Journal of Fluorine Chemistry, 30 (1985)
22-l
227-235
Received: April 16, 1985; accepted: July 28, 1985
FREE RADICAL -BORATE
HALOGENATION
PART 6[11.
OF POLYFLUORO-ETHERS
AND
ESTERS
R.D. CHAMBERS
Department Durham
CHEMISTRY.
and B. GRIEVSON
of Chemistry,
University
Science
Laboratories,
South Road,
City, DHl 3LE (U.K.)
SUMMARY
Chlorination results
and bromination
of CH30CH2CF2CFHCF3
for the site of halogenation
lateness
of the transition-state
supports
the theory.
a new route for conversion
and a rationalisation
is advanced.
Chlorination
gave contrasting
Direct
of fluorinated
of fluorinated
alkenes
based on the
fluorination
trialkylborates to fluorinated
provides acid
chlorides.
INTRODUCTION
In earlier parts of this series we described dimethylether
121 and trimethylborate
we are exploring We
alkenes.
the chemistry
studied
(2) was obtained
free-radical
[3] to various
additions
fluorinated
alkenes
of and
of these and other adducts to fluorinated
[2] chlorinations
and bromination
using bromine but chlorination
of (1) and found that
products
were very solvent
dependent.
a
H
H
H CH20CH3
(1)
CHXOCH3
a
(2)
F
+
F
F
CH20CH2X
o(3)
(X = halogen)
0022-l 139/85/$3.30
0 Elsevier Sequoia/Printed
in The Netherlands
228 RESULTS
AND DISCUSSION
In the light of the puzzling have now explored
results
the corresponding
obtained
halogenation
the product
obtained
of these studies are shown below and a preference
position
CF3CFHCF2CH20CH3
of dimethylether
with
The results terminal
from addition
in halogenation
reactions
hv,
+ Cl2
to hexafluoropropene.
In contrast,
is clearly observed.
CF3CFHCF2CHClOCH3
reaction
(6) + CF3CFHCF2CHC10CH2C1
+ CF3CFHCF2CH20CHC12 (7) Solvent
% (5)
Neat ccl4 cs2
(8)
L(7) + (a)1
(6)
6
45
47
4
49
45
16
76
7
not only differed
bromine,
through
the preference
for the position
halogenation
but, also, in the fact that substantial
dimerisation
products
(4) + Br
Sunlight 2
3
for the of (4) with
+ CF3CFHCF2CH20CH2Cl
(5)
(4)
of (1) w
(4) i.e.
It is clear, however,
were obtained.
CF3CFHCF2CHBrOCH3
of
amounts of dehydrothat although
+ CF3CFHCF2CH20H (10)
(9) + Dehydrodimers (11) Solvent
% (9)
Neat cs2 chlorination
(10)
(11)
12
38
49
81
9
9
occurs preferentially
occurs preferentially An explanation reactivity
at the internal
whereas
CH
of bromine
and chlorine
lower reactivity
[4].
bromination
lies in the relative
atoms and the consequences
postulate
with a transition-state
position,
site.
2 for these contrasting results
that stem from the Hammond reactivity
at the terminal
This approach
that resembles
would be associated
of this,
associates
greater
the initial state,
with a transition-state
closer
229
In the present
to the product.
could be represented
context,
of halogenation,
by transition-states
these situations
(12) and (13) and the consequence
of this would be that polar effects would be more important the stability
of the developing
for (12) while
radical would be more important
+
product
*
product
for (13).
’ (13) In comparing
chlorination
state for chlorination of the transition-state preferential consistent
and bromination,
it is likely that the transition-
is more like (12) and, for bromination, will move
attack of a chlorine
towards
the character
On this basis,
(13).
atom at the terminal position
with a transition-state
like (14) because
the
in (4) is
this involves
attack at
H3C-0 [CF~CFHCF~+-
[CF,CFHCF,CH,O-CH,-H----cY]
(15)
(14)
the least electrophilic group would
I%H----cl*]
inhibit formation by
be even less likely, transition-state
Electron
site.
withdrawal
of (15), while attack at the CF3CFH-site
the electrophilic
chlorine
like (13) for attack by bromine,
that (16) is preferred would be stabilised
by the polyfluoroalkyl
to (17).
by adjacent
Although oxygen
atom.
Assuming
would
a
then we can appreciate
both of these transition-states
(la), nevertheless,
(16) is preferred
CH 01 [CF3CFHCFz&----H-Br]
iCF,CFHCF,CH,'d-tH,---H-Brl
(16)
(17)
as a developing radical
E-?-R
(17).
(or RF)
secondary Although
W
-z
?&O-R
(or RF)
primary
atom at the CF3CFH site would
R = alkyl RF = Polyfluoroalkyl
1
(lab)
lead to a developing obviously
rather than the developing
attack by a bromine
(Ma)
oxygen
radical,
tertiary
less favourable
[5,6j.
radical
in the transition-state,
than the known stabilising
influence
this is of adjacent
230 A consequence fluorine chlorine. through
of this model for reactivity,
We have tested this by bubbling
a solution
of (4) in CF2ClCFC12,
products
(19) - (21) arise wholly
together
with a small amount of alcohol
induced
(4)
is that attack by a
atom on (4) should be even more governed
cleavage
F2, N2 CF2C1CFC12,
at room temperature
(10) probably
and the
arising
of (21) probably
CF3CFHCF2CH20CH2F
R.T.'
diluted with nitrogen,
from attack at the terminal position,
The formation
of (4).
by polar effects than
fluorine,
from acid-
partly arises from
(44%)
(19) + CF3CFHCF2CH20CHF2
(18%)
(20) + CF3CFHCF2CH20COH
(20%)
(21) + CF3CFHCF2CH20H
(7%)
(10) the presence
of oxygen impurity
of hydrocarbon
by other workers
shown
to fluorinated
corresponding
+
oxygen, has been reported
[3] that free-radical
alkenes,
fluorinated
e.g. (RCH~~)~B
since the functionalisatior
containing
[7,81.
We have recently borates
in the fluorine,
groups, using fluorine
cF2=cFcF
occurs readily,
trialkylborates
additions
of trialkyl-
to give high yields
(22).
of
These derivatives
Y or 3
Peroxide'
(RyH0)3B CF2CFHCF3 (22)
are readily
chlorinated
fluorinated
alkenes
and,overall,this
to corresponding
provides
a route for conversion
acid chlorides
of
(23) (see Table).
F-alkene--~(Cl)H-~-~_C0C~ (23)
Earlier adducts
’ ’
workers
have described
but these reactions
containing
usually
chlorination
of corresponding
gave complex mixtures
little or none of the acid chloride
[9,10].
methanol
of products,
231 TABLE Chlorination
of fluorinated
trialkylboratesa % Yield
AcidChloride
Borate
CF3CFHCF2COCl
B(OCH2CF2CFHCF3)3
(2)
75
(28)
83
(29)
63
COCl
F
H
0:
COCl F
Cl
[7
(a) Sealed pyrex tube, excess chlorine,
UV irradiation,
18 - 50°C.
EXPERIMENTAL
The radical
induced addition
alkenes used as starting paper
Chlorine
[3J.
by normal vacuum
products
materials
was used as supplied
line techniques.
of ethers and borates
were prepared
as outlined
and transferred
Quantitative
analyses
carried
out on a Varian 'Aerograph Model 920 equipped
balance
detector
instrument purify
(di-isodecylphthalate
equipped
the products.
Varian EM360L chemical
by glc were
with a gas density P).
with a cold trap for sample collection
spectrometer
operating
shifts are quoted relative
fluoromethane.
from the cylinder
20%, on chromosorb
Proton and fluorine
A similar
was used to
nmr spectra were recorded
on a
at 60 and 56.46 MHz respectively to tetramethylsilane
Mass spectra were recorded
and glc/ms were recorded
to fluoro-
in a previous
and
and trichloro-
on an A.E.I. MS9 spectrometer
on a V.G. Micromass
12B spectrometer
fitted with
a Pye 104 glc.
Chlorination
(a)
of 2,2,3,4,4,4-hexafluorobutylmethyl
ether (4)
Neat
Adduct
(4) (1.95 g, 10 mmol),
tap, was degassed transfer. disappeared
and chlorine
contained
The mixture was left in sunlight (5 30 mins.).
in a Pyrex tube with
(0.7 g, 10 mmol) introduced
'rotaflo'
by vacuum
until the chlorine
colour
The tap was opened and the gaseous products
232 c
vented
to give a liquid product
Separation
(2.49 g).
gave l-chloro-2,2,3,4,4,4_hexafluorobutyl
by preparative
glc
methyl ether (5) (0.14 g, 6%) (nc);
6H 3.78 (3H, s, CH3), 5.77 (IH, t (broad), CHF), 6F 74.2, 74.6 (3F, m, CF3), 122.4, 124.0, 124.7 (2F, m, CF2), and 214.9, 216.0 79(36),
m/z 195 (Mf-Cl, 12), 81(14), methyl
ether
(5) (1.10 g, 45%) (nc), b.p. 133OC (Found: C5H5C1F60
Cl, 15.7.
F, 48.5;
(lF, dm, J 44 Hz, CFH);
2,2,3,4,4,4_hexafluorobutyl C, 26.4;
H, 2.2;
C, 26.0;
requires:
chloroH, 2.3;
F, 49.5;
Cl,
15.4%);
6H 4.13 (2H, m, CH2CF2), 5.10 (lH, dm, J 44 Hz, CFH), 5.63 (2H, s,
0CH2C1),
6F 75.0 (3F, m, CF~), 117.3, 122.0 (2~, AB, J 221 Hz, CF2), and
214.3
(lF, dm, J 44 Hz, CFH);
49(100),
and a mixture
(Found:
C, 23.0;
22.6;
H, 1.5;
m/z 195 (M+-Cl, 45), 81(32),
of di-chlorinated F, 41.1;
H, 1.8;
F, 43.0;
Cl, 26.8%);
CFH) (3.8 H), 5.70 (a.6 H, s, 0CH2C1),
(b)
Carbon tetrachloride
A mixture
containing
equipped gaseous
with a rotaflo by-products
comparison
?iH4.37
(1) and (8) (1.14 g, 47%) C5H4C12F60 CF2CH20)
(m,
requires:
C,
and 5.10 (dm,
7.48 (lH, s, OcHC12).
(4) (0.99 g, 5 mmol), chlorine
(3.11 g, 20 mmol), contained
tap was irradiated
were allowed
of glc retention
51(66),
solvent
adduct
mmol) and carbon tetrachloride
species
Cl, 26.9.
79(97),
with sunlight
to evaporate
(0.51 g, 7
in a pyrex tube
for 1 hour.
The
leaving a liquid product
times with port (a) gave the chlorinated
and
adducts
(2) (4%), (5) (49%) and (I) and (8) (45%).
(c)
Carbon disulphide
A mixture
containing
solvent
adduct
6 mmol) and carbon disulphide for one hour.
The gaseous
a liquid product (Z)PlUS
(a)
adducts
to evaporate
leaving
(5) (16%), (2) (76%) and
methyl
ether (2)
Neat containing
13 mmol) contained
adduct
(4) (1.94 g, 10 mmol) and bromine
in a pyrex tube with a rotaflo
for 3 days. to evaporate
components ether
were allowed
the chlorinated
of 2,2,3,4,4,4_hexafluorobutyl
A mixture
allowed
by-products
containing
(0.45 g, with sunlight
(8) (7%).
Bromination
sunlight
(4) (1.04 g, 5 mmol), chlorine
(2.81 g, 37 mmol) was irradiated
The tube was opened to leave a yellow
by preparative
(2.04 g,
tap was irradiated
and the gaseous by-products
liquid
(2.7 g).
Separation
C, 22.1;
were
of the
glc gave l-bromo-2,2,3,4,4,4_hexafluorobutyl
(z), (0.32 g, 12%) (nc), b.p. 134OC (Found:
with
H, 1.8;
methyl F,
233
41.7;
Br, 29.7.
C5H5BrF60
requires:
C, 21.8;
H, 1.8;
F, 41.5;
Br,
6H 3.63 (3H, s, CH3), 5.27 (lH, dm, J 44 Hz, CHF), 6.00 and 6.07
29.1%);
(lH, t, J 9 Hz, CHBr);
Q
m, CF2), 215.3 and 217.3
76.1 and 76.7 (3F, m, CF3), 120.1 and 122.1 (lF, dm, J 44 Hz, CFH);
2,2,3,4,4,4-hexafluorobutan-l-o1 dehydrodimers
(2)
(2)
(1.32 g, 49%),
(2F,
m/z 195 (M+-Br, lOO%),
[ll] (1.02 g, 38%), and unassigned
(Found:
F, 58.8.
C10H10F1202
requires:
F, 58.5%), m/z 195 (100%).
(b)
Carbon disulphide
A mixture
containing
solvent
adduct
0.75 mmol) and carbon disulphide light for 72 hours. to evaporate
(4) (0.3 g, 1.5 mmol), bromine
(2.78 g, 37 mmol) was irradiated
The tube was opened and the gaseous
to leave a liquid containing
(9%). assigned
by comparison
(0.12 g, with sun-
by-products
allowed
(2) (81%), (lo) (9%) and (2)
of glc retention
times with authentic
samples
from part (a).
Fluorination
of 2,2,3,4,4,4-hexafluorobutyl
A mixture
containing
adduct
chloro-1,2,2_trifluoroethane with a reflux condenser a nitrogen ml/min.) period) 10 mins. ether 4.80
cylinder
was passed and finally
(55 g) was placed
fluorine
for 10 mins. then fluorine
(18%) (Found:
generator.
contained
(50 ml/min.)
2,2,3,4,4,4_hexafluorobutyl 4.36
Nitrogen
(50
(0.48 g over a 22 min.
flushed out with a flow of nitrogen
for
fluoromethyl
(2H, d, J 55 Hz, CH2F),
6F 76.2 (3F, m, CF3), 118.9, 123.0 (2F, AB, J 277 Hz,
CF2), 155.7 (lF, t, J 54 Hz, CH2F), 215.7 CM+-H, l%), 63(100),
in a Pyrex flask assembled
and an inlet tube attached via a three way valve to
and an electrolytic
The product
(4)
(2) (2.46 g, 12.5 mmol) and 1,1,2-tri-
(19) (44%), 6H 3.17 (2H, m, CH2CF2), (lH, m, CHF);
methyl ether
(lF, dm, J 44 Hz, CFH);
2,2,3,4,4,4-hexafluorobutyl
C, 26.1;
H, 1.9.
C5H4F80
difluoromethyl
requires:
C, 25.9;
m/z 213
ether
(20)
H, 1.7%);
6H 4.52
(2H, m, CH2), 5.23 (lH, d, J 45 Hz, CHF), 6.55 (lH, t, J 73 Hz,
CHF2);
6F 76.3 (3F, m, CF3), 88.4 (2F, d, J 71 Hz, CF2H), 120.9
CF2CH2), (1)
215.7
(lF, d, J 43 Hz, CFH), 2,2,3,4,4,4_hexafluorobutyl
[3] (20%), and 2,2,3,4,4,4-hexafluorobutan-l-01
(lo)
[III
(2F, m, formate
(7%).
234 Chlorination
(a)
of borate adducts
Tri(2,2,3,4,4,4-hexafluorobutyl)borate
A mixture
of borate
contained
mmol),
and irradiated
(with a temperature leaving
with a high pressure The gaseous
rise to 5O'C).
22.4;
(6.61 g, 93
C, 22.4; H, 0.5;
UV lamp for 1 hour
by-products
a liquid residue which was transferred
18OC to give 2,2,3,4,4,4_hexafluorobutanoyl (Found:
(24) and chlorine
in a thick pyrex tube fitted with a rotaflo valve, was
sealed under vacuum
evaporate
(0.97 g, 1 mmol)
(3)
under vacuum at
requires:
6h 5.08 (dm, J 44 Hz, CFH);
F, 53.1%);
Cl, 16.5;
to
(27) (0.85 g, 75%) (nc)
C4HC1F60
F, 49.8.
Cl, 16.1;
H, 0.7;
chloride
were allowed
C, 6F 76.0
(3F, m, CF3), 112.3, 117.1 (2F, AB, J 278 Hz, CF2), 214.2 (IF, dm, J 42 Hz, CFH);
m/z 213 CM+-H, l%), 151(58),
(b)
65(32), 63(100).
Tri[(1,2,3,3,4,4,5,5,6,6-decafluorocyclohexyl)methyl~borate
A mixture mmol),
69(95),
of borate
contained
(5)
(0.68 g, 0.8 mmol) and chlorine
and irradiated
(with a temperature
rise to 50°C).
and the remaining
with a high pressure The gaseous
59.4.
(mixture of isomers) C7HClF100
5.32 (m, CHF); 179.3
requires:
(Found: C, 25.7;
(c)
of borate
contained
temperature evaporate
(28) (0.62
H, 0.0%;
Cl, 13.4;
F,
Cl, 10.9;
F, 58.2%),
6H
AB, 4CF2), 167.5 and
(lF, dm, J 42 Hz, CFH);
m/z 291 (M'-Cl,
borate
and irradiated rise to 5OOC).
and the remaining
with a high pressure The gaseous
liquid was transferred methanoyl C5C12F60
6F 126.8
F, 44.4.
CF2), 136.2 and 141.4 CM+-Cl, 14%), 225(48),
chloride
147(68),
to
(29) (nc) (0.73 g, C, 23.0;
(2F, AB, J 214 Hz,
(lF, m, CF), 159.0 and 168.1 149(21),
were allowed
under vacuum at 18'C to
requires:
(2F, m, CF2), 122.6, 131.4
(10.34 g, 146 tap, was sealed
UV lamp for 1 hour (with a
by-products
give 3-chlorohexafluorocyclobutyl C, 22.3;
(26)
(26) (0.75 g, 1.3 mmol) and chlorine
in a thick Pyrex tube fitted with a rotaflo
63%) (Found: F, 43.7%);
chloride
Tri (1,2,3,3,4,4-hexafluorocyclobutyl)methyl
under vacuum
to
63(100).
A mixture mmol),
were allowed
under vacuum at 18'C to
hF 118.1 to 149.8 (8F, overlapping
(lF, m, CF), 210.0 and 229.3
15%), 65(56),
C, 25.9; H, 0.3;
UV lamp for 2 hours
by-products
liquid was transferred
give 1,2,3,3,4,4,5,5,6,6-decafluorocyclohexylmethanoyl g, 83%)
(6.06 g, 85
in a thick Pyrex tube fitted with a rotaflo tap, was
sealed under vacuum
evaporate
(25)
118(31),
(lF, m, CFH); 116(100),
m/z 227
65(26), 63(82).
235 ACKNOWLEDGEMENT We thank the Science maintenance
grant
and Engineering
Research
Council
for a
(to B.G.).
REFERENCES
1 4 2
Part 5.
R.D. Chambers,
J. Fluorine
B. Grievson,
F.G. Drakesmith
R.D. Chambers, R.W. Rendell,
N. Kelly, W.K.R. Musgrave, J. Fluorine
W.G.M. Jones and
Chem., 16 (1980) 351.
3
R.D. Chambers,
4
G.S. Hammond,
J. Amer. Chem. Sot., 22 (1955) 334.
5
R.W. Baldock,
P. Hudson,
Trans.1,
and R.L. Powell,
Chem., -29 (1985) 323.
B. Grievson
submitted
and N.M. Kelly, J. Chem. Sot. Perkin
for publication.
A.R. Katritzky
and F. Soti, J. Chem. Sot.
Perkin Trans. I, (1974) 1422. 6
H.G. Viehe, R. Mer&yi,
L. Stella and Z. Janousek,
7
R.J. Lagow and J.L. Margrave,
Angew. Chem. Int. Ed.,
18 (1979) 917.
references
Prog. Inorg. Chem., 26 (1979) 186 and
contained.
8
J.L. Adcock, J. Fluorine
9
N.O. Brace and W.B. McCormack,
J. Org. Chem., 26 (1961) 4005.
10 N.O. Brace and W.B. McCormack,
J. Org. Chem., 26 (1961) 5091.
11 H. Muramatsu, 903.
Chem., 16 (1980) 297.
K. Inukai and T. Ueda, Bull. Chem. Sot. Japan, 40 (1967)