The reaction of SF5Br with select 1,2-dihaloethylenes

Article abstract of DOI:10.1016/j.jfluchem.2008.06.006

SF₅Br reacts with 1,2-haloethylenes (F, Cl, Br) in distinct ways. In the case of F- and Cl-olefins, the expected addition occurs while with 1,2-dibromoethylene a metathetical reaction yielding in a clean reaction a 1:1 mixture of SF₅CH{double bond, long}CHBr and CHBr₂CHBr₂ is found. The mechanism for this reaction is discussed.

Full text of DOI:10.1016/j.jfluchem.2008.06.006

Evaluation Only. Created with Aspose.PDF. Copyright 2002-2021 Aspose Pty Ltd.
Journal of Fluorine Chemistry 129 (2008) 1041–1043
Contents lists available at ScienceDirect
Journal of Fluorine Chemistry
journal homepage: www.elsevier.com/locate/fluor
Short communication
The reaction of SF5Br with select 1,2-dihaloethylenes
*
Rolf Walter Winter, Gary L. Gard
Portland State University, Department of Chemistry, PO Box 751, Portland, OR 97207-0751, USA
A R T I C L E I N F O
A B S T R A C T
Article history:
SF5Br reacts with 1,2-haloethylenes (F, Cl, Br) in distinct ways. In the case of F- and Cl-olefins, the
expected addition occurs while with 1,2-dibromoethylene a metathetical reaction yielding in a clean
reaction a 1:1 mixture of SF5CH CHBr and CHBr2CHBr2 is found. The mechanism for this reaction is
discussed.
Received 4 April 2008
Accepted 4 June 2008
Available online 17 June 2008
ß 2008 Elsevier B.V. All rights reserved.
Keywords:
SF5-alkyl halides (Br
Cl)
SF5-addition
Substitution
Exchange
1. Introduction
When SF5Br is reacted with 1,2-dichloroethylene, the expected
simple addition occurs giving SF5CHClCHBrCl:
The first SF5-containing alkyl bromide was prepared by
reaction of SF5Br with ethylene [1]. Since 1966, our laboratory
has successfully added SF5Br to a number of fluorinated and
chlorofluorinated olefins [2]. In most cases the reaction is a one-
to-one addition of SF5Br to alkenes or alkynes; in some cases
oligomers or polymers are formed [3]. In 1996, the first
successful addition of SF5Br to the brominated olefins CH2 CHBr
CHBr and CF2 CFBr was reported [4]. However, when SF5Br is
added to 1,2-dibromoethlylene a new reaction pathway is
revealed that should be useful in preparing a large number of
interesting SF5-compounds. Further work in this area is ongoing
in our laboratory.
SF5Br þ ClCH¼CHCl ! SF5CHClCHBrCl
(1)
This result is similar to that found for additions of SF5Br to other
chlorinated olefins [6] and to the reaction of CCl3Br with
CHCl CHCl [7].
However, when SF5Br is reacted with 1,2-dibromoethylene, a
more complex reaction occurs:
SF5Br þ 2CHBr¼CHBr ! SF5CH¼CHBr þ CHBr2CHBr2
(2)
The above reaction with the bromoolefin (Eq. (2)) is interesting
because we are aware of only two similar substituent exchanges in
radical reactions; the
g-ray induced reaction of CCl3Br with
allylbromide, leading to a 1:1-mixture of CH2BrCHBrCH2Br and
(CCl3CH2)2CHBr, and similarly the reaction with CHBr CHBr,
resulting in CCl3CH CHBr and sym-C2H2Br4 in the ratio of 1:1 [7].
It should be noted that CCl3Br and 1,2-dichloro-ethylene undergo
addition in the usual manner [7].
A rationalization may be provided by the following series of
addition and abstraction reactions and agrees with the nature of
the isolated products and starting materials:
2. Results and discussion
While a significant amount of research has been carried out
with the addition of SF5Br or SF5Cl to alkenes and alkynes, only one
study has examined the reaction of SF5Br with 1,2-dihaloolefins; in
this study, the stereochemistry of the products formed from the
reaction of SF5Br with cis- and trans-1,2-difluoroethylene was
examined. The results of this study were that SF5Br reacts with cis-
and trans-1,2-difluoroethylene to give nearly the same mixture of
erythro- and threo-forms for the addition product SF5CHFCHFBr
[5].
SF5Br ¼ SF5 þ Brꢀ
ꢀ
ꢀ
CHBr ¼ CHBr þ SF5 ! ½CHBrCHBrSF5ꢁꢀ
½CHBrCHBrSF5ꢁꢀ ! CHBr ¼ CHSF5 þ Brꢀ
* Corresponding author. Fax: +1 503 725 9525.
ðor CHBrCHBrSF5ꢀ þ CHBr ¼ CHBr ! CHBr ¼ CHSF5 þ CHBrCHBr2ꢀÞ
E-mail address: gardg@pdx.edu (G.L. Gard).
0022-1139/$ – see front matter ß 2008 Elsevier B.V. All rights reserved.
doi:10.1016/j.jfluchem.2008.06.006

Evaluation Only. Created with Aspose.PDF. Copyright 2002-2021 Aspose Pty Ltd.
1042
R.W. Winter, G.L. Gard / Journal of Fluorine Chemistry 129 (2008) 1041–1043
CHBr ¼ CHBr þ Brꢀ ! ½CHBrCHBr2ꢁꢀ
HRMS value for SF5CHClCHClBr was determined on a Kratos MS
50TC spectrometer; chemical ionization with methane.
½CHBrCHBr2ꢁꢀ þ SF5Br ! SF5 þ CHBr2CHBr2
ꢀ
3.1. Reaction of 1,2-dibromoethylene and SF5Br
The above scheme accounts for all products and the exchange of
bromine for the SF5-group; a key factor is a weak C–Br bond that
allows for the loss of a Br radical from an intermediate radical in a
neighboring position. Since the C–Cl and C–F bonds are stronger
than the C–Br bond, a similar addition–elimination process with
CHX CHX (X = F, Cl) does not occur.
The reaction of SF5Br with acetylene also produces SF5CH CHBr
and is an alternative method for preparing this compound [8]. The
new method presented in this paper (see Eq. (2)) is a more
convenient pathway and avoids the inherent dangers associated
with the use of acetylene under pressure. Also, other benefits are
that this reaction may be run on a larger scale, separation of
products is easily achieved by pumping away the SF5CH CHBr (bp
A mixture of 1,2-dibromoethylene (a mixture of ꢂ40:60 of the
two isomers) and SF5Br was irradiated at a distance of 40 cm at
ambient temperature by four sunlamps for 1 day after which a
pinkish liquid was obtained. The crude product contained traces
of the 1,2-dibromoethylenes and two main products as found by
GC–MS; the main products found were F5SCH CHBr and
CHBr2CHBr2. A minor product (ꢃ1%) was also present and had
a mass spectrum very similar to that of F5SCH CHBr. The Carius
tube was heated to 95 8C and pumped on through a cold trap
(ꢄ196 8C) for 2.5 h. The material that did not transfer was found
to be virtually pure CHBr2CHBr2 (16.25 g, 98%, identified by IR
spectrum and GC–MS). The condensed product (11.75 g), also
practically pure, was distilled at atmospheric pressure to give
11.08 g of a pink liquid, bp = 86–89 8C; it was stirred for a few
minutes with 5 drops of Hg to remove any coloration and twice
vacuum-transferred, giving 10.96 g (97.1%) of SF5CH = CHBr a
pale tan liquid and which had a tendency to take on a pinkish hue
with time.
86–89 8C) into
a cold trap leaving behind the non-volatile
CHBr2CHBr2; this stoichiometric by-product may be recycled to
give the starting material, 1,2-dibromoethylene. The yield in
reaction (2) is nearly quantitative and higher than in the acetylene
reaction with SF5Br (50–80%) [8]. It is interesting that, although the
dibromoethylene used was a mixture of the geometric isomers
(ꢂ60:40, Rt = 2.95 and 3.36 min, respectively), essentially only one
isomer of SF5CH CHBr (Rt = 2.2 min.) with the trans-configuration
(NMR analysis) was obtained. However, when the crude product
was injected into the GC–mass spectrometer, a second compound
(Rt = 3 min) was present in very low amounts (less than 1%) and
had a mass spectrum very similar to that of the main compound
trans-SF5CH CHBr (it is thought that this compound in very low
amounts is the cis-isomer). Since the 1,2-dibromoethylene isomers
are separated (GC–MS) with a difference of almost one half minute,
distinction between the cis- and trans-SF5CH CHBr should be
possible. To account for the observation that essentially only the
trans-isomer is present it is assumed that at some point of the
reaction an isomerization occurs, most plausibly after addition of
the SF5-radical; the intermediate radical (F5SCHBrCHBrꢀ) may then
rotate about the C–C single bond to the preferred configuration
from which the Brꢀ would be lost, resulting in the formation of the
trans-product. The product from reaction (2) is the same as that of
SF5Br with C2H2, which produces almost exclusively the
Rt = 2.2 min compound and trace quantities of the Rt = 3 min
isomer [9].
1H NMR spectrum:
(d, J12 = 13.09 Hz, 1H). 19F NMR spectrum (AB4):
d
1 = 7.07 (dp, J12 = 13.09 Hz, 1H);
d2 = 7.30
d
A = 80.8 (nine line
pattern, 1F); dB = 64.6 (dm, JAB = 154 Hz, 4F).
GC–MS; Rt = 2.22 min, (fragment, %, assignment): 232, 234, M+,
100%, 100%; 213, 215, 6,5, (M–F)+; 153, 6, (M–Br)+; 133, 1, (M–Br–
HF)+; 127, 38, SF5+; 124, 126, 59, 57, C2H2BrF+ (rearr.); 105, 107, 84,
82, C2H2Br+; 104, 106, 8, 10, C2HBr+; 96, 2, SF2C2H2+; 89, 65, SF3
;
+
79, 81, 2,2, Br+; 70, 20, SF2+; 58, 5, C2H2S+; 57, 4, C2HS+; 56, 2, C2HS+;
51, 3, SF+; 45, 22, CHS+; 43, 4, C2F+ (rearr.); 26, 21, C2H2
.
+
IR spectrum (neat sample on KBr): 3103, w-m; 1692, w; 1611,
m-s; 1548, w; 1461, vw; 1385, w; 1304, vw; 1275, w; 1196, w-m;
1161, w; 1133, w; 1115, w; 919, s; 893, s; 869, s-vs, sh; 847, vs;
777, m; 734, vw; 708, m-s; 690, vw; 679, w; 632, m-s; 600, s; 570,
m-s.
3.2. Reaction of 1,2-dichloroethylene with SF5Br
A mixture of 1,2-dichloroethylene (9.58 g, 99 mmol), 50 ml of
methylene chloride and 17.86 g of SF5Br (86 mmol) was irradiated
at ambient temperature at a distance of 25 cm for a total of 64 h.
After removal of the solvent by distillation, 19.00 g of a light yellow
liquid remained; distillation gave 16.5 g (63% of theory) bp 72–
75 8C (48 Torr). This contained an impurity (GC–MS) and was
probably CHBrClCHClF which could almost be completely removed
by a second distillation.
The mass spectra for the compounds contained the parent ions
and appropriate fragments. The proton NMR spectrum for
SF5CH CHBr was obtained at 500 MHz; from analysis, a trans-
configuration was deduced.
1H NMR spectrum:
JHH = 1.90 Hz, 1H). 19F NMR spectrum (AB4):
pattern, 1F); B = 55.7 (dm, JAB = 147 Hz, 4F).
Infrared spectrum (neat sample on NaCl): 3014, w; 2993, w-m;
1283, w; 1268, w-vw; 1228, vw; 1181, w-m; 1026, w-m; 886, sh, s;
851, vs; 824, s-vs; 748, m; 680, w-m; 671, w-m; 651, w; 622, w;
589, w-m; 562, w.
d
1 = 5.74 (dp, JSF4 = 4.69 Hz, 1H);
d2 = 6.50 (d,
3. Experimental
d
A = 75.3 (nine line
The compound 1,2-dibromoethylene was prepared according to
the literature [10] and the 1,2-dichloroethylene was purchased
from TCI America.
All NMR spectra were run in CDCl3 with either CCl3F or Si(CH3)4
as internal standards. 1H NMR spectra were run on a GE-500
instrument (500 MHz), 19F NMR spectra on
(84.7 MHz). Gas chromatography–mass spectroscopy (GC–MS)
analysis was performed using a HP-Series 5970 instrument
(electron impact, 70 eV), with a temperature program: 50 8C/
2 min; then 11 8C/min ! 280 8C on a DB-5 column of 30 m length,
injection block at 250 8C.
The reactions were run with stirring (Teflon-coated magnetic
stirring bar) in acid-washed and thoroughly dried (heating under
high vacuum) Carius Pyrex tubes and were irradiated (250 W
lamps) at ambient temperature and a distance of 25–40 cm. The
d
a
Varian 390
GC–mass spectrum; (e/z, fragment, %): 302, 304, 306, 308, M+,
very feeble, ratio = 9 (0.1%):15:7:1; 223, 225, 227, (M–Br)+,
ratio = 8 (1.5%):5.5:1; 175, 177, 179, 181, (M–SF5)+, ratio = 10
(25%):15:7:1; 140, 142, 144, (M–SF5–Cl)+, ratio = 3 (1.6%):4:<1;
139, 141, 143, (M–SF5–Cl–H)+, ratio = 10 (9%):14:1; 129, 131,
(F2SC2Cl))+, ratio
4
(12%):1; 127 SF5
,
30%; 115, 117, 119,
+
(FCHClCHCl + H)+, ratio = 9 (100%):6:1; 96, 98, 100, (CHClCHCl
+ H)+, ratio 9 (39%):6:1; 95, 97, 99, CHClCHCl+, ratio = 9 (18%):6:1;
89, SF3+, 34%; 70, SF2+, 5%; 61, 63, C2H2Cl+, ratio = 3 (24%):1; 60, 62,
C2HCl+, ratio = 3 (10%):1.

Evaluation Only. Created with Aspose.PDF. Copyright 2002-2021 Aspose Pty Ltd.
R.W. Winter, G.L. Gard / Journal of Fluorine Chemistry 129 (2008) 1041–1043
1043
High-resolution mass spectrum: 12C21H279Br35Cl219F532S, Fd.:
301.83580. Calcd.: 301.83578.
[3] R.J. Terjeson, G.L. Gard, J. Fluor. Chem. 35 (1987) 653.
[4] R.J. Terjeson, R. Willenbring, G.L. Gard, J. Fluor. Chem. 76 (1996) 63.
[5] A.D. Berry, W.B. Fox, J. Org. Chem. 43 (1978) 365.
[6] Q.C. Mir, R. Debuhr, C. Haug, H.F. White, G.L. Gard, J. Fluor. Chem. 16 (1980)
373.
References
[7] E.A.I. Heira, L.C. Anderson, J. Am. Chem. Soc. 79 (1957) 4940.
[8] J.M. Canich, M.M. Ludwig, W.W. Paudler, G.L. Gard, J.M. Shreeve, Inorg. Chem. 24
(1985) 3668.
[9] In-house work done at Portland State University.
[10] v.d. Walle, Bull. Soc. Chim. Belg. 27 (1913) 209.
[1] C. Merrill, Ph.D. Thesis, University of Washington, 1962.
[2] R.W. Winter, R.A. Dodean, G.L. Gard, ACS Symposium Series 911 on Fluorine-
Containing Synthons, ACS Publications Division and Oxford University Press,
Washington, DC, 2005, pp. 87–118, Chapter 4.