Application of perfluoro(2-propoxypropyl vinyl ether) (PPVE-2) in the synthesis of perfluoro(propyl vinyl ether) (PPVE-1)

Article abstract of DOI:10.1016/j.jfluchem.2020.109508

A novel preparative method for the conversion of n-C₃F₇OCF(CF₃)CF₂OCF = CF₂ (PPVE-2) into n-C₃F₇OCF = CF₂ (PPVE-1) is reported. It includes the catalytic oxidation of PPVE-2 with molecular oxygen to furnish a mixture of carbonyl fluorides which are subjected to alkaline hydrolysis resulting in a mixture of salts. Subsequent thermolysis of those salts give rise to an inseparable mixture of PPVE-1 and perfluoro-2-propoxypropanoyl fluoride. Treatment of this mixture with sodium carbonate allowed to obtain sodium perfluoro-2-propoxypropionate and to isolate PPVE-1. Thermolysis of this sodium salt produced an additional amount of PPVE-1, so that the total conversion of PPVE-2 into PPVE-1 is accomplished in good yields. The reaction conditions, the choice of reagent as well as the course of competitive reactions are discussed.

Full text of DOI:10.1016/j.jfluchem.2020.109508

JournalofFluorineChemistry233(2020)109508
Contents lists available at ScienceDirect
Journal of Fluorine Chemistry
journal homepage: www.elsevier.com/locate/fluor
Application of perfluoro(2-propoxypropyl vinyl ether) (PPVE-2) in the
synthesis of perfluoro(propyl vinyl ether) (PPVE-1)
Sergey N. Tverdomeda,*, Markus E. Hirschbergb,**, Romana Pajkerta, Klaus Hintzerb,
Sean M. Smithc, Gerd-Volker Röschenthalera
a Life Sciences & Chemistry, Jacobs University Bremen, Campus Ring 1, 28759, Bremen, Germany
b 3M AdMD, Dyneon GmbH, Industrieparkstr. 1, 84508, Burgkirchen, Germany
c 3M CRML, MN 55144-1000, St. Paul, United States
A R T I C L E I N F O
A B S T R A C T
Keywords:
A novel preparative method for the conversion of n-C3F7OCF(CF3)CF2OCF = CF2 (PPVE-2) into n-C3F7OCF =
CF2 (PPVE-1) is reported. It includes the catalytic oxidation of PPVE-2 with molecular oxygen to furnish a
mixture of carbonyl fluorides which are subjected to alkaline hydrolysis resulting in a mixture of salts.
Subsequent thermolysis of those salts give rise to an inseparable mixture of PPVE-1 and perfluoro-2-propox-
ypropanoyl fluoride. Treatment of this mixture with sodium carbonate allowed to obtain sodium perfluoro-2-
propoxypropionate and to isolate PPVE-1. Thermolysis of this sodium salt produced an additional amount of
PPVE-1, so that the total conversion of PPVE-2 into PPVE-1 is accomplished in good yields. The reaction con-
ditions, the choice of reagent as well as the course of competitive reactions are discussed.
Perfluorovinyl ethers
Perfluoro(propyl vinyl ether) (PPVE-1)
Perfluoro(2-propoxypropyl vinyl ether) (PPVE-
2)
Thermal decarboxylation
Perfluorcarboxylic acid salts
1. Introduction
produced during the HFPO oligomerization process, which can be iso-
lated from HFPO-dimer acid fluoride by fractional distillation [10a].
Perfluoroalkyl vinyl ethers (RFOCF = CF2; PAVE) are important
building blocks for the synthesis of fluoropolymers (e.g. fluoroplastics
[1,2a b] and fluoroelastomers [2a-c]) via a radical polymerization
process [3]. These fluoropolymers, which are actually perfluoroalkoxy
alkane (PFA) resins, find broad application in industry due to their
unique properties and performance [4]. On a laboratory scale, per-
fluorovinyl ethers are usually prepared from fluoroalkoxide salts and
hexafluoropropylene oxide [5a] as well as by the thermal elimination of
perfluorosulfinic acids [6] and the dehalogenation of dichloro ethers
obtained from perfluoroalkyl hypofluorites with dichloroolefins [7].
However, the pyrolysis of perfluorocarboxylic acids or metal salts re-
mains still the main industrial method to PAVE [5b-c]. One of the most
important representative of this class of monomers is perfluoro(propyl
vinyl ether) (PPVE-1), which is of great importance for the polymer
industry acting as a comonomer in the synthesis of a variety of com-
mercial polymer products [8]. For industrial purposes, PPVE-1 is pre-
pared by the dimerization of hexafluoropropene oxide (HFPO), fol-
lowed by e.g. thermolysis of a mixture of carbonyl fluorides in the
presence of alkali metal carbonate, sulfate or phosphate [9]. Never-
theless, HFPO-trimer acid fluoride is one of the major by-products
These intermediate acid fluorides (HFPO-trimer and -dimer) are con-
verted to the corresponding PPVE-2 [10b] and PPVE-1 [9] after dec-
arboxylation of the precursor salt. Therefore, an efficient and new
methodology is needed for the conversion of PPVE-2 back into PPVE-1,
especially for applied organofluorine chemistry and for fluoropolymer
industry.
In this work, a synthetic strategy to PPVE-1 by the catalytic oxida-
tion of PPVE-2 was demonstrated. Subsequent functionalization and
derivatization of the corresponding oxidation products (without prior
separation) lead to PPVE-1 as the target product.
2. Results and discussion
2.1. Alkaline hydrolysis of a mixture of fluorides 2a – 3a and subsequent
thermolysis of metal salts
Recently, we have demonstrated [11a] that the oxidation of PPVE-2
1 with molecular oxygen catalyzed by V2O5 (5–20 mol%) at 95–97 °C
led to the formation of a mixture of carbonyl fluorides 2a (23 % NMR
yield) and 3a in (61 % NMR yield), as well as to some polymeric by-
⁎ Corresponding author.
⁎⁎ Corresponding author.
E-mail addresses: s.tverdomed@jacobs-university.de (S.N. Tverdomed), mhirschberg@mmm.com (M.E. Hirschberg).
https://doi.org/10.1016/j.jfluchem.2020.109508
Received 10 December 2019; Received in revised form 4 March 2020; Accepted 5 March 2020
Availableonline07March2020
0022-1139/©2020ElsevierB.V.Allrightsreserved.

S.N. Tverdomed, et al.
JournalofFluorineChemistry233(2020)109508
Scheme 1. Oxidation of PPVE-2 1.
3).
products (Scheme 1). The reaction is strongly exothermic, so the tem-
perature was controlled by the rate of addition of oxygen. Fluorides 2a
and 3a could not be separated through distillation, since they seem to
form an azeotropic mixture in a 31 : 69 mol% ratio with a constant
boiling point of 98–99 °C. Subsequent hydrolysis or methanolysis of the
mixture of 2a and 3a showed that the fluoride 2a provides a very un-
stable intermediate, which could be further decarboxylated at room
temperature to form the stable acid 2b and methyl ester 2c (Scheme 2).
Noteworthy, this route has been mentioned in literature for a single
example only [11b]. Hydrolysis of fluoride 3a under those conditions
proceeded in a classical manner to furnish acids 2b – 3b as well as
esters 2с – 3с which were separated by fractional distillation. Fur-
thermore, perfluoro-2-propoxypropionic acid 2b and its ester 2c are
popular synthetic precursors of PPVE-1 [12]. 1,1,2,3,3,3-Hexafluoro-2-
(perfluoropropoxy)propyl carbonofluoridate 2a and 2,2-difluoro-2-
(1,1,2,3,3,3-hexafluoro-2-(perfluoropropoxy)propoxy)acetyl fluoride
3a (in ratio 31 : 69 mol%) reacted smoothly with 4.1 and 2.0 equiva-
lents of potassium hydroxide respectively in a water-methanol solution
at 25 °C to the corresponding potassium salts 4 and 5 in almost quan-
titative yield (98 %) (Scheme 2). The calculation of the required
amount of potassium hydroxide for saponification was carried out se-
parately for 2a and 3a, considering the stoichiometry of each reaction.
The reaction was highly exothermic. Hence, the temperature of the
process was controlled and maintained between 27–29 °C. The total
conversion of 2a – 3a was accomplished by stirring the reaction mixture
vigorously at 50 °C for 16 h. At the end of the process, the pH value
should be around 8.0 – 8.5. Otherwise, the reaction mixture was ti-
trated with 1.0 M methanolic KOH solution to adjust the pH value to
8.5. Afterwards, the solvents were evaporated in vacuo below 50 °C
until a crystalline residue was obtained which was dried in vacuo at 100
°C for 18 h to a constant mass.
The process was conducted within 3.5 h and NMR analysis of the
reaction products showed the target products 6 (δF -81.5, -113, -122,
and -130; 45 mol%; 84 % NMR yield) [13a] and carbonyl fluoride 7 (δF
+27, -80, -81.5, -82, -87, -130, and -131; 55 mol%; 82 % NMR yield)
[13b] as well as traces of fluoride 3 and unidentified decomposition by-
products. The thermal decarboxylation of 4 even in a mixture with 5
proceeded smoothly and regioselectively to the desired PPVE-1 6 (84 %
NMR yield), as already described in the literature [12]. Contrary,
thermolysis of the previously unknown potassium salt 5 proceeded non-
specifically with the formation of carbonyl fluoride 7 (55 mol%) ac-
companied with traces of fluoride 3a. Plausibly, after typical dec-
arboxylation of 5 the intermediate anion could not be stabilized in a
typical manner, namely via elimination of a fluoride anion and forma-
tion of the double bond [9]. Instead under a formal loss of a CF2-group,
fluoride 7 [13b] was formed as the main product. It should be noted,
that we could not find any traces of tetrafluoroethylene (δF -135) [13c]
in the thermolysis products. Moreover, the salt 5 probably interacted
with F− at higher temperature and so the starting carbonyl fluoride 3a
(δF +15, -78, -82, -83, -84, 85, -131, and -148) was detected in 19F
NMR in traces. A similar course of thermolysis of perfluorocarboxylic
acid salts has not previously been reported in literature and was dis-
covered by us for the first time. As already known, carbonyl fluoride 7
is a common precursor in the synthesis of PPVE-1 6 [14]. However, the
separation of 6 and 7 via distillation of the crude product was not ef-
fective and even after three fractional distillations with a Vigreux
column (length: 330 mm, diameter: 25 mm), product 6 contained ca. 12
mol% of 7. Therefore, the crude product, consisting of 6, 7, and traces
of 3a was used in further transformations without isolation of 6.
2.2. Reaction of thermolysis products 6, 7, and 3 with sodium carbonate
and isolation of PPVE-1 6
Alkaline hydrolysis of the mixture of 2a and 3a could also be ef-
fectively conducted in aqueous solution using 4.1 and 2.05 equivalents
of KOH for 2a and 3a, respectively, at room temperature for 14 h. In
this case, 100 % conversion of 2a – 3a was achieved and the potassium
salts 4 and 5 were obtained in quantitative yield. However, in this case
the solvent evaporation was rather difficult due to an undesired foam
formation. In turn, by using a 90 % water-methanol solution the for-
mation of foam was practically not observed. As a result, salts 4 (30 mol
%) and 5 (70 mol%) were produced with a stoichiometric amount of
potassium fluoride. This mixture of potassium salts was heated to
220–240 °C in vacuo (0.7 mbar) and all volatile degradation products,
which were simultaneously formed, were collected at −196 °C (Scheme
It is well-known that perfluorocarbonyl fluorides react smoothly
with sodium carbonate to give the corresponding sodium salts and so-
dium fluoride accompanied by the release of CO2 [8]. PPVE-1 6 could
be obtained by the reaction of fluoride 7 with Na2CO3 or K2CO3 in
dimethyl or diethyl ether of diethylene glycol at 120–140 °C [8,15a] or
without any solvent at 270 °C [15b]. Moreover, no interaction of PPVE-
1 6 with alkali metal carbonates at moderate temperatures was ob-
served. Therefore, the mixture of the thermolysis products 6, 7, and 3a
was reacted with an excess of sodium carbonate in a polar aprotic
solvent under mild conditions. The fluorides 7 and 3a were converted
2

S.N. Tverdomed, et al.
JournalofFluorineChemistry233(2020)109508
Scheme 2. Alkaline hydrolysis and functionalization of a mixture of carbonyl fluorides 2a – 3a.
to the corresponding sodium salts 8 and 9 whereas PPVE-1 6 remained
without any noticeable changes (Scheme 4). Further heating of the
reaction mixture above 70–75 °C allowed to isolate pure PPVE-1 6 (b.p.
36 °C) [16a] in good yield. After evaporation of the solvent, the
remaining sodium salt 8 with traces of 9 was carefully dried at 100 °C in
high-vacuum to a constant mass to form the starting material for the
final thermolysis and converting the entire amount of the starting
PPVE-2 1 to the target PPVE-1 6. The selectivity of saponification of 7
Scheme 3. Thermal decarboxylation of a mixture of sodium salts 4 and 5.
3

S.N. Tverdomed, et al.
JournalofFluorineChemistry233(2020)109508
Scheme 4. The reaction of a mixture of PPVE-1 6, 7, and 3a with Na2CO3 under anhydrous conditions.
Scheme 5. Thermolysis of a mixture of salts 8 and 9 to form PPVE-1 6.
and 3a with sodium carbonate strongly depended both from excess of
reagent and used solvent. The best results were obtained using 210 %
excess of anhydrous Na2CO3 in dry 1,4-dioxane as reaction medium.
The process was carried out by adding a mixture 6, 7, and 3a into a
suspension of Na2CO3 at 25 °C under vigorous stirring. The total con-
version of 7 and 3a was observed after 16 h of mixing at 30 °C. After
heating of the reaction mixture up to 105 °C, unreacted PPVE-1 6 was
distilled off in 57 % yield and in 92 mol% purity (Scheme 4).
crystalline residue suitable for subsequent pyrolysis in high vacuum. In
this case, the residue was viscous and pasty. The substance contained
sodium salt 8 (77 mol%), traces of sodium salt 9, and vast amounts of
not-identified by-products. Therefore, the residue was dissolved in
methanol, 1.0 equivalent of NaOH was added and the whole mixture
was heated up to 50 °C within a few hours. After evaporation of me-
thanol, a solid crystalline residue was obtained. Subsequent drying at
0.7 mbar and 100 °C for 10 h gave the starting material which was
suitable for further vacuum thermolysis. An increase in the amount of
sodium carbonate up to 160 % and conduction the reaction of 6, 7, and
3a in dry MG at 25–35 °C enabled to distill off PPVE-1 6 in 62 % yield
and with 91 mol% purity. After evaporation of the solvent, a viscous
residue was obtained which contained the salts 8 (84 mol%) and 9 (2
mol%). According to 19F NMR spectra, the crude product also contained
a significant amount of unidentified by-products. Transformation of the
crude product into material which is suitable for thermolysis in high
vacuum was also carried out by the interaction of the crude product
with 0.6 equivalents of NaOH at 40 °C in MeOH, followed by distillation
and drying of the crystalline residue at 100 °C / 0.7 mbar for 8 h.
After evaporation of 1,4-dioxane in vacuo and drying the solid re-
sidue at 100 °C and 0.7 mbar for 8 h, 19F NMR analysis showed 92 mol
% content of the sodium salt 8 (δF -82.2, -83.1, -83.4, -87, -128, and
-133) and traces of sodium salt 9 (δF -78, -82.2, -82.4, -83.6, -84, -132,
and -147) as well as some amount of other homologues. In presence of
monoglyme (MG) as solvent and 120 % excess of Na2CO3, the reaction
of a mixture of 6, 7, and 3a was conducted at 27–35 °C for 16 h until the
signal at δF +27 in the reaction mixture disappeared. After heating the
reaction mixture up to 75–80 °C, PPVE-1 6 was distilled off in 64 %
yield and with 90 mol% purity. The evaporation of the solvent and
subsequent drying of the residue in vacuuo at 50 °C did not lead to
4

S.N. Tverdomed, et al.
JournalofFluorineChemistry233(2020)109508
2.3. Thermolysis of a mixture of sodium salts 8 and 9 with additional
formation of PPVE-1 6
obtained in up to 84 % yield. Without separation, the obtained mixture
was saponified with an excess of sodium carbonate in anhydrous 1,4-
dioxane. The first portion of PPVE-1 6 was isolated by distillation in 57
% yield, and the remaining mixture of sodium salts 8 and 9 was sub-
jected to additional thermal decarboxylation in high-vacuum at
220–240 °C to produce additional amount of PPVE-1 6 in 70 % yield.
Referring to the used amount of starting PPVE-2 1, the total yield of
PPVE-1 6 was 55 %. The variables affecting the reactivity and course of
the process as well as the reaction conditions during all synthetic steps
were discussed. The structures of all new compounds were character-
ized and confirmed by NMR spectroscopy. We also planned a special
study of the previously unknown reaction of thermolysis of salt 5 and its
transformation to carbonyl fluoride 7 using several substrates of a si-
milar structure. These results, including the likely mechanism of ther-
molysis, will be reported later in a separate publication.
The previously obtained anhydrous, solid mixture of salts 8 (77–92
mol%), 9 (1–2 mol%), and unidentified mixture of by-products was
decarboxylated under low pressure at 220–240 °C for 2.5 h with si-
multaneous collection of volatile products in a trap cooled to −196 °C.
The crude product was analyzed by NMR spectroscopy which revealed
that the course of thermolysis strongly depended on the method of
preparation of the starting material, namely an excess of Na2CO3 and
solvent (Scheme 5). During the thermolysis of the salt 8 obtained in MG
by the reaction of 1.2 equivalents of Na2CO3 and 1.0 equivalent of
NaOH, NMR analysis showed that the crude product consisted of PPVE-
1 6 (40 mol%) and of 1,2,2,2-tetrafluoroethyl heptafluoropropyl ether
(60 mol%; freon E 1) 10 (δF -82, -86, -88, and -130) [16b] in 19 % and
28 % NMR yield, respectively. Here, it is necessary to consider the
following experimental facts: 1. The formation of by-product 10 is
observed only in the presence of sodium hydroxide in the starting
material. Moreover, the content of 10 in the crude product directly
depends on the amount of used NaOH. 2. Before thermolysis, the initial
material was thoroughly dried in vacuo, and the presence of traces of
water or protic solvents during the reaction was excluded. The forma-
tion of the by-product 10 [16c-d] was probably possible due to the
addition of HF to the double bond of PPVE-1 6 at higher temperature.
The appearance of ‘free’ hydrogen fluoride in the reaction medium
could be explained by the reaction of NaOH with perfluorinated frag-
ments of the side chain at extremely high temperatures. As a result, a
metastable fluorinated alcohol is produced, which eliminates HF under
the reaction conditions. Subsequently, HF could either react with PPVE-
1 6 in the gas phase or water could be generated by the reaction of HF
with NaOH. Since the decarboxylation process involves the formation
of a carbanion [RfCF(CF3)]−, the presence of water or of any type of
proton source should then lead to the formation of the by-product 10.
Moreover, product 6 and by-product 10 could not be separated by
simple distillation due to their similar boiling points, namely 36 °C
[16a] and 41 °C [16e], respectively. The best results were obtained after
thermolysis of the salt 8, synthesized by the reaction of 1.6 equivalents
of Na2CO3 and 0.6 equivalents of NaOH in dry MG.
4. Experimental
4.1. General
All reactions were carried out in glass reaction vials under an at-
mosphere of dry argon. Monoglyme (MG) and 1,4-dioxane were dis-
tilled from sodium / benzophenone and used immediately. Unless
stated otherwise, all reagents and starting materials were purchased
from commercial sources and used without further purification. A
mixture of carbonyl fluorides 2a and 3a was synthesized according to a
common procedure [11a] with a purity of 90 %(GC–MS). All boiling
points are uncorrected. 13C NMR spectra were recorded at 100 MHz, 19
F
NMR spectra were recorded at 376 MHz on JEOL ECX400 MHz spec-
trometer. 13C and 19F NMR chemical shifts (δ) are reported in ppm from
tetramethylsilane and CFCl3, using the residual solvent resonance
(CDCl3: δC 77.4) as an internal reference. Coupling constants (J) are
given in Hz.
4.2. Oxidative cleavage of PPVE-2 1
Under anhydrous conditions, PPVE-2 1 (101 g, 0.23 mol, 60 mL)
and V2O5 (2.2 g, 12.1 mmol, 5 mol %), were added to a three-necked
100 mL flask equipped with bubbler, thermometer, and reflux con-
denser. The reaction mixture was heated to 80 °C and oxygen was
passed through. Thereby, an exothermic effect occurred and the tem-
perature raised to 95–97 °C. At this temperature, oxygen was further
added for 3.5 h. After decreasing to 77 °C, oxygen was additionally
bubbled for 30 min. Afterwards, all liquids were condensed into a trap
cooled to −90 °C (anhydrous conditions, 21 mbar). NMR analysis of the
product (83.9 g) obtained indicated a mixture of products 2a (20.7 g,
0.05 mol, yield 23 %) and 3a (63.2 g, 0.14 mol, yield 61 %).
Thermal decarboxylation of the mixture of 8 and NaF in the pre-
sence of traces of 9 at 240 °C gave the product mixture containing of
PPVE-1 6 (70 mol%; 42 % NMR yield) and the by-product 10 (30 mol%;
19 % NMR yield). In this case, reduction in the amount of NaOH led to a
sharp decrease in the content of by-product 10 in the crude product
from 60 to 30 mol%. However, to solve this problem a mixture of so-
dium salts with 92 mol% content of 8, which was obtained by the re-
action of 2.1 equivalents of Na2CO3 in dry 1,4-dioxane, had to be
decarboxylated. Thus, the crude product consisted of almost pure PPVE-
1 6 (97 mol%; isolated yield 70 %; Scheme 5). Moreover, the by-pro-
duct 10 was not detected even in traces. The combination of an optimal
excess of Na2CO3 and 1,4-dioxane as the solvent with the best dissol-
ving properties allowed to avoid the formation of non-crystalline im-
purities. Accordingly, the choice of Na2CO3 instead of NaOH resulted in
salt 8 with a higher purity (92 mol%) and enabled a higher regios-
electivity regarding the thermolysis of 8.
4.2.1. 1,1,2,3,3,3-Hexafluoro-2-(perfluoropropoxy)propyl
carbonofluoridate (2a)
19F NMR(376 MHz, neat): δ -14.4 (s, COF, 1 F), -82.0 (d, 3JFF =9 Hz,
CF3, 3 F), -83.2 (m, CF2O, 2 F), -83.6 (bs, CF3, 3 F), -89.8 (dm, 3JFF =8
3
Hz, CF2O, 2 F), -131.6 (s, CF2, 2 F), -146.5 (t, JFF =22 Hz, CF, 1 F)
[11a].
3. Conclusions
4.2.2. 2,2-Difluoro-2-(1,1,2,3,3,3-hexafluoro-2-(perfluoropropoxy)
propoxy)acetyl fluoride (3a)
For the first time, a simple and convenient method of conversion of
19F NMR (376 MHz, neat): δ +10.9 (s, COF, 1 F), -78.4 (t, 4JFF =12
3
2
PPVE-2 1, formed as
a
by-product of telomerization of hexa-
Hz, CF2, 2 F), -82.0 (d, JFF =7 Hz, CF3, 3 F), -83.1 (dm, JFF =54 Hz,
2
fluoropropene oxide (HFPO) to the target monomer PPVE-1 6, was
demonstrated. This methodology involves the oxidation of PPVE-2 1
with molecular oxygen catalyzed by vanadium(V) оxide to furnish a
mixture of fluorides 2a and 3a. Subsequent alkaline hydrolysis of 2a
and 3a by the reaction with KOH in a water-alcohol solution gave a
mixture of potassium salts 4 and 5 in quantitative yield. By thermolysis
of the salt mixture 4 and 5, the fluorides 7 and 3, and PPVE-1 6 were
CF2O, 2 F), -83.6 (bs, CF3, 3 F), -84.3 (dm, JFF =41 Hz, CF2O, 2 F),
3
-131.5 (s, CF2, 2 F), -146.7 (t, JFF =22 Hz, CF, 1 F) [11a].
4.3. Alkaline hydrolysis of carbonyl fluorides 2a [CF3CF2CF2-O-CF
(CF3)CF2-O-C(O)F] and 3a [CF3CF2CF2-O-CF(CF3)CF2-O-CF2C(O)F]
In a 1000-mL three-necked round-bottom flask, a solution of KOH
5

S.N. Tverdomed, et al.
JournalofFluorineChemistry233(2020)109508
3
2
(49.2 g, 0.88 mol), MeOH (540 mL), and deionized water (135 mL) was
prepared. The solution was cooled down to 10–15 °C using an ice bath
and 128 g of a mixture of 2a (37.1 g, 93.3 mmol, 29 wt%) and 3a (90.9
g, 202.9 mmol, 71 wt%) was added in such a rate that the temperature
was maintained below 23 °C. Then, the reaction mixture was stirred at
50 °C for 18 h. Next, the solvents were evaporated under reduced
pressure at 25–50 °C to obtain a solid residue. The mixture of salts 4 and
5 as well as potassium fluoride was additionally dried for 18–20 hrs at
100 °C / 0.7 mbar. Compounds 4 (34.0 g, 96 % yield, 29 mol% content)
and 5 (94.5 g, 97 % yield, 71 mol% content) were obtained in a mixture
with KF as a white powder.
=7.2 Hz, CF3, 3 F), -84.5 (d, JFF =3 Hz, CF3, 3 F), -86.1 (dm, JFF
=152 Hz [9a,16d,17a-b], CF2O, 1 F), -127.2 (dd, 3JFF =17 Hz, 3JFF =6
3
Hz, CF, 1 F), -131.3 (m, JFF =10 Hz, CF2, 2 F).
2
13C NMR (101 MHz, CD3OD): δ 161.1 (d, JCF =26 Hz, C(O), 1C),
119.5 (qd, 1JCF =285 Hz, 2JCF =33 Hz, CF3, 1C), 117.3 (qt, 1JCF =286
Hz, 2JCF =34 Hz, CF3, 1C), 115.9 (ttd, 1JCF =285 Hz, 2JCF =33 Hz, 3JCF
1
2
=2 Hz, CF2, 1C), 106.8 (tsxt, JCF =267 Hz, JCF =38 Hz, CF2, 1C),
1
2
102.2 (dq, JCF =265 Hz, JCF =37 Hz, CF, 1C).
4.5.2. Sodium 2,2-difluoro-2-(1,1,2,3,3,3-hexafluoro-2-(perfluoropropoxy)
propoxy) acetate (9)
3
3
19F NMR (376 MHz, CD3OD): δ -79.8 (ddd, JFF =20 Hz, JFF =13
Hz, 4JFF =6 Hz, OCF2, 2 F), -82.8 (dd, 3JFF =19 Hz, 3JFF =8 Hz, CF3, 3
F), -83.5 (dm, 2JFF =94 Hz, CF2O, 2 F), -83.7 (t, 3JFF =6 Hz, CF3, 3 F),
4.3.1. Potassium 2,3,3,3-tetrafluoro-2-(perfluoropropoxy) propanoate (4)
19F NMR (376 MHz, CD3OD):
δ
-82.7 (ddd, JFF =150 Hz
2
[9a,16d,17a-b], 3JFF =18 Hz, 3JFF =8 Hz, OCF2, 1 F), -82.9 (t, 3JFF =7
Hz, CF3, 3 F), -83.4 (d, 3JFF =3 Hz, CF3, 3 F), -87.3 (dm, 2JFF =151 Hz
[9a,16d,17a-b], CF2O, 1 F), -128.0 (dd, 3JFF =17 Hz, 3JFF =6 Hz, CF, 1
-85.6 (dm, JFF =32 Hz, CF2O, 2 F), -132.6 (t, JFF =3 Hz, CF2, 2 F),
2
3
3
-147.2 (t, JFF =22 Hz, CF, 1 F).
3
F), -131.2 (m, JFF =10 Hz, CF2, 2 F).
4.6. Thermolysis of 8 Na[CF3CF2CF2-O-CF(CF3)CO2] and 9 Na
[CF3CF2CF2-O-CF(CF3)CF2-O-CF2−CO2]
4.3.2. Potassium 2,2-difluoro-2-(1,1,2,3,3,3-hexafluoro-2-(perfluoropropoxy)
propoxy) acetate (5)
Under anhydrous conditions, a one-neck round-bottom flask (1 L),
connected to a cooling trap (−196 °C) and a pump, was charged with a
mixture of 8 (27 g, 77 mmol), 9 (traces), and NaF/Na2CO3 (12 g). The
mixture was heated between 220 and 240 °C in vacuo (0.7 mbar). After
2.5 h, 6 (15 g, 56 mmol) was obtained as a colorless liquid in 70 %
yield.
19F NMR (376 MHz, CD3OD): δ -78.7 (ddd, JFF =18 Hz, JFF =13
Hz, 4JFF =6 Hz, OCF2, 2 F), -81.6 (dd, 3JFF =18 Hz, 3JFF =9 Hz, CF3, 3
F), -82.3 (dm, 2JFF =95 Hz, CF2O, 2 F), -82.6 (t, 3JFF =7 Hz, CF3, 3 F),
3
3
2
3
-84.0 (dm, JFF =31 Hz, CF2O, 2 F), -131.2 (t, JFF =3 Hz, CF2, 2 F),
3
-147.3 (t, JFF =22 Hz, CF, 1 F).
4.4. Thermolysis of potassium salt 4 K[CF3CF2CF2-O-CF(CF3)CO2] and 5
4.6.1. 1,1,1,2,2,3,3-Heptafluoro-3-((1,2,2-trifluorovinyl) oxy) propane
(6)
K[CF3CF2CF2-O-CF(CF3)-CF2-O-CF2CO2]
19F NMR (376 MHz, CDCl3): δ -81.7 (t, 3JFF =7 Hz, CF3, 3 F), -86.3
(dt, 4JFF =13 Hz, 3JFF =6 Hz, OCF2, 2 F), -113.7 (dd, 2JFF =84 Hz, 3JFF
Under anhydrous conditions, a one-necked round-bottom flask (1 L)
connected to a cooling trap (−196 °C) and a vacuum pump, was
charged with a mixture of 4 (34 g, 92 mmol), 5 (95 g, 196 mmol), and
KF (17 g, 0.29 mol). The mixture was heated to 220–240 °C in vacuo
(0.7 mbar). After 3.5 h, the crude product mixture (total amount: 90 g)
of 6 (36 g, 135 mmol; 84 % NMR yield), 7 (54 g, 163 mmol, 82 % NMR
yield), and 3a (traces) was obtained.
3
3
=67 Hz, CF = CFF, 1 Fcis), -121.9 (ddt, JFF =84 Hz, JFF =113 Hz,
5JFF =6 Hz, CF = CFF, 1 Ftrans), -129.9 (bs, CF2, 2 F), -135.5 (ddt, 3JFF
3
4
=113 Hz, JFF =65 Hz, JFF =6 Hz, CF=CF2, 1 F).
13C NMR (101 MHz, CDCl3): δ 147.1 (tdd, 1JCF =279 Hz, 2JCF =53
4
1
2
Hz, JCF =3 Hz, =CF2, 1C), 129.5 (dtt, JCF =270 Hz, JCF =48 Hz,
3JCF =1 Hz, CF = CF2, 1C), 117.1 (qt, 1JCF =287 Hz, 2JCF =33 Hz, CF3,
1
2
3
1C), 115.8 (ttq, JCF =285 Hz, JCF =28 Hz, JCF =4 Hz, OCF2, 1C),
1
2
4.4.1. 2,3,3,3-Tetrafluoro-2-(perfluoropropoxy)propanoyl fluoride (7)
106.6 (tsex, JCF =268 Hz, JCF =39 Hz, CF2, 1C).
Declaration of Competing Interest
We declare no conflict of interests.
4
19F NMR (376 MHz, CDCl3): δ +26.7 (q, JFF =6 Hz, C(O)F, 1 F),
2
3
5
-79.5 (ddq, JFF =148 Hz, JFF =19 Hz, JFF =7 Hz, OCF2, 1 F), -81.9
(t, 3JFF =7 Hz, CF3, 3 F), -82.0 (dd, 3JFF =4 Hz, 4JFF =2 Hz, CF3, 3 F),
2
5
-87.4 (dq, JFF =149 Hz, JFF =6 Hz, CF2O, 1 F), -129.7 (s, CF2, 2 F),
3
3
-131.3 (dd, JFF =19 Hz, JFF =2 Hz, CF, 1 F).
Appendix A. Supplementary data
4.5. Reaction of 6 [PPVE-1] and 7 [CF3CF2CF2-O-CF(CF3)C(O)F] with
Na2CO3 in 1,4-dioxane
Supplementary material related to this article can be found, in the
online version, at doi:https://doi.org/10.1016/j.jfluchem.2020.
109508.
Under anhydrous conditions, a three-neck round-bottom flask (250
mL) equipped with a magnetic stir bar, reflux condenser and a dropping
funnel, was charged with Na2CO3 (20 g, 0.19 mol) and 1,4-dioxane
(135 mL). A mixture of 6 (18 g, 68 mmol) and 7 (27 g, 81 mmol) was
added at such a rate that the temperature could be maintained below 25
°C. Afterwards, the mixture was stirred at 30 °C for 18 h. Then, the
mixture was cooled to RT and the cooling condenser was replaced by a
distillation set with a Vigreux column. The mixture was slowly heated
up to 100 °C. At around 75–80 °C a colorless liquid was collected
(37–41 °C at 1013 mbar). PPVE-1 6 (10 g, 38 mmol) was isolated in 57
% yield. The remaining suspension was concentrated in vacuo at 25–40
°C and the obtained crystalline residue was dried at 100 °C/0.7 mbar for
8 h. A mixture of 8 (27 g, 77 mmol), 9 (traces), and NaF/Na2CO3 (12 g)
was obtained as a yellow powder.
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