Antioxidant properties of some thiourea derivatives

Article abstract of DOI:10.1134/S1070427211080167

Antioxidant properties of some thiourea derivatives in model reactions were studied. Pleiades Publishing, Ltd., 2011.

Full text of DOI:10.1134/S1070427211080167

ISSN 1070-4272, Russian Journal of Applied Chemistry, 2011, Vol. 84, No. 8, pp. 1394–1397. © Pleiades Publishing, Ltd., 2011.
Original Russian Text © A.R. Sudzhaev, I.A. Rzaeva, R.A. Nadzhafova, Yu.S. Safarov, M.A. Allakhverdiev, 2011, published in Zhurnal Prikladnoi Khimii,
2011, Vol. 84, No. 8, pp. 1329–1332.
ORGANIC SYNTHESIS AND INDUSTRIAL
ORGANIC CHEMISTRY
Antioxidant Properties of Some Thiourea Derivatives
A. R. Sudzhaev, I. A. Rzaeva, R. A. Nadzhafova,
Yu. S. Safarov, and M. A. Allakhverdiev
Kuliev Institute of Chemistry of Additives, National Academy of Sciences of Azerbaijan, Baku, Azerbaijan
Received October 22, 2010
Abstract—Antioxidant properties of some thiourea derivatives in model reactions were studied.
DOI: 10.1134/S1070427211080167
Proceeding with studies in the field of synthesis
[1, 2] and antioxidant properties [3–5] of thiourea
derivatives, we synthesized some thiourea derivatives
and examined their antioxidant properties in model
reactions.
amine yields N,N'-(iminodiethane-2,1-diyl)bis(thio-
urea) II.
An increase in the amount of thiourea taken for the
reaction leads to the substitution of both hydroxy
groups in the diethanolamine molecule by thiourea
residues.
Our experiments showed that the reaction of
thiourea with ethanolamine yields 1-(2-aminoethyl)
thiourea I.
The reaction of 1-(N-phenylamino)-2-propanol with
thiourea yields 1-[1-methyl-2-(phenylamino)ethyl)]
thiourea III.
Similarly, the reaction of thiourea with diethanol-
H
H2N
NH2
OH
N
NH2
+
_H2O
H2N
H2N
S
S
I
N
H
NH2
H
N
H N
2
NH2
2
+
H2C
H2C
CH2
CH2
HN
HN
NH2
_2H2O
S
S
S
OH
HO
II
CH3
CH
OH
CH2 NHC6H5 + NH2
C
S
NH2
CH3
CH
CH2 NHC6H5
_H2O
NH
C
NH2
S
III
The reaction is usually accompanied by the heat
release, with the temperature of the reaction mixture
reaching 80–90°С. At this temperature, after heating
for 1 h, 1-[1-methyl-2-(phenylamino)ethyl)]thiourea
III is formed in 82% yield. This compound is liquid
and can be distilled in a vacuum. After a certain time,
it crystallizes to form fine crystals.
To evaluate the antioxidant activity of thiourea
derivatives I–III, we used a comprehensively studied
1394

1395
ANTIOXIDANT PROPERTIES OF SOME THIOUREA DERIVATIVES
t, min
Fig. 1. Kinetic curves of cumene autooxidation with the
t, min
participation of I–III. Т = 110°С, [InH] = 5 × 10–5 M.
[V(O2)] Volume of oxygen taken up and (t) time; the same
for Fig. 2. (1') No inhibitor; (1–3) oxidation in the presence
of I–III, respectively; the same for Fig. 2.
Fig. 2. Kinetic curves of initiated oxidation of cumene in
the presence of I–III. Т = 60°C, [InH] = 5 × 10–4 M.
fk7[InH]0
reaction of cumene oxidation. A study of the cumene
autooxidation in the presence of these compounds
showed that they inhibit the autooxidation. Figure 1
shows the kinetic curves of cumene oxidation in the
presence of I–III at 110°С.
tan α =
k2[RH]Wi
we found
tan αk2[RH]Wi
.
k7 =
f[InH]0
We studied the reactions of I–III with cumylperoxy
radicals at a constant initiator (AIBN) concentration of
2 × 10–2 M and temperature of 60°С. The kinetic
curves of the initiated cumene oxidation in the
presence of I–III show that these compounds
terminate the oxidation chain in the reaction with
cumylperoxy radicals (Fig. 2).
where k2 is the rate constant of the reaction of the RO2·
radical with the hydrocarbon molecule at 60°С,
1.5 l mol–1 s–1; [RH] = 7.17 M for neat cumene [8].
The kinetic parameters characterizing the anti-
oxidant properties of I–III are given in the table.
As seen from the table, the stoichiometric inhibition
coefficients f of I–III vary within 3.6–5.04, with the
highest value observed with N,N'-(iminodiethane-2,1-
diyl)bis(thiourea) II.
From the length of the induction period τ (min), we
calculated the stoichiometric inhibition coefficient f.
This parameter is equal to the number of oxidation
chains terminated on one inhibitor molecule and its
transformation products and is calculated by the
formula
The induction period with this compound is
relatively long, 265 min. The inhibition rate constant k7
for II is 3.26 × 104 l mol–1 s–1. Similarly, for I, k7 is
2.28 × 104, and for III, 2.56 × 104 l mol–1 s–1.
f = (τWi)/[InH]0,
where Wi is the initiation rate, 2 × 10–7 mol l–1 s–1;
The reactions of I–III with cumyl hydroperoxide
(CHP) were performed at 110°С in chlorobenzene
solution in a nitrogen atmosphere. We found that
compounds I–III catalytically decompose cumyl
hydroperoxide. The kinetic curve of the decomposition
of N,N'-(iminodiethane-2,1-diyl)bis(thiourea) II is
shown in Fig. 3.
[InH]0, initial inhibitor concentration, 5 × 10–4 M.
From the kinetics of the oxygen uptake, we
calculated the rate constant of the reaction of the
inhibitor with cumylperoxy radicals k7. To determine
k7, the kinetic curves of the initiated cumene oxidation
were transformed from the coordinates Δ[О2]–t to the
coordinates Δ[О2]–1–t–1, and from the slope of the
straight line [7].
The catalytic factor ν given in the table shows how
many CHP molecules decompose under the action of
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1396
SUDZHAEV et al.
factor, ν = 22 000, is observed for II. Compound III
also shows relatively high activity: ν = 20 000. 1-(2-
Aminoethyl)thiourea is the least active: ν = 17 000.
The rate constant k of cumyl hydroperoxide decom-
position depends on the antioxidant structure. Anti-
oxidants I–III are characterized not only by high cata-
lytic factors, but also by high rate constants. For example,
at 110°С, k for II is 11, and for I, 10.5 l mol–1 s–1.
t, min
Fig. 3. Kinetic curve of cumyl hydroperoxide decom-
position in the presence of N,N'-(iminodiethane-2,1-diyl)bis-
(thiourea) II. Т = 110°C, [InH] = 5 × 10–4 M. ([ROOH], M)
Cumyl hydroperoxide concentration and (t) time.
Thus, thiourea derivatives I–III, showing increased
activity as inhibitors, not only catalytically decompose
cumyl hydroperoxide, but also react with cumylperoxy
radicals, terminating oxidation chains.
EXPERIMENTAL
one inhibitor molecule and its transformation products.
This is clear from the following formula:
The structures of the compounds synthesized were
[ROOH]0 – [ROOH]∞
1
,
ν =
determined by IR and H and 13C NMR spectroscopy
[InH]0
and by liquid chromatography. The purity of the
compounds was checked by thin-layer chromatography
on Silufol UV-254 plates. As eluent we used a mixture
of isopropyl alcohol with hexane (3 : 5). In each case,
one spot was observed after exposure to iodine vapor.
where [ROOH]0 is the initial, and [ROOH]∞, final
CHP concentration.
Summarizing the results obtained, we can note that
the antioxidant properties of substituted thioureas are
gradually enhanced with an increase in the number of
nitrogen atoms in the molecule. Analysis of the kinetic
parameters of the cumyl hydroperoxide decomposition
shows that the catalytic activity depends on the
structure of the compounds. The highest catalytic
1-(2-Aminoethyl)thiourea I. A flask was charged
with a mixture of 6.1 g (0.1 mol) of ethanolamine, 7.6 g
(0.1 mol) of thiourea, and 10 ml of trifluoroacetic acid.
The mixture was stirred for 11 h at 45–50°C. The
reaction progress was monitored by thin-layer
Kinetic parameters of reactions of I–III with cumylperoxy radicals and of cumyl hydroperoxide decomposition
Т = 60°C
Т = 110°C
Comp.
no.
Formula
τ, min
k7×10–4,
k,
f
ν
l mol–1 s–1
2.28
l mol–1 s–1
8.6
I
3.6
17000
200
NH2
HN
NH2
S
II
III
5.04
3.84
3.26
2.56
11
22000
20000
265
220
NH
NH2
HN
NH2
HN
S
S
10.5
NH
NH2
HN
S
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 84 No. 8 2011

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ANTIOXIDANT PROPERTIES OF SOME THIOUREA DERIVATIVES
chromatography. After the reaction completion,
trifluoroacetic acid was distilled off. The organic
product was extracted with CCl4 and ether. 1-(2-
Aminoethyl)thiourea I was obtained in 58% yield, mp
108°C, Rf 0.21. Found, %: C 30.18, H 7.72, N 35.19, S
26.85. C3H9N3S. Calculated, %: C 30.23, H 7.61, N
35.26, S 26.90.
(2) These compounds take active part in scavenging
of cumylperoxy radicals and simultaneously effect
catalytic decomposition of cumyl hydroperoxide.
REFERENCES
1. Magerramov, A.M., Mekhtieva, G.R., Abdinbekova, R.T.,
et al., Vestn. Bakinsk. Univ., Ser. Estestv. Nauk, 2002,
no. 3, pp. 5–10.
N,N'-(Iminodiethane-2,1-diyl)bis(thiourea)
II
was prepared similarly. A flask was charged with a
mixture of 4.2 g (0.04 mol) of diethanolamine, 3.04 g
(0.04 mol) of thiourea, and 5 ml of trifluoroacetic acid.
The mixture was stirred for 8 h at 40–45°C. The
reaction progress was monitored by thin-layer
chromatography. After the reaction completion, tri-
fluoroacetic acid was distilled off. The product, N,N'-
(iminodiethane-2,1-diyl)bis(thiourea) II, was crystal-
lized from ethanol. Yield 90%, mp 119°C, Rf 0.34.
2. Magerramov, A.M., Abdinbekova, R.T., Kurbanova, M.M.,
et al., Processes Petrochem. Refin., 2003, no. 3, p. 50.
3. Farzaliev, V.M., Allakhverdiev, M.A., and Rzaeva, I.A.,
Zh. Prikl. Khim., 1994, vol. 67, no. 6, pp. 1025–1028.
4. Farzaliev, V.M., Allakhverdiev, M.A., and Rzaev, I.A.,
Neftekhimiya, 1998, vol. 38, no. 2, p. 137.
5. Farzaliev, V.M., Magerramov, A.M., Allakhverdiev, M.A.,
and Rzaev, I.A., Zh. Prikl. Khim., 2001, vol. 74, no. 1,
pp. 110–113.
Found, %:
С
32.49,
H
6.94,
N
31.59,
S
28.88.C6H15N5S2. Calculated, %: C 32.56, H 6.83, N
31.64, S 28.97.
6. Sudzhaev, A.R., Nadzhafova, R.A., Allakhverdiev, M.A.,
and Safarov, Yu.S., Nauchn. Novosti, 2007, no. 2,
pp. 36–40.
Compound III was prepared similarly from 7.6 g
(0.1 mol) of thiourea and 15.1 g (0.1 mol) of 1-(N-
phenylamino)-2-propanol. Yield 10 g (82%), mp 145°C,
Rf 0.53. Found, %: C 57.38, H 7.23, N 20.01, S 15.27.
C10H15N3S. Calculated, %: C 57.42, H 7.18, N 20.09, S
15.31.
7. Denisov, E.T., Kharitonov, V.V., and Fedorov, V.V.,
Metod transformatsii kineticheskikh krivykh kak sposob
otsenki effektivnosti ingibitorov okisleniya (Trans-
formation of Kinetic Curves as a Method for Evaluating
the Performance of Oxidation Inhibitors), Cherno-
golovka, 1973.
CONCLUSIONS
8. Denisov, E.T., Konstanty skorosti gomoliticheskikh
zhidkofaznykh reaktsii (Rate Constants of Homolytic
Liquid-Phase Reactions), Moscow: Nauka, 1971.
(1) A series of thiourea derivatives were syn-
thesized.
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