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AKHMEDOV et al.
∆V , ml
0.3
0.2
0.1
O
2
(‡)
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
V
I
III
IV
II
5
10 15 20 25 30
t, min
(b)
0.3
0.2
0.1
20 60 100 140 180 220 260 300
40 80 120 160 200 240 280
t, min
Fig. 2. Kinetic curves of the cumene autooxidation in the
presence of the synthesized compounds: í = 110°ë, VO is
2
the oxygen volume (ml), t is the time (min), and the other
parameters are the same as specified in the legend to Fig. 1.
–1
[InH] (mol l ) (I) 0.
5 10 15 20 25 30
t, min
The data presented in Table 2 show that the value of
the stoichiometric factor f for compounds I–VI ranges
from 0.96 to 34. The inhibition rate constant k7 varies
from 2.00 × 10–4 to 7.05 × 10–4 l mol–1 s–1.
Fig. 3. Kinetic curves for the catalytic decomposition of
CHP (a) in the presence of 3-thietanylisothiocyanate I at
–4
–1
–1
c
= 1 × 10 mol l , 110°ë, and [CHP] = 0.27 mol l
(I)
0
and (b) by the action of compounds I, IV, and V at c
=
(II, IV, V)
–4
–1
5 × 10 mol l and an initial CHP concentration of
–1
0.32 mol l ; t is the time in min.
The data in Table 2 also indicate that the reaction of
3-thietanylthiocarbamides I–VI with cumene peroxide
radicals reveals a substantial effect of the nature of the
substituent in the thiocarbamide group upon the reac-
tivity toward these radicals. Investigations have shown
that all compounds containing the thioamide moiety
retard the initiated oxidation of cumene.
To determine the catalytic factor ν of the reaction,
CHP was taken in excess. The values of ν were calcu-
lated from the relationship:
[CHP]0 – [CHP]exc
ν = ---------------------------------------------- ,
[InH]0
As is seen from the data presented in Table 2, thio-
carbamide that contains the benzyl radical (II) multiply
terminates the oxidation chain (f = 34) as compared to
the case of naphthyl, phenyl, and piperidyl radicals, and
displays a very high reactivity toward cumene peroxide
radicals (k7 = 7.05 × 10–4 l mol–1 s–1). The study of
cumene autooxidation (110°ë) in the presence of com-
pounds II–V ([InH] = 5 × 10–5 mol l–1) has shown
(Fig. 2) that these compounds inhibit the autooxidation
process.
where [CHP]0 and [CHP]exc are the initial and final con-
centrations of cumene hydroperoxide, respectively,
andν shows how many CHP molecules are decomposed
by one inhibitor molecule. One molecule of test inhibi-
tors I–VI decomposed a few thousand CHP molecules.
The highest catalytic activity is displayed by compound
II. One molecule of this compound decomposes
5.86 × 105 CHP molecules.
The results of the study show that all of the synthe-
sized compounds actively decompose cumene hydrop-
eroxide (Figs. 3a, 3b). The autocatalytic character of
the rate curves suggest that CHP degradation is medi-
ated by the products of the conversion of 3-thietanylth-
iocarbamides at the first step in the slow reaction with
cumene hydroperoxide, rather than the reactant substi-
tuted thiocarbamides.
REFERENCES
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To determine the reaction rate order, we studied the
dependence of the initial rate of the catalytic degrada-
tion reaction of cumene hydroperoxide on the concen-
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PETROLEUM CHEMISTRY Vol. 49 No. 5 2009