Fluorination of etheric substrates adsorbed on porous aluminium fluoride by gaseous fluorine

Article abstract of DOI:10.1016/S0022-1139(00)00317-1

A novel fluorination procedure of etheric substrates adsorbed on porous aluminium fluoride (PAF) using gaseous fluorine has been investigated. The reaction of ethyl 1,1,2,2-tetrafluoroethylether 1 and 2-chloro-1,1,2-trifluoroethylmethylether 9 with fluorine proceeds with upto 58% selectivity for α-monofluorinated 1 and 96% selectivity for α-monofluorinated 9. At the same time, charring can be avoided in the fluorination process.

Full text of DOI:10.1016/S0022-1139(00)00317-1

Journal of Fluorine Chemistry 106 (2000) 121±125
Fluorination of etheric substrates adsorbed on porous
aluminium ¯uoride by gaseous ¯uorine
Heng-dao Quana, Masanori Tamurab,1, Junji Murataa, Ren-xiao Gaob, Akira Sekiyab,*
aDepartment for New Refrigerants Research, Research Institute of Innovative Technology for the Earth (RITE), c/o NIMC,
1-1 Higashi, Tsukuba, Ibaraki 305-8565, Japan
bNational Institute of Materials and Chemical Research (NIMC), 1-1 Higashi, Tsukuba, Ibaraki 305-8565, Japan
Received 22 March 2000; received in revised form 9 June 2000; accepted 26 June 2000
Abstract
A novel ¯uorination procedure of etheric substrates adsorbed on porous aluminium ¯uoride (PAF) using gaseous ¯uorine has been
investigated. The reaction of ethyl 1,1,2,2-tetra¯uoroethylether 1 and 2-chloro-1,1,2-tri¯uoroethylmethylether 9 with ¯uorine proceeds with
upto 58% selectivity for a-mono¯uorinated 1 and 96% selectivity for a-mono¯uorinated 9. At the same time, charring can be avoided in the
¯uorination process. # 2000 Elsevier Science S.A. All rights reserved.
Keywords: Porous aluminium ¯uoride; Fluorination; Ethyl 1,1,2,2-tetra¯uoroethylether; 2-chloro-1,1,2-tri¯uoroethylmethylether
1. Introduction
position of carbon chain in starting materials can be attacked
easily by ¯uorine in homogenous phase [8,9].
Some of partly ¯uorinated ethers (FEs) have a lower
ozone depletion potential (ODP) and global warming poten-
tial (GWP) [1]. They will be possible substitutes of CFCs
and HFCs [2±4].
Previously, we reported some results about the ¯uorina-
tion of n-dodecane adsorbed on porous aluminium ¯uoride
(PAF), which is one of porous materials to adsorb substrates,
by gaseous ¯uorine [10].
The substitution of hydrogen atoms in ethers by gaseous
¯uorine is extremely exothermic and uncontrollable. Even
with the re®ned techniques, the use of elemental ¯uorine for
the replacement of individual hydrogen atoms is still rather
limited. The reaction proceeds mainly by a free-radical
mechanism with little or no selectivity, and produces pro-
ducts resulting from the cleavage of C±C bonds of the
organic molecule and recombination of the fragments [5].
Although above disadvantages may partly be overcome
and diminished by using diluted ¯uorine with an inert gas or
dissolving the organic compound in solvents as a heat sink
which do not react with ¯uorine [6,7], it is dif®cult to obtain
products with high selectivity. The non-catalytic ¯uorination
of hydrocarbons is sometimes dif®cult to stop at a certain
stage as some of the partly ¯uorinated products react with
¯uorine faster than the starting materials and also every
We have found PAF can also be used as a support to
adsorb some kinds of etheric substrates in the reaction with
gaseous ¯uorine and afford products with high selectivity,
although the structure of substrates is much different from
that of hydrocarbon. The reaction of ethyl 1,1,2,2-tetra¯uor-
oethylether 1 and 2-chloro-1,1,2-tri¯uoroethylmethylether 9
with gaseous ¯uorine proceeds with upto 58% selectivity
for a-mono¯uorinated 1 and 96% selectivity for a-mono-
¯uorinated 9, and burning is avoided in the reaction success-
fully.
2. Experimental
2.1. Chemicals
The surface area and pore volume of PAF, a-AlF3 and
MgF2 are 75.0, 1.1, 3.9 m2/g and 0.29, 0.01 and 0.02 cm3/g,
respectively. Ethyl 1,1,2,2-tetra¯uoroethylether (purity
> 97:0%) and 2-chloro-1,1,2-tri¯uoroethylmethylether
(purity > 97:0%) were purchased from SynQuest Lab.Inc.,
USA. Fluorine was from Kanto Denka Co., Japan.
* Corresponding author. Tel.: ‡81-298-54-4570; fax: ‡81-298-54-4570.
E-mail addresses: mtamura@home.nimc.go.jp (M. Tamura),
sekiya@nimc.go.jp (A. Sekiya).
1 Co-corresponding author.
0022-1139/00/$ ± see front matter # 2000 Elsevier Science S.A. All rights reserved.
PII: S 0 0 2 2 - 1 1 3 9 ( 0 0 ) 0 0 3 1 7 - 1

122
H.-d. Quan et al. / Journal of Fluorine Chemistry 106 (2000) 121±125
2.2. Instrument
analysed by GC±MS and NMR. The conversion of 1 and
selectivity of products were calculated on the basis of GC
area. The conversion of 1 was 32% and GC showed the
products contain eight components.
The BET surface area and the distribution of pore dia-
meter of PAF were determined by means of low temperature
adsorption of nitrogen using NOVA 1000 (Yuasa Ionics Co.).
The samples were degassed under vacuum at 3508C for 3 h
before measurement.
Compound 1: Unreacted starting material, ethyl 1,1,2,2-
tetra¯uoroethylether was determined by MS and NMR [11].
Compound 2: (1-Fluoroethyl 1,1,2,2-tetra¯uoroethyl-
ether). Compound 3: (2-Fluoroethyl 1,1,2,2-tetra¯uoroethyl-
ether) were new compounds which were obtained as major
products. Their selectivity was 58 and 32%, respectively
(Scheme 1). MS signi®cant peaks of structural importance
and NMR peaks of new compounds are listed. Chemical
1H NMR and 19F NMR spectra were recorded on JNM-
EX270 (JEOL, 270 MHz) at 258C.
FT±IR spectrometer (FT±IR-620, Japan Spectroscopic
Co. Ltd.) was used to determine products auxiliary.
GC±MS was a Hewlett-Packard 5790 series system
equipped with a jet separator for the 5890A GC. The
capillary column was Pora plot Q with 0.32 mm i.d. and
25 m length from J and W Scienti®c Inc. The operation
condition of GC is as follows: column temperature 808C for
2 min and heated for 20 min at a rate of 108C/min; detector
temperature 2008C; carrier gas ꢀ1 mL He/min; split ratio
45:1; sample size 1.2 ml; pressure 50 k Pa.
1
shifts are in ppm from internal (CH3)4Si for H NMR and
from internal CFCl3 for 19F NMR in which positive values
indicate up®eld shifts.
Compound 2: 1-Fluoroethyl 1,1,2,2-tetra¯uoroethylether.
‡
‡
m/e: 163, CH2CHFOCF2CF2H ; 149, CHFOCF2CF2H ;
‡
‡
‡
131, CH2OCF2CF2H ; 101, CF2CF2H ; 47, CHFCH3
NMR peaks:
.
Products were handled in glass and metal vacuum line
system. Amounts and molecular weight of products were
determined by measuring the sample pressure under a
certain volume in the vacuum line.
H1 (3) d 1.59 d,d J1,2 5.0, J1,3 20.4; H2 (1) d 6.09 q,d, J1,2
5.0, J2,3 57.8; H5 (1) d 5.80 t,t, J5,6 53.2; F3 (1) d 18.8 m; F4
(2) d 92.44 m; F6 (2) d 137.83 m.
2.3. Fluorination procedure
Compound 3: 2-Fluoroethyl 1,1,2,2-tetra¯uoroethylether.
‡
A typical procedure for the ¯uorination is as follows.
About 5 g of support was placed in a stainless steel reactor
with 80 cm3 volume and 1 mmol of starting material was
transferred into the reactor. The reactor was cooled to
1968C and 1±3 mmol of gaseous ¯uorine was introduced
into the reactor. The reactor was placed on a bath at about
1008C and allowed to warm up slowly from 100 to 208C
overnight. Unreacted ¯uorine was measured and pumped
out. The products were transferred to a trap ( 1968C) and
their amount and molecular weight were measured using
vacuum line after separation ( 1008C and 1968C). Then
‡
m/e:163, CHFCH2OCF2CF2H ; 145, CH2CH2OCF2CF2H ;
‡
‡
‡
131, CH2OCF2CF2H ; 101, CF2CF2H ; 51, CHF2
NMR peaks:
.
H1 (2) d 4.62 d,t, J1,3 4.2, J1,2 47.1; H3 (2) d 4.20 d,t, J1,3
4.2, J2,3 27.4; H5 (1) d 5.74 t,t, J4,5 3.0, J5,6 53.3; F2 (1) d
225.7 t,t, J1,2 47.3, J2,3 27.5; F4 (2) d 92.44 m; F6 (2) d
137.36 m.
As the amount of other ¯uorination products was small
only the MS spectroscopic date were obtained. Their pos-
sible structures which were determined by studying mass
spectroscopic data are listed as follows.
1
products were analysed by FT±IR, GC±MS and H NMR
and 19F NMR.
3. Results and discussion
Compound 4: 1,1-Di¯uoroethyl 1,1,2,2-tetra¯uoroethy-
‡
‡
3.1. Fluorination of ethyl 1,1,2,2-tetrafluoroethylether (1)
lether. m/e: 167, CF2OCF2CF2H ; 101, CF2CF2H ; 65,
‡
‡
CF2CH3 ; 51, CHF2
Compound 5: 2,2-Di¯uoroethyl 1,1,2,2-tetra¯uoroethy-
.
In a typical run, 1.0 mmol of 1 adsorbed on 5 g of PAF
was ¯uorinated by 1.5 mmol of ¯uorine. The products were
‡
lether. m/e: 181, CF2CH2OCF2CF2H ; 163, CHFCH2OCF2-
Scheme 1. Reaction of ethyl 1,1,2,2-tetrafluoroethylether adsorbed on PAF with F2.

H.-d. Quan et al. / Journal of Fluorine Chemistry 106 (2000) 121±125
123
Scheme 2. Reaction of 2-chloro-1,1,2-trifluoroethylether adsorbed on PAF with F2.
‡
‡
‡
CF2H ; 131, CH2OCF2CF2H ; 101, CF2CF2H ; 65,
‡
Compound 11: 1,1,2,2-Tetra¯uoroethylmethylether. m/e:
‡
‡
‡
‡
CH2CF2H ; 51, CHF2
Compound 6: 1,2-Di¯uoroethyl 1,1,2,2-tetra¯uoroethyl-
.
131, CH2OCF2CF2H ; 101, CF2CF2H ; 81, CH3OCF2 ;
‡
‡
51, CF2H ; 15, CH3
Compound 12: 2-Chloro-1,1,2,2-tetra¯uoroethyl¯uoro-
.
‡
ether. m/e: 181, CHFCHFOCF2CF2H ; 163, CH2CHFO-
‡
‡
‡
‡ ‡
CF2CF2H ; 149, CHFOCF2CF2H ; 101, CF2CF2H ; 65,
‡
methylether. m/e:165, CH2OCF2CF2Cl ; 135, CF2CF2Cl ;
‡
‡
‡
‡
CH2FCHF ; 51, CHF2
Compound 7: 1,2,2-Tri¯uoroethyl 1,1,2,2-tetra¯uoro-
.
99, CFH2OCF2 ; 85, CClF2 ; 33 CH2F .
Compound 13: 2-Chloro-1,1,2-tri¯uoroethyldi¯uoro-
‡
‡
ethylether. m/e: 181, CHFCHFOCF2CF2H ; 149, CHFO-
‡
methylether. m/e: 165, CHF2OCF2CHCl ; 149, CHF2-
‡
‡
‡
‡
‡
‡
‡
CF2CF2H ; 101, CF2CF2H ; 83, CHFCF2H ; 51, CHF2
Compound 8: 1,1,2,2-Tetra¯uoroethyl ¯uoromethyl ether.
.
OCF2CHF ; 117, CF2CHClF ; 67, CHClF ; 51, CHF2
Compound 14: 2-Chloro-1,1,2-tri¯uoroethylchlorome-
.
‡
‡
‡
‡
‡
m/e: 99, (M-F) CH2FOCF2 ; 51, (CHF2 ); 33, (CH2F ).
Above results indicate the reaction of 1 adsorbed on PAF
with gaseous ¯uorine run as shown in Scheme 1 and also a
typical reaction data is listed on the scheme.
thylether. m/e: 147, CH2OCF2CHFCl ; 115, CClH2OCF2 ;
‡
‡
81, CH3OCF2 ; 67, CHClF .
Analytical results indicate the reaction of 9 adsorbed on
PAF with gaseous ¯uorine run as Scheme 2 (including a
typical reaction date).
3.2. Fluorination of 2-chloro-1,1,2-
trifluoroethylmethylether (9)
3.3. Results of fluorination using different support and
ratio of F2/substrate and discussion
Fluorination of 9 was conducted in a similar manner to the
process of ¯uorination of 1. The mixture of ¯uorinated
products was measured by GC±MS and NMR. GC showed
that products consisted of six components. The conversion
of 9 and selectivity of products were calculated on the basis
of GC area. The conversion of 9 was 28%. 2-chloro-1,1,2-
tri¯uoroethyl¯uoromethylether was obtained as the main
product and its selectivity was 96%.
Compound 9: Unreacted starting material, 2-chloro-1,1,2-
tri¯uoroethylmethylether [12].
Compound 10: 2-Chloro-1,1,2-tri¯uoroethyl¯uoromethyl-
ether was determined by studying MS and NMR spectral
data [13].
The results of ¯uorination using different support and
ratio of F2/substrate 1 or 9 are summarised in Tables 1±4.
When 1 and 9 were reacted with ¯uorine gas without PAF
a certain amount of low boiling point products such as CF4
and CHF3 formed and charring occurred as shown in Tables 1
and 3. The result indicates the cleavage of C±C bonds occurs
in the reaction which might result from every carbon atom in
substrates can be attacked by ¯uorine.
On the other hand, when 1 and 9 adsorbed on PAF were
reacted with a certain amount of ¯uorine, formation of a-
mono¯uorinated products was predominant and no charring
occurs. The results can be explained as follows. Around
Ê
30 A size of pore has the largest surface area [10]. Since the
pore diameter of PAF is slightly bigger than the molecular
size of substrates, the molecules of substrates can enter
For other ¯uorination compounds only MS spectroscopic
data were taken because of small amount of sample. Their
possible structure are listed as follows.
Table 1
Effect of different support for fluorination reaction of CH3CH2OCF2CF2H with F2
Experiment number
F2/1
Support
Conversion of 1 (%)a
Selectivity of
CH3CFHOCF2CF2H (%)a
1b
2
3b
4b
0.7
1.5
1.5
1.5
None
PAF
±
32
±
±
58
±
a-AlF3
MgF2
±
±
a Determined by GC (area percent).
b Charring.

124
H.-d. Quan et al. / Journal of Fluorine Chemistry 106 (2000) 121±125
Table 2
Effect of ratio of F2/CH3CH2OCF2CF2H for fluorination reaction
Experiment number
F2/1
Support
Conversion of 1 (%)a
Selectivity of
CH3CFHOCF2CF2H (%)a
1b
2
0.7
1.0
1.5
2.0
3.0
None
PAF
PAF
PAF
PAF
±
4
±
±
3
32
80
21
58
45
±
4
5b
a Determined by GC (area percent).
b Charring.
Table 3
Effect of different support for fluorination reaction of CH3OCF2CHFCl with F2
Experiment number
F2/9
Support
Conversion of 9 (%)a
Selectivity of
CH2FOCF2CHFCl (%)a
1b
2
3b
0.8
1.6
1.5
None
PAF
±
29
21
±
95
±
a-AlF3
a Determined by GC (area percent).
b Charring.
Table 4
Effect of ratio of F2/CH3OCF2CHFCl for fluorination reaction
Experiment number
F2/9
Support
Conversion of 9 (%)a
Selectivity of
CH2FOCF2CHFCl (%)a
1b
2
0.8
0.7
1.0
1.6
2.1
None
PAF
PAF
PAF
PAF
±
4
±
93
96
95
±
3
17
29
±
4
5b
a Determined by GC (area percent).
b Charring.
easily into the pores and are adsorbed on the internal surface
of PAF, which protects the substrates from the attack by
¯uorine and avoids the cleavage of C±C bonds.
From Tables 2 and 4 we ®nd the reaction using PAF as a
support has a selectivity for a-position of the substrate. The
selectivity was 58% for a-mono¯uorinated 1 and 96% for a-
mono¯uorinated 9 which might be attributed that PAF is a
strong Lewis acid and a kind of material with bigger surface
area [14,15].
amount of cleavage on C±O bond. Fluorination of 1 and 9
adsorbed on PAF with gaseous ¯uorine proceeds with a high
selectivity for a-mono¯uorinated substrates compared with
that of neat substrates and substrates adsorbed on a-AlF3 and
MgF2. The selectivity gets to 58% for a-mono¯uorinated 1
and 96% for a-mono¯uorinated 9 when the ratio of F2/
substrate is about 1.5. The selectivity decreases with an
increase of the amount of ¯uorine and burning occurs in the
reaction when the ratio of F2/substrates is more than 3.0.
From these results it was shown that PAF is effective as a
support in the ¯uorination of ethers with gaseous ¯uorine to
afford ¯uorinated ethers without a cleavage of ether bond,
although PAF is a strong Lewis acid.
Acknowledgements
We gratefully acknowledge the support of this investiga-
tion by NEDO (Energy and Industrial Technology Depart-
ment Organization) of Japan.
Above method can be used to prepare FEs but the
mechanistic aspects of elemental ¯uorine for the reaction
of substrates adsorbed on support is not clear by now.
4. Conclusion
References
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¯uorine can be carried out without accompanying serious
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