Synthesis and antioxidative effect of aromatic bisulfides

Article abstract of DOI:10.1023/B:RJAC.0000008302.82961.e7

Bis(4-hydroxy-3-formylphenyl) and bis[3-alkyl(aryl)iminomethyl-4- hydroxyphenyl] disulfides were prepared. Their reaction with cumylperoxy radicals was studied, and the inhibiting effect on the cumene oxidation was examined.

Full text of DOI:10.1023/B:RJAC.0000008302.82961.e7

Russian Journal of Applied Chemistry, Vol. 76, No. 8, 2003, pp. 1284 1287. Translated from Zhurnal Prikladnoi Khimii, Vol. 76, No. 8, 2003,
pp. 1321 1324.
Original Russian Text Copyright
2003 by Farzaliev, Allakhverdiev, Aliev, Babai, Rzaeva, Khalilova, Ismailov.
ORGANIC SYNTHESIS
AND INDUSTRIAL ORGANIC CHEMISTRY
Synthesis and Antioxidative Effect of Aromatic Disulfides
V. M. Farzaliev, M. A. Allakhverdiev, Sh. R. Aliev, R. M. Babai, I. A. Rzaeva,
A. Z. Khalilova, and E. Z. Ismailov
Kuliev Institute of Chemistry of Additives, National Academy of Sciences of Azerbaijan, Baku, Azerbaijan
Baku State University, Baku, Azerbaijan
Received February 27, 2003
Abstract Bis(4-hydroxy-3-formylphenyl) and bis[3-alkyl(aryl)iminomethyl-4-hydroxyphenyl] disulfides were
prepared. Their reaction with cumylperoxy radicals was studied, and the inhibiting effect on the cumene oxi-
dation was examined.
We has show previously [1] that bis[3-alkyl(aryl)-
aminomethyl-4-hydroxyphenyl] sulfides effectively in-
hibit cumene oxidation. Proceeding with studies aimed
at preparing various classes of organosulfur compounds
and elucidating the mechanism of their inhibiting ef-
fect [2 4], we prepared in this work aromatic disul-
fides with azomethine fragments and evaluated their
antioxidative performance in oxidation of cumene.
The IR spectra of II V contain azomethine bands at
1
1639 1640 cm , and the hydroxyl band is shifted to
1
3165 cm .
1
In the H NMR spectra of II V, we have not re-
vealed, in contrast to the spectrum of I, the broadened
signal of the formyl proton (10.37 ppm). The spectra
contain proton signals of radicals R at the N atom;
the signals of nonequivalent protons of two symmet-
rically arranged benzene rings give a doublet at 7.0
and 7.4 ppm. The signals of the hydroxyl protons are
shifted downfield by 0.4 ppm relative to I, giving a
doublet at 10.9 11.6 ppm. This may be due to weaker
intramolecular hydrogen bonding between the hy-
droxy group and azomethine nitrogen atom, compared
to the carbonyl oxygen atom in I.
The starting compound, bis(4-hydroxy-3-formyl-
phenyl) disulfide, was prepared by the reaction of
salicylaldehyde with S2Cl2 in the presence of zinc as
catalyst:
CHO
OH + S2Cl2
OHC
HO
CHO
OH
S S
2
2HCl
To evaluate the antioxidative performance of I V in
elementary steps of inhibition of cumene oxidation, we
studied the reactions of these compounds with cumyl-
peroxy radicals (CPR) and cumyl hydroperoxide (CHP).
I
Subsequent condensation of I with primary ali-
phatic and aromatic amines gave the corresponding
bis[3-alkyl(aryl)iminomethyl-4-hydroxyphenyl] disul-
fides II V in high yields:
The capability of disulfides II V to terminate oxi-
dation chains in reactions with peroxy radicals was
evaluated for the example of cumene oxidation at
60 C, initiated by azobis(isobutyronitrile) (AIBN), in
the presence of II (Fig. 1).
RN HC
HO
CH NR
OH
S S
I + 2RNH2
2H2O
II IV
From the induction period, we calculated the stoi-
chiometric coefficient of inhibition, f, equal to the
number of oxidation chains terminating in molecule
of the inhibitor and its transformation products:
where R = CH3 (II), tert-C4H9 (III), C6H5 (IV),
C6H5CH2 (V).
The purity of II V was checked by thin-layer chro-
matography, and the composition and structure were
confirmed by elemental analysis and by IR and H
f = vi/[In]0,
1
NMR spectroscopies.
where v1 is the initiation rate (under the examined
7
1
The IR spectrum of I contains characteristic ab-
sorption bands of the hydroxy group at 3320 cm .
conditions, v1 = 2 10 l mol 1 s , and [In]0 is
1
the initial inhibitor concentration.
1070-4272/03/7608-1284 $25.00 2003 MAIK Nauka/Interperiodica

SYNTHESIS AND ANTIOXIDATIVE EFFECT OF AROMATIC DISULFIDES
From the kinetics of oxygen uptake, we calculated
1285
the rate constants of the reactions of the inhibitors
with CPR, k7 [5, 6]. For this purpose, the kinetic
curves of oxygen uptake were transformed from
1
1
the coordinates [O2] to the coordinates [O2]
:
k7 = tan k2 [RH]vi / f [In]0,
where tan is the slope of the straight line in the co-
1
1
ordinates [O2]
1; k2 = 1.51 l mol 1 s , rate con-
stant of chain initiation [1, 2]; [RH] = 6.9 M, con-
centration of the substance subject to oxidation; and
vi, initiation rate (under our conditions, vi = 2
7
1
10 l mol 1 s ).
Fig. 1. Variation of CHP concentration [ROOH] with time
in initiated oxidation of cumene (1) in the absence and
The high antioxidative performance of II V was
also confirmed by experiments on cumene autooxida-
tion at 110 C (Fig. 2), and the kinetic parameters
of the reaction were determined (Fig. 2). As seen from
Table 1, the parameters f for II V vary in the range
from 1.8 to 2.4, and the rate constant k7 of the reac-
tion of inhibitors with peroxy radicals, from 1.92
2
(2) in the presence of II. [AIBN] = 2 10 , [In] = 3
4
10 M; 60 C.
1
104 to 2.72 104 l mol 1 s . The products of trans-
formations of II V in reaction with CPR also show
a certain inhibiting effect: The oxidation rate after
the induction period is somewhat lower than the rate
of uninhibited oxidation (Fig. 1).
We found that all the compounds I V actively
decompose CHP.
The kinetic curve of CHP decomposition in the
presence of I V is typical of autocatalytic reactions
(Fig. 3). The autocatalytic character of the kinetic
curves shows that decomposition of CHP is effected
not by compounds I V themselves, but by products
of their transformation in the first, slow, step of the
reaction with CHP.
Fig. 2. Volume V
of oxygen taken up in autooxida-
O2
tion of cumene at 110 C vs. time . Inhibitor added
6
([In] = 5 10 M): (1) none, (2) II, (3) III, and (4) V.
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 and CHP.
To determine the reaction stoichiometry, CHP was
taken in excess. The stoichiometric coefficient was
calculated by the formula
Fig. 3. Variation with time of the CHP concentration
[ROOH] in the course of decomposition in the presence
5
of inhibitor I ([In] = 5 10 M, 110 C).
[ROOH]0 [ROOH]
=
,
As seen from Table 1, one inhibitor molecule (with
its transformation products) decomposes more than
104 CHP molecules.
[In]0
where [ROOH]0 and [ROOH] are, respectively,
the initial and final CHP concentrations, and [In]0 is
the initial inhibitor concentration.
Table 1 shows that the coefficient f increases
from 1.6 to 1.8 2.4 in going from disulfide I to II V.
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 76 No. 8 2003

1286
FARZALIEV et al.
Table 1. Parameters of reactions of I V with CPR and those of catalytic decomposition of CHP
4
4
Com-
pound
k7 10 ,
Com-
pound
k7 10 ,
f
f
l mol 1 s
l mol 1 s
1
1
I
II
III
1.6
2.4
1.8
1.92
2.72
2.12
18000
24000
38000
IV
V
2.2
2.1
2.5
2.4
26000
20000
Table 2. Characteristics of compounds II V
Found, %/Calculated, %
Com-
pound
Yield, %
mp,
C
Formula
C
H
S
N
57.42
57.81
63.72
63.44
68.10
68.41
62.65
69.40
5.19
4.85
6.46
6.77
4.67
4.41
5.15
4.99
19.80
19.29
15.79
15.39
13.60
14.05
13.61
13.23
8.91
8.43
7.25
6.73
6.39
6.14
5.33
5.78
II
55
60
75
80
144 145
127 128
119 120
131 132
C16H16N2O2S2
C22H28N2O2S2
C26H20N2O2S2
C28H24N2O2S2
III
IV
V
This may be due to the presence of the N=C bond,
which also terminates oxidation chains. A similar
trend is observed with the parameter . The highest ,
38000, is exhibited by tert-butyl-substituted disul-
fide III.
bubbler in an inert gas atmosphere; the CHP concen-
tration was varied within 0.16 0.64 M, and the con-
5
3
centrations of I V, within 10
5
10 M.
Experiments on initiated oxidation of cumene were
performed on a manometric unit [9]; as initiator served
1
Table 1 shows that f and k strongly depend on
the radical R in II V. As compared to the related
sulfides ( = 5680 9000), disulfides II V have
higher , i.e., their inhibiting power is considerably
higher; the k7 and f values are, by contrast, somewhat
higher for sulfides [ f = 1.36 6.00, k7 = (1.99 7.96)
AIBN (initiation rate constant at 60 C 10 5 l mol 1 s
2
[10]). The initiator concentration was 2 10 M in
all the experiments, and the concentration of I V,
4
(1 5) 10 M.
Bis(4-hydroxy-3-formylphenyl) disulfide I. A so-
lution of 6.7 g (0.05 mol) of S2Cl2 in 20 ml of CCl4
was added with stirring to a solution of 12.2 g
(0.1 mol) of salicylaldehyde in 30 ml of absolute
CCl4. The mixture was allowed to stand for 24 h,
after which the solvent was distilled off and the re-
sidue was triturated with benzene. Yield of disulfide
II 6.5 g (72%), mp 105 C.
4
1
10 l mol 1 s ] [1].
EXPERIMENTAL
The IR spectra were recorded on a Specord 75-IR
1
spectrophotometer, and the H NMR spectra, on a
Bruker spectrometer (300 MHz); the chemical shifts
(ppm) are given in the
TMS.
scale relative to internal
Found, %: C 54.49, H 3.68, S 20.56.
C14H10O2S2.
Cumyl hydroperoxide was purified as described in
[7], with the subsequent distillation; chlorobenzene
and cumene were purified by a common procedure
based on sulfonation of impurities with concentrated
sulfuric acid [8, 9]. The CHP concentration was deter-
mined by iodometric titration [7] of intermittently
taken samples. Experiments on CHP decomposition
were performed in chlorobenzene at 110 C in a glass
Calculated, %: C 54.90, H 3.29, S 20.93.
Bis[3-alkyl(aryl)iminomethyl-4-hydroxyphenyl]
disulfides II V. A three-necked 100-ml flask equipped
with a stirrer, reflux condenser, and dropping funnel
was charged with a solution of 0.05 mol of disulfide I
in 30 ml of anhydrous CCl4, and 0.1 mol of appro-
priate amine was added dropwise over a period of 5 h
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 76 No. 8 2003

SYNTHESIS AND ANTIOXIDATIVE EFFECT OF AROMATIC DISULFIDES
1287
with stirring and cooling with ice. Then the mixture
was stirred for 5 h at 30 40 C. The reaction product
was washed with water and dried over Na2SO4; the
solvent was distilled off, and the residue was re-
crystallized. The yields, melting points, and elemental
analyses of II V are listed in Table 2.
mov, A.M., et al., Zh. Prikl. Khim., 2001, vol. 74,
no. 1, pp. 114 118.
4. Farzaliev, V.M., Allakhverdiev, M.A., Rzaeva, I.A.,
et al., Zh. Prikl. Khim., 1994, vol. 67, no. 6, pp.
1025 1028.
5. Emanuel’, N.M., Denisov, E.T., and Maizus, Z.K.,
Tsepnye reaktsii okisleniya uglevodorodov v zhidkoi
faze (Chain Reactions of Liquid-Phase Oxidation of
Hydrocarbons), Moscow: Nauka, 1965.
CONCLUSION
6. Emanuel’, N.M. and Denisov, E.T., Neftekhimiya,
1976, vol. 16, no. 13, pp. 366 368.
7. Karnojitzki, V., Les peroxides organiques, Paris:
Bis(4-hydroxy-3-formylphenyl) disulfide was pre-
pared; its reactions with primary amines gave the cor-
responding bis[3-alkyl(aryl)iminomethyl-4-hydroxy-
phenyl] disulfides. These disulfides inhibit cumene
oxidation and catalytically decompose cumyl hydro-
peroxide.
Hermann, 1958.
8. Weissberger, A. and Proskauer, E.S., Organic Sol-
vents. Physical Properties and Methods of Purifica-
tion, Riddick, J.A. and Toops, E.E., Eds., New York:
Interscience, 1955.
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