The addition of (CF3SO2)2CHBr to vinylidene fluoride

Article abstract of DOI:10.1016/j.jfluchem.2006.05.023

It has been found that a mixture of (CF₃SO₂)₂CH₂ and (CF₃SO₂)₂CBr₂ can be used instead of (CF₃SO₂)₂CHBr in the radical addition to H₂C{double bond, long}CF₂; the 1:1 and 1:2 adducts have been isolated and characterized. An improved synthesis of (CF₃SO₂)₂CBr₂ is also reported.

Full text of DOI:10.1016/j.jfluchem.2006.05.023

Journal of Fluorine Chemistry 127 (2006) 1324–1327
www.elsevier.com/locate/fluor
Short communication
The addition of (CF3SO2)2CHBr to vinylidene fluoride
*
Rolf W. Winter, G.L. Gard
Department of Chemistry, Portland State University, Portland, OR 97207, USA
Received 23 March 2006; received in revised form 24 May 2006; accepted 24 May 2006
Available online 7 June 2006
Abstract
It has been found that a mixture of (CF3SO2)2CH2 and (CF3SO2)2CBr2 can be used instead of (CF3SO2)2CHBr in the radical addition to
H2C CF2; the 1:1 and 1:2 adducts have been isolated and characterized. An improved synthesis of (CF3SO2)2CBr2 is also reported.
# 2006 Elsevier B.V. All rights reserved.
Keywords: Bis(trifluoromethanesulfonyl) derivatives; Vinylidene adducts with (CF3SO2)2CHBr
1. Introduction
2. Results and discussion
The fact that SF5CH2CF2SO3Li (prepared from
SF5CH2CF2Br) formed the first organic superconductor with
bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF) [1] has
prompted us to try to prepare the structural congener
(CF3SO2)2CHCH2CF2SO3Li from (CF3SO2)2CHCH2CF2Br,
which in turn is prepared from (CF3SO2)2CHBr; this compound
is not as readily prepared as was expected [2]. The previous
work found that treating (CF3SO2)2CHK with Br2 in CCl4 only
formed (CF3SO2)2CHBr [2]; in our laboratory with CH2Cl2 as
the solvent, a mixture of (CF3SO2)2CH2, (CF3SO2)2CHBr and
(CF3SO2)2CBr2, was obtained in the molar ratio of 8:19:4 (19F
NMR).
A 1:1 mixture of (CF3SO2)2CH2 (1) and (CF3SO2)2CBr2 (2)
rapidly converts into a mixture of (CF3SO2)2CHBr (3, 66%),
17% (1) and 17% (2) as determined from 19F NMR; each
compound appears as a singlet at ꢀ78.0 (1), ꢀ63.5 (2), and
ꢀ72.0 (3) ppm. This ratio is found 15 min after mixing and is
1
unchanged after heating at 80 8C for 5 days. The H NMR
spectrum of the 1:1 mixture of (1) and (2) contains two singlets
at 4.97 (3) and 6.18 (1) ppm with a respective molar ratio of
77:23 (Fig. 1). Attempts at obtaining pure (3) by repeatedly
acidifying re-crystallized (CF3SO2)2CBrNa or treating the
mercurial salt [(CF3SO2)2CH]2Hg with bromine in F-113
resulted in mixtures.
Koshar and Mitsch reported in their original work that the
monobromo-compound would add in a free-radical process to
several terminal olefins [2]. Their work did not encompass
fluorinated olefins and they reported only mono-addition
products. In a preliminary run with this mixture, we found that
H2C CF2 and benzoyl peroxide heated to about 80 8C for 1
week showed (19F NMR analysis) that the crude product
contained the 1:1 adduct, (CF3SO2)2CHCH2CF2Br, and very
little (CF3SO2)2CH2 and (CF3SO2)2CBr2. It was concluded
from this result that a 1:1 mixture of (CF3SO2)2CH2 and
(CF3SO2)2CBr2 could be used in lieu of (CF3SO2)2CHBr. Also,
since the dibromo-compound was needed, a simplified
procedure for its preparation was developed.
In order to simplify the preparation of (2), it was found that
several additions and removal of a small amount of water to a
CH2Cl2 solution containing (1) and a slight excess of bromine
resulted in a yield of (3) near 100%. Previous attempts at this
preparation using an alkaline bromine solution gave a yield of
only 47% [2]. It appears that the water removes HBr from the
equilibrium shown below thereby favoring the formation of the
dibromo-product (2):
ðCF3SO2Þ2CH22Br2 ðCF3SO2Þ2CBr22HBr
ð1Þ
ð2Þ
Similar equilibria were investigated by Altschul and Bartlett [3]
and the same type of reaction is evident with (CF3SO2)3CCl
which oxidizes iodide [4].
With a high yield preparation of (CF3SO2)2CBr2 (2) in hand,
it was possible with (CF3SO2)2CH2 (1) to generate in situ
(CF3SO2)2CHBr (3) and study its addition to H2C CF2. In this
* Corresponding author. Fax: +1 503 725 9525.
E-mail address: gardg@pdx.edu (G.L. Gard).
0022-1139/$ – see front matter # 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.jfluchem.2006.05.023

R.W. Winter, G.L. Gard / Journal of Fluorine Chemistry 127 (2006) 1324–1327
1325
Fig. 1. Equilibrium of the three bis(trifluoromethanesulfonyl)methane compounds.
manner the mono- and di-adducts were formed (see equation
3. Experimental
below). It was found that increasing the reaction temperature
from ꢁ80 8C to 90–100 8C led to a greater degree of formation
of the di-adduct. The best results were obtained when a slight
molar excess (ꢁ5%) of (2) was used which simplified the
otherwise difficult separation from unreacted reactants due to
co-distillation. Also, addition products were not formed when
the free-radical initiator was absent:
The compound (CF3SO2)2CH2 was obtained from 3M
company and was sublimed prior to use. The vinylidene
fluoride was obtained from PCR while the bromine was
obtained from the Aldrich Chemical Co.; both chemicals were
used as received.
The infrared spectra of the compounds were obtained on a
Perkin-Elmer 2000 FTIR spectrometer operating at 1.0 cmꢀ1
resolution using KBr windows. The NMR spectra were
recorded in CDCl3-solutions on a Varian EM-390 spectrometer
for fluorine (84.7 MHz, CCl3F (internal) = 0) and on a GE-500
spectrometer (500 (1H) and 100 (13C) MHz, Si(CH3)4 (inter-
nal) = 0). Gas chromatography–mass spectroscopy (GC–MS)
results were obtained using a Hewlett-Packard HP5890 mass
selective detector (operating at 70 eV) and a DB5 column.
Elemental analysis by Mikroanalytisches Laboratorium Beller,
ðCF3SO2Þ2CHCH2CF2Br
ð4Þ
ðCF3SO2Þ2CHBr
ðCF3SO2Þ2CHCH2CF2CH2CF2Br
ꢂ ð1 or 2Þ CH2CF2
ð5Þ
ð3Þ
Both adducts are soluble in water, producing a strongly acidic
solution; adduct (4) is a liquid and adduct (5) is a solid.
Unfortunately, treatment of (CF3SO2)2CHCH2CF2Br (4)
with an excess of one equivalent of sodium sulfite at 115–
135 8C for 2 weeks failed to give (CF3SO2)2CHCH2CF2SO3Na.
The infrared spectra for the new adducts (4 and 5) exhibit
¨
Gottingen, Bundesrepublik Deutschland.
3.1. (CF3SO2)2CBr2
strong absorption bands in the C–F region (1100–1400 cmꢀ1
)
[5]. The SO2 asym. and sym. stretching bands for compounds (4
and 5) are located in the 1391–1399 and 1111–1119 cmꢀ1
region [6]. The C–H absorption bands for (4 and 5) are located
A vigorously stirred mixture of bis(trifluoromethanesulfo-
nyl)methane (20.06 g, 71.6 mmol), methylene chloride (25 ml)
and water (15 ml) was treated with bromine (9.5 ml, 184 mmol)
in five equal portions during a 5 min period; initially, the
bromine color lightened quickly and warming was noted. After
15 min of stirring, a brown two-phase mixture was obtained.
The lower layer was drawn off with a separatory funnel and the
aqueous phase extracted with 5 ml of methylene chloride
(which was now the upper layer). The organic phases were
combined and stirred with 15 ml of water for (1/2) h, where a
lightening of the color was observed. There were still three
species observed in the 19F NMR spectrum with a strongly
increased singlet at ꢀ63.5 ppm for the dibromo-compound, as
compared to the first reaction step. Separating the organic layer
and stirring with another 15 ml of water for 0.5 h again led to
completion of the bromination (there was only the signal for
(CF3SO2)2CBr2 in the 19F NMR spectrum). Drying of the
organic phase overnight with anhydrous magnesium sulfate,
filtering by suction, washing the MgSO4 with CH2Cl2 (25 ml),
removal of the methylene chloride by atmospheric distillation
and vacuum-distilling the product gave 30.06 g (96% of theory)
of (CF3SO2)2CBr2, boiling at 68–72 8C/2.0 Torr, as a light-
brown oil. The lit. value is 107–108 8C/17 Torr [2]. The purity
>98%, the impurity is (CF3SO2)2CHBr by 19F NMR spectro-
scopy and was present after but not before drying; storage over
K2CO3 prevents formation of (3). 19F NMR spectrum:
w1 = ꢀ63.5 ppm, s.
near 3000 cmꢀ1
.
The 1H, 19F and 13C NMR values for the new adducts
(Tables 1 and 2) are in agreement with a structures resulting
from the attachment at the methylene portion of the vinylidene
fluoride molecule. An interesting feature in the 19F NMR
spectra (4 and 5) is the splitting of the CF3 groupings. These are
usually recorded as singlets but for both adducts triplet splitting
is found; there is a long-range interaction which is larger
6
(4.4 Hz) for JFF in the di-adduct then in the mono-adduct
(3.2 Hz). While for the pentane derivative the C(3)F2-unit
appears as a symmetric multiplet and its long-range interaction
can only be inferred by the CF3-splitting in the bis(trifluor-
omethanesulfonyl) methyl grouping, the reciprocity of splitting
between CF2Br and (CF3SO2)2C is clearly seen in the propane
derivative. Gutowsky and Belford [7] found such long-range
coupling with six intervening bonds in the compound
(CF3)2NCF2CFBrCF3 and attributed the coupling observed
between the propyl-CF3 and the amine-CF3 groups to a close
spatial approach between the two centers. The chemical shifts
and splittings of our telomers are correspondingly in close
agreement with those found for CCl3CH2CF2Cl and
CCl3CH2CF2CH2CF2Cl [8] and for CCl3CH2CF2Br [9].
The mass spectrum contained fragments that support the
assigned structure.

1326
R.W. Winter, G.L. Gard / Journal of Fluorine Chemistry 127 (2006) 1324–1327
Table 1
NMR data on 1-bromo-1,1-difluoro-3,3-bis(trifluoromethanesulfonyl)-propane
(CF3SO2)2
CH
CH2
CF2Br
1H NMR
d = 5.06, t, 1.0H,
J = 4.45 Hz
d = 3.28, d-t,
3J23 = 4.49,
3J12 = 13.51, 2.0H
19F NMR
w = ꢀ73.8, t,
6JFF = 3.1, 6.0F
d = 119.41, q,
J = 329.5
w = ꢀ49.0, t-sept.,
6
3J12 = 14.1, JFF = 3.2, 2.0F
13C NMR 1H-decoupled
d = 72.83, s
d = 31.33, t, J = 25.50
d = 116.46, t, J = 305.73
3.2. Bis(trifluoromethanesulfonyl)bromomethane
CHBr), 210 mg of (PhCOO)2 and 11.28 g of vinylidene fluoride
(176 mmol) were added to a 75 ml steel bomb tube and heated
(3d, 105–1108). After cooling, the excess vinylidene fluoride
was condensed into a cold trap (ꢀ1968) and the bomb tube
opened. A dark liquid was found, consisting of some (CF3SO2)2
CH2, (CF3SO2)2CBr2, (CF3SO2)2CHBr, (CF3SO2)2 CHCH2
CF2Br and what was afterwards identified as (CF3SO2)2CHCH2
CF2CH2CF2Br (19F NMR ratio = 4:1:5:23:11, in the above
sequence).
The compound was initially synthesized according to the
directions given by Koshar and Mitsch with the exception that
the potassium salt of bis(trifluoromethanesulfonyl)methane
was made in methanol instead of in ethanol and brominated in
methylene chloride instead of carbon tetrachloride. In this way,
22.68 g of the dry potassium salt was obtained from 20.00 g of
bis(trifluoromethanesulfonyl)methane. 15.57 g of the potas-
sium salt gave 13.95 g of bromination product. This boiled at
64–68 8C/2.5 Torr and consisted (19F NMR spectrum) of an
8:19:4 molar mixture of (CF3SO2)2CH2, (CF3SO2)2CHBr and
(CF3SO2)2CBr2.
After re-sealing the steel tube, and without adding any more
benzoyl peroxide, the vinylidene fluoride previously collected
in the cold trap was re-introduced into the reaction vessel at
ꢀ196 8C and heating was continued for three more days at 105–
110 8C. After bleeding off of the olefin, practically no change in
the composition of the mixture was noted. The crude product
was vacuum-distilled at ꢁ70 8C/3.5–4 Torr, yielding 11.42 g of
a clear liquid, consisting ꢁ60% of 1-bromo-1,1-difluoro-3,3-
bis(trifluoromethanesulfonyl)-propane, the rest was bis(triflu-
oromethanesulfonyl)methane (18%), bis(trifluoromethanesul-
fonyl)bromomethane (18%) and bis(trifluoromethanesulfonyl)-
dibromomethane (4%) by 19F NMR spectroscopy. Further
distillation of the pot residue at 75–938/1 Torr gave a product
that solidified in the condenser. The water flow was interrupted
and the condenser warmed up with a heat gun in order to melt
the solid; distillation was continued with these conditions. This
resulted in 6.01 g (28.5% yield) of a semi-solid in the collection
flask. Separation from 1-bromo-1,1-difluoro-3,3-bis(trifluoro-
methanesulfonyl)-propane was achieved by sublimation at
30 mm and ambient temperature overnight (the cold finger, held
at 3–4 8C, was initially wrapped in cellulose paper to absorb the
collecting liquid and prevent it from falling back into the
sample); the paper is removed and the sublimation temperature
is raised to 55 8C. At 55 8C, any additional propane derivative is
removed by wiping until a solid is collected. The solid obtained
contained a small amount of the propane derivative and was
3.3. Run 1: preparation of (CF3SO2)2CHCH2CF2Br (4)
Theabove mixture containing 8 parts(CF3SO2)2CH2, 19parts
(CF3SO2)2CHBr and 4 parts (CF3SO2)2CBr2 (total wt., 7.77 g)
was heated in a 75 ml steel bomb tube with 2.7 g vinylidene
fluoride and 100 mg of (PhCOO)2 for 1 week at 75–85 8C. The
crude product, 8.79 g of a pale brown liquid, contained very little
(CF3SO2)2CH2 and (CF3SO2)2CBr2 and a new compound (19F
NMR spectroscopy). Distillation at 1–2 Torr and 63–66 8C, gave
7.32 g (ꢁ80% yield of a clear, colorless, oily liquid, identified
as 1-bromo-1,1-difluoro-3,3-bis(trifluoromethanesulfonyl)-pro-
pane (4). A careful examination of the 19F NMR spectrum of the
reaction mixture revealed that there was also present a very small
amount of 1-bromo-1,1,3,3-tetrafluoro-5,5-bis(trifluorometha-
nesulfonyl)-pentane (5). Analytical data of (4) are given below.
3.4. Run 2: preparation of
(CF3SO2)2CHCH2CF2CH2CF2Br (5)
15.50 g of a 1:1 (molar) mixture of (CF3SO2)2CH2 and
(CF3SO2)2CBr2, corresponding to 43.2 mmol of (CF3SO2)2
Table 2
NMR data on 1-bromo-1,1,3,3-tetrafluoro-5,5-bis(trifluoromethanesulfonyl)-pentane
(CF3SO2)2
CH
CH2
CF2
CH2
CF2Br
1H NMR
d = 5.19, t, 1.0H,
J = 4.39 Hz
d = 3.23, d-t,
3J45 = 4.49,
3J34 = 13.69
d = 3.29, t-t,
3J12 = 3J23 = 13.77;
d2 + d4 = 4.0H
19F NMR
w = ꢀ74.2, t, 6.0F,
6JFF = 4.4
w = ꢀ96.3,
m, 2.0F
w = ꢀ45.7, t-t, J12 = 14.7,
3
4J13 = 9.6, 2.0F
13C NMR 1H-decoupled
d = 119.45, q,
J = 329.59
d = 71.36, s
d = 32.32, t,
J = 23.89
d = 117.41, t,
J = 248.50
d = 50.39, quintet,
J = 25.02 (av.)
d = 115.39, t, J = 305.23

R.W. Winter, G.L. Gard / Journal of Fluorine Chemistry 127 (2006) 1324–1327
1327
re-sublimed in the same manner at 40 8C. Finally, 1-bromo-
1,1,3,3-tetrafluoro-5,5-bis(trifluoromethanesulfonyl)-pentane
(2.82 g, 13.4% yield) was obtained as a white solid. This
material developed a pinkish tint after a few weeks.
1002, w-m; 972, vvw; 942, m; 905, vvw; 888, m-s; 828, m-s;
805, w; 777, w-m; 773, w,sh; 748, m; 715, m; 669, vvw; 649, w;
633, vvw; 611, m; 599, m; 576, w-m; 557, w; 554, w; 539, vvw;
508, m; 489, m; 481, w-m,sh; 448, m.
Gas chromatogram–mass spectrum (DB5, 12 m, 50 8C/
4 min, then at 18 8C/min to 280 8C, injection block
temperature = 250 8C): Rt = 8.31 min; mass, %, fragment:
265, 263, 0.6, 0.6%, CSCCH2CF2CH2CF2Br+; 253, 27.1%,
3.5. 1-Bromo-1,1-difluoro-3,3-
bis(trifluoromethanesulfonyl)-propane
(CF3SO2)2CHCH2CF2Br (4)
CF3SO2CCH2CF2CHCF+; 229, 11.6%, C5H3F2O4S2 ; 135,
+
+
Infrared spectrum (neat sample on KBr): 3012, vw; 2947,
vw; 2898, vw; 1428, w-m; 1399, s; 1216, vs; 1111, vs; 1019,
w-m; 948, m; 907, w; 823, vw; 814, vw; 791, vvw; 771, vw;
741, vw; 713, w; 701, w,sh; 661, vw; 643, w; 630, w; 591, w;
582, w; 552, vvw; 542, vvw; 509, m; 501, m; 488, m.
6.8%, C4HF2OS+; 113, 11.0%, C2F3S+; 91, 5.9%, C4H5F2 ; 77,
+
+
+
16.0%, C3H3F2 ; 75, 14.5%, C3HF2 ; 69, 100%, CF3 ; 51,
15.2% (CF2 + H)+.
M.p. = 57–58 8C. Anal. calcd.: for C7H5BrF10O4S2: C,
17.26; H, 1.03; S, 13.16; F, 39.0. Found: C, 17.35; H, 1.09; S,
13.04; F, 38.8%.
Gas chromatogram–ass spectrum (DB5, 12 m, 50 8C/4 min,
then at 18 8C/min to 280 8C, injection block tempera-
ture = 250 8C): Rt = 5.95 min; mass, %, fragment: 229, 4.3%,
Acknowledgement
C5H3F2O4S2 ; 209, 3.0%, (M-CF3SO2-HBr)+; 133, 3.2%,
+
CF3SO2 ; 125, 11.4%, C3F3S+, C3H3F2OS+; 121, 3.8%,
+
We thank Mrs. J. Kelly, Ph.D., of Portland State University
1
+
C3H2FS2 ; 93, 8.2%, C2H2FOS+; 91, 14.2%, C2H3O2S+,
for recording the H and 13C NMR spectra.
+
+
C2FOS+; 77, 17.9%, C3H3F2 , CHO2S+; 76, 5.1%, C3H2F2 ,
+
+
+
CO2S+; 75, 13.9%, C3HF2 ; 69, 100%, CF3 ; 64, 4.0%, SO2 ,
C2H2F2 ; 57, 3.6%, C2HS+, C3H2F+.
+
References
B.p. = 63–66 8C (1–1(1/2) Torr). Anal. calcd.: for
C5H3BrF8O4S2: C, 14.19; H, 0.71; S, 15.15; F, 36.0. Found:
C, 14.10; H, 0.70; S, 15.00; F, 35.9%.
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3.6. 1-Bromo-1,1,3,3-tetrafluoro-5,5-
bis(trifluoromethanesulfonyl)-pentane
(CF3SO2)2CH(CH2CF2)2Br (5)
Infrared spectrum (neat sample on KBr): 3019, w; 2994, w;
2974, w; 2967, w; 2941, m; 1439, w; 1403, m-s; 1391, m-s;
1382, s; 1370, m-s; 1329, w; 1252, m-s; 1226, vs; 1209, vs;
1200, s-vs; 1183, m; 1148, m-s; 1119, s; 1100, vs; 1040, w;
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