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fluorinated alkyl chloroformates [Rf = X(CF2)nCH2, X =
H or F, n = 1, 2, 4,6].
additional 14.85 g of gaseous phosgene was passed
through it in the course of 2.5 h. The target product,
43.8 g (93%), was formed, bp 35°C (32 mm Hg), nD20
1.3520, d420 1.5179. The other chloroformates were
prepared analogously.
The treatment with phosgen of polyfluorinated
alcohols in the presence of DMF increased the yield of
polyfluorinated chloroformates to 90%, and therewith
the phosgen consumption decreased three times and
the use of diethyl ether as solvent was unnecessary.
The smallest amount of DMF exhibiting the noticeable
catalytic effect is 0.01 mol/mol of alcohol. Under these
conditions the yield of polufluorinated chloroformate
is 70%. At the DMF content 0.05 mol/mol of alcohol
the yield increases to 86%, and when the amount of
catalyst is 0.07 mol/mol of alcohol the 90% yield of
chloroformate is achieved. Further increase in the
DMF content does not affect the yield of the target
product. The optimal reaction conditions are as
follows: the alcohol : phosgen : catalyst ratio 1:1.2:0.05,
the starting reaction temperature 0°C, the final reaction
temperature 90°C, the reaction time 2.5 h.
1,1-Dihydroperfluoropropyl chloroformate (X =
F, n = 1). Yield 90%, bp 40°C (165 mm Hg), nD20
1.3210, d420 1.4896.
1,1,5-Trihydroperfluoropentyl chloroformate (X =
H, n = 4). Yield 90%, bp 50°C (11 mm Hg), nD20
1.3376, d420 1.6475.
1.1-Dihydroperfluoropentyl chloroformate (X =
F, n = 4). Yield 88%, bp 36°C (15 mm Hg), nD20
1.3182, d420 1.6200.
1,1-Dihydroperfluoroheptyl chloroformate (X =
F, n = 6). Yield 88%, bp 59°C (13 mm Hg), nD20
1.3188, d420 1.7105.
1,1,7-Trihydroperfluoroheptyl chloroformate (X =
H, n = 6). Yield 87%, bp 63°C (3 mm Hg), nD20 1.3338,
d420 1.7240.
It cannot be excluded that high catalytic activity of
DMF is due to its ability to form stable associates with
polyfluorinated alcohols [3] resulting in the
polarization of O−H bond of the alcohol that facilitates
the nucleophilic substitution of chlorine in phosgen
with polyfluoroalkoxy group.
REFERENCES
1. US patent no 4022609 (1977); Ross. Zh. Khim., 1978,
no. 3, p. 88, 9362P.
1,1,3-Trihydroperfluoropropyl chloroformate (X =
H, n = 2). A mixture of 33.0 g of 1,1,3-trihydro-
perfluoropropanol and 0.57 g of DMF was cooled to 0°C
and 14.85 g of liquid phosgen was added to it. After
that the reaction mixture was heated to 90°C and the
2. Babad, H. and Zeiler, A.G., Chem. Rev., 1973, vol. 73,
p. 75
3. Rakhimov, A.I., Nalesnaya, A.V., Vostrikova, O.V., and
Storozhakova, N.A., Izv. Volg. Gos. Tekhn. Univ, 2004,
vol. 1, no. 2, p. 39.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 78 No. 5 2008