Mechanism of the antioxidative effect of bis(4-hydroxy-3,5-di-tert-butylphenyl) sulfide and polysulfides in cumene oxidation

Article abstract of DOI:10.1023/A:1015507226514

Bis(4-hydroxy-3,5-di-tert-butylphenyl) sulfide and polysulfides were prepared, and their inhibiting power was studied in relation to the number of sulfur atoms.

Full text of DOI:10.1023/A:1015507226514

Russian Journal of Applied Chemistry, Vol. 74, No. 12, 2001, pp. 2083 2086. Translated from Zhurnal Prikladnoi Khimii, Vol. 74, No. 12, 2001,
pp. 2023 2026.
Original Russian Text Copyright
2001 by Farzaliev, Allakhverdiev, Sattar-zade, Rzaeva.
ORGANIC SYNTHESIS
AND INDUSTRIAL ORGANIC CHEMISTRY
Mechanism of the Antioxidative Effect
of Bis(4-hydroxy-3,5-di-tert-butylphenyl) Sulfide
and Polysulfides in Cumene Oxidation
V. M. Farzaliev, M. A. Allakhverdiev, R. I. Sattar-zade, and I. A. Rzaeva
Institute of the Chemistry of Additives, Academy of Sciences of Azerbaijan, Baku, Azerbaijan
Baku State University, Baku, Azerbaijan
Received May 15, 2001
Abstract Bis(4-hydroxy-3,5-di-tert-butylphenyl) sulfide and polysulfides were prepared, and their inhibiting
power was studied in relation to the number of sulfur atoms.
Studies concerned with synthesis of oxidation in-
hibitors and the mechanism of their antioxidative ef-
fect showed that hydroxyaryl sulfides and polysul-
fides [1, 2] containing simultaneously a phenolic moi-
ety and sulfur atom(s) are oxidation inhibitors with
a complex effect.
Bu-t
OH
[H]
III
2HS
Bu-t
IV
Proceeding with studies in this field [3 10], we
prepared new compounds of this group and examined
their inhibiting effect on cumene oxidation in relation
to the number of sulfur atoms.
Bu-t
Bu-t
HO
OH
CCl2
2HCl
S
Bu-t
S
S
S
t-Bu
As the initial compound we chose commercially
available 2,6-di-tert-butylphenol (I).
V
IV +
Bu-t
Bu-t
t-Bu
OH
Bu-t
HO
S2Cl2
2HCl
HO
t-Bu
+ SnCl2
S
S
S
t-Bu
VI
I
To evaluate the antioxidative power of II VI in
elementary stages of cumene oxidation, we studied
the reactions of these compounds with cumylperoxy
radicals and cumyl hydroperoxide (CHP). The cap-
ability of mono- and polysulfides II VI to terminate
oxidation chains by reaction with peroxy radicals was
studied for the example of cumene oxidation at 60 C,
intiated with azobis(isobutyronitrile) (AIBN). As seen
from Fig. 1, sulfides II VI suppress initiated oxida-
tion of cumene.
Bu-t
OH,
Bu-t
t-Bu
HO
t-Bu
[S]n
II, III
where n = 1 (II), 2 (III).
Reduction of bis(4-hydroxy-3,5-di-tert-butylphenyl)
disulfide (III) with hydrogen yielded 4-hydroxy-3,5-
di-tert-butylthiophenol (IV), which is a precursor of
the corresponding trisulfide (V) and tetrasulfide (VI).
From the duration of the induction period we cal-
culated the stoichiometric coefficient of inhibition f,
equal to the number of oxidation chains terminated on
1070-4272/01/7412-2083 $25.00 2001 MAIK Nauka/Interperiodica

2084
FARZALIEV et al.
From the kinetics of oxygen uptake, we calculated
the rate constants of the reactions of II VI with per-
oxy radicals k7 [11, 12]. To do this, we plotted the
1
1
oxygen uptake curves in the coordinates [O2]
and determined k7 from the slope of the straight line
[11]:
f
[InH]0
k7
k2[R H ]v
tan
=
,
i
tan k2 [R H ]v
f [InH]0
i
k 7
=
,
1
where k2 = 1.51 l mol 1 s is the rate constant of
chain initiation [11, 12]; [RH] = 6.9 M.
The high antioxidative activity of II VI is also
manifested in autooxidation of cumene at 110 C
(Fig. 2).
Fig. 1. Initiated oxidation of cumene in the presence of IV.
(V ) Oxygen volume and ( ) time; the same for Fig. 2.
O2
4
4
4
c
, M: (1) 0, (2) 3 10 , (3) 4 10 , and (4) 5 10 .
IV
The kinetic parameters of the reactions of II VI
with cumylperoxy radicals are listed in Table 1. It is
seen that the stoichiometric coefficient f for II VI
varies from 1.08 to 2.80. The inhibition rate constant
4
4
1
k7 varies from 2.24 10 to 6.4 10 l mol 1 s .
Inhibitors with f 1 usually terminate a single oxida-
tion change. Since the molecules under consideration
contain two functional groups, sulfide and hydroxy,
the coefficient f is somewhat higher than unity. The
products formed in reactions of II VI with cumylper-
oxy radicals also show certain inhibiting power: The
oxidation rate after the induction period is somewhat
lower than in the case of noninhibited oxidation.
Fig. 2. Autooxidation of cumene in the presence of III V
at 60 C. Inhibitor (10 M): (1) none, (2) III, (3) IV,
and (4) V.
In initiated oxidation of cumene in the presence of
sulfides II VI, in which the sulfur atom is directly
bonded to the benzene ring, the stoichiometric coeffi-
cient of inhibition f is close to unity (Table 1). In
compounds in which the sulfur atom is linked to the
benzene ring via methylene bridge, f = 2 [13].
5
one molecule of the inhibitor and its transformation
products:
f = vi / [InH]0,
It is known that for alkylphenols f = 2 [12, 14],
i.e., they terminate two oxidation chains:
where is the induction period (s), vi is the initiation
7
1
rate (under our conditions, vi = 2 10 mol l 1 s ),
.
.
RO2
RO2
and [InH]0 is the initial inhibitor concentration.
.
InH
In
Inactive products.
Table 1. Kinetic parameters of reactions of sulfides II VI
with cumylperoxy radicals
Presumably, termination of only one oxidation
chain by monosulfides in which the sulfur atom is di-
rectly bonded to the benzene ring is due to stabiliza-
tion of the arising phenoxy radical by resonance with
electron delocalization involving the unpaired electron
of oxygen and the vacant 3d orbital of sulfur. In hy-
droxyaryl sulfides containing a methylene group be-
tween the benzene ring and sulfur atom, the p d con-
jugation is impossible, and the arising phenoxy radical
is capable of reacting with the second peroxy radical.
1
Compound
f
k7, l mol 1 s
II
1.96
1.08
2.80
2.30
2.80
2.69
2.24
4.18
5.82
6.43
III
IV
V
VI
2
7
1
1
Note: 60 C, [AIBN] = 2 10 M, v = 2 10 mol l
s .
i
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 74 No. 12 2001

MECHANISM OF THE ANTIOXIDATIVE EFFECT
In the case of disulfides, thiyl radicals [7] formed
2085
by homolysis of the S S bond can participate along
with OH groups in reaction with peroxy radicals. This
fact probably accounts for the high inhibiting power
of disulfides.
Our studies showed that all the compounds II VI
actively decompose CHP. The kinetic curve of CHP
decomposition in the presence of the examined com-
pounds has a shape typical of autocatalytic reactions
(Fig. 3). The autocatalytic character of the kinetic
curves shows that CHP decomposition is effected by
products formed in the first, slow stage of the reac-
tion, rather than by inhibitors II VI proper.
To determine the reaction order, we studied how
the initial rate of catalytic decomposition of CHP
depends on the reactant concentrations. We found that
the reaction is first-order with respect to both inhibitor
(InH) and CHP:
Fig. 3. Catalytic decomposition of CHP under the action
of V (4 10 M) at 110 C. [CHP] CHP concentration
and ( ) time.
5
Cumyl hydroperoxide was purified according to
[15] with subsequent distillation; chlorobenzene and
cumene were purified by a conventional procedure
based on sulfonation of impurities with concentrated
sulfuric acid [16, 17]. The CHP concentration was de-
termined by iodometric titration [15] of samples taken
at regular intervals. Experiments on decomposition of
CHP were performed in chlorobenzene at 110 C in a
glass bubbler in an inert atmosphere; the CHP concen-
tration was varied within 0.16 0.64 M, and the con-
v = k[InH][CHP].
To determine the reaction stoichiometry, CHP was
taken in excess. The stoichiometric coefficient was
calculated by the formula
[ROOH]0
[ROOH]
=
,
[InH]0
where [ROOH]0 and [ROOH] are, respectively, the
initial and final concentrations of CHP and [InH]0 is
the initial concentration of the inhibitor.
4
4
centration of the inhibitors, from 10 to 5 10 M.
Experiments on initiated oxidation of cumene
were performed on a manometric installation [17].
The initiator was AIBN; at 60 C, its initiation rate
Our data show that transformation products of a
single inhibitor molecule decompose from several hun-
dreds to several tens of thousands of CHP molecules.
6
1
constant is 10
s
[18]. The initiator concentration
2
was 2 10 M in all the experiments, and the con-
centration of the inhibitors, 10 M.
The kinetic parameters of catalytic decomposition
of CHP under the action of II VI are listed in Ta-
ble 2. Similarly to the reaction with cumylperoxy rad-
icals, the catalytic activity of II VI in decomposition
of CHP depends on the number of sulfur atoms. The
greater the number of sulfur atoms in the molecule,
the higher k, and tetrasulfide VI is the most active.
5
Bis(4-hydroxy-3,5-di-tert-butylphenyl) sulfide II,
mp 139 C, was prepared by reaction of SCl2 with
phenol I in acetonitrile at a temperature from 15 to
30 C.
Table 2. Kinetic parameters of catalytic decomposition of
CHP under the action of II VI at 110 C
EXPERIMENTAL
The IR spectra were recorded on a Specord IR-75
spectrophotometer (mulls in mineral oil), and the
1H NMR spectra, on Varian-60 and Tesla (80 MHz)
spectrometers; the chemical shifts (ppm) are given
relative to TMS as internal reference.
1
Compound
k, l mol 1 s
II
9.5
18.6
29.8
42.7
46.0
6900
12500
32600
58500
60800
III
IV
V
Thin-layer chromatography was performed on Silu-
fol UV-254 plates, with ethanol hexane (1 : 5) as
eluent.
VI
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 74 No. 12 2001

2086
FARZALIEV et al.
and Voronkov, M.G., Zh. Org. Khim., 1981, vol. 17,
Bis(4-hydroxy-3,5-di-tert-butylphenyl) disulfide
III was prepared similarly by reaction of S2Cl2 with
phenol I; mp 145 146 C [19, 20].
no. 8, pp. 1699 1703.
4. Kuliev, A.M., Farzaliev, V.M., Mamedov, Ch.I.,
et al., Zh. Obshch. Khim., 1982, vol. 52, no. 9,
pp. 2122 2126.
5. Medzhidov, A.A., Kasumov, V.T., Farzaliev, V.M.,
et al., Zh. Obshch. Khim., 1982, vol. 52, no. 1,
pp. 101 106.
6. Gasanov, B.R., Farzaliev, V.M., Allakhverdiev, M.A.,
et al., Zh. Obshch. Khim., 1988, vol. 58, no. 1,
pp. 120 128.
7. Magerramov, A.M., Sattar-zade, R.I., Farzaliev, V.M.,
et al., Vestn. Bakinsk. Gos. Univ., Estestv. Nauki,
2000, no. 3, pp. 26 31.
4-Hydroxy-2,5-di-tert-butylthiophenol was pre-
pared according to [21].
Bis(4-hydroxy-3,5-di-tert-butylphenyl) trisulfide
V. A mixture of 12 g of thiophenol IV and 50 ml of
acetonitrile was cooled to a temperature from 15 to
30 C, and a solution of 2.5 g of SCl2 in 20 ml of
acetonitrile was added. The mixture was stirred at the
same temperature for 1 h, washed with water, and
treated with diethyl ether. After distillation of the sol-
vent, the product was recrystallized from hexane. Yield
8. Magerramov, A.M., Sattar-zade, R.I., Farzaliev, V.M.,
et al., Vestn. Bakinsk. Gos. Univ., Estestv. Nauki,
2000, no. 4, p. 5.
1
of V 10.7 g (85%), mp 129 130 C, Rf 0.52. H NMR
spectrum, , ppm: 1.45 s (36H), 4.75 s (2H), 6.85 s
(2H). IR spectrum, , cm : 3625, 1805, 685, 465.
1
9. Kuliev, A.M., Farzaliev, V.M., Allakhverdiev, M.A.,
et al., Abstracts of Papers, XVI Nauchnaya sessiya po
khimii i tekhnologii organicheskikh soedinenii sery
i sernistykh soedinenii (XVI Scientific Session on
Chemistry and Technology of Organic Sulfur Com-
pounds and Sulfur-Containing Compounds), Riga,
1984, p. 98.
10. Farzaliev, V.M., Allakhverdiev, M.A., Rzaeva, I.A.,
et al., Zh. Prikl. Khim., 1994, vol. 67, no. 6,
pp. 1025 1028.
Found, %: C 66.51, H 8.51, S 18.31.
C28H42O2S3.
Calculated, %: C 66.35, H 8.35, S 18.98.
Bis(4-hydroxy-3,5-di-tert-butylphenyl) tetrasul-
fide VI was prepared similarly from 12 g of thiophe-
nol IV and 3.4 g of S2Cl2; yield 12 g (90%), Rf 0.46.
1H NMR spectrum, , ppm: 1.41 s (36H), 4.83 s (2H),
6.73 s (2H). IR spectrum, , cm : 3620, 1810, 690,
475.
11. Emanuel’, N.M., Denisov, E.T., and Maizus, Z.K.,
Tsepnye reaktsii okisleniya uglevodorodov v zhidkoi
faze (Chain Oxidation of Hydrocarbons in the Liquid
Phase), Moscow: Nauka, 1965.
1
Found, %: C 64.62, H 8.01, S 23.17.
C28H42O2S4.
12. Emanuel’, N.M. and Denisov, E.T., Neftekhimiya,
1976, vol. 16, no. 13, pp. 366 368.
Calculated, %: C 62.41, H 7.86, S 23.80.
13. Denisov, E.T. and Kovalov, G.I., Okislenie i stabili-
zatsiya reaktivnykh topliv (Oxidation and Stabilization
of Jet Fuels), Moscow: Khimiya, 1983, p. 178.
CONCLUSIONS
14. Denisov, E.T., Usp. Khim., 1973, vol. 42, no. 3,
pp. 361 390.
(1) Bis(4-hydroxy-3,5-di-tert-butylphenyl) sulfide
15. Karnojitzki, V., Les peroxides organiques, Paris:
and polysulfides were prepared and characterized.
Hermann, 1958.
(2) These compounds effectively reduce the rate
of cumene oxidation by catalyzing decomposition of
the hydroperoxide and terminating the oxidation
chains via reaction with peroxy radicals generated
from cumene. The inhibiting activity of the com-
pounds grows with the increasing number of sulfur
atoms in the molecule.
16. Organic Solvents. Physical Properties and Methods
of Purification, Weissberger, A., Proskauer, E.S.,
Riddick, J.A. and Toops, E.E., Eds., New York: In-
terscience, 1955.
17. Emanuel’, N.M., Gladyshev, G.P., Denisov, E.T.,
et al., Order of Testing Chemical Compounds as Sta-
bilizers of Polymeric Materials, Preprint of the Inst. of
Chemical Physics, USSR Acad. Sci., Chernogolovka,
1976.
REFERENCES
18. Denisov, E.T., Konstanty skorosti gomoliticheskikh
zhidkofaznykh reaktsii (Rate Constants of Homolytic
Liquid-Phase Reactions), Moscow: Nauka, 1971.
1. Kuliev, F.A., Farzaliev, V.M., Denisov, E.T., et al.,
Neftekhimiya, 1981, vol. 21, no. 6, pp. 898 905.
19. US Patent 3211794.
20. US Patent 3250712.
21. Muller, E., Stegmann, H., and Scheffer, R., Lieb.
Ann., 1961, vol. 645, no. 1, p. 79.
2. Aliev, A.S., Farzaliev, V.M., Abdullaeva, F.A., and
Denisov, E.T., Neftekhimiya, 1975, vol. 15, no. 6,
pp. 890 895.
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RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 74 No. 12 2001