The use of perfluoroalkyl hypofluorites for an efficient synthesis of perfluorinated ethers characterized by low Ostwald coefficient

Article abstract of DOI:10.1016/j.jfluchem.2008.05.018

In the reaction between perfluoroolefins and perfluoroalkylhypofluorites the existence of two different free radical reaction mechanisms is demonstrated by the presence of characteristic byproducts. These kinetic schemes can be experimentally controlled b

Full text of DOI:10.1016/j.jfluchem.2008.05.018

Journal of Fluorine Chemistry 129 (2008) 680–685
Contents lists available at ScienceDirect
Journal of Fluorine Chemistry
journal homepage: www.elsevier.com/locate/fluor
The use of perfluoroalkyl hypofluorites for an efficient synthesis
of perfluorinated ethers characterized by low Ostwald coefficient
a,
a
a
a
Walter Navarrini *, Francesco Venturini , Maurizio Sansotera , Maurizio Ursini ,
a
a
b
Pierangelo Metrangolo , Giuseppe Resnati , Marco Galimberti ,
b
b
Emma Barchiesi , Patrizia Dardani
a
Dipartimento di Chimica, Materiali e Ingegneria Chimica, Politecnico di Milano, 7, via Mancinelli, I-20131 Milano, Italy
Solvay-Solexis, R&D Centre, 20, viale Lombardia, I-20021 Bollate (MI), Italy
b
A R T I C L E I N F O
A B S T R A C T
Article history:
In the reaction between perfluoroolefins and perfluoroalkylhypofluorites the existence of two different free
radical reaction mechanisms is demonstrated by the presence of characteristic byproducts. These kinetic
schemes can be experimentally controlled by tuning the hypofluorite concentration in the reaction media.
In particular, in the reactions between trifluoromethyl hypofluorite and highly reactive perfluor-
Received 19 March 2008
Received in revised form 29 May 2008
Accepted 29 May 2008
Available online 5 June 2008
oolefins like CF
2
CFOCF
3
and CF
2
2
CF , the free radical oligomerization and dimerization products can be
suppressed by utilizing the opportune experimental conditions.
Keywords:
The pure perfluorinated ethers obtained, having low Ostwald coefficient, can be utilized as contrast
agents for diagnostic ultrasound imaging injectable microbubbles composition.
ß 2008 Elsevier B.V. All rights reserved.
Trifluoromethyl hypofluorites
Ostwald coefficient
Perfluorinated ethers
Kinetic
Synthesis
1
. Introduction
Perfluoroalkylhypofluorites are important intermediates uti-
TFE, conducted in high excess of BDM, we observed the substantial
absence of polymeric products deriving from TFE monomer [1].
This observation prompted us to study the addition of highly
reactive fluoroolefins to perfluoromethyl hypofluorite taking into
account the concentration of the hypofluorite in the reaction
media. This experimental approach allowed the identification of a
straight and economical methodology for the preparation of highly
pure perfluoroethers having low boiling point and low Ostwald
coefficient [11]. These perfluoroethers have been recently tested as
fluids for the preparation of injectable microbubbles composition
as contrast agents in diagnostic ultrasound imaging [12]. In many
ultrasound imaging applications there is the need for contrast
agents and efforts to develop suitable materials are ongoing.
Gaseous micro bubbles that are effective contrast agents tend to
shrink rapidly due to gas diffusion in the liquid media, therefore
microbubble stability is an important issue in this application [13].
Low solubility of the gas in blood stream has been shown to be an
important factor in gas microbubble stability and dimension.
Industrial attention has recently focused on perfluoroethers
biocompatible gases characterized by low water solubility [12].
lized in the industrial process for the preparation of fluorinated
key monomers like perfluoroalkylvinylethers [1] sulfonic-per-
fluoroalkylvinylethers [2] cyclic vinylethers monomers [3] as wall
as catalyst for fluoroolefins oxidations [4]. The addiction reaction
of hypofluorite to halogenated olefins has been studied in the
previous years [5,6], kinetics studies of the free radical reaction in
gas-phase [7] as well as in condensed phase have been analysed
in detail [8,9]. Hypofluorites are also an important source of
electrophilic fluorine and these reagents are utilized in specific
and selective fluorination [10,6].
The majority of studies on perfluoroalkyl hypofluorites utilized
3
the CF OF due to its kinetic stability compared to longer chain
perfluoroalkyl hypofluorites perfluoro propionyl hypofluorite.
On the other hand, as pointed out in previous publications, all
perfluoroalkyl hypofluorite are thermodynamically unstable [2]. In
our previous studies, we have noticed that the concentration of
hypofluorite in the reaction media is an important variable to
control the course of the main reaction. In particular in the reaction
with bis-fluoroxydifluoromethane BDM and tetrafluoroethylene
2. Discussion
*
Corresponding author. Tel.: +39 02 2399 3029; fax: +39 02 2399 3080.
The synthetic methodologies adopted utilize the availability
E-mail address: walter.navarrini@polimi.it (W. Navarrini).
3 2 2 2
of highly pure perfluoromonomers CF OCF CF and CF CF as
0022-1139/$ – see front matter ß 2008 Elsevier B.V. All rights reserved.
doi:10.1016/j.jfluchem.2008.05.018

W. Navarrini et al. / Journal of Fluorine Chemistry 129 (2008) 680–685
681
starting material. The addition of CF
synthesis of fluoroethers has been already investigated and it has
been recognized as a fast free radical chain reaction propagated by
3
OF to fluoroolefins for the
different from the standard methodologies described in the
literature were the hypofluorite is added to the olefin.
The standard addition methodology herein referred as ‘‘direct
hypofluorite addition’’ where the olefin concentration was
maintained always above zero, is characterized by the presence
of olefin during the addition reaction and can be performed by
adding the hypofluorite to the olefin. The termination product
3
the radical CF O [2,9,14] and its reaction mechanism is summar-
ized in Scheme 1 below.
3
We have studied the reaction between the hypofluorite CF OF
2 3 2 2
with the olefin CF CFOCF and CF CF .
The main products of the addition of CF
3
OF with CF
2
CFOCF
3
C
8
F
18
O
4
deriving from reaction (8) of Scheme 1 was observed only
were perfluoro-1,1-bis-(methoxy)-ethane (L) and perfluoro-1,2-
bis-(methoxy)-ethane (K) in the molar ratio of 20% to 80%,
respectively, as shown in reaction (9) below:
when the reactions of CF OF with CF CFOCF was conducted in
3
2
3
the ‘‘direct hypofluorite addition’’ condition. Generally this
experimental choice is mainly due to safety reasons since the
perfluoroalkyl hypofluorites are thermodynamically unstable and
may undergo to self-decomposed [2].
CF
3
OF þ CF
2
¼CFOCF
3
! CF
3
OCF
2
CF
2
OCF
3
þ ðCF OÞ CFCF
3
3
(9)
2
L
80%
K 20%
2.1. ‘‘Direct hypofluorite addition’’
The main products of the addition of CF
3
OF to CF
2
CF
2
was
perfluoro 1-methoxy-ethane as shown in reaction (10) below and
depending on the reaction condition a big amount of polymeric
products were also present, see Section 4.4.2:
In this experimental set we have observed the presence of
termination products deriving from the reaction (8) of Scheme 1. In
the reaction mixture traces of CF OOCF were also present, but this
compoundwas also prepared from CF OF and carbonyl fluoride [15].
In fact traces of CF OOCF were also observed when a stream of
crude CF OF was bubbled through a perfluorinated solvent in
absenceofolefin.Therefore, weconsidertheoccurrenceofCF OOCF
as impurity already present in the reagent CF OF and not due to
reaction (6). Moreover, in the ‘‘reverse hypofluorite addition’’
described in Section 2.2 below, the amount of CF OOCF increased
3
3
CF
3
OF þ CF
2
¼CF
2
! CF
3
OCF
2
CF
3
(10)
3
3
3
In the reaction mixture we have specifically looked for the
3
presence of the termination products deriving from reaction (5) to
8) of Scheme 1. The termination products are normally found at
3
3
(
3
very low concentrations in the reaction media. Therefore, it was
possible to detect and analyse them only when they were
substantially different from the main reaction products in terms
of molecular weight, allowing separation or a substantial purifica-
tion from the crude mixture by distillation. Interestingly termina-
tion products distribution and nature depends on the experimental
conditions adopted in carrying out the reaction trials.
3
3
compare tothe amount present inthe ‘‘directhypofluoriteaddition’’.
It is also important to observe that when adopting the ‘‘reverse
hypofluorite addition’’ the termination products deriving from
reaction (8) of Scheme 2 were completely absent.
In the ‘‘direct hypofluorite addition’’, due to the starvation of
The termination product CF
Scheme 1 was clearly present in the reaction where the CF
concentration was maintained always above zero, on the contrary
in this experimental condition the termination product C
deriving from the reactions (8) was completely absent. In this
condition also the oligomerization and polymerization of the
perfluoroolefins were substantially suppressed, also in the case of
the very reactive TFE, see Section 4.4.3 for details.
These experimental conditions are characterized by the
presence of hypofluorite during the addition reaction and can be
performed by adding the olefin to the hypofluorite, these
conditions herein referred as ‘‘reverse hypofluorite addition’’ are
3
OOCF
3
deriving from reaction (6) of
3
CF OF in the reaction media, we have supposed the presence of a
OF
relatively high concentration of the radical (E) deriving from the
propagation reaction (3) shown in Scheme 2.
This is in agreement with the experimental finding where
the termination products derive substantially from the
reaction (8) when adopting the ‘‘direct hypofluorite addition’’
procedure.
Based on the above experimental finding, the mechanism of
Scheme 1 can be simplified for the kinetic of the ‘‘direct
hypofluorite addition’’ as shown in Scheme 2.
3
8
F
18
O
4
Since in the reaction between CF
3
OF and CF
2
3
CFOCF there are
two possible, but not equal addition sites of the CF
3
O on the olefin,
F
Scheme 1. Free radical pathway for the reaction of perfluoroalkyl hypofluorites R OF with olefin C C.

6
82
W. Navarrini et al. / Journal of Fluorine Chemistry 129 (2008) 680–685
F
Scheme 2. Free radical pathway for the ‘‘direct hypofluorites addition’’ of perfluoroalkyl hypofluorites R OF to olefin C C.
we assume that the two radical species I and J of Fig. 1, deriving
from propagation step (3) of Scheme 2, are present in the ‘‘direct
hypofluorite addition’’ procedure.
The radical species I and J following reaction (8) of Scheme 2
combine giving the terminating chain products P, Q and O deriving
from the reactions (11a), (11b) and (11c) are shown:
(11a)
(11b)
(11c)
Reactions (11a), (11b), (11c) and regiochemistry of the termination
reaction (8) of Scheme 2 when the hypofluorite is CF OF and the
olefin is CF OCF CF
3
3
2
.
Since the termination reaction (8) generates high molecular
weight products, those can be concentrated by distillation of the
low boiling products and then detected at higher concentration in
the residue of distillation. In addition we have not observed any
oligomerization of the vinylether, this can be predicted since
perfluorovinylether do not omopolymerize especially at tempera-
ture as low as ꢀ70 8C. In the reactions products the molar ratio
Fig. 1. Radical I and J deriving from the addition of radical CF
3
O to CF
2
3
CFOCF .

W. Navarrini et al. / Journal of Fluorine Chemistry 129 (2008) 680–685
683
between linear L to branched K is 4:1, therefore we expect that the
relative amounts of termination products in the crude reaction
mixture should be in the range of O (64%) > Q (32%) > P (4%).
In the setting of the differential equations, we have
considered negligible the product deriving from initiation
reactions (Product D of Scheme 2) compared to the addition
product F.
Eq. Set 2. Applied to the ‘‘direct hypofluorite addition’’
methodology in the steady state hypothesis.
In particular, equation (Eq. (I)) below describes the consump-
tion rate of the perfluoroolefins in the ‘‘direct hypofluorite
addition’’ methodology:
sffiffiffiffiffiffiffi
qffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
pffiffiffiffiffiffi
d
k
k
11
3
We have applied the steady state hypothesis to the radical
½¼ꢃ ꢂ ꢀk
4
½R
F
OFꢃ ½¼ꢃ
(I)
dt
T8
i t
species and by taking into account the general equation V = V we
have obtained Equations Set 1 as shown:
8
9
>
v
d
1
¼ v
2
¼ v
1
8
ꢁ v
3
¼ v
4
>
>
>
2.2. ‘‘Reverse hypofluorite addition’’
>
>
>
>
>
>
>
C
C
C
¼ v þ v
þ v
ꢀ v
¼ 0 >
>
<
C
E
Z
2
4
3
>
=
dt
d
In this particular experimental addition methodology, the
reaction is carried out in excess of hypofluorite avoiding the
formation of oligomers and dimeric byproducts that normally are
formed utilizing the standard hypofluorite addition to free radical
reactive olefins [16,17]. This lack of high molecular weight is
mainly due to severe olefin starvation and high hypofluorite
concentration in the reaction media.
>
¼ v
3
1
ꢀ v
4
2
ꢀ 2v
8
¼ 0
>
>
>
>
dt
d
>
>
>
>
>
>
>
>
:
>
;
¼ v
ꢀ v
¼ 0
dt
Eq. Set 1. Applied the ‘‘direct hypofluorite addition’’ of
perfluoroalkyl hypofluorites R
state hypothesis.
F
OF to olefin C C in the steady
This experimental methodology, allows the synthesis of
perfluoroethers in purity above 98% already in the crude reaction
mixture [11]. The good purity of the desired product in the crude
reaction mixture promptly facilitates the isolation of the
perfluoroethers main products in high purity normally needed
for biomedical application. In fact due to the relatively high excess
of hypofluorite the sole termination product was the volatile
Consequently the kinetic system can be simplified as shown in
Equations Set 2:
8
sffiffiffiffiffiffiffi
9
qffiffiffiffiffi
>
d
k
k
pffiffiffiffiffi
>
>
11
>
>
3
>
>
C
C
C
A
B
C
ꢂ ꢀv
4
3
¼ ꢀk
4
3
C
C
A
C
E
¼ ꢀk
4
C
C
B
>
>
A
>
>
dt
>
>
T8
>
>
sffiffiffiffiffiffiffi
>
>
>
>
qffiffiffiffiffi
>
>
pffiffiffiffiffi >
>
d
k
>
>
11
3
>
>
>
>
ꢂ ꢀv
¼ ꢀk
C
C
B
¼ ꢀv
4
¼ ꢀk
4
C
C
B
>
>
A
>
>
dt
k
>
>
T8
>
>
sffiffiffiffiffiffiffisffiffiffiffiffi
>
>
>
>
>
3 3
compound CF OOCF .
>
3
>
>
d
dt
d
k
k
k
C
C
>
>
4
11
A
>
>
>
Base on the above experimental finding the mechanism of
Scheme 1 can be simplified for the kinetic of the ‘‘reverse
hypofluorite addition’’ as shown in Scheme 3.
Similarly to the ‘‘direct hypofluorite addition’’ methodology, we
have applied the steady state hypothesis:
>
¼ 0
¼ 0
C
C
¼ k
>
>
>
>
>
>
3
T8
B
>
>
>
>
>
>
<
k
>
=
11
C
C
Z
C
Z
¼
C
B
dt
d
k
2
>
>
>
>
>
>
>
>
>
D
¼ v
1
¼ k11
C
C
B
¼ v
2
>
>
A
>
>
dt
d
>
>
sffiffiffiffiffiffiffi
>
>
>
>
>
8
9
>
pffiffiffiffiffiffipffiffiffiffiffi
>
>
k
k
>
>
11
>
> v
1
¼ v
2
¼ v
1
6
ꢁ v
3
¼ v
4
>
>
C
¼ 0
C
¼
C
C
>
>
>
>
E
E
A
B
>
>
>
>
>
> d
>
>
dt
T8
>
>
>
>
>
>
>
>
sffiffiffiffiffiffiffi
>
>
<
C
C
¼ v þ v
2
þ v
4
ꢀ v
3
ꢀ 2v
6
¼ 0 >
>
>
=
>
qffiffiffiffiffi
>
dt
>
pffiffiffiffiffi
>
>
d
dt
d
k
k
11
>
>
3
A
>
d
>
C
C
¼ v
4
¼ k
C
C
¼ k
C
C
>
>
F
4
A
E
4
B
>
>
CE ¼ v ꢀ v ¼ 0
>
>
>
>
3
4
>
>
T8
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
:
>
;
>
2
E
:
;
H
¼ v
8
¼ kT8
C
¼ v
1
¼ k11
C
A
C
B
C
Z
¼ v
1
ꢀ v
2
¼ 0
dt
dt
F
Scheme 3. Free radical pathway for the ‘‘reverse hypofluorite addition’’ of olefin C C to perfluoroalkyl hypofluorites R OF.

6
84
W. Navarrini et al. / Journal of Fluorine Chemistry 129 (2008) 680–685
Eq. Set (3). Applied to the ‘‘reverse hypofluorite addition’’ of
ꢄ
Off-line IR spectra of the purified mixture of isomers has been
olefin C C to perfluoroalkyl hypofluorites R
hypothesis.
F
OF in the steady state
obtained on a Thermo Nicolet 380 FT-IR with a glass made gas-
3
phase cell, volume 56 cm , length 10 cm, equipped with KBr
In particular, equation (Eq. (II)) below describes the consump-
tion rate of the perfluoroolefins in the ‘‘reverse hypofluorite
addition’’ methodology:
windows and filled with less than 5 mbar of product.
1
9
ꢄ
ꢄ
F NMR spectra were recorded on a Bruker AV 500 MHz
spectrometer; chemical shifts are expressed as values with neat
CFCl as an internal reference (ppm = 0).
d
3
sffiffiffiffiffiffiffi
qffiffiffiffiffiffiffiffiffi
pffiffiffiffiffiffiffiffiffiffiffiffiffiffi
Mass spectra were performed on a Varian Mat CH-A spectro-
meter in the electron impact mode at ionization energy of 70 eV.
d
k
k
11
3
½
¼ꢃ ꢂ ꢀk
3
½R
F
OFꢃ ½¼ꢃ
(II)
dt
T6
3
. Conclusions
4.3. Direct hypofluorite addition
Analysis of the products present in the reaction between CF
3
OF
4.3.1. General procedure
and CF CFOCF , including the termination products, confirmed
the mechanisms proposed for two different experimental addition
methodologies. In the ‘‘direct hypofluorite addition’’, where the
2
3
The ‘‘direct hypofluorite addition’’ procedure consists of
bubbling a stream of hypofluorite into a solution of the olefin
maintained at the desired temperature in a semi-batch method in
order to operate in excess of olefin. The addition reactor is standard
dimensions designed 250 ml AISI 316 cooled by an external vessel.
The reactor is realized with a discharge bottom valve and two
feeding tubes. The reactor’s head is equipped with: an outgoing
tube for collecting the off-gas stream and a mechanical/magnetic
transmission stirring system. The feed of the addition reactor and
the off-gases are analysed on-line via IR, GC-TCD and GC-IR. At the
end of the addiction the reactor has been stripped with 4 nL/h of
helium for abut 30 min, the vessel is unloaded and the resulting
CF
oligomers were present in the crude reaction mixture. In the
‘reverse hypofluorite addition’’, where the fluoroolefin concentra-
tion was close to zero, dimeric like products or oligomers of the
fluoroolefins were absent and the peroxide CF OOCF was the
3
OF concentration was close to zero, dimeric like products or
‘
3
3
unique termination product. This experimental approach allowed
the identification of a straight and economical methodology for the
preparation of highly pure perfluoroethers having low boiling
point and low Ostwald coefficient.
1
9
mixture has been analysed via GC, GC-MS e NMR F. The raw
reaction mixture has been distilled in vacuum or at atmospheric
pressure.
4
. Experimental
4.1. Safety
4
.3.2. Reaction of CF
The addition reaction is operated in a semi-batch technique,
120 g of a solution containing 50% of CF OCF CF (MVE) in CF Cl–
CFCl–CFCl–CF Cl are introduced in the reactor as described in
3 2 3
OF with CF CFOCF
Based on the literature data [18] organic hypofluorites should
be always regarded as potential explosives. For safety reasons
CF OF was diluted with helium in a molar ratio of 1/1. Any contact
3
2
2
3
2
between hypofluorites and the operator must be avoided; the
reactors and the hypofluorite plant must be perfectly sealed and
located in a dedicated area. More information regarding the
toxicity and handle information of these chemical categories are
available in the literature [2,19]. In particular information on
Section 4.3.1 above. The mixture into the addition reaction is
cooled at the temperature of ꢀ80 8C. The charged reactor has been
fed with a stream containing CF
0.4 nL/h. for about 3 h.
3 2
OF 2.3 nL/h, He 2.5 nL/h and COF
During the reaction time it has been observed the presence of
O–CF –CF in the off-gases by on line GC-IR analysis, this
product derive from the initiation reaction (1) and (2) of Scheme 2,
the toxicity of the volatile termination product CF
been recently reported [20]. The aggressive volatiles CF
and CF OOCF , due to their low boiling point, can be directly
3
OOCF
3
have
CF
3
2
3
3
OF
1
9
this product has been also recognized by NMR F as traces in the
volatile fraction after distillation [21].
3
3
eliminated through the vent of the reaction mixture at the end of
the reaction.
The raw mixture contains the solvent CF
the main products L and K in the ratio L/K = 4, the unreacted
CF OCF CF and dimeric like products (C ) deriving from
2 2
Cl–CFCl–CFCl–CF Cl,
4.2. Methods
3
2
8 18 4
F O
reaction (8) of Scheme 2, these products are also described in
literature [16]. Selectivity of the reaction defined as moles of the
addition products L + K over moles of reacted alkene is 94%.
ꢄ
3
The synthesis of CF OF was carried following a modified
procedure described in the literature [16] using an under-
stoichiometric amount of fluorine in order to avoid the presence
of byproducts induced by the presence of fluorine. Depending on
the relative amounts of reagents it can take about 30 min for
3 2 2 3 3 2 3
Characterization of CF OCF CF OCF and (CF O) CFCF : The linear
product L and the ramified K have very similar S.B.P. Therefore,
they have been characterized as one pseudo compound. Standard
boiling point 19.9 ꢅ 0.5 8C.
3
reaching the steady state. The preparation and reactions of CF OF
were realized in a continuous S.S. laboratory scale apparatus
equipped with on line GC/TCD, 8 m PTFE + Kel-F oil packed
Antoine equation parameters:
A
B
C
¼ ꢀ4754:5159
column and on line Thermo Nicolet 380 FT-IR, PTFE gas-phase
¼ þ1227925345:2414
¼ ꢀ258557:7393
3
cell with CaF
Reagents CF
CFCl–CFCl–CF
utilized without any further purification.
2
windows, volume 8 cm , length 10 cm.
ꢄ
ꢄ
3
OCF CF
2 2 2 2
, CF CF , CFCl CFCl and solvent CF Cl–
(
A ꢀ (B/(T + C))
2
Cl were purchased from Solvay Solexis and
P8 = 10
Enthalpy of vaporization evaluated at the boiling point
[bar] T [K].
Off-line volatile compounds were handled assuming ideal gas
behaviour in a glass and/or stainless-steel system equipped with
glass/PTFE or stainless-steel valves. Pressures were measured
with an Endress + Hauser transducer PMP 131-A3BO1A2N
coupled with an Endress + Hauser RIA 250 digital display.
30.2 ꢅ 0.1 kJ/mole.
Entropy of vaporization evaluated at the boiling point =103.2 J/
mole ꢅ ꢀ0.6 J/(mole K).
The entropy of vaporization has been calculated following the
Trouton’s rule. (DSev = R ln(Pvap/Prif) + DHev/Tev = DHev/Tev).

W. Navarrini et al. / Journal of Fluorine Chemistry 129 (2008) 680–685
685
1
9
F NMR (L):
OCF CF OCF
F NMR (K):
O) CFCF
), ꢀ102.6 (m, 1F, (CF
MS m/z (rel. int.): 135(6), 119(30), 97(4), 69(100), 50(6), 47(5).
d
).
ꢀ57.8 (s, 6F, CF
3
OCF
2
CF
2
OCF
3
), ꢀ92.7 (m, 4F,
Those products G and D have been also found in the reaction raw
mixture and have been recognized respectively as CF OOCF [23–
25] and CF O–CF –CF [21] from data available in the literature. It
is important to note that products P, Q, O described in Section 4.3.2,
are completely absent in the reaction mixture.
Selectivity defined as moles of the addition products L + K over
moles of reacted alkene is 98%.
CF
3
1
2
2
3
3
3
9
d
ꢀ57.1 (s, 6F, (CF
3
O)
2
CFCF
).
3
), ꢀ88.3 (d, 3F,
3
2
3
(
(
CF
3
2
3
3
O) CFCF
2
3
ꢀ
1
IR (cm ) of the mixture L 80%, B 20%: 1291 (s), 1251 (s), 1199
m), 1167 (s), 1153 (s), 1128 (m), 1102 (w).
4
.3.3. Reaction of CF
The reactor is charged with about 176 g of PFPE Galden LS155
b.p. 155 8C) and cooled to ꢀ100 8C. A gaseous stream constituted
of CF CF (TFE) 3 nL/h and He 3 nL/h, has been fed until 18.0 g of
TFE are condensed in the reactor, the gaseous stream of TFE is then
stopped. Subsequently a stream constituted by CF OF 1.8 nL/h, He
.0 nL/h, has been fed in the addition reactor for 1 h.
The raw reaction mixture contains the solvent, the product
OCF CF and a complex mixture of polymeric and oligomeric
OCF CF
3
OF with CF
2
CF
2
4.4.3. Reaction of CF
The reactor is initially filled with about 176 g of PFPE Galden
LS155 (b.p. 155 8C) and cooled to ꢀ100 8C. After a saturation period
of 12 min with CF OF (2.0 nL/h), He (4.0 nL/h) a gaseous stream
constituted by CF CF (1.8 nL/h) and He (2 nL/h) is also introduce
in the addition reactor, both gaseous stream are maintained for 3 h,
the molar ratio between TFE and CF3OF is 0.90/1. After interrupting
the regent flow, the liquid phase, mantained at a temperature of
ꢀ90 8C, has been stripped for 30 minutes with 4.2 nL/h of helium.
During the reaction time it has been observed evidences for the
2 2 3
CF with CF OF
1
1
(
2
2
3
2
2
3
4
CF
3
2
3
byproducts. The characterization data of the ether CF
3
2
3
match with the data available in the literature [21]. Selectivity
defined as moles of the addition products over moles of reacted
alkene is 48%.
3 3
formation of the products G (CF OOCF ) deriving from termination
step 6) of Scheme 3.
The raw reaction mixture contains the solvent, the product
OCF CF and only traces of CF OCF CF CF CF
Selectivity defined as moles of the addition products over moles
CF
3
2
3
3
2
2
2
3
.
4
4
.4. Reverse hypofluorite addition
of reacted alkene is 99%.
.4.1. General procedure
The ‘‘reverse hypofluorite addition’’ procedure consists of
bubbling a stream of olefin into a solution of the hypofluorite in
order to operate in excess of hypofluorite at the desired
temperature.
References
[
[
1] W. Navarrini, S. Corti, J. Fluorine Chem. 125 (2004) 189–197.
2] W. Navarrini, V. Tortelli, A. Russo, S. Corti, J. Fluorine Chem. 95 (1999) 27–39.
The reaction is carried in the CSTR described in Section 4.3.1
with a continuous feed of both the reagents.
[3] A. Russo, W. Navarrini, J. Fluorine Chem. 125 (2004) 73–78.
[4] R.M. Romano, C.O. DellaVedova, J. Czarnowski, Int. J. Chem. Kinet. (2003) 533–540.
[
5] W. Navarrini, L. Bragante, S. Fontana, V. Tortelli, A. Zedda, J. Fluorine Chem. 71
1995) 11–117.
6] S. Rozen, Chem. Rev. 96 (1996) 1717–1736.
The reactor is charged with the solvent, cooled at the desired
(
temperature and a gaseous stream consisting of CF
3
OF (2.35 nL/h),
[
He (2.5 nL/h), COF (0.3 nL/h) is fed in the reactor for about 12 min
2
[7] H. Di Loreto, J. Czarnowski, J. Fluorine Chem. 66 (1994) 1.
[
8] C. Corvaja, F. Cremonese, W. Navarrini, V. Tortelli, J. Chem. Soc. Faraday Trans. 91
1995) 3813.
9] W. Navarrini, A. Russo, V. Tortelli, J. Org. Chem. 60 (1995) 6441–6443.
before starting to add the olefin. After adding the olefin, for safety
reasons it is compulsory to eliminate the residual hypofluorite
before opening the reactor. In order to remove the majority of the
overloaded hypofluorite from the bulk, the liquid phase has been
stripped with an stream of 4 nL/h of helium for abut 30 min at the
temperature between ꢀ80 and ꢀ90 8C, after that maintaining the
temperature in the range ꢀ80 to ꢀ90 8C about 2 ml of CFCl CFCl
have been added in the reactor to eliminate the reaming traces of
hypofluorite. The traces of CF3OF react completely with CFCl CFCl
(
[
[10] R.D. Chambers, Fluorine in Organic Chemistry, Blackwell Publishing Ltd., Oxford,
004, pp. 56–57, 258–259.
2
[
11] W. Navarrini, G. Resnati, P. Metrangolo, M. Cantini, F. Venturini, Italian Patent
Application, Filing No. MI2007A001481 (2007).
[12] A. Kabalnov, E.G. Schutt, J.G. Weers, US Patent 6,193,952 (2001).
[
13] E.G. Schutt, D.H. Klein, R.M. Mattrey, J.G. Riess, Angew. Chem. Int. Ed. 42 (2003)
218–3235.
14] Z. Czarnowski, J. Czarnowski, J. Chem. Soc. Faraday Trans. 89 (1993) 451–455.
3
[
[15] R.G. Syvret, B.A. Campion, G.A. Cooper, EP Patent Application 1757581A1 (2007).
[
[
[
16] A. Marraccini, A. Pasquale, T. Fiorani, W. Navarrini, US Patent 5,877,357 (1999).
17] R.S. Porter, G.H. Cady, J. Am. Chem. Soc. 79 (1957) 5625–5627.
18] W. Navarrini, A. Russo, V. Tortelli, Recent Res. Dev. Org. Chem. 8 (2004) 281–322,
Publisher: Transworld research network, can 144:51911.
producing CF
3
O–CFCl–CF
2
Cl [22].
4
.4.2. Reaction of CF
In the reactor are introduced 60 g of CF
solvent and cooled at ꢀ80 8C. After the CF
2 min a pure stream of gaseous of CF OCF CF
feed in the reactor, the molar ratio between the regents
CF OCF CF and CF OF is 0.94/1. The reaction is carried on for
h. During the reaction time it has been observed in the off-gas the
presence of the lightweight termination and initiation byproducts.
2
CFOCF
3
with CF OF
3
2
Cl–CFCl–CFCl–CF
OF saturation period of
(2.21 nL/h) is also
2
Cl as
[19] K. Ulm, Houben-Weyl, vol. E 10a, Toxicity (2000) 33–58.
[
20] http://www.stanford.edu/dept/EHS/prod/researchlab/lab/tgo/tgodata.html;
http://www.chem.purdue.edu/chemsafety/Chem/poisongases.htm.
21] A. Sekiya, K. Ueda, Chem. Lett. 4 (1990) 609–612.
3
1
3
2
[
[22] K.K. Johri, D.D. DesMarteau, J. Org. Chem. 48 (1983) 242.
[
[
23] R.S. Porter, G.H. Cady, J. Am. Chem. Soc. 79 (1957) 5628–5631.
19
3
2
3
24] C.H. Dungan, J.R. Van Wazen, Compilation of F NMR Chemical Shifts 1951 to Mid
967, Wiley Interscience, Reference Number 3792.
[25] J.L. Huston, M.H. Studier, J. Fluorine Chem. 14 (1979) 235–249.
4
1