Role of peroxy compounds in oxidation of crotonaldehyde with molecular oxygen

Article abstract of DOI:10.1023/B:RJAC.0000044131.17073.de

Oxidation of crotonaldehyde with molecular oxygen and the role of percrotonic acid accumulating in the process were studied.

Full text of DOI:10.1023/B:RJAC.0000044131.17073.de

Russian Journal of Applied Chemistry, Vol. 77, No. 6, 2004, pp. 998 1001. Translated from Zhurnal Prikladnoi Khimii, Vol. 77, No. 6, 2004,
pp. 1011 1015.
Original Russian Text Copyright
2004 by O. Fedevich, Levush, E. Fedevich, Kit.
MACROMOLECULAR CHEMISTRY
AND POLYMERIC MATERIALS
Role of Peroxy Compounds in Oxidation of Crotonaldehyde
with Molecular Oxygen
O. E. Fedevich, S. S. Levush, E. V. Fedevich, and Yu. V. Kit
L’vivs’ka Politekhnika National University, Lviv, Ukraine
Lviv State Agricultural University, Lviv, Ukraine
Received November 19, 2003; in final form, March 2004
Abstract Oxidation of crotonaldehyde with molecular oxygen and the role of percrotonic acid accumu-
lating in the process were studied.
Crotonic acid (CAc) and its derivatives are used as
comonomers in production of rubbers, latexes, adhe-
sives, and plastics. Some crotonic acid esters exhibit
insecticidal or herbicidal properties.
graph (2000 3-mm column; sorbent Polysorb-1,
0.1 0.25 mm; column and vaporizer temperatures 423
and 463 K, respectively; thermal conductivity de-
tector). In the oxidate, we determined the content of
CAl and CAc. The total content of carbonyl com-
pounds was determined by the hydroxylamine method
The main synthetic route to CAc is oxidation of
crotonaldehyde (CAl). In oxidation of CAl with mo-
lecular oxygen at atmospheric [1, 2] or elevated [3]
pressure, peroxy compounds accumulate in concentra-
tions comparable with that of the forming CAc.
[
0
4], and the total content of acids, by titration with
.1 N NaOH in the presence of phenolphthalein. The
content of peroxides was determined by iodometric
titration in glacial acetic acid.
Our goal was to examine the possibility of using
peroxides accumulating in the oxidate to raise the
yield of CAc.
The gas chromatographic analysis gives the total
content of crotonic and percrotonic (PCAc) acids,
because PCAc transforms into CAc in the vaporizer.
To confirm this conclusion, we performed absolute cal-
ibration with respect to CAc in the system CAc ethyl
acetate. Percrotonic acid was prepared by oxidation of
CAc in ethyl acetate at a low temperature. For exam-
ple, in oxidation of CAl at 12 C to 15% conversion,
the content of PCAc in the sum of acids reaches 93%.
Such an oxidate gives a chromatographic peak of
CAc, whose area corresponds to the total calculated
amount of PCAc and CAc and is consistent with the
total acid content determined by chemical analysis.
EXPERIMENTAL
Pure-grade CAl was distilled before use on a labor-
atory column (10 TP, reflux ratio 2); the fraction with
bp 375 376 K was collected. Crotonaldehyde was
kept under argon at 253 K. An additional purification
was performed by steam distillation, with the collec-
tion of the azeotrope (75.7 wt % CAl, 24.3 wt %
H O), from which water was frozen out at 223 K, and
2
CAl was dried over MgSO and distilled on a column.
4
In oxidation of CAl under various conditions, the
oxidate always contains PCAc and CAc (Table 1).
The PCAc : CAc ratio decreases with increasing tem-
perature, oxidation time, and partial oxygen pressure.
Peroxy compounds disappear from the oxidate upon
prolonged storage (100 150 h). The approximate
composition of the oxidate stored for 150 h at 20 C
is as follows (wt %): ethyl acetate 75.04, CAl 8.97,
CAc 12.46, propionaldehyde 0.40, propionic acid
0.50, formic acid 1.20, propenyl formate 0.60, and
1,2-epoxypropenyl formate 0.60.
A chromatographically pure CAl was thus obtained
(
for CAl oxidation, from the viewpoint of CAc yield,
is ethyl acetate [1]. We used ethyl acetate of analyti-
bp 375 K, d 42 0 0.853 g cm ). The optimal medium
3
cally pure grade ; it was dried over CaCl and distilled
2
before use.
Qualitative and quantitative analyses were per-
formed by chemical methods [4], gas chromatog-
raphy, and IR spectroscopy. Chromatographic ana-
lyses were carried out on a Tsvet-100 chromato-
1
070-4272/04/7706-0998 2004 MAIK Nauka/Interperiodica

ROLE OF PEROXY COMPOUNDS IN OXIDATION OF CROTONALDEHYDE
999
Table 1. Influence of the oxygen pressure and temperature on oxidation of CAl in ethyl acetate* (c0 = 2.46 M)
CAl
cPCAc
cCAc
SPCAc
SCAc
S CAc + PCAc
p , atm
, min
35
cCAl, M
XCAl, %
O
2
M
%
T = 300 K
1
4
2.09
1.99
1.60
1.23
1.95
1.83
1.12
0.61
15.0
19.1
35.0
50.0
20.7
25.6
54.5
75.2
0.25
0.32
0.55
0.70
0.33
0.40
0.78
0.96
0.06
0.08
0.18
0.33
0.08
0.12
0.33
0.54
67.6
67.9
65.1
56.9
64.7
63.5
58.2
51.9
14.8
17.6
19.9
27.1
15.7
19.0
24.6
29.2
82.4
85.5
85.0
84.0
80.4
82.5
82.8
81.1
6
0
1
1
20
80
30
6
0
120
80
1
T = 309 K
1
6
30
1.93
1.64
1.17
0.68
1.66
1.07
0.59
0.38
21.5
33.3
52.4
72.4
32.5
56.5
76.0
84.6
0.33
0.53
0.75
0.95
0.42
0.81
1.07
1.00
0.09
0.17
0.33
0.53
0.18
0.34
0.47
0.66
62.2
64.6
58.1
53.3
52.5
59.0
57.7
49.0
17.0
19.9
25.7
29.8
22.5
23.7
24.8
31.0
79.2
84.5
83.8
83.1
75.0
82.7
82.5
80.0
60
1
1
20
80
30
1
6
20
80
0
1
1
*
(
p
) O pressure, ( ) time from the start of the reaction, (c) concentration, (X) conversion, and (S) selectivity.
O2 2
According to [5], CAc is formed by a parallel-
along with per acids. Quantitative data on the compo-
sition of peroxy compounds in oxidation of CAl are
lacking. This stimulated us to evaluate the content of
undesirable stable peroxides in oxidation of CAl. For
this purpose, after completion of the experiments and
determination in oxidates of CAc and sum of peroxy
compounds, the oxidates were stored for a long time
at room temperature, after which the content of perox-
ides, CAc, and CAl was determined. The results are
listed in Table 2.
consecutive mechanism directly from CAl and via
PCAc. Table 1 shows that the selectivity of CAc
formation grows with conversion, and the selectivity
of PCAc formation decreases. Apparently, the consec-
utive formation CAc via PCAc is the major pathway.
According to the classical autooxidation scheme,
peroxy compounds accumulating in oxidation of un-
saturated aldehydes are mainly the corresponding per
acids. As shown by Boboleva et al. [6], the poor se-
lectivity of CAc formation in autooxidation of CAl at
elevated temperature is due to consumption of PCAc
in side processes, rather than to cleavage of the C=C
bond in the course of oxidation. They believe that
PCAc not only transforms into CAc, but also under-
goes a radical decomposition:
It is seen that 95 98% of peroxides accumulated
by the end of experiments are unstable and undergo
consecutive transformations at room temperature. This
means that thermally stable peroxides incapable of
reacting with CAl are formed in oxidation of CAl in
very low amounts ( 0.04 M). Presumably, the perox-
ides in the oxidate are mainly PCAc and certain
amount of H O . The content of H O in the oxidate
2
2
2
2
RC(O)OOH
RC(O)O
RC(O)O + OH,
CO2 + R .
must not be significant, since, as seen from Table 2,
in some experiments (nos. 8, 10, 12, 13, 15), when the
content of CAl exceeds that of peroxides, CAl trans-
forms into CAc within the storage time in the amount
equivalent to the content of peroxy compounds in the
oxidate. This means that all the peroxides in the oxi-
date oxidize CAl to CAc. At the same time, hydrogen
peroxide oxidizes CAl to CAc only in the presence of
catalysts, Se4 compounds [7]. Hence, hydroperoxides
accumulating in oxidation of CAl with molecular
With decreasing temperature, the decomposition
decelerates [6], and the selectivity with respect to the
sum of CAc and PCAc increases. Thus, by-products
formed in CA oxidation mainly arise from radical
decomposition of PCAc. There are also indications [7]
that H O , diacyl peroxides, and polyperoxides are
+
2
2
also formed in oxidation of unsaturated aldehydes
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 77 No. 6 2004

1000
FEDEVICH et al.
Table 2. Composition of CAl oxidate before and after storage at 293 295 K*
0
c0
0
Storage
time,
c
c
HP
cCAl
c CAc + PCAc
cHP
CAl
CAc + PCAc
Run no.
days
M
1
2
3
4
5
6
7
8
9
90
88
88
86
82
79
51
49
44
41
37
37
37
35
35
0.52
0.34
0.17
0.48
0.59
0.90
0.94
1.12
0.69
1.13
0.33
1.63
1.23
0.74
3.30
1.84
1.98
2.04
1.84
1.65
1.35
1.38
1.21
1.71
1.20
1.86
0.84
1.14
1.50
1.30
1.09
1.31
1.20
1.23
0.85
0.79
0.84
0.63
1.18
0.63
1.02
0.67
0.86
0.84
0.57
0.02
0.01
0.03
0.02
0.04
0.10
0.06
0.52
0.01
0.54
0.01
0.95
0.43
0.01
2.75
2.34
2.28
2.18
2.28
2.20
2.10
2.10
1.80
2.36
1.75
2.18
1.52
1.92
2.20
1.83
0.04
0.05
0.03
0.03
0.02
0.02
0.03
0.02
0.05
0.03
0.04
0.02
0.03
0.04
0.02
10
11
12
13
14
15
*
0
(
c ) Content after oxidation, (c ) content after storage, ( CAc + PCAc) sum of acids, and (HP) hydroperoxides.
oxygen under the experimental conditions consist
mainly of PCAc, which oxidizes CAl to CAc in the
course of storage of the oxidate at room temperature,
transforming itself into CAc. In the absence of a suf-
ficient amount of CAl in the oxidate, PCAc also trans-
forms into CAc (Table 2, run nos. 1, 2, 4, 9, 11, 14),
but less selectively.
concentration of unchanged CAl should only slightly
exceed the PCAc concentration (Table 2, run nos. 6,
7). In the course of storage, CAl virtually quantitative-
ly transforms into CAc in the reaction with PCAc.
For practical synthesis of CAc, it is necessary to
find the optimal temperature for decomposition of
PCAc in the oxidate, because at room temperature
the reaction is too slow. The kinetics of PCAc and
CAl consumption and CAc accumulation in the ox-
idate was studied at 318 and 333 K. After oxidation
for 100 min at 309 K, the oxygen supply was stopped,
the system was purged with argon and then heated to
the required temperature, and the oxidate composition
was monitored. The results of some experiments are
shown as example in Fig. 1. As seen from Fig. 1a,
The fact that PCAc, one of the major products of
CAl oxidation, virtually quantitatively transforms into
CAc on keeping the oxidate at room temperature and
oxidizes in the process an equimolar amount of CAl
can be used to achieve the maximum yield of CAc.
Oxidation of CAl with molecular oxygen should be
performed up to accumulation of the maximum con-
centration of PCAc in the oxidate. In so doing, the
Fig. 1. Kinetic curves of (1, 1 ) consumption of PCAc, (2, 2 ) consumption of CAl, and (3, 3 ) accumulation of the sum of
CAc and PCAc at (a) 318 and (b) 333 K. (c) Concentration and ( ) time. (1, 1 , 2, 2 , 3, 3 ) Results of replicate runs.
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 77 No. 6 2004

ROLE OF PEROXY COMPOUNDS IN OXIDATION OF CROTONALDEHYDE
1001
Table 3. Characteristics of the oxidate after oxidation and storage (CAl content at the beginning of experiments 2.46 M, oxidation
time 180 min, storage for 7 h at 318 K)
0
0
0
c
c
c
CAc
xCAl
S CAc + PCAc
%
cCAl
cPCAc
M
cCAc
xCAl
SCAc
CAl
PCAc
p ,
atm
T,*
K
O
2
M
%
3
3
3
3
3
00
00
00
09
09
1
2
4
1
16
1.23
0.96
0.61
0.68
0.38
0.70
1.03
0.96
0.95
1.00
0.33
0.47
0.54
0.53
0.66
50.0
61.0
75.2
72.4
84.6
84.0
83.0
81.1
83.1
80.0
0.52
0.05
0.02
0.03
0.01
0.02
0.03
0.02
0.03
0.03
1.69
2.28
2.05
2.09
1.99
79.7
98.0
99.1
98.8
99.6
87.1
94.6
84.0
86.0
81.2
*
(
T) Oxidation temperature.
the concentrations of CAl and PCAc decrease to a
similar extent, with the total concentration of CAc
and PCAc growing simultaneously. For example, in
The results of these studies allowed development
of an efficient procedure for preparing CAc [8].
7
h, the PCAc concentration decreased by 0.61 M;
CONCLUSION
that of CAl, by 0.59 M; and that of the sum of CAc
and PCAc increased by 0.6 M. Within the same time,
To achieve the maximum yield of crotonic acid, it
is appropriate to perform oxidation of crotonaldehyde
with molecular oxygen at 300 310 K to 55 65% con-
version of crotonaldehyde, when the concentrations of
perctoronic acid and unchanged crotonaldehyde in the
oxidate become approximately equal. The unchanged
crotonaldehyde is subsequently oxidized with percro-
tonic acid at 315 320 K within 7.0 7.5 h.
9
.6 ml of CO and 2.4 ml of CO evolved from the
2
oxidate (30 ml). Hence, at 318 K only 1 2% of PCAc
is spent for side reactions (initiated radical decomposi-
tion), whereas 98 99% of PCAc reacts with CAl to
form CAc.
At 333 K (Fig. 1b), PCAc is consumed considera-
bly faster, and the process is complete within approx-
imately 4 h. However, the relative contribution of
PCAc decomposition grows. For example, 15 ml of
REFERENCES
CO and 5.4 ml of CO evolved from the reactor in
1. Fedevich, O.E., Levush, S.S., and Kit, Yu.V., Visn.
Derzh. Univ. L’vivs’ka Politekh., Khim., Tekhnol.
Rech. Ikh Zastosuv., 1998, no. 339, pp. 165 167.
2. Fedevich, O.E., Levush, S.S., and Kit, Yu.V., Teor.
Eksp. Khim., 1999, vol. 35, no. 5, pp. 332 337.
2
4
h. Percrotonic acid is consumed noticeably faster
than CAl: in 4 h, the PCAc concentration decreased
by 0.62 M, and that of CAl, by 0.56 M. The total
concentration of CAc and PCAc grew by only 0.54 M
(
87% of the consumed PCAc).
3. Fedevich, O.E., Levush, S.S., Fedevich, E.V., and
Kit, Yu.V., Zh. Prikl. Khim., 2002, vol. 75, no. 7,
pp. 1146 1150.
Apparently, to ensure the most efficient utilization
of PCAc and maximum yield of CAc, the oxidate
should be kept at relatively low temperatures. Table 3
illustrates the variation of the oxidate composition at
4
. Houben Weyl, Methoden der organischen Chemie,
vol. 2: Analytische Methoden, Stuttgart: Thieme, 1953.
5
. Fedevich, O.E., Levush, S.S., Fedevich, E.V., and
Kit, Yu.V., Zh. Org. Khim., 2003, vol. 39, no. 1,
pp. 41 43.
3
18 K in the course of 7 h. It is seen that oxidation of
CAl to CAc with PCAc occurs more selectively than
oxidation with molecular oxygen to CAc and PCAc.
Table 3 shows that the maximum efficiency is reached
when the concentrations of the accumulated PCAc and
unchanged CAl in the oxidate by the end of autooxi-
dation are approximately equal. This situation is at-
tained at 60% conversion of CAl. In the course of
storage, unchanged CAl is oxidized with PCAc, and
the total selectivity with respect to CAc reaches 94%.
6
7
. Boboleva, S.P., Bulygin, M.V., Valov, P.I., and Blyum-
berg, E.A., Neftekhimiya, 1990, vol. 30, no. 2,
pp. 239 243.
. Pikh, Z.G., Selective Oxidation of Unsaturated Com-
pounds with Bound Oxygen, Doctoral Dissertation,
Lviv, 1994.
8. Ukrainian Patent, Method for Preparing Crotonic Acid,
Promysl. Vlasp., 2002, no. 6.
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 77 No. 6 2004