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EMEL’YANOV et al.
42°C/8 mm Hg and perfluoro-1-hydro-4,6,8,10,12,14-
hexaoxa-1-iodopentadecane at 58–60°C/2 mm Hg.
7.9 ppm corresponding to the terminal СFHI group
and the doublet of multiplets at 5.5 ppm associated
with the middle –CFН group whose geminal constants
are close to 46 Hz in both cases were characterized
by the same intensity ratio of 1 : 2.3. Evidently, this
ratio is indicative of a much higher accessibility of the
hydrogen-containing end group of trifluoroethylene
The 19F NMR spectrum of the perfluoroallyl ether,
the dehydrohalogenation product of perfluoro-2-
hydro-4,6,8,10,12,14-hexaoxa-1-iodopentadecane, is
presented in Table 2; it corresponds to that described
1
earlier [5]. Table 2 also lists the 19F and Н NMR
·
for the attack by the CF3O–(CF2O)nCF2 radical. The
spectra of perfluoro-1-hydro-4,6,8,10,12,14-hexaoxa-1-
iodopentadecane and perfluoro-2-hydro-4,6,8,10,12,14-
hexaoxa-1-iodopentadecane isolated by the same
procedure, as well as their corresponding signals in the
spectrum of the mixture of monoadducts.
structure of the radical of such monoadduct is virtually
identical to that of the initial iodide, which suggests that
the same ratio of isomers will be preserved when the
monoadduct radical will attack further trifluoroethylene
molecule.
The assignment of the signals observed in the
19F NMR spectrum of the fraction containing 10%
diadducts is complicated by superimposition of the
chemical shifts of the signals from their common
and magnetically nonequivalent nuclei and spin-spin
coupling constants, especially of geminal fluorine–
proton spin-spin coupling constants.
This presumption is confirmed by the fact that, in
the 19F NMR spectrum of the sample of the rectification
fraction comprising 10 wt% diadduct mixture, there
are signals from single fluorine nuclei geminal to the
proton at 200–202 ppm. They are manifested in the case
of RFОCF2CF2CFHCFHCF2I as a doublet of multiplets,
overlapped by the signals from the corresponding
monoadduct, which prevents calculation of their ratio.
However, examination of the 1H NMR spectrum of the
sample of this fraction allows quantitatively assessing
the mixture composition, despite superimposition
of some signals from the monoadducts, as well as
calculating the mole fraction of each of the mixture
components. These data suggest identical activities of
The distribution of mono-, di-, and polyadducts in
the reaction mixture depends on the reactant ratio. Each
adduct contains 2n orientation isomers whose amounts
are related to the stability of the radicals rather than to
the ratio of the reactants. Analysis of the distribution
of these isomers provides insight into selectivity of the
process examined. The activity of the radical center
depends on the composition of no larger than two–three
preceding methylene groups. Hence, based on analysis
of the structure of the isomers in the two initial stages, it
is possible to determine the subsequent transformation
pathway.
·
the CF3O(CF2O)nCF2CF2CFH radical when attacking
the proton-containing and perfluorinated end groups of
trifluoroethylene.
Thus, the general scheme of the telomerization
can be illustrated by the yields of various compounds,
expressed as mole percents of the initial iodides in the
reactions proceeding in the first and second stages of
telomerization:
1
Based on the intensity of the Н NMR signals from
the protons geminal to the fluorine nucleus, we fairly
precisely estimated the ratio of the monoadducts
yielded by telomerization. The doublet of doublets near
The reactivity of the radicals is affected by two–three
neighbor atoms at the most. Hence, further telomers will
be obtained in the same yields as determined by different
activities exhibited by the perfluorinated and hydrogen-
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 84 No. 2 2011
Emel'yanov
