Synthesis and features of thermolysis of fluorine-containing aromatic 1-hydroxy-1-hydroperoxides and 1,1′-dihydroperoxides

Article abstract of DOI:10.1134/S1070363209020121

Aromatic fluorine-containing 1-hydroxy-1-hydroperoxides and 1,1′-dihydroxyperoxides were obtained and their thermolysis features were studied. The fluorine atoms incorporation into the aromatic ring of 1-hydroxy-1-hydroperoxides was found to lead to their

Full text of DOI:10.1134/S1070363209020121

ISSN 1070-3632, Russian Journal of General Chemistry, 2009, Vol. 79, No. 2, pp. 242–245. © Pleiades Publishing, Ltd., 2009.
Original Russian Text © V.V. Chapurkin, A.I. Rakhimov, S.V. Chapurkin, 2009, published in Zhurnal Obshchei Khimii, 2009, Vol. 79, No. 2, pp. 254–257.
Synthesis and Features of Thermolysis
of Fluorine-containing Aromatic 1-Hydroxy-1-hydroperoxides
and 1,1'-Dihydroperoxides
V. V. Chapurkin, A. I. Rakhimov, and S. V. Chapurkin
Volgograd State Technical University,
pr. Lenina, 28, Volgograd, 400131 Russia
e-mail: chapurkin@vstu.ru
Received May 15, 2008
Abstract―Aromatic fluorine-containing 1-hydroxy-1-hydroperoxides and 1,1'-dihydroxyperoxides were
obtained and their thermolysis features were studied. The fluorine atoms incorporation into the aromatic ring of
1-hydroxy-1-hydroperoxides was found to lead to their thermal stability increase. 1,1'-Dihydroxyperoxides are
the less thermal stable than 1-hydroxy-1-hydroperoxides. Compared to the fluorine atoms, incorporation of
fluoroalkyl groups into the aromatic ring exerts greater effect on the stability of the peroxide.
DOI: 10.1134/S1070363209020121
Homolysis yielding free radicals is the most im-
portant reaction of peroxide compounds. Peroxide
thermolysis studying allows regularities of influence of
structure on their reactivity to be established that is of
great importance to detection of possible practical use
of peroxide compounds as initiators for free-radical
processes [1]. Reactivity of the both peroxides and the
generated free radicals is determined by their electronic
structure and depends considerably on the reaction
medium and temperature conditions. Study of the
character of peroxide with solvent interaction, thermo-
lysis and decay products composition allows to
establish the reaction mechanism, to estimate a
possibility of peroxides use in various technological
processes and to select optimal temperature condition.
Аr–CH=O + HOOH → Ar–CH(OH)–OOH,
Іа–Id
Ar = C6H5 (а), p-FC6H4 (b), C6F5 (c), о-CF3C6H4 (d).
Reaction was carried out at –25 to –20°С in tetra-
chloromethane solution distilled previously over Р2О5.
70–98% Hydrogen peroxide was used.
Thermolysis of the fluorine-containing aryl-1-hyd-
roxy-1-hydroperoxides Ia–Ic prepared proceeds in
chlorobenzene at the initial concentration of hydroxy-
hydroperoxide of 0.01–0.02 mol l–1 in the temperature
range of 323–373 K. Thermolysis at the initial time
point was established to be described satisfactorily
with the first-order equation. Kinetics studying results
are given in Table 1.
Thermolysis of the fluorinated organic peroxide
derivatives of carbonyl compounds is not virtually
examined. It is known [2] that dihydroperoxides on the
matrix of the fluorinated aliphatic ketones are the less
flammable and shock and friction sensitive than their
unsubstituted analogs. But they are the less stable than
hydroperoxides, into which they are transforming for
one day at 25°С.
The data obtained show that the thermal stability of
aromatic hydroxyperoxides increases, when the
fluorine atoms are incorporated into the peroxide
molecule. The presence of the five fluorine atoms in
the ring leads to increase thermolysis activation energy
by 38 kJ mol–1 in comparison with the unsubstituted
compound. This rise is due to the strong electro-
negative inductive effect of the fluorine atoms decreas-
ing electron density on the oxygen atoms of the
peroxide bond. The latter results in hydroxyhydro-
peroxides thermal stability growth.
In the present work the synthesis of fluorine-
containing aryl-1-hydroxy-1-hydroperoxides Іа–Id by
the reaction of benzaldehyde and its fluorine-
substituted analogues with hydrogen peroxide is given.
242

SYNTHESIS AND FEATURES OF THERMOLYSIS
243
4
3
2
1
4
3
2
1
10
9
8
7
6
5
4
3
2
10
8
7
6
5
δ, ppm
δ, ppm
Fig. 1. The 1Н NMR spectra of peroxide [C6H5–CH(ОН)–O]2
at 60°С, τ, min: (1) 0, (2) 3, (3) 7, and (4) 15.
Fig. 2. The 1Н NMR spectra of peroxide [C6F5–CH(ОН)–O]2
at 90°С, τ, min: (1) 0, (2) 2, (3) 4, and (4) 20.
1
The fluorine-containing aryl-1,1'-dihydrohydroxyper-
In the studies of the Н NMR spectra of starting
oxides were prepared by the reaction of benzaldehyde
and its fluorine-substituted analogues with 30%
hydrogen peroxide.
benzal-dehyde, benzoic acid and 1-hydroxy-1-
hydroperoxide Іа the signal at 6.03 ppm was found to
correspond to СН-group of Ia and the signal at δ 10.01
ppm belongs to CH-moiety of initial benzaldehyde.
2 Аr–CH=O + HOOH → Ar–CH(OH)–ОО–CH(OH)–Ar,
ІІа–IId
There are two signals at 2.48 ppm (ОН) and 6.56 ppm
1
(СН) in the Н NMR spectrum of ІІc. Within 2 min
Ar = C6 H5 (a), p-F-C6H4 (b), C6F5 (c), о-CF3C6 H4 (d).
intensities of these signals decrease and a new signal at
δ 6.30 appears. After 4 min the CH signal (6.56 ppm)
disappears; the signal at δ 6.30 grows and a new signal
at δ 10.17 ppm appears. After 20 min of thermolysis of
ІІc in acetonitrile at 90ºС only one signal at δ 10.17
ppm is observed in the spectrum. Intensity of the latter
does not change during 30–60 min. Analysis of the 1Н
NMR spectra of pentafluorobenzaldehyde, pentafluoro-
benzoic acid and 1-hydroxy-1-hydroperoxide Іc showed
that the signal at 6.30 ppm belongs to CH-moiety of Іc,
and the signal at δ 10.17 ppm corresponds to СН-
moiety of pentafluorobenzaldehyde.
Reaction was carried out using fivefold excess of
hydrogen peroxide. The excess decreasing leads to a
drop in the target product yield. Yield of peroxides
achieves 74–98%.
Thermolysis of aryl-1,1'-dihydroxyperoxides ІІa–
IId was found to proceed through a stage of hydroxyl-
hydroperoxide formation. Therefore iodometric method
was unusable. Thermolysis of the fluorine-containing
aryl-1,1'-dihydrohydroxyperoxides ІІa-IId was ex-
mined employing the 1Н NMR spectroscopy.
Thermolysis was carried out in acetonitrile since
dihydroxyperoxides are insoluble in the other nonpolar
solvents such as chlorobenzene, ethylbenzene and
Table 1. Rate constants of thermolysis and activation
energies of fluorine-containing aralkyl-1-hydroxy-1-hydro-
peroxides
1
cumene. Variations with time in the Н NMR spectra
of peroxides ІІa and ІІb occurring at their thermolysis
are shown on Figs. 1 and 2.
Compound
Т, °С
κ×105, s–1
Е, kJ mol–1
60
70
75
0.69
2.55
4.43
122.5
Iа
1
In the Н NMR spectrum of ІІa the signals of OH-
(5.45 ppm) and CH-moieties (6.31 ppm) decrease at
60°С. Within 3 min a new signal at δ 6.03 ppm ap-
pears. After 7 min the signal of СН (6.31 ppm)
disappears fully. Intensity of the signal at δ 6.03 ppm
increases and a new signal at δ 10.01 appears. Within
15 min the signal at δ 6.03 disappears, but intensity of
the signal at δ 10.01 ppm grows and does not change
during 20–30 min.
50
60
70
0.34
1.39
5.69
129.2
160.9
Ib
Ic
80
90
100
0.41
1.83
7.65
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 79 No. 2 2009

244
CHAPURKIN et al.
Thermolysis of compounds ІІa-IId was carried out
in condensation processes of polyester resins, but also
for improving properties of paints and varnish
covering obtained.
in the temperature range of 313–363 K using initial
concentration of peroxide 0.05–0.1 mol l–1. The found
rate constants of thermolysis and activation energies
are given in Table 2.
EXPERIMENTAL
Data obtained show that essential growth of the
heat stability of peroxides studied is observed, when
trifluoromethyl group is incorporated (compound IId).
The rate constants of thermolysis of ІІd at 70°С is 6–
7 times lower than for compounds ІІb and ІІc. The
absence of electron-accepting effect of the five
fluorine atoms in aromatic ring on the heat stability of
IIc can be explained with solvating effect of polar
solvent (CH3CN).
Hydroxyhydroperoxyphenylmethane (Іа). A mix-
ture of 10.6 g (0.1 mol) of benzaldehyde and 3.4 g
(0.1 mol) of 98% hydrogen peroxide in 50 ml of an-
hydrous tetrachlorometane was stirred at –15 to –10°С
for 1.5 h. Crystals precipitated were filtered off,
washed with cold petroleum ether and recrystalled
from chloroform. Yield 12.5 g (89%), mp 30–31°С.
Found, %: С 60.31; Н 5.99; Оact 11.40. С7Н8О3.
Calculated, %: С 60.01; Н 5.71; Оact 11.42.
It was be shown earlier that activation energy
increase by 36 kJ mol–1 on incorporating of the five
fluorine atoms into aromatic ring, when thermolysis of
aryl-1-hydroxy-1-hydroperoxides Ia–Ic (Table 1) was
carried out in chlorobenzene.
Hydroxyhydroperoxy(4-fluorophenyl)methane
(Іb) was prepared similarly from 12.4 g (0.1 mol) of 4-
fluorobenzaldehyde and 3.4 g (0.1 mol) of 98%
hydrogen peroxide in 10 ml of hexane. Yield 14.0 g
(87%), mp 41–42°С. Found, %: С 52.93; Н 4.57; Оact
10.21. С7Н7FО3. Calculated, %: С 53.16; Н 4.43; Оact
10.13.
Hence in studies of fluoroperoxides thermolysis the
features of solvent effect on the fluorine atoms in the
ring and perfluoroperoxides are observed. It is due to
solvating effect described by authors [3].
Hydroxyhydroperoxyperfluorophenylmethane
(Іc) was prepared similarly from 2.0 g (0.01 mol) of
perfluorobenzaldehyde and 0.3 g (0.01 mol) of 98%
hydrogen peroxide in 10 ml of anhydrous pentane.
Yield 1.9 g (83%), mp 105–106°С. Found, %: С
36.28; Н 1.53; Оact 6.87. С7Н3F5О3. Calculated, %: С
36.52; Н 1.30; Оact 6.96.
The present of hydroxyl- and hydroperoxide
moieties in the examined peroxides structure and
thermolysis temperature range of 60–100°С are suited
to the requirements made on the peroxide initiators
used in condensation processes of polyester lacquers
[4]. The prepared fluroperoxides can not only be used
Hydroxyhydroperoxy(2-trifluorophenyl)methane
(Іd) was prepared similarly from 1.7 g (0.01 mol) of 4-
trifluoromethylbenzaldehyde and 0.3 g (0.01 mol) of
70–98% hydrogen peroxide. Yield 1.5 g (72%), mp
50–51°С. Found, %: С 46.32; Н 3.57; Оact 7.61.
С8Н7F3О3. Calculated, %: С 45.71; Н 3.33; Оact 7.62.
Table 2. Rate constants of thermolysis and activation
energies of fluorine-containing aryl-1,1'-dihydroxyhydroper-
oxides
Compound
Т, °С
κ×105, s–1
Е, kJ mol–1
40
50
60
0.71
1.75
7.15
98.3
ІІа
Di(hydroxybenzyl)peroxide (ІIa). To 3.2 g
(0.03 mol) of benzaldehyde was added dropwise 8.5 g
(0.075 mol) of 30% hydrogen peroxide under stirring
at 0–5°С. Then temperature was elevated to 20°С and
held for 1 h. The precipitated product was filtered off,
washed with hexane and cold ether and recrystallized
from benzene. Yield 3.3 g (90%), mp 63–64°С. Found,
%: С 67.96; Н 5.76; Оact 6.49. С14Н14О4. Calculated,
%: С 68.29; Н 6.69; Оact 6.50.
70
80
90
2.10
4.95
86.5
113.91
148.5
ІІb
ІІc
ІІd
11.03
70
80
90
1.83
5.75
14.22
Di[1-hydroxy(4-fluorophenyl)methyl]peroxide
(ІІb) was prepared similarly from 2.5 g (0.02 mol) of
4-fluorobnzaldehyde and 5.7 g (0.05 mol) of 30%
hydrogen peroxide. Yield 2.8 g (98%), mp 77–78°С.
70
75
80
0.28
0.58
1.19
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 79 No. 2 2009

SYNTHESIS AND FEATURES OF THERMOLYSIS
245
Found, %: С 59.26; Н 4.28; Оact 5.76. С14Н12F2О4.
Calculated, %: С 59.57; Н 4.25; Оact 5.67.
Tesla BS-567А spectrometer (100 МHz) relative to
internal HMDS.
Di(1-hydroxyperfluorophenylmethyl)peroxide
(ІІc) was prepared similarly from 1.9 g (0.01 mol) of
perfluorobenzaldehyde and 2.9 g (0.025 mol) of 30%
hydrogen peroxide. Yield 2.1 g (96%), mp 124–125°С.
Found, %: С 39.26; Н 1.12; Оact 3.51. С14Н4F10О4.
Calculated, %: С 39.44; Н 0.94; Оact 3.75.
REFERENCES
1. Chapurkin, V.V., Rakhimov, A.I., Dolzhikov, Yu.S.,
and Blintsova, N.V., Zh. Org. Khim., 1994, vol. 30, no. 8,
p. 1248.
2. Rakhimov, A.I., Khimiya
i
tekhnologiya ftoror-
ganicheskikh soedinenii (Chemistry and Technology of
Organofluorine Compounds), Moscow: Khimiya, 1986,
p. 272.
Di[1-hydroxy(2-trifluoromethylphenyl)methyl]
peroxide (ІІd) was prepared similarly from 1.7 g (0.01
mol) of 2-trifluoromethylbenzaldehyde and 2.9 g
(0.025 mol) of 30% hydrogen peroxide. Yield 1.4 g
(74%), mp 85–86°С. Found, %: С 39.06; Н 3.91; Оact
5.11. С16Н12F6О4. Calculated, %: С 39.10; Н 3.85; Оact
5.13.
3. Vlasov, V.M. and Yakobson, G.G., Usp. Khim., 1974,
vol. 43, no. 19, p. 1642.
4. Gol’dberg, М.М., Materialy dlya lakokrasochnykh
pokrytii (Materials for Paint Films), Moscow: Khimiya,
1972, p. 343.
Kinetics data of thermolysis for fluorine-containing
peroxide compounds Ia–Id were measured by iodo-
metry method [5]. Thermolysis of peroxides IIa–IId
5. Antonovskii, V.L., and Buzlanova, M.M., Analitiches-
kaya khimiya organicheskikh peroksidnykh soedinenii
(Analytical Chemistry of Organic Peroxide Compounds),
Moscow: Khimiya, 1978, p. 309.
1
was studied using the Н NMR spectroscopy on a
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 79 No. 2 2009