Synthesis of telogens and optimization of tetrafluoroethene telomerization process

Article abstract of DOI:10.1016/j.jfluchem.2006.01.002

The most advantageous technological parameters of tetrafluoroethene telomerization using 1-chloro-2-iodohexafluoropropane (telogen) towards the telomers n2-n4 or n1-n4 were experimentally established. The telomers n1-n4 were prepared with the yield of 48 mol% under the following conditions: temperature 170°C, the molar ratio of 1-chloro-2-iodohexafluoropropane to tetrafluoroethene equal to 1.2, the autoclave filling of 1.5 kg dm^-3. The maximum yield of telomers n2-n4 amounted to 27 mol% when the molar ratio of telogen to tetrafluoroethene was decreased to 0.7 and the other parameters of synthesis remained the same. The optimum parameters for the synthesis of telogens: 1-chloro-2-iodohexafluoropropane and 2-iodoheptafluoropropane have been also determined.

Full text of DOI:10.1016/j.jfluchem.2006.01.002

Journal of Fluorine Chemistry 127 (2006) 337–344
www.elsevier.com/locate/fluor
Synthesis of telogens and optimization of tetrafluoroethene
telomerization process
*
Grzegorz Lewandowski , Egbert Meissner, Eugeniusz Milchert
ˇ
ˇ
Institute of Chemical Organic Technology, Szczecin University of Technology, PL-70-322 Szczecin, Pulaskiego 10, Poland
Received 13 May 2005; received in revised form 31 December 2005; accepted 7 January 2006
Available online 14 February 2006
Abstract
The most advantageous technological parameters of tetrafluoroethene telomerization using 1-chloro-2-iodohexafluoropropane (telogen)
towards the telomers n2–n4 or n1–n4 were experimentally established. The telomers n1–n4 were prepared with the yield of 48 mol% under the
following conditions: temperature 170 8C, the molar ratio of 1-chloro-2-iodohexafluoropropane to tetrafluoroethene equal to 1.2, the autoclave
filling of 1.5 kg dmꢀ3. The maximum yield of telomers n2–n4 amounted to 27 mol% when the molar ratio of telogen to tetrafluoroethene was
decreased to 0.7 and the other parameters of synthesis remained the same. The optimum parameters for the synthesis of telogens: 1-chloro-2-
iodohexafluoropropane and 2-iodoheptafluoropropane have been also determined.
# 2006 Elsevier B.V. All rights reserved.
Keywords: Telomerization; Tetrafluoroethene; 1-Chloro-2-iodohexafluoropropane; 2-Iodoheptafluoropropane; Optimization
1. Introduction
fluoride was introduced by Krespan [8,9]. The other group of
methods is based on the reaction of perfluoroalkene with iodine
and hydrogen fluoride in the presence of oxidizing agents
[10,11] as well as the decarboxylation of silver salts of
perfluorocarboxylic acid in the presence of iodine. However,
these methods are of smaller importance [12].
Telomerization of tetrafluoroethene (TFE) is a particularly
useful method for the preparation of many technically
important compounds and intermediates. The addition of
different amounts of TFE (taxogen) to telogen (XY) proceeds in
accordance with the reaction (Scheme 1).
The first work concerning the telomerization of TFE in the
presence of iodine derivatives, e.g. CF3CCl2I, as telogens was
reported by Hauptschein and co-workers [13–15]. The
processes were carried out batchwise at temperatures of
120–160 8C, at the pressures up to 70 atm over the time of 1–
20 h in the absence of peroxide initiators (thermal initiation).
More recently, a comprehensive review of the telomerization
methods was presented by Ameduri et al. [16].
Typical initiators of polymerization include peroxides,
percarbonates, 2,20-azobis(isobutyronitrile) (AIBN) (radical
initiation) as well as light (photochemical initiation) and
elevated temperature (thermal initiation) methods. In the
telogen molecule X is most often perfluoroalkyl, chloroper-
fluoroalkyl, perfluoroalkenyl, and perfluorocycloalkyl.
denotes iodine or bromine.
Y
A method of synthesis of such telogens [1–4] relies on the
reaction of a perfluoroalkene with iodine and iodine(V) fluoride
in the presence of catalysts, for example metallic aluminium,
aluminium iodine, aluminium bromide [5], SbF5, SbF3, ZnF2
[6], and TiCl4, ZrCl4, VF5 [7] (Scheme 2).
The telomers of TFE can be used in a wide range of
processes as solid lubricators and anti-adhesive agents,
finishing ingredients, heat transfer agents [15,17,18]. Some
of the practical applications of telomers especially in the
production of the surface-active agents for galvanizing bath and
fire-extinguishing agents are given in [19].
A more beneficial method of telogen synthesis, which relies
on the reaction of a perfluoroalkene with iodine and potassium
Although the methods of telomerization are known, the
descriptions of the telomerization of TFE are based only on the
patent literature, and do not discuss the influence of
technological parameters on the course of this process. The
aim of this work was to establish the effect of the technological
* Corresponding author. Tel.: +48 91 449 48 91; fax: +48 91 449 43 65.
E-mail address: Grzegorz.Lewandowski@ps.pl (G. Lewandowski).
0022-1139/$ – see front matter # 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.jfluchem.2006.01.002

338
G. Lewandowski et al. / Journal of Fluorine Chemistry 127 (2006) 337–344
Scheme 1.
Scheme 2.
Scheme 3.
parameters and the optimum parameters of the telomerization
of TFE as well as the optimum parameters for the synthesis of
telogens: 1-chloro-2-iodohexafluoropropane and 2-iodohepta-
fluoropropane using statistical methods of experimental design.
Fig. 1. The influence of the technological parameters (in the coded form) on the
yield of 2-iodoheptafluoropropane. Real values of parameters are presented in
Table 1.
2. Results and discussion
where xi is the coded variable value in the point of the
experiment plan (i = 1–4), Xi the natural variable value in
the point of the experiment plan (i = 1–4), Xi0 the natural
variable value in the central point of experiment plan, and
DXi is the step value along the X-axis (natural).
2.1. Synthesis of telogens
2.1.1. Synthesis of 2-iodoheptafluoropropane
Table 1 presents the real and coded values of the
experimental parameters of the design of experiments.
The yield of 2-iodoheptafluoropropane was assumed as the
response function describing the process. It was defined as the
amount of 2-iodoheptafluoropropane obtained in relation to
(HFP) introduced into the autoclave.
The synthesis of 2-iodoheptafluoropropane relies on the
reaction of hexafluoropropene (HFP) with iodine and potassium
fluoride in acetonitrile (Scheme 3) (Krespan’s method [8]).
Preliminary investigations revealed that the yield of 2-
iodoheptafluoropropane is influenced by parameters such as:
iodine/HFP and potassium fluoride/HFP molar ratios, tempera-
ture and reaction time (independent variables). For the
optimization of the 2-iodoheptafluoropropane synthesis the
experiments were performed according to quaternary rotatable-
uniform design of the second order. The design of experiments
was performed for four independent variables established in the
preliminary investigations in the following ranges of changes:
X1, I2/HFP molar ratio (1.0–1.4); X2, KF/HFP molar ratio (1.0–
2.6); X3, temperature (100–140 8C); X4, reaction time (11–15 h).
The transition from the system of independent factors in the
natural form to coded (dimensionless) form was performed by a
linear transformation of variables:
The design of experiments, determination of coefficients of
the polynomial describing the process (the yield of 2-
iodoheptafluoropropane) and the statistical analysis of the
results were performed using the Statistica computer program
[20].
The analysis revealed that the yield of 2-iodoheptafluor-
opropane depends on all the technological parameters
investigated. The greatest influence on the yield of 2-
iodoheptafluoropropane is the KF/HFP molar ratio (Fig. 1).
Its rise, from 1 (coded value ꢀ2) to 2 (coded value 0.5), results
in the yield increase from 25 to 90 mol%. A further increase, in
the KF/HFP molar ratio to 2.6 (coded value 2), causes lowering
of the yield to 70 mol%. The rise of any other parameters from
xi ¼ ðXi ꢀ Xi0Þ=DXi
(1)
Table 1
Real and coded values of experimental parameters of the 2-iodoheptafluoropropane synthesis
Level
Coded parameter (xi)
Real values of parameters (Xi)
Molar ratio I2/HFP
Molar ratio KF/HFP
Temperature (8C)
Reaction time (h)
Basic
0
1
1.2
1.3
1.1
1.4
1.0
1.8
2.2
1.4
2.6
1.0
120
130
110
140
100
13
14
12
15
11
Higher
Lower
ꢀ1
2
Star higher
Star lower
ꢀ2

G. Lewandowski et al. / Journal of Fluorine Chemistry 127 (2006) 337–344
339
Scheme 4.
Scheme 5.
minimum to maximum value caused an increase in the yield of
2-iodoheptafluoropropane. The best results of the 2-iodohepta-
fluoropropane synthesis in the ranges of parameters changes
investigated were for the following ranges of parameters: KF/
HFP molar ratio (1.8–2.2), I2/HFP molar ratio (1.33–1.40),
temperature (133–140 8C), and reaction time (14.3–15.0 h).
Under these conditions the yield of 2-iodoheptafluoropropane
was above 85 mol%.
2.1.2. Synthesis of 1-chloro-2-iodohexafluoropropane
The synthesis of 1-chloro-2-iodohexafluoropropane involves
the addition of iodine chloride to HFP according to Scheme 4
(Haupstchein’s method [1]).
2-Chloro-1-iodohexafluoropropane is formed simultaneo-
usly and the following reactions proceed (Scheme 5).
The experiments were performed in the following range of
changes of parameters: temperature (70–170 8C), the autoclave
filling (0.64–1.05 kg dmꢀ3), molar ratio of substrates (0.78–
1.3:1). The results of the GC analysis of the raw product show
that the highest selectivity of 2-iodoheptafluoropropane
(approximately 97 mol%) was obtained at the lowest tempera-
ture i.e. approximately 70 8C (Fig. 2). However, the conversion
of HFP is rather small (55 mol%) at this temperature. The range
of 100–110 8C should be considered as the optimum
temperature. The high HFP conversion (approximately
87 mol%) is achieved with a relatively low content of by-
products (selectivity of by-products less than 10 mol%). Rise of
temperature above 110 8C increases the by-products, 2-chloro-
1-iodohexafluoropropane and 1,2-dichlorohexafluoropropane
(selectivity of by-products exceeds 14 mol%). A further
increase in temperature causes a decrease of HFP conversion.
Scheme 6.
The temperature affects the selectivity of isomers, 1-chloro-2-
iodohexafluoropropane and 2-chloro-1-iodohexafluoropropane
(Fig. 2). When the reaction is performed at temperature 70 8C,
the ratio of isomer equal to 39 can be achieved, whereas, at
temperature 170 8C the ratio of isomers amounts 5. The
addition of iodine chloride to HFP can proceed according to
either ionic or radical mechanism [21] as shown in Scheme 6.
A comparison of the results of the preliminary studies (not
included in this work) carried out at various autoclave filling
(0.64–1.05 kg dmꢀ3) demonstrates that the best result of the 1-
chloro-2-iodohexafluoropropane synthesis (HFP conversion
approximately 90 mol%) was achieved at relatively high
autoclave filling (approximately 0.75 kg dmꢀ3). At this
autoclave filing the resulting reaction pressure (autogenic)
was approximately 32 atm. Over the course of reaction, the
pressure drops to approximately 9.5 atm and remains constant.
About 70% of the pressure drop occurred in the first 2 h of the
reaction. Enhancement of autoclave filling and consequently
the reaction pressure generate a concentration effect, which
probably changes the reaction kinetics and therefore the
addition reaction of chlorine to HFP proceeds less intensively.
Examination of the influence of the molar ratio of substrates
shows that the most advantageous is the ratio of iodine chloride
to HFP from 1.1 to 1.15:1. At this molar ratio and at
temperatures of 100–110 8C, the HFP conversion amounts 86–
92 mol% and the yield of 1-chloro-2-iodohexafluoropropane
was 77–79 mol%.
2.2. Telomerization of tetrafluoroethene
Fig. 2. The influence of the temperature on the conversion of HFP (^) and
selectivity to: 1-chloro-2-iodohexafluoropropane (&), 1,2-dichlorohexafluor-
opropane (*), 2-chloro-1-iodohexafluoropropane (~). Filling of the autoclave
0.75 kg dmꢀ3, molar ratio of substrates 1.15.
Thermal or radical initiation by AIBN or BP was employed
for telomerization. The technological parameters of the process

340
G. Lewandowski et al. / Journal of Fluorine Chemistry 127 (2006) 337–344
Scheme 7.
in the preliminary experiments were as follows: the molar ratio
of 1-chloro-2-iodohexafluoropropane (telogen) to TFE (taxo-
gen) as 1:1, autoclave filling 1 kg dmꢀ3. For the radical
initiation process the reaction was performed at a temperature
chosen at which their half-live were close to 1 h: AIBN 78 8C,
BP at 140 8C. For the reactions with thermal initiation a
temperature of 150 8C and telomerization time 18 h was used.
Additionally, in each experiment the taxogen pressure was
controlled because it is an important parameter of the
telomerization reactions.
In order to determine of the activation energy E the studies
were conducted at 110, 130, 150, and 170 8C. These
experiments were monitored by GC and conversions of 1-
chloro-2-iodohexafluoropropane (a) to telomers: n1–n4 were
determined. Approximately values of the activation energy E
were calculated according to equation [23]:
E ¼ ꢀ2:3RA
(2)
where E is the activation energy (J molꢀ1), R the gas constant
(8.314 J molꢀ1 degꢀ1), A the slope of the straight lines of a plot
of log a versus 1/T.
A plot of log a versus 1/T (where T represents temperature)
decreased linearly (Fig. 3) and the slopes of the straight lines (A)
provides the activation energy E of thermal mono- di-, tri-, and
terta-addition of 1-chloro-2-iodohexafluoropropane onto TFE,
respectively: n1, E = 12.5 kJ molꢀ1; n2, E = 13.6 kJ molꢀ1; n3,
E = 15.3 kJ molꢀ1; E = 16.2 kJ molꢀ1. These results confirm the
The thermally initiated process reaction commenced after
360 min. Application of the initiators: AIBN or BP (0.05–
1.00 wt.%) decreased this time to about 60 min. Typical latency
times are on the order of 1–2 h for RfCF2ꢁ + CH2 = CH2 and 2–
3 h for CF2 = CF2. This is a clear indication of the difficulty to
propagate a radical with a taxogen containing an increasing
number of F atoms. An essential difference occurs in the
telomer composition. The fraction of telomers n9–n15
amounted to about 10 mol% in the thermally initiated process.
In the process initiated by AIBN or BP these telomers were not
formed or were formed in an amount up to 2 mol%. However, in
the case when the radical initiators were used the resulting
reaction pressure was unexpectedly high (300 atm) in some
experiments, probably as a result of an initiator decomposition.
Telogen in the form of 2-iodoheptafluoropropane, acted in the
same manner as 1-chloro-2-iodohexafluoropropane. Straight-
chain telomers are formed exclusively, in accordance with the
general mechanism of the radical telomerization [22] (Scheme
7) independently of the telomerization method.
The formation of additional compounds was found only in
the case of an initiator (BP) concentration of 1 wt.%. On the
basis of both the GC-MS analysis and the elementary analysis
the presence of iodine can be excluded. The compound
comprises a derivative of the initiator, BP. Taking into
consideration a relatively high danger associated with
application of radical initiators as well as the formation of
additional compounds, the thermal initiation method was used
in further optimization studies.
Fig. 3. Plot of log a vs. 1/T: n1 (^), n2 (&), n3 (~), n4 (*).

G. Lewandowski et al. / Journal of Fluorine Chemistry 127 (2006) 337–344
341
Table 2
The design matrix and the experimental value of the response functions of the
TFE telomerization with 1-chloro-2-iodohexafluoropropane
No.
x1
x2
x3
Y1–4
Y2–4
1
2
ꢀ1
+1
ꢀ1
+1
ꢀ1
+1
ꢀ1
+1
0
ꢀ1
ꢀ1
+1
+1
ꢀ1
ꢀ1
+1
+1
0
ꢀ1
ꢀ1
ꢀ1
ꢀ1
+1
+1
+1
+1
0
12.6
44.1
31.0
17.6
35.0
43.0
48.5
18.9
30.2
32.0
31.3
9.1
24.4
13.0
7.5
3
4
5
22.2
27.0
23.5
10.0
17.0
17.7
16.6
6
7
8
9
10
11
0
0
0
0
0
0
x1, temperature; x2, molar ratio of telogen to taxogen; x3, reactor filling; reaction
time was 18 h in all experiments; Y2–4, yield of telomers n2–n4; Y1–4, yield of
telomers n1–n4 (response functions describing the process).
Fig. 5. The influence of the temperature and telogen/taxogen molar ratio on the
yield of n1–n4 telomers: reaction time 18 h, filling of the reactor 1.5 kg dmꢀ3
.
result obtained by Tedder and co-workers [24,25] for mono-
additionof perfluoroalkyl iodides onto TFE(E = 14.3 kJ molꢀ1).
Optimization of the technological parameters (independent
variables) of TFE (taxogen) telomerization using 1-chloro-2-
iodohexafluoropropane (telogen) and thermal initiation method
was performed in the following ranges of changes of
parameters: X1, temperature (110–170 8C); X2, molar ratio of
telogen to taxogen of (0.7–1.2); X3, reactor filling (0.7–
1.5 kg dmꢀ3). The reaction time was 18 h in all experiments.
The transition from the system of independent factors in the
natural form to the coded (dimensionless) form was performed
according to equations:
where xi is the coded variable value in the point of the
experiment plan (i = 1–3), and Xi is the natural variable value
in the point of the experiment plan (i = 1–3).
The yield of telomers n2–n4 (Y2–4) and the yield of telomers
n1–n4 (Y1–4) were assumed as the response functions
describing the process. Experiments were performed with
the application of three factors, three-level design of the first
order. The design matrix in coded form (xi) and the
experimental value of the response functions are presented
in Table 2.
Figs. 4–6 present the influence of changes of parameters on
the course of Y1–4 function in the system of two independent
variables system, the third independent variable determining
the maximum of Y1mꢀa4x function. The courses of the yield lines in
Figs. 4–6 indicate a significant influence of temperature and a
less significant effect of the reactor filling and molar ratio of
telogen to taxogen. A rise of temperature increases the yield of
TFE telomers. The effect of a larger filling of the reactor is of a
smaller importance. An increase in the yield caused by
x1 ¼ 0:0333ðX1 ꢀ 110:0Þ ꢀ 1
x2 ¼ 4:0000ðX2 ꢀ 0:7Þ ꢀ 1
x3 ¼ 2:5000ðX3 ꢀ 0:7Þ ꢀ 1
(4)
(5)
(6)
Fig. 4. The influence of the temperature and filling of the reactor on the yield of
n1–n4 telomers: reaction time 18 h, telogen/taxogen molar ratio 0.7.
Fig. 6. The influence of telogen/taxogen molar ratio and filling of the reactor on
the yield of n1–n4 telomers: reaction time 18 h, temperature 170 8C.

342
G. Lewandowski et al. / Journal of Fluorine Chemistry 127 (2006) 337–344
Fig. 7. The influence of the temperature and telogen/taxogen molar ratio on the
yield of n2–n4 telomers: reaction time 18 h, filling of the reactor 1.5 kg dmꢀ3
Fig. 9. The influence of telogen/taxogen molar ratio and filling of the reactor on
.
the yield of n2–n4 telomers: reaction time 18 h, temperature 170 8C.
increasing the reactor filling is greater at higher temperatures
and higher telogen/taxogen molar ratios. The above result may
be explained by a concentration effect caused by increased
reaction pressure, especially at higher temperatures, which
probably changes the reaction kinetics as was observed for
telogen synthesis from ICl and HFP. An increase of the
resulting reaction pressure was approximately 30–65 atm at the
start of reaction.
indicates that the telomer yield is relatively high and does not
change markedly with the changes in the telogen/taxogen molar
ratio at the optimum temperature. There is no need to carry out
the telomerization at 170 8C as the satisfactory yields of
telomers n2–n4 are achieved at 130–140 8C at the optimum
telogen/taxogen molar ratio equal to 0.7 and at the optimum
reactor filling 1.5 kg dmꢀ1. Such regularity can be seen for all
the parameters investigated (Figs. 8 and 9).
The influence of technological parameters on the course of
Y2–4 function in the process with the use of 2-iodoheptafluor-
opropane telogen is presented in Figs. 7–9.
On the basis of analysis of function Y2–4 it can be concluded
that the telomerization process seems to be relatively simple
from the technological point of view. Even a considerable
change of one of the technological parameters does not cause a
marked reduction of the yield of the telomers n2–n4, provided
that the remaining parameters are maintained at the optimum
level. However, a simultaneous change of two parameters,
even when the third parameter is maintained at the optimum
level, causes a rapid decrease of the value of function Y2–4
The isolines in Figs. 7–9 indicate that independent
parameters established in the preliminary investigations
influence significantly the yield of telomers n2–n4. The
temperature and molar ratio of reagents appear to be great
importance in achieving high yields of telomers. At the reactor
filling 1.5 kg dmꢀ1 and at temperature 170 8C an increase in the
telogen/taxogen molar ratio from 0.7 to 1.2 lowers slightly the
yield of n2–n4 telomers from 27 to 24 mol% (Fig. 7). This
(Figs. 7–9).
max
2ꢀ4
The highest yield of telomers n2–n4 (Y
achieved under the conditions presented in Table 3. In a
¼ 27 mol%) was
comparison with the conditions ensuring the highest yield of
max
telomers n1–n4 (Y
¼ 48 mol%) it is necessary to apply a
1ꢀ4
lower molar ratio of telogen to taxogen (0.7). Under the
conditions of the highest yield of telomers n1–n4 (Y1mꢀa4x) the
yield of n2–n4 amounted to 24 mol%. Under the conditions of
the highest yield of telomers n2–n4 (Y2mꢀa4x) the yield of n1–n4
amounted to 43 mol%.
Table 3
Maximum value of the response functions of the TFE telomerization with 1-
chloro-2-iodohexafluoropropane
Maximum
Temperature Molar ratio of
Reactor filling
function value (K)
telogen to taxogen (kg molꢀ1
)
max
1ꢀ4
max
2ꢀ4
Y
Y
48.4
27.0
443
443
1.2
0.7
1.5
1.5
Fig. 8. The influence of the temperature and filling of the reactor on the n2–n4
telomers yield: reaction time 18 h, telogen/taxogen molar ratio 0.7.
Y2mꢀa4x, maximum yield of telomers n2–n4; Y1mꢀa4x, maximum yield of telomers
n1–n4.

G. Lewandowski et al. / Journal of Fluorine Chemistry 127 (2006) 337–344
343
3. Conclusions
never exceed a partial pressure of 20 atm of TFE in the gas
phase at 20 8C.
The most useful telomers of tetrafluoroethene n2–n4 can be
prepared with maximum yield of 27 mol% under conditions of
thermal initiation at 170 8C and at the autogenic pressure
(maximum 65 atm), at the molar ratio of 1-chloro-2-
iodohexafluoropropane (telogen) to tetrafluoroethene (taxo-
gen) of 0.7, and autoclave filling of 1.5 kg dmꢀ3. Elevations of
the molar ratio of telogen to taxogen to 1.2 increase
significantly the amount of telomer n1 and the yield of
telomes n1–n4 increases to maximum of 48 mol%. Although
the most useful products of the technological process are n2–
n4 telomers, their maximum yield is relatively low (27 mol%)
in comparison to the maximum yield of n1–n4 telomers
TFE should be handled in such a way that air or oxygen will
not be introduced into the system. Material that has been
vaporized from the cylinder source should not be collected and
stored without the addition of inhibitor.
4.3. General procedure for the telomerization
Telomerization was performed in the high-pressure auto-
clave made of chromium–nickel–molybdenum steel of 1 dm3
capacity. Mixing of the reactor content proceeded as a result of
the swinging motion. A known (fixed) amount of telogen was
introduced to the autoclave. The autoclave was cooled to
temperature of ꢀ80 8C. The temperature was regulated and
controlled by means of a thermocouple placed in a thermo-
metric well in the furnace wall. After the crystallization of
telogen, the air was removed from the autoclave by means of oil
vacuum pump (1 Torr). From a tank cooled in the liquid
nitrogen a known amount of TFE was distilling off into the
autoclave. The rate of distillation was controlled so that the
overpressure does not exceed 0.66 atm. Each experiment was
carried out for 18 h.
(48 mol%). Thus, it is advisable to carry out the process under
max
the Y
to the process.
conditions utilizing n1 telomers or recycling them
1ꢀ4
4. Experimental
4.1. Raw materials
TFE and HFP were prepared by the pyrolysis of waste PTFF
in accordance with the literature description [26]. Iodine, KF,
ICl were purchased from POCh Gliwice, Poland; 2,20-
azobis(isobutyronitrile) (AIBN) and benzoyl peroxide (BP)
from Fluka.
At the end of the reaction the autoclave was cooled down and
the product was analysed by GC. The mass balance was
performed based on the composition of the post-reactive
mixture. The telomers yield and the conversion of TFE were
calculated.
4.2. TFE handling
The consecutive telomers n1–n4 were separated from the
post-reactive mixture using a Fischer distillation column
containing 70 theoretical plates. The purity of prepared
telomers was verified by GC and at least 98.8% of purity
was achieved. The basic physicochemical properties of
obtained telomers were presented in Tables 4 and 5 and
compared with literature value. Tails containing more than four
taxomons in a molecule of telomer (solid) was not separated
and characterized.
Handling with more than a few grams of the TFE, outside of
a barricaded facility should never be considered. The
spontaneous and violent (explosive) exothermic homopoly-
merization of TFE may take place. In addition, the monomer
can undergo a very exothermic disproportionation, which is
difficult to inhibit except by dilution. Moreover, highly toxic
fumes of perfluoroisobutene are emitted. In any case one must
Table 4
Refractive TFE telomers obtained using 2-iodoheptafluoropropane as telogen
Refracting index nD30
No.
Telomer
B.p. (8C/Torr)
Literature value
Ref.
Literature value
Ref.
1
2
3
4
(CF3)2CFCF2CF2I
94/760
74/70
69/52
91/68
94/760, 95/760
70/70, 63/48
[14,15]
[14,15]
[14,15]
[14,15]
1.3375a
1.3296
1.3287
1.3910
1.3370a
1.3298
1.3290
1.3914
[14]
[14]
[14]
[14]
(CF3)2CF(CF2CF2)2I
(CF3)2CF(CF2CF2)3I
(CF3)2CF(CF2CF2)4I
101.5/70, 83/23
125/70, 111/23
a
n2D5
.
Table 5
TFE telomers obtained using 1-chloro-2-iodohexafluoropropane as telogen
Refracting index nD28
No.
Telomer
B.p. (8C/Torr)
Literature value
Ref.
Literature value
Ref.
1
2
3
4
CF3(CF2Cl)CFCF2CF2I
CF3(CF2Cl)CF(CF2CF2)2I
CF3(CF2Cl)CF(CF2CF2)3I
CF3(CF2Cl)CF(CF2CF2)4I
45–47/40
45/40
[14]
[14]
[14]
[14]
1.3636
1.3554
1.3496
1.3387a
1.3638
1.3552
1.3492
1.3390a
[14]
[14]
[14]
[14]
78–79/36
78/36
106–107/34
130–131/30
106/34
130/30
a
n5D0
.

344
G. Lewandowski et al. / Journal of Fluorine Chemistry 127 (2006) 337–344
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3 m ꢂ 3 mm was made of stainless steel and the stationary
phase was silicone oil 5% on Chromosorbe W-NAW (60–80
mesh). The flow rates of gases were as follows: nitrogen
30 cm3 minꢀ1, air 400 cm3 minꢀ1 and hydrogen 40 cm3 minꢀ1
.
The column was operated under the conditions of a gradual
increase of temperature: isothermally at 55 8C for 5 min,
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