Fluorinated olefins and oleum

Article abstract of DOI:10.1016/S0022-1139(03)00005-8

Oleum has some advantages over pure sulfur trioxide and may be successfully used for preparation of beta-sultones from hexafluoropropene, 2H-pentafluoropropene, 6H-perfluoro-1-hexene and perfluoro(propylvinyl) ether (VE). Depending on the reaction conditi

Full text of DOI:10.1016/S0022-1139(03)00005-8

Journal of Fluorine Chemistry 121 (2003) 147–152
Fluorinated olefins and oleum
Yuri Cheburkov*, William M. Lamanna
3M Company, 3M Center, St. Paul, MN 55144, USA
Received 11 November 2002; received in revised form 26 November 2002; accepted 6 December 2002
Abstract
Oleum has some advantages over pure sulfur trioxide and may be successfully used for preparation of beta-sultones from hexafluor-
opropene, 2H-pentafluoropropene, 6H-perfluoro-1-hexene and perfluoro(propylvinyl) ether (VE). Depending on the reaction conditions, the
VE-sultone and tetrafluoroethane-beta-sultone (TFE-sultone) are different from other sultones. They are not stable in the presence of oleum
and the oxidation of –CF2–SO2-group in the sultones leads to some new fluorooxalate derivatives.
# 2003 Elsevier Science B.V. All rights reserved.
Keywords: Fluorinated beta-sultones; Oleum; Fluoroolefins
1. Introduction
Pure monomeric and liquid sulfur trioxide is available from
DuPont company but it should be shipped and stored at a
temperature close to the boiling point of sulfur trioxide
(45 8C) to prevent undesired polymerization.
In contrast to pure sulfur trioxide, the storage and hand-
ling of fuming sulfuric acid (or oleum), which may contain
as much as 67 wt.% of monomeric SO3, requires no tem-
perature control or special containment. Oleum is not sub-
ject to polymer formation on freezing and it may be shipped
and stored at any temperature and thus provides significant
handling and safety advantages over pure sulfur trioxide.
Fluorinated beta-sultones are well documented com-
pounds in fluorine chemistry [1,2]. Many sultones have been
synthesized and used for the preparation of surfactants,
battery electrolytes, alkylating agents and ion exchange
resins. The interest in sultones increased after DuPont com-
mercialized perfluorinated ionomer membranes (NafionTM),
where the linear isomer of tetrafluoroethane-beta-sultone
(TFE-sultone) was used as a source of pendant perfluoroalk-
ylsulfonate groups in Nafion polymer [3]. Successful synth-
esis of fluorinated sultones depends on many conditions but
there is reportedly one critical aspect in this synthesis: only
pure, freshly distilled sulfur trioxide reacts with fluoroolefins
to give sultones. Commercially available inhibited sulfur
trioxide ‘‘Sulfan’’, or solid polymeric sulfur trioxide (trimer),
or even freshly distilled but not dry sulfur trioxide are not
useful for TFE-sultone synthesis because of low yields and
the formation of many by-products. On the other hand, pure
uninhibited sulfur trioxide is difficult to handle because
it readily polymerizes, sometimes even during distillation
if the condenser is too cold or is not thoroughly dried.
Proper methods of sulfur trioxide handling may be found
in a review [2] and in the work of England et al. [4]. Those
methods include the use of sulfur trioxide complexes
with organic solvents or dry box handling of SO3 for dis-
tillation and charging the reactor. The use of organic solvents
or a dry box is impractical for commercial processing.
2. Results and discussion
We investigated the reactions of oleum with hexafluoro-
propene, 2H-pentafluoropropene, 6H-perfluoro-1-hexene
[5], perfluoro(propylvinyl) ether (VE) and tetrafluoroethy-
lene and have found that in most cases oleum may be used
in place of pure sulfur trioxide for the preparation of the
corresponding sultones.
In the case of hexafluoropropene (1a), thereaction with oleum
is fast and slightly exothermic, even at low temperatures
(20 8C), indicating that sulfuric acid promotes the reaction.
The analogous reaction of HFP with freshly distilled sulfur
trioxide is much slower, requiring heating to 100 8C for many
* Corresponding author. Tel: þ1-651-731-1452.
E-mail address: yche28@visi.com (Y. Cheburkov).
0022-1139/03/$ – see front matter # 2003 Elsevier Science B.V. All rights reserved.
doi:10.1016/S0022-1139(03)00005-8

148
Y. Cheburkov, W.M. Lamanna / Journal of Fluorine Chemistry 121 (2003) 147–152
hours [4] to achieve high conversions. Along with the
product sultones (2) and their linear isomers (3), the reac-
tions with oleum always produce fluorosulfuric acid (4) and
many other by-products (5–8). The source of fluorosulfuric
acid may be any reaction that produces hydrogen fluoride,
which is readily scavenged by SO3 to give FSO3H. For
instance, the reaction of concentrated sulfuric acid with
compounds containing difluoromethylene groups adjacent
to oxygen atom (–OCF2–) as in alkylperfluoroalkyl ethers,
perfluoroalkylsulfonates etc, is well known to produce
hydrogen fluoride (fluorosulfuric acid in case of oleum).
Fluorosulfuric acid may react with the fluorinated propenes
1a and 1b to give fluoroalkylfluorosulfates (5a and 5b) and
the products of further transformations of the sulfates like
2H-terafluoropropionyl fluoride (6), 2H-terafluoropropionic
acid (7) and the 2H-terafluoropropionylfluorosulfate (8).
compounds like 12 and 15 containing the CF2–O–SO2
fragments.
The fluorooxalate 14e is the product of sulfuryl fluoride
elimination from the VE-sulfate linear isomer 12e. The
sulfonic acid 13e is probably the product of exchange
between fluorine in 11 and the OH group in sulfuric acid.
The second product of this exchange is fluorosulfuric acid,
HSO3F. The perfluorodiester 15e appears to be a product of
condensation of heptafluoropropylfluorooxalate 14e with the
sultone 9e. Although the mechanistic details are unclear, this
reaction could be viewed as proceeding by the reaction of the
fluorooxalate 14 with fluoride ion to give the corresponding
alkoxide anion followed by nucleophilic ring opening of the
sultone. However, it would be somewhat surprising that this
mechanism could be operative in the presence of concen-
trated sulfuric acid.
We believe that many other fluoroolefins will react with
oleum this same way, with the exception of fluorinated
ethylenes and vinyl ethers, which are investigated in this
work, and probably perfluorovinyl amines [6].
Both TFE-sultone (9d) and VE-sultone (9e) [4,7,8] are
distinct from other fluorinated sultones because of the
presence of a difluoromethylene—sulfurdioxide bond in
the molecule. This structural feature appears to influence
the final products obtained from the reaction of fluorinated
ethylenes and vinyl ethers with oleum. Reaction of perfluor-
o(propylvinyl) ether with oleum gives VE-sultone 9e in high
yield and takes only 2–3 h to complete at 0 8C. A high yield
of the sultone may also be obtained in reactions run at room
temperature. In this case, the reaction exotherm and reaction
time must be controlled in order to prevent further trans-
formations of the sultone product. The reaction is generally
complete in 10 min at room temperature to give the
VE-sultone in 68% yield after quenching. Therefore, sulfu-
ric acid promotes the sultone formation exactly the same
as in the case of HFP-sultone. If the reaction of perfluoro-
(propylvinyl)ether with oleum is not quenched in 10 min and
allowed to run until the exotherm has subsided, there will be
no VE-sultone remaining and four new products are formed:
heptafluoropropyloxycarbonyldifluoromethanesulfonic acid
(13e), heptafluoropropylfluorosulfatodifluoroacetate (12e),
heptafluoropropylfluorooxalate (14e) and the condensation
product of the oxalate with the sultone—perfluorodiester
with sulfonato group in the middle of the molecule (15e).
The main step in this process is probably the oxidation of
carbon–sulfur bond in the sultone 9e followed by isomer-
ization of both 9e and the cyclic sulfate 10e into their linear
isomers 11e and 12e. Though the cyclic sulfate 10 has not
been found in the reaction mixture, its existence as an
intermediate compound is surmised from identification of
In contrast to other known fluorinated beta-sultones, the
reaction of the VE-sultone with just a few drops of triethy-
lamine does not give the sultone linear isomer 11e, but only
its decomposition products, pentafluoropionyl fluoride (16)
and fluorosulfonyldifluoroacetyl fluoride (11d)—the linear
isomer of the TFE-sultone.
The reaction allows preparation of commercially important
fluorosulfonyldifluoroacetylfluoride from any trifluorovinyl
ethers or their mixtures using inexpensive reagents via a
simple procedure.
It is known that when TFE is bubbled through sulfur
trioxide at atmospheric pressure in a moisture-protected
flask, essentially no reaction is observed [4]. In 1969, Russian
chemists described the reaction of TFE-sultone with sulfu-
ric acid to give difluoroacetic and fluorosulfuric acids [9].

Y. Cheburkov, W.M. Lamanna / Journal of Fluorine Chemistry 121 (2003) 147–152
149
They used sulfur trioxide and sulfuric acid independently as
reagents, not as a mixture (oleum) as we report here. In our
hands, TFE reacted with 65% oleum exothermically, even
while bubbling, but no sultone or difluoroacetic acid was
found in the reaction mixture. TFE-sultone, like VE-sultone,
contains the –CF2–SO2– fragment in the four-membered
ring and this is probably why we observe the evidence of
oxidation of the presumed sultone intermediate. The main
reaction products are gases: sulfur dioxide and oxalyldi-
fluoride (14d) as well as its low boiling precursor fluoro-
sulfatodifluoroacetylfluoride (12d). Small amounts of liquid
condensation products were also identified after methanol
quenching, including the methyl diesters (17) and (18). The
sulfate 18 is probably the product of cyclic sulfate 10d ring
opening by XCOCF2OÀ anion.
methane as the reagent gas. A gas chromatograph HP
5890 Series 2 with a J&W Scientific fused silica capillary
column DB 210 (30 m  0:325 mm) with an FID detector
was used for GC analysis. IR spectra were recorded on a
Digilab FTS-40 spectrometer.
3.1. Reaction HFP with oleum
A 100 ml ParrTM reactor was charged with 63.8 g of 65%
oleum (0.52 mol SO3), cooled to À45 8C, slightly evacuated
and charged with 62 g (0.44 mol) liquid HFP 1a from a cold
trap. The reaction mixture was allowed to warm to room
temperature and at 20 8C, a slight exotherm was observed
with a maximum temperature of 56 8C and pressure 8.96 bar
over a 9-min period. The reactor was heated at 42 8C for 6 h
while the mixture was agitated to give 103.8 g of a two-
phase reaction product. The upper organic layer (90.6 g)
was separated, washed with concentrated sulfuric acid to
remove residual SO3 and distilled to give 63.3 g (66%) of
HFP-sultone 2a with bp 47 8C (Lit. [4] bp 46.5 8C). The
sultone 19F and 1H NMR (CFCl3): À73.69 (CF3 ddd), À51.8
(CF 5-fold), À82.3 m and À88.2 q (CF2 ABq). NMR ana-
lysis of higher boiling point fraction (25 g, bp 50–167 8C)
revealed a mixture of CF3CHFCOOH 19F NMR (CFCl3):
À75.47 (CF3 dd), À204.1 (CF dq); CF3CHFCOOSO2F 19F
NMR: À75.13 (CF3 dd), À203.8 (CHF dq) 47.29 (SO2F s)
and HSO3F 19F NMR: 41.74 (SO3F s), 10.28 (H s).
Chlorotrifluoroethylene (CTFE) reacts with oleum in the
same way as tetrafluoroethylene. The main reaction products
are oxalylchloridefluoride and sulfur dioxide. Because two
different halogens are present in CTFE molecule, the reac-
tion mixture is very complex. For instance, for halogenosul-
fatodihalogenoacetic acid halide, we observed three isomers
in the mass spectrum with M212: probably FSO3CFClCOF,
FSO3CF2COCl and ClSO3CF2COF.
In summary, the perfluorosultones with CF2–SO2 frag-
ments in the four-membered ring, like TFE/VE/CTFE-
sultones, react with oleum via carbon–sulfur bond oxidation
to give derivatives of alkylsulfonates and dialkylsulfates.
Most other known fluorinated sultones, like HFP-sultone,
are stable in the presence of concentrated sulfuric acid and
oleum.
3.2. Reaction 2H-pentafluoropropene (PFP) with oleum
PFP 1b (22 g) was bubbled from a cold trap through
20.2 g of 67 wt.% oleum (0.17 mol SO3) in a flask, fitted
with magnetic bar stirrer and two condensers in series at
À8 8C and À78 8C. A slight exotherm was observed during
the addition. The reaction mixture was held at room tem-
perature for 4 h and then purged with nitrogen to sweep
unreacted PFP into the end trap. A total of 18.6 g (0.14 mol)
of PFP was consumed. The reaction mixture (39.8 g) was
distilled on an ACE Glass Inc. concentric tube column to
give 10.3 g (34%) of a mixture of PFP-sultone 2b and its
linear isomer 3b with bp 85–87 8C (Lit. [11] sultone bp
92 8C). The sultone 19F and 1H NMR (CFCl3): À65.31 (CF3
ddd), À70.80 and À83.65 (CF2 ABq), 5.57 (CH m); MS: 213
[(m þ 1)þ 100]; the linear isomer CF3CH(SO2F)COF 19F
3. Experimental details
Analytical data was provided by Specialty Materials
1
Manufacturing Division analytical group at 3 M. The H
and 19F NMR spectra were acquired using Varian UNITY
1
plus 400 FT-NMR spectrometer and include 400 MHz H
and 376 MHz 19F spectra. The samples were placed in an
NMR tube, spiked with small amount CFCl3 and TMS for
1
and H NMR: À67.70 (CF3 m), 63.73 (SO2F dqd), 49.74
1
both 19F and H chemical shifts zero references given in
(COF 5-fold), 5.17 (CH ddq). Also isolated by distilla-
tion was 3.94 g (12%) of the fluorosulphonate 5b with bp
ppm, and spiked with small amount of p-hexafluoroxylene
(p-HFX) for use as a cross integration standard. Use of
p-HFX facilitates the cross-correlation of various fluorine
and proton signal intensities for quantitative purposes [10].
CDCl3 was the solvent for 19F as well as 1H NMR spectro-
scopy, unless otherwise noted. GC/MS analysis was per-
formed using an HP 5890 Series 2 gas chromatograph with a
105 m  0:32 mm Rtx-5 capillary column to introduce the
sample to a Finnigan SSQ-700 mass spectrometer. The
samples were ionized using chemical ionization with
1
92–108 8C CF3CH2CF2OSO2F 19F and H NMR (CFCl3):
À63.19 (CF3 5-fold), À66.27 (CF2 7-fold), 48.10 (SO2F t),
3.08 (CH2 tq); MS: 233 [(m þ 1)þ 16], 213 (20), 133 (100),
113 (76) and 9.7 g HSO3F with bp 165–168 8C.
3.3. Reaction 6H-perfluoro-1-hexene with oleum
The hexene 1c (2.27 g, 8 mmol) and 1.57 g of 65% oleum
(13 mmol SO3) were heated in a sealed glass tube for 13 h at

150
Y. Cheburkov, W.M. Lamanna / Journal of Fluorine Chemistry 121 (2003) 147–152
100 8C to give a two-phase reaction product. The upper
sultone layer (2.69 g) was separated, washed with conc.
sulfuric acid and distilled to yield 2.25 g (77%) sultone 2c
3.6. Reaction of VE with excess oleum and
complete homogenization
with bp 40 8C/13 mm, HCF2 CF2 CF2 CF2 CFeCF2 OSO2
To 42.7 g 65% oleum (0.35 mol SO3) in a flask with
magnetic bar stirrer, reflux condenser at À9 8C and end trap
(À78 8C) was added 50.9 g (0.19 mol) VE at 0 8C. After
addition was complete, the agitated mixture was allowed to
warm to room temperature. An exothermic reaction was
noted after about 10 min, which caused the VE to reflux.
Refluxing continued until the reaction mixture became
homogeneous (in 30 min). Then, the mixture was heated
for 3 h at 50–55 8C to complete collection of 8.6 g sulfur
dioxide in the end trap. The residue was washed two times
by 7 ml portions of conc. H2SO4 to give 55.5 g of a mixture
consisting of four main components (by GC) with 20–26%
of each. Distillation on the ACE Glass Inc. concentric tube
column gave: (1) bp 69.5 8C fluorooxalate 14e with purity
a
b
c
d
f
(cyclic CFe–OSO2) 19F and H NMR (CFCl3): À137.3 (a,
1
CF2 d), À129.2 m and À129.7 (b, CF2 ABq), À121.1 m and
À121.6 m (c, CF2 ABq), À116.8 m and À118.1 m (d, CF2
ABq), À151.5 (e, CF m), À82.55 m and À85.88 m (f, CF2
ABq), 5.94 (CH tt); MS: 363 [(m þ 1)þ 100], 299 (24), 279
(20), 263 (8).
3.4. Reaction perfluoro(propylvinyl) ether (VE)
with oleum
At 0 8C, a mixture of 20.0 g (7.5 mmol) VE with purity
99.9% and 13.77 g of 65% oleum (11 mmol SO3) was stirred
for 2 h, left to heat to room temperature and then heated to
40 8C to melt the bottom crystalline solid sulfuric acid phase
to allow the two layers to be separated. The mixture was
cooled again causing the bottom acid layer to freeze forming
a separate upper liquid organic layer (26.8 g), which was
decanted. Distillation of the decanted phase afforded 19.2 g
(63% yield) of the sultone 9e and 4.94 g of a high boiling
fraction with bp 50–80 8C/2 mm. To remove fuming SO3
impurity, the sultone was washed with 3 g of concentrated
sulfuric acid and re-distilled to give a mixture of the sultone
9e (85.7%) and its linear isomer 11e (6%) with bp 103–
105 8C (Lit. [7] sultone bp 66 8C/180 mm). The sultone
b
c
d
96.9%, FaCOCOOCF2 CF2 CF3 19F NMR (CFCl3): 20.68
(a, FCO s), À89.06 (b, CF2 q), À130.03 (c, CF2 s), À81.77
(d, CF3 t); MS: 261 [(m þ 1)þ 100], 233 (30), 169 (36), 75
(50); IR (neat, KBr, cmÀ1): 1824 (CO), 1868 (COF); (2)
bp 103 8C difluoroacetate 12e with purity 94.9% FaSO2-
b
c
d
e
OCF2 COOCF2 CF2 CF3 19F NMR (neat): 49.48 (a, FSO2
t), À78.18 (b, CF2 d), À87.90 (c, CF2 q), À130.08 (d, CF2 s),
À81.84 (e, CF3 t); MS: 363 [(m þ 1)þ 100], 343 (2), 315
(2), 269 (30), 169 (8), 149 (80); IR (neat, KBr, cmÀ1):
1487 (SO), 1848 (CO); (3) bp 54 8C/3 mm diester 15e
a
b
c
d
e
with purity 94.5% CF3 CF2 CF2 OCOCF2 SO2OCF2 -
CF3 CF2 CF2 OCFdCF2 SO2O (cyclic CFd–OSO2) 19F and
1H NMR (neat): À81.4 (a, CF3 t), À129.41 (b, CF2 s),
À84.44 m and À81.95 5-fold (c, CF2 ABq J ¼ 161:1 Hz),
À88.15 (d, CF 7-fold), À97.52 d and 98.92 t (e, CF2 ABq
J ¼ 150:5 Hz); MS:347[(m þ 1)þ 18], 283(8), 233 (62), 169
COOCF2 CF2 CF3 19F NMR (CFCl3): À81.92 (a, CF3 t),
À130.18 (b, CF2 s), À88.01 (c, CF2 q), À104.72 (d, CF2 t), –
74.65 (e, CF2 t), À87.60 (f, CF2 q), À130.11 (g, CF2 s),
À81.88 (h, CF3 t); MS: 607 [(m þ 1)þ 10), 543 (8), 393
(2), 329 (32), 261 (22); IR (neat, KBr, cmÀ1): 1451 (SO),
1844 (CO); (4) bp 88–89 8C/3 mm sulfonic acid 13e with
a
b
c
e
f
g
h
a
b
c
d
(100); the linear isomer 11e CF3 CF2 CF2 OCOCF2 SO2Fe
19F NMR: À81.40 (a, CF3 t), À129.62 (b, CF2 s), À86.84 (c,
CF2 q), À104.29 (d, CF2 d), 43.12 (e, SO2F t); MS: 347
[(m þ 1)þ 100], 283 (30), 261 (28), 233 (18), 169 (52). The
high boiling material (4.94 g) is a mixture with the main
components: sulfonic acid 13e (see MS and NMR in the
experiment in Section 3.6) and HSO3F.
a
b
c
d
purity (NMR) 97% CF3 CF2 CF2 OCOCF2 SO3H 19F
and 1H NMR: À81.30 (a, CF3 t), À129.38 (b, CF2 s),
À86.89 (c, CF2 q), À106.98 (d, CF2 s), 7.70 (OH);
MS: 345 [(m þ 1)þ 8], 343 [(m À 1)þ 100], 261 (2), 249
(8); IR (neat, KBr, cmÀ1): 1399 (SO), 1835 (CO), 2100–
3400 (OH).
3.5. Interrupted reaction perfluoro(propylvinyl)
ether (VE) with oleum
3.7. Fluorosulfonyldifluoroacetyl fluoride from
VE-sultone
At room temperature, 13.3 g (50 mmol) VE was carefully
added to 6.24 g 65% oleum (51 mmol SO3) trying not to mix
layers. While stirring, an exothermic reaction ensued caus-
ing the vinyl ether to boil and reflux. Boiling subsided in
10 min though the exothermic reaction continued and the
reaction mixture formed two layers. The mixture was cooled
to 0 8C, the bottom sulfuric acid phase (2.34 g) was sepa-
rated, the upper sultone layer was washed two times with
two 2-ml portions of concentrated sulfuric acid to obtain
16 g of crude VE-sultone 9e. Distillation of the product with
a few not removed drops of H2SO4 gave 11.9 g (69%) of the
VE-sultone with bp 98–105 8C.
To chilled and solid VE-sultone (7.0 g with purity 86%,
17 mmol) in a flask with magnetic bar stirrer, condenser
at –22 8C and the end trap at À78 8C was added three drops
(0.028 g) triethylamine. Immediate melting and a gas evolu-
tion were observed. In approximately 1.5 h, after gas evolu-
tion ceased, three more drops of triethylamine was added
and the reaction continued with reflux for three more hours.
Perfluoropropionyl fluoride 16 (2.42 g, 84% yield) was
collected in the end trap. Following this, distillation of
the residue in the reactor gave 2.85 g (80% yield) fluoride
11d with bp 24–31 8C and purity (GC) 88% (see NMR and
MS in the experiment in Section 3.9).

Y. Cheburkov, W.M. Lamanna / Journal of Fluorine Chemistry 121 (2003) 147–152
151
3.8. Reaction TFE with oleum in open system
bp 155–172 8C. The fraction with a bp of 96–100 8C was
treated with methanol to yield a mixture of two diesters
(NMR, wt.%): 69.5% SO3(CF2COOCH3)2 and 12.8%
SO2(OCF2COOCH3)2 (NMR and MS see in the experiment
in Section 3.8). The main products of the reaction of
TFE with oleum and yields are: oxalyldifluoride (COF)2
25%, fluorosulfonyldifluoroacetyl fluoride FSO2CF2COF
3%, fluorosulfatodifluoroacetyl fluoride FSO2OCF2COF
3% and also difluoride FCOCF2SO2OCF2COF and sulfate
(FCOCF2)2SO4 (identified as dimethyl esters 17 and 18) 3%.
TFE from a cylinder was bubbled through 14.0 g 67%
oleum (117 mmol SO3) in a two-neck flask equipped with a
magnetic stir bar, a condenser at À8 8C and an end trap
(À78 8C). The slightly exothermic reaction with TFE ended
in approximately 5 h and 7.8 g (78 mmol) of TFE was
consumed to give a clear liquid in the reactor and 4.85 g
of low boilers (mainly SO2 according to FTIR) in the end
trap. The clear liquid was distilled under vacuum up to
70 8C/25 mmHg to give a distillate that was in turn com-
bined and treated with methanol at À20 8C, washed with
water and dried to yield 2.16 g of mixed methyl esters.
The main component of the mixture was dimethyloxalate
(COOCH3)2 (GC 73%). The other compounds identified
were known [4] methylfluorosulfonyldifluoroacetate (5.1%)
FSO2CF2COOCH3 19F and 1H NMR: 40.82 (FSO2 t),
À103.75 (CF2 d), 4.09 (CH3 s) and [12] methylfluorosul-
fatodifluoroacetate (1.8%) FSO2OCF2COOCH3 19F and
1H NMR (CFCl3): 48.55 (FSO2 t), À77.72 (CF2 d), 3.93
3.10. Reaction CTFE with oleum in an open system
CTFE (43.4 g) from steel cylinder was bubbled through
50.2 g 65% oleum (0.4 mol SO3) stirred at 5–8 8C in a round
bottom flask equipped with a condenser at 0 8C and an end
trap (À78 8C). In 4 h, the CTFE addition was ended after
21.6 g (0.18 mol) CTFE was consumed. Excess CTFE,
sulfur dioxide and low boiling products (15.6 g) collected
in the trap were treated with methanol to give 5.1 g of a
mixture of two esters (NMR wt.%): 60% methyldifluoro-
fluorochloroacetate and 32% dimethyloxalate along with 6%
difluorochloroacetic acid. The clear liquid left in the reactor
was distilled under vacuum to give 37.7 g of distillate
(collected in À78 8C trap) with a bp up to 81 8C/25 mm
and 32.6 g of non-distilled residue. Re-distillation using an
Ace Glass concentric tube column gave a low boiling
fraction comprising SO2 (in the trap) and 2.44 g of oxalyl-
chloridefluoride [13] with a bp 23–27 8C and purity 88%,
MS (CCl4): 111 [(m þ 1)þ 24), 75 (100). The following
impurities were detected (GC/MS); 1.8% (COF)2, 4.8%
SO2 and 4.8% fluorosulfatofluorochloroacetylfluoride
FSO3CFClCOF or isomers. Continuation of the distillation
gave a 7.0 g fraction with a bp of 74–89 8C and 18.7 g of a
mixture of chloro- and fluoro-sulfonic acids with a bp of
145–165 8C. GC/MS analysis of the fraction with bp 74–
89 8C showed that it consisted of: 21% of a compound with
M132 (possibly CF2ClCOF/isomer), 3.5% of compound
with M196 (possibly FSO2CFClCOF/isomers) and 27%
of three isomeric compounds with M212 (possibly FSO3-
CFClCOF and isomers).
a
(CH3 s) and also diester 17 (3.7%) CH3OCOCF2 SO2-
b
OCF2 COOCH3 19F and 1H NMR: À104.39 (a, CF2 t),
À74.27 (b, CF2 t), 3.89 (CH3 s); MS: 299 [(m þ 1)þ 82],
235 (30), 215 (64), 173 (20), 109 (100) and bis(metho-
xycarbonyldifluoromethyl)sulfate 18 (5.1%) SO2(OCF2-
COOCH3)2 19F and 1H NMR: À77.63 (CF2 s), 3.93 (CH3 s);
MS: 315 [(m þ 1)þ 44], 189 (100).
3.9. Reaction TFE with oleum in pressure reactor
A 100 ml Parr reactor was charged with 32.9 g 67%
oleum (0.27 mol SO3), cooled to 10 8C and briefly evacu-
ated. TFE was then charged at 10–15 8C from a steel
cylinder to 2.8 bar. TFE was periodically added to maintain
the pressure at 2.8 bar. In 4 h after 28.5 g TFE was charged
to the Parr reactor, there was no evidence of reaction. The
reactor was then heated at 60–70 8C for 3 h, slowly vented at
70 8C through two À78 8C traps in series (the second trap
with methanol) and a gas bag at the end to give 38.2 g
fuming liquid in reactor, 20.0 g in the first trap, 0.24 g
CF3COF in the second trap with methanol (identified by
GC as methyltrifluoroacetate) and 0.95 g TFE were col-
lected in the gas bag. A total of 27.1 g (0.27 mol) of TFE was
consumed. The material collected in the first trap consisted
mainly of SO2 (34%) and 32% oxalylfluoride (COF)2 FTIR
(cmÀ1): 1860.7 and 1896.8 (CO) and also 3% fluoride 11d
FSO2CF2COF 19F NMR (CCl4): 24.07 (FCO q), À104.98
(CF2 t), 42.82 (FSO2 q) and 7% fluoride 12d [12]
FSO2OCF2COF 19F NMR (CCl4): 15.14 (FCO t), À77.57
(CF2 dd), 49.94 (FSO2 t); MS: 197 [(m þ 1)þ 60], 149 (100),
Acknowledgements
The authors are grateful to the Specialty Materials
Division Analytical group (T.A. Kestner, S.D. Kromer,
G.J. Lillquist and J.F. Schulz) for MS and NMR spectra
interpretation of complex mixtures of fluorine compounds.
b
c
97 (14); plus 2% difluoride 15d FaCOCF2 SO2OCF2 COFd
19F NMR (CCl4): 25.07 (a, F t), À104.61 (b, CF2 q), À73.80
(c, CF2 t), 15.14 (d, F t); MS: 275 [(m þ 1)þ 20], 161 (36),
133 (36), 97 (100). The clear fuming liquid in reactor was
distilled (with decomposition) to give: 1.26 g fraction
with bp 96–100 8C and 25.6 g fluoro-sulfonic acid with
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