Synthesis of di(polyfluoroalkyl) ethers

Article abstract of DOI:10.1007/s11167-005-0073-x

New procedures for preparing di(polyfluoroalkyl) ethers by reactions of polyfluoropropyl chlorosulfonites with polyfluorinated alcohols were tested.

Full text of DOI:10.1007/s11167-005-0073-x

Russian Journal of Applied Chemistry, Vol. 77, No. 9, 2004, pp. 1561 1563. Translated from Zhurnal Prikladnoi Khimii, Vol. 77, No. 9,
004, pp. 1573 1574.
Original Russian Text Copyright
2
2004 by Rakhimov, Nalesnaya, Vostrikova.
BRIEF
COMMUNICATIONS
Synthesis of Di(polyfluoroalkyl) Ethers
A. I. Rakhimov, A. V. Nalesnaya, and O. V. Vostrikova
Institute of Chemical Problems of Ecology, Volgograd State Technical University, Volgograd, Russia
Received July 6, 2004
Abstract New procedures for preparing di(polyfluoroalkyl) ethers by reactions of polyfluoropropyl chloro-
sulfonites with polyfluorinated alcohols were tested.
Polyfluorinated dialkyl ethers are promising ozone-
friendly and moderately toxic solvents [1]. In particu-
lar, tetrafluoroethyl difluoromethyl ether and its clos-
est homolog, di(tetrafluoropropyl) ether can be used
instead of perfluorohydrocarbons for dry etching in
microelectronics [2], and, with subsequent electro-
chemical afterfluorination in anhydrous HF, these
compounds can be recommended for cleaning of elec-
tronic circuits and as polymerization media [3 5].
Polyfluorinated ethers of higher molecular weight are
used as compression, motor, and vacuum oils [6].
where R = R = H(CF CF ) (I), HCF CF (II),
F F 2 2 2 2 2
H(CF CF ) (III), R = HCF CF , R = H(CF CF )
2
2 3
F
2
2
F
2
2 2
(IV), R = HCF CF , R = H(CF CF ) (V), R =
F
2
2
F
2
2 3
F
HCF CF , R = H(CF CF ) (VI), R = H(CF CF ) ,
2
2
F
2
2 4
F
2
2 2
RF = H(CF CF ) (VII).
2
2 3
In procedure (1), a solution of polyfluoroalkyl
chlorosulfonite was added to appropriate alcohol con-
taining DMF (molar ratio from 1 : 0.005 to 1 : 0.01)
at 10 C; the mixture was allowed to stand for 24 h
at room temperature. After distilling off the solvent
(
chloroform, diethyl ether), the product was distilled;
Alkyl polyfluoroalkyl ethers are prepared by addi-
tion of polyfluorinated alcohols to alkenes and fluoro-
alkenes [1, 7] and by alkylation of alcoholates derived
from polyfluorinated alcohols with alkyl halides [8, 9].
yield 59 98%.
In procedure (2), a solution of polyfluoroalkyl
chlorosulfonite was added at 10 C to a complex
of alcohol with triethylamine, prepared in advance;
the resulting mixture (solvent pentane or hexane)
was allowed to stand for 24 h at room temperature.
The triethylammonium chloride precipitate was
filtered off, and the fluorinated ether was distilled;
yield 52 85%.
We suggest a procedure for preparing polyfluori-
nated ethers from available raw materials, polyfluori-
nated alcohols and thionyl chloride, via intermediate
polyfluoroalkyl chlorosulfonites [10]. This procedure
is environmentally safe and economically attractive,
as its cost is determined by the cost of polyfluorinated
alcohols (some of them are production wastes) and
thionyl choride and by small production expenditures.
Symmetrical ethers I III were prepared by reac-
tions of polyfluoroalkyl chlorosulfonites with the re-
lated alcohols. The highest yield (98%) was attained
with the most reactive tetrafluoropropyl chlorosulfo-
nite in the presence of DMF. With increasing length
of the fluorocarbon chain, the yield of di(polyfluoro-
alkyl) ethers decreases. Tetrafluoropropyl octafluoro-
pentyl ether was obtained in 85% yield, and the yields
of the ethers with longer fluorocarbon chains were
still lower.
With the aim to extend the homologous series of
symmetrical and unsymmetrical di(polyfluoroalkyl)
ethers, we suggested catalytic and noncatalytic proce-
dures based on reactions of polyfluoroalkyl chlorosul-
fonites with polyfluorinated alcohols. The catalytic
reaction (1) is performed in the presence of dimethyl-
formamide (DMF) as catalyst, and the noncatalytic
reaction (2), in the presence of triethylamine:
DMF
Although both procedures allow preparation of the
ethers in similar yields, the catalytic process is pre-
ferable because of lower production cost and higher
purity of the target product; the triethylammonium salt
formed in reaction (2) appreciably contaminates the
resulting ether.
R CH OS(O)Cl + R CH OH
R CH OCH R + SO
F 2 2 F
F
2
F
2
2
+
HCl,
NEt
(1)
3
R CH OS(O)Cl + R CH OH
R CH OCH R + SO
F 2 2 F
F
2
F
2
2
+
NEt3 HCl,
(2)
1
070-4272/04/7709-1561 2004 MAIK Nauka/Interperiodica

1562
RAKHIMOV et al.
0
EXPERIMENTAL
The structures of ethers I VII were proved by IR
bp 83 C (2 mm Hg), n2 1.3500, d 24 0 1.6790. IR spec-
D
1
trum, , cm : 1116 s ( C O C), 1242 s ( CF ),
2860 w, 2934 w, 2980 m ( CH ), 3017 w ( CHF ).
H NMR spectrum, , ppm (J, Hz): 5.966 t.t (H ,
J 51.6, 5.4), 5.810 t.t (H , J 52.1, 3.8), 4.432 t (H ,
2
2
2
1
and H NMR spectroscopy. The IR spectra were re-
corded on a Specord-M82 spectrometer (thin films).
1
8
1
3
1
The H NMR spectra were taken on a Varian Mercu-
4
J 13.2), 4.255 t (H , J 12.6).
ry-300 spectrometer (working frequency 300 MHz,
internal reference tetramethylsilane, solvent CCl4).
1,1,7-Trihydroperfluoro-1-(1,1,3-trihydroperflu-
oropropyloxy)heptane V. Procedure (b). Yield 51%,
Di(1,1,5-trihydroperfluoropentyl) ether I.
a) A 4.4-g portion of 1,1,5-trihydroperfluoro-1-pen-
tanol was mixed with 0.015 ml of DMF in 15 ml of
chloroform and cooled to 10 C; a solution of 5.9 g
of 1,1,5-trihydroperfluoropentyl chlorosulfonite in
2
0
20
bp 95 C (1 mm Hg), n 1.3450, d4 1.7310. IR spec-
(
D
1
trum, , cm : 1116 s ( C O C), 1223 s ( CF ),
868 w, 2937 w, 2968 m ( CH ), 3014 w ( CHF ).
2
2
2 2
1
,1,9-Trihydroperfluoro-1-(1,1,3-trihydroperflu-
oropropyloxy)nonane VI. Procedure (a). Yield 34%,
mp 49 C, bp 130 C (1 mm Hg). IR spectrum,
1
0 ml of chloroform was added with stirring, with the
temperature maintained at 10 C. Then the mixture
was allowed to warm up to 20 C and was kept at this
temperature for 2 h, with bubbling of dry air to re-
move the released hydrogen chloride. After that, the
mixture was allowed to stand for 24 h at room tem-
perature. The solvent was distilled off, and the prod-
uct was distilled in a vacuum. Yield of I 4.5 g (59%),
,
1
cm : 1120 s ( C O C), 1216 s ( CF ), 2856 m,
2
1
2
894 w, 2932 m ( CH ), 2954 w ( CHF ). H NMR
2 2
1
12
spectrum, , ppm (J, Hz): 5.975 t.t (H , H , J 52,
3
4
5
.1), 4.359 t (J 16.6) and 4.331 t (J 12.3) (H , H ).
,1,7-Trihydroperfluoro-1-(1,1,5-trihydroperflu-
oropentyloxy)heptane VII. Procedure (a). Yield
62%, bp 110 C (1 mm Hg), n 1.3380, d4 1.7647.
IR spectrum, , cm : 1120 s ( C O C), 1220 s
1
2
0
20
bp 103 C (2 mm Hg), n 1.3385, d4 1.7344. IR
D
1
20
20
spectrum, , cm : 1137 s ( C O C), 1176 s ( CF ),
860 w, 2946 m ( CH ), 3016 w ( CHF ).
2
D
1
2
2
2
(
(
CF ), 2864 w, 2932 m, 2961 m ( CH ), 3009 w
CHF2).
(
b) A 5.0-g portion of 1,1,5-trihydroperfluoro-1-
2
2
pentanol was mixed with 2.1 of triethylamine in 15 ml
of hexane and cooled to 10 C; a solution of 6.7 g of
1
,1,5-trihydroperfluoropentyl chlorosulfonite in 10 ml
CONCLUSION
A catalytic reaction of polyfluorinated alcohols
with polyfluoroalkyl chlorosulfonites in the presence
of DMF allows preparation of the corresponding
di(polyfluoroalkyl) ethers in 59 98% yield.
of hexane was gradually added with stirring, with the
temperature maintained at 10 C. Then the mixture
was allowed to warm up to 20 C and to stand at this
temperature for 24 h. The precipitated salt was fil-
tered off, the solvent was distilled off, and the product
was vacuum-distilled. Yield of I 5.2 g (52%).
Compounds II VII were prepared similarly to I by
procedure (a) or (b).
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3
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RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 77 No. 9 2004

SYNTHESIS OF DI(POLYFLUOROALKYL) ETHERS
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RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 77 No. 9 2004