Process for preparing telomers from ethylene and alpha, omega-dibromoperfluoroalkylalkanes in the presence of organic free-radical generators

A process is disclosed wherein a telomer having the formula BrCH.sub.2 CH.sub.2 (CF.sub.2 CFX).sub.n CH.sub.2 CH.sub.2 Br is prepared by reacting a telogen of the formula Br(CF.sub.2 CFX).sub.n CH.sub.2 CH.sub.2 Br with ethylene in the presence of an organic free-radical generator, wherein X is fluorine or a trifluoromethyl radical and n is an integer having a value of 1-5. It has been found that, when at least 0.05 mole of said free-radical generator is used for each mole of said telogen, the conversion of the telogen to the telomer is surprisingly increased.

FIELD OF THE INVENTION 
The present invention relates to telomers of ethylene and 
alpha,omega-dibromoperfluoroalkylalkane telogens. More particularly, the 
invention is directed to an improved process for synthesizing specific 
industrially important telomers wherein at least 0.05 moles of an organic 
free-radical generator is added for each mole of 
alpha,omega-dibromoperfluoroalkylalkane telogen to be reacted with the 
ethylene. 
BACKGROUND OF THE INVENTION 
Fluorosilicone elastomers have long been known for their solvent 
resistance, flexibility at low temperatures and excellent high temperature 
properties. Many industrial and military applications have been developed 
which exploit these desirable characteristics (e.g., aircraft sealant in 
view of good resistance to jet fuel). A fluorosilicone-fluorocarbon hybrid 
system described by Pierce et al. (Applied Polymer Symposium, No. 22, 
103-125, 1973) is stated to be particularly resistant to reversion at 
elevated temperatures, the repeat unit of such a hybrid polymer being 
exemplified by the formula --RR SiCH.sub.2 CH.sub.2 CF.sub.2 CF.sub.2 
CH.sub.2 CH.sub.2 SiRR'--wherein R is a methyl radical and R' is a 
trifluoropropyl radical. This hybrid polymer can be prepared by reacting a 
terminally unsaturated intermediate of the formula CH.sub.2 
.dbd.CHCF.sub.2 CF.sub.2 CH.dbd.CH.sub.2 with a chlorosilane of the 
formula RR'SiHCl in the presence of a platinum catalyst, followed by 
hydrolysis and condensation of the resulting chlorine-terminated monomer. 
The terminally unsaturated intermediate, in turn, is prepared by the 
following series of steps: 
##STR1## 
wherein the synthesis of dibromoperfluoroalkylalkanes (II) and (III) each 
takes place in the presence of a catalytic amount of an organic 
free-radical generator. Pierce et al, noted that, while the formation of 
compound (II) according to the first of these reactions is relatively 
facile, only "trace" amounts of the desired compound (III) result 
according to the second reaction wherein about 3 mole percent of an 
organic peroxide was used as the catalyst. This conclusion was also 
reported by Kim et al, in a previous paper (J. Fluorine Chem., 1, 203-218, 
1971). 
Although it is possible to produce small yields of telomer (III) directly 
from compound (I), this is not desirable. Under these conditions, it has 
been observed that a large excess of ethylene must be used and significant 
quantities of unwanted telomers of the type BrCF.sub.2 CF.sub.2 (CH.sub.2 
CH.sub.2).sub.j Br, in which j is an integer having a value of 2 to 10, 
are formed as byproducts. Therefore, the above describe sequence, wherein 
(I) is reacted with a deficiency of ethylene to form (II), the latter is 
isolated and subsequently further reacted with ethylene to form telomer 
(III), is the preferred route. 
Reactions similar to those discussed by Pierce et al, and Kim et al., cited 
supra, are disclosed in U.S. Pat. No. 3,055,953 to Smeltz. Here, compounds 
of the type Br(CH.sub.2 CH.sub.2).sub.m (CF.sub.2 CF.sub.2).sub.n 
(CH.sub.2 CH.sub.2).sub.p Br and Br(CF.sub.2 CF.sub.2).sub.n (CH.sub.2 
CH.sub.2).sub.p Br, in which m and p are integers in the range 1 to 6 and 
n is an integer in the range of 1 to 10, are prepared by reacting 
Br(CF.sub.2 CF.sub.2).sub.n Br or Br(CF.sub.2 CF.sub.2).sub.n (CH.sub.2 
CH.sub.2).sub.p Br with ethylene. These reactions are carried out at 
superatmospheric pressures at 50.degree. C. to 200.degree. C. in the 
presence of a free-radical generating catalyst. Starting pressures of at 
least 150 psi (1,034 kPa) are used and the molar ratio of peroxide 
catalyst to the bromofluorocarbon reactant was no greater than 0.043 in 
any of the examples. Example 5 of the Smeltz patent explicitly discloses 
the high pressure reaction of Br(CF.sub.2 CF.sub.2).sub.2 CH.sub.2 
CH.sub.2 Br with ethylene using a catalytic amount of t-butyl peroxide 
(i.e., peroxide/dibromide reactant in a molar ratio of 0.02/0.46=0.043. 
However, this reference does not specifically teach the corresponding 
reaction of BrCF.sub.2 CF.sub.2 CH.sub.2 CH.sub.2 Br (II) with ethylene to 
produce the highly desirable product BrCH.sub.2 CH.sub.2 CF.sub.2 CF.sub.2 
CH.sub.2 CH.sub.2 Br (III). 
Although the above references suggest that compounds of the type BrCH.sub.2 
CH.sub.2 CF.sub.2 CF.sub.2 CH.sub.2 CH.sub.2 Br can be prepared by the 
free-radical catalyzed telomerization of ethylene with a telogen of the 
type BrCF.sub.2 CF.sub.2 CH.sub.2 CH.sub.2 Br, the yield of the desired 
telomer product is relatively small, and these reactions are therefore 
more of academic than practical interest. Moreover, when the present 
inventor employed the methods of Kim et al. to react BrCF.sub.2 CF.sub.2 
CH.sub.2 CH.sub.2 Br with ethylene in the presence of t-butyl peroxide, 
the conversion of the telogen and yield of BrCH.sub.2 CH.sub.2 CF.sub.2 
CF.sub.2 CH.sub.2 CH.sub.2 Br were even lower than the corresponding 
values reported by Kim et al. It is believed that these lower values can 
be attributed, at least in part, to a more careful workup (i.e., 
distillation, analysis and material balance) of the reaction product 
mixture than was undertaken by Kim et al. There is therefore still a need 
for an improved process for synthesizing the highly desirable telomers 
described supra. 
SUMMARY OF THE INVENTION 
It has now been discovered that the conversion of telogens of the type 
illustrated above to the corresponding ethylene telomer can be 
significantly increased beyond the teachings of the above prior art. 
Contrary to these teachings, wherein a free-radical generator is merely 
considered a catalyst for the telomerization reaction, it has now been 
surprisingly found that this "catalyst" apparently partakes in the 
reaction, although its stoichiometry is yet to be elucidated. Also 
contrary to the teachings of the prior art, it has been discovered that 
there is no need to conduct the telomerization reaction at high pressures. 
Indeed, as described infra, the telomerization reaction is actually more 
efficient at lower pressures and can even be carried out at atmospheric 
pressure. 
The present invention therefore relates to a process for the preparation of 
a telomer having the formula BrCH.sub.2 CH.sub.2 (CF.sub.2 CFX).sub.n 
CH.sub.2 CH.sub.2 Br by reacting a telogen of the formula Br(CF.sub.2 
CFX).sub.n CH.sub.2 CH.sub.2 Br with ethylene in the presence of an 
organic free-radical generator, wherein X is independently selected from 
the group consisting of a fluorine radical and a trifluoromethyl radical 
and n is an integer having a value of 1-5, inclusive, wherein at least 
0.05 mole of said free-radical generator is used for each mole of said 
telogen present. Although a strict definition of a telomer would require 
the value of n to be at least two, those skilled in the art should not be 
confused by the the terms "telogen" and "telomer"0 as used herein.

DETAILED DESCRIPTION OF THE INVENTION 
In the telomerization process of the present invention, a telogen of the 
formula Br(CF.sub.2 CFX).sub.n CH.sub.2 CH.sub.2 Br, in which X is 
independently selected from the group consisting of a fluorine radical and 
a trifluoromethyl radical and n is an integer having a value of 1-5 
inclusive, is reacted with ethylene and at least 0.05 moles of an organic 
free-radical generator for each mole of said telogen. The desired telomer 
product of this process has the structure BrCH.sub.2 CH.sub.2 (CF.sub.2 
CFX).sub.n CH.sub.2 CH.sub.2 Br, in which X and n have their previously 
defined meanings. Although the value of n in the above formulae can be 
greater then about 5, these telomers are not readily distilled and are 
therefore of little commercial value. Additionally, it is preferred that n 
is no more than 3 when the telomer is to be employed in the above 
described preparation of fluorosilicone elastomers. When n is more than 3 
the resultant fluorosilicon polymers generally have too high a glass 
transition temperature and tend to be more plastic than elastomeric in 
nature. Most preferably, n=1. 
The group X in the above formulae representing the telogens and telomers of 
the present invention can be fluorine or a trifluoromethyl radical (i.e., 
--CF.sub.3). Again, for the purposes of preparing the above described 
fluorosilicone elastomers, it is preferred that X is F. Thus, the most 
preferred telogen of the invention has the structure BrCF.sub.2 CF.sub.2 
CH.sub.2 CH.sub.2 Br and the associated telomer product has the structure 
BrCH.sub.2 CH.sub.2 CF.sub.2 CF.sub.2 CH.sub.2 CH.sub.2 Br, these 
compounds also being denoted herein by the Roman numerals (II) and (III), 
respectively. 
The type of organic free-radical generator used in the process of the 
present invention is not specifically limited. This component may be 
selected from any of the known azo or diazo compounds, such as 2,2 
azobisisobutyronitrile. Preferably, the free-radical generator is selected 
from organic peroxides such as hydroperoxides, diacyl peroxides, ketone 
peroxides, peroxyesters, dialkyl peroxides, peroxydicarbonates, 
peroxyketals, peroxy acids, acyl alkylsulfonyl peroxides and alkyl 
monoperoxydicarbonates. 
It is further preferred that the free-radical generator have a 10-hour half 
life temperature within the approximate range 100.degree. C. to 
160.degree. C. However, free-radical generators having a 10-hour half life 
temperature below about 100.degree. C. may still be used provided that 
they are slowly and continuously introduced to the reaction mixture. It 
has been found that, when the telomerization reaction is carried out below 
about 100.degree. C. the telogen Br(CF.sub.2 CFX).sub.n CH.sub.2 CH.sub.2 
Br tends to add multiple ethylene units to yield telomers of the general 
formula Br(CH.sub.2 CH.sub.2).sub.j (CF.sub.2 CFX).sub.n (CH.sub.2 
CH.sub.2)Br, in which j is an integer having a value of 2 or more. On the 
other hand, when the reaction temperature is above about 160.degree. C. 
there is an increasing tendency toward side reactions and the formation of 
undesirable residues. 
Specific examples of suitable peroxides which may be used according to the 
process of the present invention include benzoyl peroxide, t-butyl peroxy 
O-toluate, cyclic peroxyketal, t-butyl hydroperoxide, t-butyl 
peroxypivalate, lauroyl peroxide and t-amyl peroxy 2-ethylhexanoate, inter 
alia. Examples of organic peroxides which fall into the above defined 
10-hour half life temperature range include such compounds as di-t-butyl 
peroxide, 1,3-bis(t-butylperoxyisopropyl) benzene, 
2,2,4-trimethylpentyl-2-hydroperoxide, 
2,5-bis(t-butylperoxy)-2,5-dimethylhexyne-3, cumyl hydroperoxide, t-butyl 
peroxybenzoate and diisopropylbenzene mono hydroperoxide, inter alia. For 
the purposes of the process of the invention, it is preferred that the 
peroxide is di-tert-butyl peroxide (also referred to as t-butyl peroxide 
herein). 
In order to practice the process of the present invention the above 
described telogen of the general formula Br(CF.sub.2 CFX).sub.n CH.sub.2 
CH.sub.2 Br is reacted with ethylene and a free-radical generator such 
that at least 0.05 mole of the free-radical generator is added for each 
mole of the telogen used, said reaction being carried out in the liquid 
state. As previously mentioned, the conversion of the telogen to the 
telomer is surprisingly increased as the amount of the free-radical 
generator is increased. Although no particular upper limit on the amount 
of free-radical generator has been observed, practical considerations 
would limit the level of this component. Thus, for example, a molar ratio 
of the free-radical generator to the telogen of much greater than about 
two would generally not be advisable based on process throughput 
efficiency, as well as safety, considerations. Preferably, about 0.06 to 
about 1.8 mole, and most preferably about 0.1 to 0.2 mole, of the peroxide 
free-radical generator is employed for each mole of the telogen. 
The temperature at which the instant process is run depends upon the 
particular free-radical generator selected, but is preferably within the 
above stated preferred range. The duration of the telomerization reaction 
is, of course, a function of reaction temperature, a total time of at 
least one half life of the free-radical generator under these conditions 
generally being sufficient if the unreacted free-radical generator can be 
recovered and recycled. It is preferred that the ethylene partial pressure 
during the telomerization reaction is below approximately seven 
atmospheres (absolute pressure), most preferably in the range of about 1 
to 2 atmospheres. It has been observed that the conversion of the telogen 
to the telomer, and the yield of the telomer, generally decline as the 
partial pressure is raised beyond the above mentioned range. Moreover, as 
the ethylene partial pressure is reduced, the amounts of byproducts such 
as Br(CH.sub.2 CH.sub.2).sub.2 (CF.sub.2 CFX).sub.n (CH.sub.2 CH.sub.2)Br, 
as well as non-volatile residue, drops relative to desired telomer 
product. As used herein, the percent conversion of telogen to telomer is 
defined as: 
(moles of telomer formed/moles of telogen supplied).times.100; the percent 
yield of telomer is defined as: 
(moles of telomer formed/moles of telogen consumed).times.100. 
The telomerization reaction can be carried out in either batch or 
continuous fashion, the following general processes types being 
illustrative: 
Process A--A tube or autoclave is charged with all ingredients. sealed and 
heated. In this design, the pressure is determined by the amounts of 
ethylene and telogen charged. The use of large amounts of reactants leads 
to undesirably high pressures. Additionally, this could result in a 
dangerous exothermic reaction and this process type is therefore not 
preferred. 
Process B--Same as above described Process A with the exception that the 
ethylene is continuously introduced at a rate sufficient to maintain the 
pressure in the autoclave at a preset level, but no material exits the 
system during the course of the reaction. Since the byproducts of 
decomposition of the free-radical generator are generally volatile, they 
contribute to the total pressure and therefore limit the amount of 
ethylene which can be introduced. 
Process C--Same as above Process B with the exception that the ethylene is 
fed at a constant mass rate and the free-radical generator may be present 
initially or metered to the system at a controlled rate. As in Process B, 
no material exits the system during the course of the reaction. 
Process D--Ethylene and the free-radical generator are fed at a constant 
rate to the bottom of a reactor initially charged with the telogen. The 
temperature at the top of the reactor can be independently controlled so 
as to reflux reactants back into the reactor while allowing byproducts to 
escape through an exit port. This exit port, also located at the top of 
the reactor, can be used to provide a constant back-pressure to the 
system. 
Process E--Same as above Process D with the exception that the free-radical 
generator and the telogen are both charged to the reactor initially and 
the ethylene is introduced at a constant rate to the bottom of the 
reactor. 
For the purposes of the present invention, it is preferred to employ a 
flow-through process such as Process D or Process E, particularly the 
latter, at a pressure in the range of about one to two atmospheres. For 
optimum conversion, the unreacted telogen may be recycled. Likewise, 
unreacted free-radical generator can also be recycled. 
EXAMPLES 
The following examples are presented to further illustrate the process of 
this invention, but are not to be construed as limiting the invention, 
which is delineated in the appended claims. All parts and percentages in 
the examples are on a weight basis and the pressure measurements are 
reported in terms of gage pressures above atmospheric pressure (e.g., 
psig), unless indicated to the contrary. 
In addition, an abbreviated notation has been used to represent the 
fluorocarbons having the following formulae: 
EQU BrCF.sub.2 CF.sub.2 Br= (I) 
EQU BrCF.sub.2 CF.sub.2 CH.sub.2 CH.sub.2 Br= (II) 
EQU BrCH.sub.2 CH.sub.2 CF.sub.2 CF.sub.2 CH.sub.2 CH.sub.2 Br=(III) 
In the following examples products were identified by capillary gas-liquid 
chromatography (GLC) using 25 meter.times.0.2mm glass column and a flame 
ionization detector (FID). Oven temperature was programed at 40.degree. C. 
for 5 minutes followed by heating at 10.degree. C. per minute to 
270.degree. C. Peaks were identified by gas-liquid chromatography 
(GLC)/Mass Spectroscopy (MS). Major products were isolated by distillation 
or preparative GLC and identities confirmed by exact mass determinations 
and .sup.19 F and .sup.1 H nuclear magnetic resonance (NMR) studies. FID 
area percents were converted to weight percents using response factors 
previously determined by injecting known weight ratios of pure components 
into the GLC instrument. 
EXAMPLE 1 
In a typical synthesis of compound II from I, a Hastalloy.TM. "C" autoclave 
was charged with 2,556 g (9.8 moles) of compound I. The compound I used 
was 96.7% pure (acetone and t-butyl alcohol impurities) and was recycled 
from a previous similar preparation of compound II. A small amount of 
ethylene was then used to purge the autoclave at atmospheric pressure. The 
autoclave was heated to 135.degree. C. and the heat turned off. As the 
temperature started to drop, t-butyl peroxide (16.4g: 0.11 mol) was added 
rapidly, and then a continuous flow of ethylene was introduced to the 
bottom of the autoclave through a dip tube. The ethylene flow rate was 
controlled with a needle valve such that a flow of 2 liter/min was 
obtained when the flow was diverted to discharge at atmospheric pressure. 
A resulting exotherm again brought the temperature to 140.degree. C. 
whereupon cooling water was applied to reduce to the autoclave temperature 
to 134.degree. C. Ten such cycles between 134.degree. and 140.degree. C. 
were carried out over a 30 minute period. After 60 minutes from the start 
of ethylene flow the pressure in the autoclave rose to 146 psi (1.007 kPa) 
and the reaction was terminated by closing the ethylene flow and cooling 
to room temperature. 
The product (2.637 g) was removed via the dip tube from the unopened 
autoclave. FID GLC analysis indicated that this product consisted 
essentially of compound I (42.15 Area%). compound II 44.91 area, and minor 
impurity peaks. This product was distilled to recover 99.99% pure II. A 
material balance calculation indicated a 28% conversion and 80% yield of 
compound II based on the amount of compound I consumed. 
EXAMPLE 2 
Synthesis of compound III in a closed autoclave using slow ethylene feed 
(Process C was carried out as follows. A two-liter Hastalloy.TM. autoclave 
was equipped with a stirrer, thermocouple wells, an electronic pressure 
transducer, a 3,000 psi (20,684 kPa) bursting disk, heating jacket and 
water cooling coils. The latter coils were activated to cool the system 
when the reaction temperature was .gtoreq.139.degree. C. Compound II (as 
prepared in Example 1) (327 g, 98% pure; 1.113 mol) was charged to the 
autoclave. The system was cooled to 0.degree. C. evacuated to an absolute 
pressure of 0.2 torr (27 Pa) and then purged with ethylene three times to 
remove oxygen. The autoclave was heated to 135.degree. C. and 5 g of 
t-butyl peroxide was initially introduced, and then fed at a rate of 1.92 
g/hr. using a high pressure metering pump. Ethylene gas was then fed 
continuously through a dip tube beneath the liquid surface. The ethylene 
was supplied at a pressure of 400 psi (2.758 kPa) and was fed to the 
autoclave through a needle valve which was adjusted to give a flow rate of 
10 cc/min when the flow was diverted to discharge at atmospheric pressure. 
After six hours, the total pressure was 40 psi (276 kPa). After 13.5 
hours, the peroxide feed was cut off and the reaction was continued for a 
total of 20 hours, at which point the total pressure was 114 psig (786 
kPa). the total peroxide introduced being 37.3 g (0.2555 mole). Thus, a 
total of 0.22 mole of peroxide was used for each mole of compound II 
charged. The ethylene flow was then cut off and the system cooled, 
whereupon the pressure dropped to 38 psi (262 kPa) at 38.degree. C. 
At the conclusion of the reaction the autoclave contained a total of 362 g 
of a liquid mixture. This mixture was worked up by stripping and 
fractional vacuum distillation to isolate 37.0 g of 79.3% pure III. This 
product was further purified by recrystalization wherein it was mixed with 
iso-octane and cooled to -78.degree. C. to provide a precipitate of 96% 
pure compound III having a melting point of 58.degree. C. after being 
dried under vacuum. GLC analysis of the distillates in conjunction with an 
overall material balance calculation indicated that the product contained 
200.3 g of unreacted II (0.703 mole), 29.5 g of product III (0.0933 mole), 
40.8 g of residue, 58.3 g of low boilers consisting essentially of acetone 
and t-butyl alcohol, trace amounts of the compounds BrCH.sub.2 CH.sub.2 
CF.sub.2 CF.sub.2 CH.sub.2 CH.sub.3, BrCH.sub.2 CH.sub.2 CF.sub.2 CF.sub.2 
CH.sub.2 CH.sub.2 CH.sub.2 CH.sub.2 Br and unreacted peroxide. From the 
material balance and the known quantity of compound II charged to the 
reactor, the conversion of II to III and yield of this reaction were: 
Conversion=100.times.0.0933/1.113=8.4% 
Yield=100.times.0.942/(1.113-0.703)=22.8% 
EXAMPLE 3 
The following example illustrates the synthesis of compound III in a flow 
reactor using a metered peroxide and ethylene feed (Process D). 
A stainless steel pressure cylinder (300 cc capacity) was equipped with a 
heating jacket and an 1/8 in (3.2 mm) diameter dip tube positioned near 
its bottom for the introduction of reactants. A tube leading from an 
outlet port situated at the top of the cylinder was connected to a cold 
trap (-78.degree. C.) which was fitted with a compressed air source to 
provide a back pressure of 10 psi (69 kPa). The cylinder was charged with 
350.4 g (1.217 moles) of compound II and heated to a temperature of 
140.degree. C. and controlled at this set point. Feeds of ethylene gas and 
liquid t-butyl peroxide were combined and delivered to the cylinder 
through the dip tube. The ethylene flow rate was set at 22 cc/min 
(calibrated at atmospheric pressure). The peroxide was fed from a 
calibrated metering pump at a rate of 4.0 g/hr. During this run, the exit 
port and tubing above the reactor cylinder were separately maintained at a 
temperature of 45.degree. C. 
Reaction was carried out for 7.8 hours, at which point a total of 29.7 g 
(0.203 mole) t-butyl peroxide and 0.46 mole of ethylene had been fed to 
the cylinder. Thus, a total of 0.17 mole of peroxide was used for each 
mole of compound II. 
At the conclusion of the reaction the cylinder contained a total of 334.4 g 
of a liquid mixture and the cold trap contained an additional 20.6 g of 
liquid. The contents of the cylinder were worked up by stripping and 
fractional vacuum distillation to isolate 39.1 g of 81.0% pure III. 
Analysis of the distillates, and cold trap contents, in conjunction with 
an overall material balance calculation, indicated that the product 
contained 23.4 g low boilers (mostly the byproducts t-butyl alcohol and 
acetone). 2.4 g of unreacted peroxide (0.0165 mole), 259.0 g of unreacted 
II (0.8992 mole), 32.9 g of product III (0.1041 mole), 26.6 g of residue 
and trace amounts of the compounds BrCH.sub.2 CH.sub.2 CF.sub.2 CF.sub.2 
CH.sub.2 CH.sub.3 and BrCH.sub.2 CH.sub.2 CF.sub.2 CF.sub.2 CH.sub.2 
CH.sub.2 CH.sub.2 CH.sub.2 Br. From the material balance and the known 
quantity of compound II charged to the reactor, the conversion and yield 
of this reaction were: 
Conversion=100.times.0.1041/1.217=8.6% 
Yield=100.times.0.1052/(1.229-0.9089)=32.9% 
EXAMPLES 4-11 
Synthesis of compound III according to the procedure of Example 3 was 
repeated wherein the molar ratio of the peroxide to the compound II 
introduced was varied between 0.01 and 1.76. In each case, the reaction 
pressure was held at 10 psi (69 kPa) the temperature was 
137.degree.-140.degree. C. and the reaction time was 10-26 hours. Table 1 
presents a summary of these parameters for each experiment, along with the 
respective conversion of II to III and the yield of the latter material. 
TABLE 1 
______________________________________ 
Con- 
Ex- Reactor Reaction Mole Ratio 
version 
Yield 
ample Temp. (.degree.C.) 
Time (hr) Peroxide/II 
(%) (%) 
______________________________________ 
4* 137 26 0.49 6.5 39.3 
5* 140 20 1.76 16.9 23.0 
6* 140 24 1.44 16.6 33.4 
7* 140 24 0.82 10.8 31.6 
8 140 20 0.54 9.0 17.9 
9 140 10 0.17 8.6 30.2 
10 140 14 0.06 5.3 27.8 
11 140 16 0.01 3.2 21.8 
______________________________________ 
*approximately 1/20th scale runs; calculated values believed to be less 
accurate than those for fullscale runs. 
The % conversion from Table 1 is plotted as a function of the peroxide mole 
ratio in FIG. 1, the plot being forced through the theoretical (0, 0) 
point. From this figure and Table 1 it can be seen that there is a drastic 
drop off in the conversion of compound II to compound III when the molar 
ratio of peroxide to compound II charged falls below about 0.05. Since the 
half-life of the t-butyl peroxide at the above reaction temperatures is 
less than about one hour, the variation of reaction time should have no 
impact after approximately four hours. 
Synthesis of compound III according to the procedure of Example 9 was 
repeated wherein the molar ratio of the peroxide to the compound II 
introduced was 0.18, the temperature was 140.degree. C. the reaction time 
was 18 hours and the pressure was 100 psi (689 kPa). The conversion of II 
to III was 6.0% and the yield was 19.6%. It can be seen that, even though 
this reaction was carried out for a longer time than that of Example 9, 
the effect of increased pressure resulted in diminished conversion and 
yield. 
EXAMPLE 13 
The following example illustrates the synthesis of compound III in a flow 
reactor using a metered ethylene feed wherein all the peroxide is 
initially present (Process E). 
The reactor cylinder used in Example 3 was charged with 352.3 g of compound 
II (1.223 moles) and 30.5 g (0.211 mole) of liquid t-butyl peroxide. The 
reactor temperature was set at 113.degree. C. and ethylene gas was fed 
beneath the liquid surface through the dip tube at a flow rate of 17 
cc/min. The exit port and tubing above the reactor were heated separately 
at 45.degree. C. and were connected to a cold trap held at -78.degree. C. 
and under a back pressure of 10 psi (69 kPa). After 22 hours the 
temperature was raised to 125.degree. C. and then slowly to 140.degree. C. 
At this point, 25 hours had elapsed and a total of 1.1 moles of ethylene 
had been introduced; the run was terminated. In this example, a total of 
0.17 mole of peroxide was used for each mole of compound II. 
At the conclusion of the reaction the cylinder contained a total of 351.2 g 
of a liquid mixture and the cold trap contained no additional liquid. The 
contents of the cylinder were worked up by stripping and fractional vacuum 
distillation to isolate 48.3 g of 83.7% pure III. Analysis of the 
distillates, in conjunction with an overall material balance calculation, 
indicated that the product contained the byproducts t-butyl alcohol and 
acetone, 0.4 g of unreacted peroxide, 241.3 g of unreacted II (0.8377 
mole), 40.4 g of product 111 (0.1278 mole), 38.1 g of residue and trace 
amounts of the compounds BrCH.sub.2 CH.sub.2 CF.sub.2 CF.sub.2 CH.sub.2 
CH.sub.3 and BrCH.sub.2 CH.sub.2 CF.sub.2 CF.sub.2 CH.sub.2 CH.sub.2 
CH.sub.2 CH.sub.2 Br. From the material balance and the known quantity of 
compound II charged to the reactor, the conversion and yield of this 
reaction were: 
Conversion=100.times.0.1278/1.223=10.5% 
Yield=100.times.0.1278/(1.223-0.8377)=33.2% 
EXAMPLES 14-17 
Synthesis of compound III according to the procedure of Example 13 was 
repeated under the conditions shown in Table 2 and at a pressure of 10 psi 
(689 kPa). The calculated conversion and yield are also presented for each 
experiment. 
TABLE 2 
______________________________________ 
Reactor Conditions 
Mole Ratio 
Conversion 
Yield 
Example 
(.degree.C.) 
(hr) Peroxide/II 
(%) (%) 
______________________________________ 
14 113 22 0.17 9.6 35.7 
15* 113-126 25 0.17 9.0 33.6 
16* 113-140 40 0.18 10.8 35.3 
17* 113-140 41 0.18 11.8 38.1 
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*scaled up approximately ten fold in a onegallon (.apprxeq.4 liter) 
reactor. 
EXAMPLE 18 
The following example illustrates the preparation of compound III at 
atmospheric pressure in a flow reactor (Process E). 
A 500 ml three-necked flask equipped with a sintered, stainless steel 
dispersion tube and a thermometer was charged with 350.6 g (1.211 mole) of 
compound II (99.5% pure) and 31.5 g (0.216 mole) of t-butyl peroxide. The 
flask was fitted with a 3 cm diameter.times.35 cm long Vigreux 
distillation column which was topped by a distillation head and a reflux 
condenser. The distillation head was connected to a dry ice trap in series 
with an oil-filled bubble tube and then vented to the atmosphere. After 
purging the flask with ethylene to remove oxygen, heat was applied so as 
to control the temperature of the reaction at 116.degree. C. Ethylene gas 
from a feed cylinder was then introduced beneath the surface of the above 
mentioned liquid reactants through the dispersion tube at a rate of 22 
cc/min. In addition, ethylene was recirculated from the top of the reflux 
condenser back to the dispersion tube by means of a bellows pump at a rate 
of 104 cc/min. Thus, the total ethylene flow through the dispersion tube 
was at 126 cc/min. After 1.5 hours the ethylene flow from the feed 
cylinder was reduced to 12 cc/min. After 24.5 hours the temperature was 
raised to 124.degree. C. and allowed to increase such that the contents 
reached 135.degree. C. after 48 hours, at which point a total of 1.5 moles 
of ethylene had been introduced and the reaction was terminated. In this 
example, a total of 0.18 mole of peroxide was used for each mole of 
compound II. 
The flask contained a total of 342 g of a liquid mixture and the cold trap 
contained 16 g of additional liquid. These liquids were worked up as 
before. Analysis and an overall material balance calculation indicated 
that the liquids contained 15.8 g of a mixture of the byproducts t-butyl 
alcohol and acetone, 2.3 g of unreacted peroxidaa 226 g of unreacted II 
(0.785 mole), 44.8 g of product III (0.142 mole), 34.5 g of residue and 
trace amounts of the compounds BrCH.sub.2 CH.sub.2 CF.sub.2 CF.sub.2 
CH.sub.2 CH.sub.2 and BrCH.sub.2 CH.sub.2 CF.sub.2 CF.sub.2 CH.sub.2 
CH.sub.2 CH.sub.2 CH.sub.2 Br. The conversion and yield of this reaction 
were: 
Conversion=100.times.0.142/1.211=11.7% 
Yield=100.times.0.142/(1.211-0.785)=34.2% 
EXAMPLE 19 
The following example illustrates the synthesis of compound III in a flow 
reactor using a metered ethylene feed wherein all the peroxide was present 
initially (Process E) and the pressure was maintained at 115 psi (793 
kPa). 
A 600 cc Hastalloy,.TM. "C" autoclave was fitted with a stirrer, 
thermocouple, electronic pressure transducer, a bursting disk, a heating 
jacket, water cooling coil and an inlet dip tube. The dip tube of the 
autoclave was connected to a metered ethylene gas supply. An exit stream 
from the autoclave was also metered and connected to a cold trap such that 
gasses could be vented at a controlled rate. 
The autoclave was charged with 351.0 g of compound II (1.219 moles, 99.9% 
purity) and 30.9 g (0.211 mole) of liquid t-butyl peroxide. Nitrogen gas 
(100 cc/min) was fed through the dip tube for 20 minutes with the exit 
metering valve open and the temperature set at 25.degree. C. to purge the 
system of oxygen. After this purging step, the inlet and exit valves were 
closed and the autoclave was heated to 113.degree. C. Ethylene was fed 
through the dip tube at a rate of .ltoreq.50 cc/min until the pressure in 
the autoclave was 115 psi (793 kPa). The gas exit piping above the reactor 
was heated separately to 45.degree. C. The exit valve was opened so as to 
allow a flow of 20 cc/min of excess ethylene to pass through the cold 
trap, the latter being maintained at -78.degree. C. After 21 hours, the 
temperature was slowly raised to 139.degree. C. the run being terminated 
after a total of 26.7 hours had elapsed. A total of 2.4 moles of ethylene 
were fed and 0.17 mole of peroxide was used for each mole of compound II 
charged. 
At the conclusion of the reaction, the autoclave contained a total of 395.4 
g of a liquid mixture and the cold trap contained 4.5 g of low boilers 
which were mostly tert-butanol and acetone. The contents of the autoclave 
were worked up by stripping and fractional distillation to isolate 34.8 g 
of 81.6% pure III. Analysis of the distillates in conjunction with an 
overall material balance calculation indicated that the product contained 
the byproducts acetone and t-butyl alcohol, 4.4 g unreacted peroxide, 
233.3 g of unreacted compound II (0.8099 mole), 28.6 g of product III 
(0.0905 mole), 56.3 g residue and trace amounts of BrCH.sub.2 CH.sub.2 
CF.sub.2 CF.sub.2 CH.sub.2 CH.sub.3 and BrCH.sub.2 CH.sub.2 CF.sub.2 
CF.sub.2 CH.sub.2 CH.sub.2 CH.sub.2 CH.sub.2 Br. The calculated conversion 
and yield of this reaction were: 
Conversion=100.times.0.0905/1.219=7.4 % 
Yield=100.times.0.0905/(1.219-0.8099)=22.1% 
EXAMPLE 20 
The following example illustrates the synthesis of compound III wherein 
ethylene is metered into a reactor but no stream exits the reactor 
(Process B). 
The procedure of Example 19 was followed with the exception that the exit 
valve remained closed and, when the autoclave temperature reached 
113.degree. C. ethylene gas was fed through the dip tube so as to maintain 
a pressure of 115 psi (793 kPa) for a period of 21 hours. 
At the conclusion of the reaction, the autoclave contained a total of 380.0 
g of a liquid mixture which was stripped to isolate 305.3 g of a mixture 
containing 5.6 wt % of pure compound III. Analysis of the distillate in 
conjunction with an overall material balance calculation, indicated that 
the product contained the byproducts acetone and t-butyl alcohol, 19.0 g 
of unreacted peroxide, 247.2 g of unreacted compound II (0.8582 mole), 
17.0 g of product III (0.0538 mole), 46.8 g residue and trace amounts of 
BrCH.sub.2 CH.sub.2 CF.sub.2 CF.sub.2 CH.sub.2 CH.sub.2 and BrCH.sub.2 
CH.sub.2 CF.sub.2 CF.sub.2 CH.sub.2 CH.sub.2 CH.sub.2 CH.sub.2 Br. The 
calculated conversion and yield of this reaction were: 
Conversion=100.times.0.0538/1.219=4.4% 
Yield=100.times.0.0538/(1.219-0.8582)=14.9%