
110 8C, while the yield of F8E increased sharply from 0.1% to 32.5%
with increasing temperature in the range of 50–110 8C. The
formation of F6-13 and F6-12 at 50 8C indicated the isomerization
from F6-14 to F6-13 and F6-12 in the fluorination process of F6-14
with KF in the solvent DMF. However, the product F6-12 can react
easily with KF and can be exhausted with increasing temperature.
In the fluorination, the existence of F7-1 other than 4-chlorohepta-
fluorocyclopentene revealed that the reactivity of sp3-Cl from –
CClF– was stronger than the one of sp2-Cl from –CCl55CF–.
In the fluorination of F6-13, the yield of F7-1 increased gently
from 0.3% to 4.7% with increasing temperature in the range of 50–
110 8C, while the yield of F8E increased sharply from 0.1% to 21.6%
with increasing temperature in the same range. The yield of F6-12
maintained zero at temperatures between 50 and 110 8C, which is
properly resulted from that F6-12 reacted easily with KF and can be
exhausted with increasing temperature. In the fluorination, the
existence of F7-1 other than 3-chloroheptafluorocyclopentene
illustrated that the reactivity of sp3-Cl from –CClF– was stronger
than the one of sp2-Cl from –CCl55CF–.
F5-133 has higher energy than F5-123, and the difference is
larger than 5.5 kcal/mol. This leads to the conclusion that the
Table 5
Compound energy calculations using Gaussian09.
Compounds
ESCF/Hartreea
F5-144
F5-133
F5-123
F5-124
F6-14
ꢀ2070.59077091
ꢀ2070.59352292
ꢀ2070.60232192
ꢀ2070.60259146
ꢀ1710.24504538
ꢀ1710.24419985
ꢀ1710.25740780
In the fluorination of F6-12, the yield of F7-1 increased sharply
from 1.3% to 78.6% with increasing temperature in the range of 50–
110 8C, while the yield of F8E increased gently from zero to 1.7% in
the same range of temperature.
In addition, compared with F6-14 and F6-13, F6-12 can be easily
fluorinated to produce more F7-1 other than F8E, which is more
F6-13
F6-12
a
1 Hartree = 627.5095 kcal/mol.

14
C. Zhang et al. / Journal of Fluorine Chemistry 181 (2016) 11–16
isomerization from F5-133 to F5-123 was not
a
chemical
energy. The theoretical value for equilibrium constant (K1)
equilibrium due to the huge difference between F5-133 and
F5-123 in compound energy. In addition, the energy of F5-133
is lower than that of F5-144 by 1.73 kcal/mol, which shows that
F5-133 and F5-144 are in a chemical equilibrium due to the
small difference between F5-144 and F5-133 in compound
from F5-144 to F5-133 is approximately 9.7, which was
calculated as follows: K1 = exp[ꢀ
D
G/(RT)] ꢁ exp[ꢀ
DESCF/(RT)] =
exp[1.727*4184/(8.314*383)] = exp(2.269) = 9.7. On the other
hand, the experimental value for the equilibrium constant
was calculated from the results of F5-144 at the temperature of
KF
N
F
H
F
N
H
N
H
OK
I-1
O
O
Two resonance forms of DMF
Cl
Cl
N
H
Cl
Cl
F
F
Cl
F
Cl
Cl
Cl
Cl
F
Cl
Cl
Cl
Cl
Cl
Cl
Cl
F
2F
Cl
F
OK
F
Cl
Cl
Cl
Cl
I-3
Cl
HCCPD
Cl
Cl
F2-123445
I-2
K
+ C + OH +
N
-Cl
Cl
Cl
Cl
F
F
F
F
F
F
F
F
Cl
Cl
Cl
F
Cl
Cl
F
F
F
Cl
Cl
Rearrangement
F
F
F
Rearrangement
F
F
F
Cl
Cl
F
F
F
F
F
F
F
F
F
Cl
I-4
Cl
I-5
Cl
Cl
I-6
Cl
I-7
F3-13345
-2Cl
-F
-F
F
2F
F
F
-F
F
F
-F
F
F
Cl
Cl
Cl
F
F
F
F
Cl
Cl
Cl
F
F
F
F
F
F
Cl
Cl
F
F
F
F
F
F
F
F
Cl
Cl
F5-123
Cl
F5-133
Cl
F5-144
F5-124
F
F
-Cl
F
F
-Cl
F
F
F
F
F
F
Cl
Cl
Cl
F
F
F
Cl
Cl
F
F
F
F
F
F
F
-Cl
F
F
F
Cl
I-9
Cl
I-8
Cl
I-10
-Cl
F
-F
F
F
F
F
F
F
F
F
F
F
F
Cl
F
Cl
F
Cl
F
F
F
F
F
F
F
F
F
F
-F
F
Rearrangement
F
Cl
F
Cl
F
F
F
F
F
F
F
F
Cl
Cl
F6-12
Cl
F6-14
Cl
I-12
Cl
I-11
F6-13
-Cl
F
-Cl
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
-Cl
-Cl
F
F
Cl
F
F
F
F
F
F
F
F
F
F
Cl
Cl
Cl
F
F8E
I-13
F7-1
I-14
H2
Pd/C
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
H2
F
H
Pd/C
H
H
H
H
-HCl
H2
Pd/C
H
H
H
F
H
F
F
F
-HF
Cl
F
F
F7E
H
F6A
F7A-1
F7A
Scheme 2. The mechanisms of multi-step reactions for preparation of 1,1,2,2,3,3,4-heptafluorocyclopentene.

C. Zhang et al. / Journal of Fluorine Chemistry 181 (2016) 11–16
15
110 8C in Table
2
as follows: K01 ¼ ½F5-133ꢂ=½F5-144ꢂ ¼
DMF, the attack of F anion on F5-144 resulted in F6-14, with Cl
anion ejected as the leaving group; (10) the C55C of F6-14
underwent nucleophilic attack by the incoming F anion to give a
tetrahedral intermediate I-8, which proceeded to the product F6-
13 by elimination of F anion. It comprised 2-addition of F anion to a
strongly deficient C55C bond followed by 5-elimination of F anion,
which was a chemical equilibrium; (11) the C55C of F6-13
underwent nucleophilic attack by the incoming F anion to give a
tetrahedral intermediate I-11, which proceeded to the intermedi-
ate I-12 and the product F6-12 via arrangement of I-11 followed by
elimination of F anion. It comprised 1-addition of F anion to a
strongly deficient C55C bond and transfer from 3-Cl into 2-Cl and
followed by 1-elimination of F anion, which was not a chemical
equilibrium; (12) in the presence of KF in DMF, the attack of F anion
on F5-133 resulted in F6-13, with Cl anion ejected as the leaving
group; (13) the C55C of F5-123 underwent nucleophilic attack by
the incoming F anion to give a tetrahedral intermediate I-9, which
proceeded to the product F6-13 by elimination of Cl anion. It
comprised 2-addition of F anion to a strongly deficient C55C bond
followed by 2-elimination of Cl anion; (14) the C55C of F5-124
underwent nucleophilic attack by the incoming F anion to give a
tetrahedral intermediate I-10, which proceeded to the product F6-
14 by elimination of Cl anion. It comprised 2-addition of F anion to
a strongly deficient C55C bond followed by 2-elimination of Cl
anion; (15) in the presence of KF in DMF, the attack of F anion on
F6-14 resulted in F7-1, with Cl anion ejected as the leaving group;
(16) in the presence of KF in DMF, the attack of F anion on F6-13
resulted in F7-1, with Cl anion ejected as the leaving group; (17)
the C55C of F6-12 underwent nucleophilic attack by the incoming F
anion to give a tetrahedral intermediate I-13, which proceeded
to the product F7-1 by elimination of Cl anion. It comprised 1-
addition of F anion to a strongly deficient C55C bond followed by 1-
elimination of Cl anion; (18) the C55C of F7-1 underwent
nucleophilic attack by the incoming F anion to give a tetrahedral
intermediate I-14, which proceeded to the product F8E by
elimination of Cl anion. It 1-addition of F anion to a strongly
deficient C55C bond followed by 1-elimination of Cl anion; (19) F7-
1 reacted with hydrogen to generate F7A-1 in the presence of Pd-
based catalyst via 1,2-addition; (20) F7A-1 was dehydrochlori-
nated to form F7E; (21) F7E reacted with hydrogen to generate F7A
in the presence of Pd-based catalyst via 1,2-addition; (22) F7A was
hydrodefluorinated to form F6A in the presence of Pd-based
catalyst via hydrodefluorination of –CHF– group [21].
67:2%=10:6% ¼ 6:4. Therefore, the experimental value K01 for
equilibrium constant was not in agreement with the theoretical
value K1, which was probably attributed to shorter reaction time
compared with long enough equilibrium time. Besides, the
energy of F5-123 is larger than that of F5-124 by 0.17 kcal/mol,
which shows that F5-123 and F5-124 are in
equilibrium due to the small difference between F5-123 and
F5-124 in compound energy.
a chemical
F6-12 has lower energy than F6-13, and the difference is larger
than 7 kcal/mol. This leads to the conclusion that the isomerization
from F6-13 to F6-12 was not a chemical equilibrium due to the
huge difference between F6-13 and F6-12 in compound energy. In
addition, the energy of F6-13 is lower than that of F6-14 by
0.53 kcal/mol, which shows that F6-13 and F6-14 are in a chemical
equilibrium due to the small difference between F6-14 and F6-13
in compound energy. The theoretical value for equilibrium
constant (K2) from F6-14 to F6-13 is approximately 2, which
was calculated as follows: K2 = exp[ꢀ
D
G/(RT)] ꢁ exp[ꢀDESCF/
(RT)] = exp[0.53*4184/(8.314*383)] = exp(0.6977) = 2. On the oth-
er hand, the experimental value for the equilibrium constant
was calculated from the results of mixture of F5-123 and
F5-124 at the temperature of 110 8C in Table 2 as follows:
K02 ¼ ½F6-13ꢂ=½F6-14ꢂ ¼ 22:8%=10:7% ¼ 2:1. Therefore, the experi-
mental value K02 for equilibrium constant was in agreement with
the theoretical value K2, which reflected the rationality of our
speculation on the isomerization equilibrium between F6-14 and
F6-13.
Based on the results of our experiments, the possible
mechanisms of multi-step reactions for preparation of F7A were
proposed as follows (Scheme 2): (1) in DMF, the carbonyl carbon
was bonded to a nitrogen, the nitrogen was less electronegative
than the oxygen and was very able to transfer electron density
through resonance to the carbonyl oxygen [19]; (2) KF could be
dissolved in DMF [20] to produce the intermediate I-1, which could
provide F anion and [(DMF)K]+ complex cation; (3) in the presence
of KF in DMF, the C55C of HCCPD underwent nucleophilic attack by
the incoming F anion to give a tetrahedral intermediate I-2 with
two negative charges, which proceeded to the product F2-123445
by elimination of two negative charges followed via formation of
C55C bond during the oxidation-reduction reaction. It comprised
1,4-addition of F anions to a strongly deficient C55C bond followed
by 2,3-elimination of negative charges; (4) the C55C of F2-123445
underwent nucleophilic attack by the incoming F anion to give a
tetrahedral intermediate I-3, which proceeded to the product F3-
13345 by elimination of Cl anion. It comprised 1-addition of F
anion to a strongly deficient C55C bond followed by 3-elimination
of Cl anion; (5) in the presence of KF in DMF, the attack of F anion
on F3-13345 resulted in F5-133, with Cl anion ejected as the
leaving group; (6) the C55C of F5-133 underwent nucleophilic
attack by the incoming F anion to give a tetrahedral intermediate I-
4, which proceeded to the product F5-144 by elimination of F
anion. It comprised 2-addition of F anion to a strongly deficient
C55C bond followed by 5-elimination of F anion. It was a chemical
equilibrium; (7) the C55C of F5-133 underwent nucleophilic attack
by the incoming F anion to give a tetrahedral intermediate I-5,
which proceeded to the intermediate I-6 and the product F5-123
via arrangement of I-5 followed by elimination of Cl anion. It
comprised 1-addition of F anion to a strongly deficient C55C bond
followed by arrangement of 3-Cl and 1-elimination of F anion; (8)
the C55C of F5-123 underwent nucleophilic attack by the incoming
F anion to give a tetrahedral intermediate I-6, which proceeded to
the intermediate I-7 and the product F5-124 via arrangement of I-6
followed by elimination of F anion. It comprised 1-addition of F
anion to a strongly deficient C55C bond and arrangement of 3-Cl
followed by 1-elimination of F anion; (9) in the presence of KF in
3. Conclusions
In conclusion, the synthesis of F7A was studied by liquid-phase
fluorinations followed via gas-phase hydrogenation. The results
from the fluorination experiments showed that various chlorine
were arranged in order from stronger to weaker reactivity in
perhalogenated cyclopentene as follows: –CCl55CCl– > –CClF– > –
CCl2– > –CCl55CF–. Quantum chemical calculations for the isomers
energies using Gaussian09 were conducted to verify the chemical
equilibrium between isomers in the fluorination reactions.
Possible mechanisms for 1,1,2,2,3,3,4-heptafluorocyclopentane
synthesis were proposed.
4. Experimental
4.1. Chemicals
Hexachlorocyclopentadiene (HCCPD) 99.5+% was purchased
from Leap Labchem Co., Ltd. (China). Chloroform-d (CDCl3) at
99.8 atom%D, potassium fluoride 99.0+%, N,N-dimethylformamide
(DMF) 99.8+%, molecular sieve 4A 1/8, 5%Pd/C (unreduced) were

16
C. Zhang et al. / Journal of Fluorine Chemistry 181 (2016) 11–16
purchased from J&K Scientific Ltd. (China). CCl3F (CFC-11) 99.0+%
was purchased from Synquest Labs, Inc. (USA).
equipped with a thermometer and an agitating device. The flask
was dipped in the oil bath and heated to a different temperature.
Then F6-14, F6-13 or F6-12 of 7.32 g (0.03 mol) was added by drops
into the above solution. Under magnetic stirring for 6 h, the
products’ temperature dropped to room temperature, and they
were scrubbed with 100 mL H2O to remove KF, KCl and DMF and
dried with 4A molecular sieve to obtain the organic phase of the
product. The organic phase of the product was detected by 19F
NMR. The results were shown in Table 4.
4.2. Instruments and apparatus
The mass spectrometer was a GC-MS-QP2010 Ultra (Shimadzu).
The column temperature program of GC–MS was as follows: 40 8C
for 4 min; 10 8C/min to 230 8C; hold for 8 min. Both the injection
port and the thermal conductivity detector were maintained at
200 8C, and the carrier gas was He introduced at a rate of 10 mL/
min.
The gas chromatograph was a GC-2010 (Shimadzu) with a
Poraplot Q capillary column (i.d. 0.32 mm; length 25 m; J&W
Scientific Inc.). The column temperature program was as follows:
40 8C for 4 min; 10 8C/min to 230 8C; hold for 8 min. Both the
injection port and the thermal conductivity detector were
maintained at 200 8C, and the carrier gas was He introduced at
a rate of 10 mL/min.
Synthesis of F7A: F7-1 reacted with hydrogen in the presence of
Pd-based catalyst at different temperatures to produce our target
compound F7A [15].
Acknowledgments
We thank Zeon (Japan) for their financial support and thank
Prof. Maxim V. Borzov and Prof. Wanli Nie for their valuable
comments and advices.
19F NMR spectra of the intermediates and products during the
synthesis were recorded on a Bruker AVANCE 400 (400 MHz) NMR
with CFC-11 as internal standards in CDCl3 at 25 8C.
13C NMR spectra 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 8C.
Appendix A. Supplementary data
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.jfluchem.2015.
10.012.
4.3. Synthesis processes
References
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(0.50 mol) and 100 mL of DMF were placed into a 250 mL, three-
necked, round-bottomed flask equipped with a thermometer
and an agitating device. The flask was dipped in the oil bath and
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Synthesis of F6-14, F6-13 and F6-12: KF 3.49 g (0.06 mol) and
20.0 mL of DMF were placed into a 50 mL, three-necked, round-
bottomed flask equipped with a thermometer and an agitating
device. The flask was dipped in the oil bath and heated to a different
temperature. Then F5-144, F5-133 or the mixture of F5-123 (70%)
and F5-124 (30%) of 7.80 g (0.03 mol) was added by drops into the
above solution. Under magnetic stirring for 7 h, the products from
the above system experienced a temperature decrease to room
temperature and were scrubbed with 100 mL H2O to remove KF, KCl
and DMF and dried with 4A molecular sieve to obtain the organic
phase of the product. The organic phase of the product was detected
by 19F NMR. The results were shown in Table 3.
Synthesis of F7-1: KF 3.49 g (0.06 mol) and 20.0 mL of DMF
were placed into a 50 mL, three-necked, round-bottomed flask