Synthesis of 1,2,3,4ꢀtetrachlorohexafluorobutane
Russ.Chem.Bull., Int.Ed., Vol. 53, No. 10, October, 2004
2337
consumed iodide 5, small amounts of tetrachlorohexaꢀ
fluorobutanes 6 and 7, and AcOEt. Compound 1 containꢀ
ing ≤4% of compounds 6 and 7 as impurities can be isoꢀ
lated by fractional distillation; however, we used the crude
mixture for the synthesis of hexafluorobutadiene.
1,2,3,4ꢀTetrachlorohexafluorobutane (1). Granulated Zn
7.15 g, 0.11 mol) (grain size 3—5 mm) was added with stirring
over a period of 1 h at 20 °C to a mixture of iodides 3 + 5 (55.8 g,
.2 mol) in 2 mL of anhydrous AcOEt. The reaction mixture was
stirred for 40 h at 20 °C and diluted with 50 mL of water. The
organic layer was separated, washed with water (2×10 mL), and
(
0
GC/MS analysis of compound 1 on a capillary colꢀ
umn at 30 °C revealed the presence of two diastereomers
in approximately equal amounts, the mass spectra of both
dried with MgSO to give 35.0 g of as mixture of 1,2,3,4ꢀtetraꢀ
4
chlorohexafluorobutane (1), iodide 5, two butane isomers 6
and 7, and AcOEt in 70 : 26 : 1 : 1 : 2 ratio (GC/MS analysis).
Fractional distillation (column, h = 30 cm) gave 24.6 g of a
mixture of compounds 1, 6, and 7. The total content of comꢀ
pounds 6 and 7 was not higher than 4%, the yield of the target
1
9
diastereomers being identical. The F NMR spectrum
shows splitting of signals due to chirality.
Dechlorination of 1,2,3,4ꢀtetrachlorohexafluoroꢀ
2
0
i
product 1 was 97% (relative to 3), b.p. 134—135 °C, n
1.3855
butane (1) with Zn dust in Pr OH at 80 °C furnishes
D
13
(
(
2
cf. Ref. 3: b.p. 134—134.5 °C, nD23 1.382). C NMR, δ: 106.6
chromatographically pure hexafluorobutadiene (2) in
quantitative yield. Hexafluorobutadiene is successfully
used as a crossꢀlinking reagent in the synthesis of therꢀ
mally and chemically stable and frostꢀresistant polymers
based on perfluoroalkylene oxides containing peroxide
groups according to a known procedure.9
Thus, we demonstrated that 1,2ꢀdichloroꢀ1,2,2ꢀtriꢀ
fluoroꢀ1ꢀiodoethane is quantitatively condensed on treatꢀ
ment with granulated zinc at 20 °C without a solvent in
the presence of catalytic amounts of ethyl acetate.
1
dm, 2 CF, JC,F = 279.2 Hz); 124.3 (dt, 2 CF , J
= 303.4 Hz,
2
C,F
19
JC,F = 32.5 Hz). F NMR, δ: –120.6 (br.s, 2 CF, mesoꢀform);
–
120.9 (m, 2 CF, d,lꢀform); –61.5 (m, 2 CF ). MS,
2
+
+
m/z (Irel (%)): 267 [M – Cl] (0.1), 217 [M – CF Cl] (1.2),
2
+
+
198 [M – CF Cl – F] (0.9), 182 [M – CF Cl – Cl] (7.4), 163
[M – CF Cl – Cl – F] (2.4), 151 [C F Cl ] (23.6), 147
[C3F4Cl] (11.1), 135 [C2F4Cl] (14.6), 116 [C2F3Cl] (9.1),
2
2
+
+
2
+
2
3
2
+
+
+
+
+
1
[
01 [CFCl ] (10.5), 93 [C F ] (3.7), 85 [CF Cl] (100), 69
2 3 3 2
+
CF3] (11.4) (cf. Ref. 7).
Hexafluorobutadiene (2) was prepared by analogy with a
known procedure by the reaction of 1,2,3,4ꢀtetrachloroꢀ
2
i
hexafluorobutane (1) with Zn dust in Pr OH for 2 h at 80 °C.
Experimental
The syntheses were carried out with both purified compound 1
containing ≤4% of butanes 6 and 7 and a crude mixture of
compounds 1, 5, 6, 7, and AcOEt in 70 : 26 : 1 : 1 : 2 ratio. The
chromatographic yield of hexafluorobutadiene (2) was 93—98%
relative to hexafluorotetrachlorobutane 1, b.p. 5—6 °C (cf. Ref. 2:
b.p. 5.8 °C).
13C and 19F NMR spectra were recorded on a Вruker
ACꢀ200 P spectrometer for CDCl solutions; the chemical shifts
3
are given in the δ scale relative to Me Si and CFCl . Mass
4
3
spectra were run on a VGꢀ7070 E GC/MS instrument (EI,
0 eV) with a capillary column (SEꢀ54, 50 m × 0.2 mm, Hе as
the carrier gas), the thermostat temperature was raised at a rate
of 10 °C min . The reaction was monitored on a Chromꢀ5B
gas liquid chromatograph (SEꢀ30 columns for liquids and
PORAPAK Q columns for gases, 2.5 m × 2.0 mm). The starting
mixture of iodides 3 + 5 (4 : 1) was prepared by a known proꢀ
cedure.3
7
References
–
1
1
2
. M. Prober and W. T. Miller, J. Am. Chem. Soc., 1949, 71, 598.
. Sintezy Ftororganicheskikh Soedinenii [Syntheses of Organoꢀ
fluorine Compounds], Eds I. L. Knunyants and G. G. Yakobson,
Khimiya, Moscow, 1973, 17 (in Russian).
Chlorotrifluoroethylene (4). Freshly distilled CH Cl , AcOEt,
and Zn dust (activated by brief treatment with 10% aqueous
HCl, repeated washing with distilled H O to a neutral pH, and
2
2
3
4
5
. R. Haszeldine, J. Chem. Soc., 1952, 4423.
. T. M. Keller and P. Tarrant, J. Fluor. Chem., 1975, 6, 105.
. A. L. Henne and W. Postelneck, J. Am. Chem. Soc., 1955,
2
drying for 10 h at 200 °C in vacuo (10 Torr)) were used in the
reaction. The reaction was carried out a fourꢀnecked flask
equipped with a stirrer, a thermometer, a device for the addition
of Zn dust, and a reflux condenser with a trap cooled to –70 °C.
Zinc dust (6.5 g, 0.1 mol) was added in portions at 0 °C over a
period of 1 h to a vigorously stirred solution of iodides 3 + 5
7
7, 2334.
6
. M. Van Der Puy, R. K. Belter, R. J. Borowski, L. A. S. Ellis,
P. J. Persichini, A. J. Poss, T. P. Rygas, and H. S. Tung,
J. Fluor. Chem., 1995, 71, 59.
. K. C. Eapen and C. Tamborski, J. Fluor. Chem., 1987, 35, 421.
. B. Ameduri, B. Boutevin, G. K. Kostov, and P. Petrova,
J. Fluor. Chem., 1995, 74, 261.
. A. A. Glazkov, A. V. Ignatenko, S. P. Krukovskii, and V. A.
Ponomarenko, Zhurn. Organ. Khim., 1994, 30, 1193 [Russ.
J. Org. Chem., 1994, 30 (Engl. Transl.)].
7
8
(
22.5 g, 0.08 mol) in 36 mL of a CH Cl —AcOEt mixture (1 : 1).
2 2
After addition of every portion, violent foaming and gas evoluꢀ
tion were observed. The reaction mixture was stirred for 1 h at
9
2
0 °C and filtered to remove Zn salts. The filtrate was analyzed
by GLC/MS, which showed the presence of CH Cl , AcOEt,
2
2
and iodide 5. The contents of the trap represented chromatoꢀ
graphically pure chlorotrifluoroethylene (4). Yield 7.0 g (93%,
relative to iodide 3).
Received January 26, 2004;
in revised form June 17, 2004