440
PETROV, SOLYANIKOV
we can say conclude that the quantitative differences
[CSE]0, [FSE]0, mol/l
in the parameters of the SE, CSE, and FSE oxidation
parameters do not causes qualitative differences. In
other words, the oxidation of the three epoxides proꢀ
ceeds follows within the same mechanism, presumobꢀ
ably, with the intermediate formation of carbene,
which can absorb oxygen to afford carbonyl oxide [5].
Indeed fact, the expression for of the oxidation rate as
through the concentrationsa function of the reacꢀ
0
0.2
0.4
0.6
0.8
1.0
1.2
24
20
16
12
8
1
1'
2
tagents has the same form for these epoxides, VO
k
=
2
2'
'[SE]0[TSA]1[O2]n = [SE]0[TSA]1. The oxidation of
k
SE and CSE yields the same main products, the correꢀ
sponding aldehyde and hydrogen peroxide. As menꢀ
tioned above, the yields of the latter are very close for
these two epoxides. The Arrhenius dependences
expressions for the pseudoꢀfirstꢀorder rate constants
4
of the SE and CSE oxidation are similar:
109exp(–83.6 kJ mol–1 RT) s–1 and kCSE = 7.57
109exp(–84.8 kJ mol–1 RT) s–1. The effect of the haloꢀ
gen substituent is clearly observed: kSE kCSE kFSE
(343 K) : 5.5
10–4 < 7.9 10–4 < 3.8 10–3 s–1.
kSE = 3.32
×
0
10
20
×
103, mol/l
30
/
×
[TSA]
/
<
<
Fig. 5. The rates of oxidation by oxygen for the binary sysꢀ
tems (1, 1') CSE + TSA and (2, 2') FSE + TSA as a funcꢀ
tion of reagent concentrations (mol/l) in BUC solutions at
343 K: (1) [TSA], [CSE] = 0.33; (1') [CSE], [TSA] =
0.019; (
0.0031.
×
×
×
Substituted epoxides, especially fluoride, are oxiꢀ
dized more easierly than the styrene epoxide per se. A
similar picture is observed when we compare the data
on the overall conversion of SE and CSE. As menꢀ
tioned above, the concentration dependences of the
overall SE conversion and oxidation, buildup of the
main products, and even the degradation of hydroperꢀ
oxides added to BS(SE + TSA) in the an oxygenꢀfree
0
2) [TSA], [FSE] = 0.51; and (2') [FSE], [TSA] =
low [FSE]0 and [CSE]0 for unknown reasons (see also
the first column in Table 1). Then, the value av = 61%
P
for experiments in pure oxygen at [FSE]0 > 0.5 mol/l,
which is higher than the peroxide yield for SE and
CSE by a factor of 1.5–1.6. It seems is improbable
unlikely that this discrepancy implies a serious differꢀ
ence in the oxidation mechanism between the test
epoxides. We assume that the FSE oxidation products
atmosphere are similar. In all these cases, Vj
=
kj[SE]0[TSA]1 [1–4]. Now, this list is complemented
by the study of the pꢀchloroineꢀ substituted epoxide,
for which the expressions for the rate of oxidation and
of the overallꢀ conversion rates have the same form
(see Figs. 1 and 3) has the same form: the zero order in
with respect to CSE (the constant rate of consumption
rate independent of the extent of reaction depth) and
the first order in respect to the acid. The pseudoꢀfirstꢀ
order rate constant of the overall CSE consumption
(for example, the pꢀfluorobenzaldehyde) form the a
triple ternary system with the BS(FSE + TSA binary sysꢀ
tem);, i.e., the radical chain oxidation of the intermeꢀ
diate labile product begins, as it was observed in the
experiments with the introduction of styrene and isoꢀ
propanol into the SE + TSA binary system [5]. In this
case, iodometric titration gives the sum [H2O2] +
[ROOH], where ROOH is the hydroperoxide from the
labile intermediate produced during the oxidation of
the binary system,. thereby explaining This results in
kc,SE
was found from the slope of curve
constant of the overall consumption of unsubstituted
styrene epoxide c,CSE = 1.4
10–2 s–1 [2] is close to
this value. This means that the ꢀchloroine substituent
=
kр.CSE = (
Δ
V
р/[TSA] ) = 1.28
×
10–2 s–1 (343 K)
in Fig. 3. The rate
1
k
×
p
the overestimateding of the value of P = [H2O2]/[O2] <
slightly affects the rate of heterolytic conversion, but
significantly increases the oxygen uptake. From the
([H2O2] + [ROOH])/[O2], determined by the titration.
This assumption needs additional verification, which
is beyond the framework scope of this study.
ratio of the slopes of curves
1 and 2 (Fig. 3), we found
that only one CSE molecule from out of 18 CSE molꢀ
In summaryconclusion, comparing the oxidation ecules converted is consumed in the reaction with the
of SE [1–4] and with that of CSE and FSE given here, participation of oxygen. This ratio for SE is 25 : 1 [2].
Table 2. The yield of H2O2 (%) in the oxidation of BS(FSE + TSA)
[TSA], mol/l
[FSE]0, mol/l
[O2], %
0.0031
0.51
21
0.0031
0.51
32
0.0031
0.135
100
0.0052
0.507
100
0.0031
0.51
100
0.0031
0.68
100
0.0031
0.85
100
P
, %
33
21
33
69
50
68
59
PETROLEUM CHEMISTRY Vol. 50
No. 6
2010