Polarographic study of reactions in the system 2-furaldehyde-hydrogen peroxide-NaVO3

Article abstract of DOI:10.1023/A:1013191807272

The oxidation of 2-furaldehyde to β-formylacrylic acid in 0.1 N HClO₄ containing hydrogen peroxide and sodium vanadate was studied by polarography using a dropping mercury electrode. The conversion of 2-furaldehyde and the yield of the products were found to depend on the reactant ratio. A mechanism was proposed which includes preliminary complex formation between the reactants.

Full text of DOI:10.1023/A:1013191807272

Russian Journal of Organic Chemistry, Vol. 37, No. 9, 2001, pp. 1313 1317. Translated from Zhurnal Organicheskoi Khimii, Vol. 37, No. 9, 2001,
pp. 1379 1383.
Original Russian Text Copyright
2001 by Strizhov, Poskonin, Oganova, Badovskaya.
Polarographic Study of Reactions in the System
-Furaldehyde Hydrogen Peroxide NaVO3
2
N. K. Strizhov, V. V. Poskonin, O. A. Oganova, and L. A. Badovskaya
Kuban’ State Technological University, ul. Moskovskaya 2, Krasnodar, 350072 Russia
e-mail: k-obh@kubstu.ru
Received April 13, 1999
Abstract The oxidation of 2-furaldehyde to -formylacrylic acid in 0.1 N HClO containing hydrogen
4
peroxide and sodium vanadate was studied by polarography using a dropping mercury electrode. The conver-
sion of 2-furaldehyde and the yield of the products were found to depend on the reactant ratio. A mechanism
was proposed which includes preliminary complex formation between the reactants.
We previously showed [1] that the reaction of
-furaldehyde (I) with hydrogen peroxide in the pres-
ence of vanadium(IV) or vanadium(V) compounds at
pH < 7 yields mainly cis- -formylacrylic acid (II)
which was isolated as the corresponding cyclic
tautomer, 5-hydroxyfuran-2(5H)-one (III) [2]
the pH range where variation of proton concentration
due to accumulation of acid products did not affect the
limiting currents for reduction of 2-furaldehyde and
cis- -formylacrylic acid.
2
Preliminary experiments showed that in 0.1 N
perchloric acid 2-furaldehyde and NaVO , taken
3
(
Scheme 1). Another product of 2-furaldehyde oxida-
separately, are reduced at comparable potentials,
giving clearly defined waves (Fig. 1, plots 2 and 3).
Mixing of solutions containing equimolar amounts of
tion in the same system was maleic acid (IV). Ap-
preciable amounts of cis- -formylacrylic acid as
tautomeric mixture II+III and acid IV accumulate
in the reaction mixture even in the initial period, and
their yields can vary over a wide range depending on
the reaction conditions.
With the goal of elucidating fine details of the
mechanism of oxidation of 2-furaldehyde (I) to give
products II+III and IV we performed polarographic
study of the reaction in the system 2-furaldehyde
2
-furaldehyde and NaVO3 gives rise to two new
waves which are strongly displaced toward the nega-
tive region (Fig. 1, plot 1). These findings suggest
formation of an intermediate complex of vanadium(V)
with 2-furaldehyde. According to our data [6], the
complex has the composition ML (V) and is fairly
2
5
stable: its stability constant
is 5.2 10 l/mol.
2
Hydrogen peroxide is also readily reduced under
the above conditions (Fig. 2, plots 2 and 5). Addition
of hydrogen peroxide to a solution of compound I
leads to a considerable variation of the general reduc-
tion pattern. With insufficient H O , a joint wave is
hydrogen peroxide NaVO . The reaction was carried
3
out directly in a polarographic cell under conditions
differing from those reported for preparative syntheses
1]: The reactant concentrations were fairly small,
[
2
2
and their ratio was varied over a wide range.
formed (Fig. 2, plot 4), whose shape resembles the
reduction wave of pure 2-furaldehyde; however, it is
reversible to a lesser extent, and the limiting current
is lower than that corresponding to the initial wave
of compound I (Fig. 2, plot 3) which was observed
before addition of hydrogen peroxide. These data
Compounds I, II, and IV are known to be polaro-
graphically active; the limiting diffusion current for
I and II depends on the pH value in a definite pH
range [3 5]. Therefore, the oxidation was carried out
at a constant ionic strength in 0.1 N HClO ; i.e., in
4
Scheme 1.
1
070-4280/01/3709-1313$25.00 2001 MAIK Nauka/Interperiodica

1
314
STRIZHOV et al.
hyde hydrogen peroxide NaVO ) a new wave system
3
appears on the polarogram, which indicates complex
formation between the reactants. The wave shapes
almost do not depend on the order of mixing of the
components, but they change during the process
together with the magnitudes.
Unlike binary systems 2-furaldehyde H O and
2
2
2
-furaldehyde NaVO , the transformations of 2-fur-
3
aldehyde and hydrogen peroxide in the presence of
NaVO are fairly fast. As in preparative experiments
3
[
1], these transformations lead to predominant forma-
tion of tautomeric mixture II+III (Fig. 4). On the
other hand, the yield of acid IV as a result of further
oxidation is quite small, and it almost does not
depend on the conditions. The limiting currents for
compounds I and II+III are very similar (provided
that their concentrations are also similar) and are
twice as low as the limiting current for reduction of
the ethylene bond in maleic and fumaric acids. This
means that the reduction involves aldehyde groups.
Fig. 1. Polarographic curves for (1) a mixture of 2-fur-
3
aldehyde and NaVO ; (2) 2-furaldehyde, c = 5 10 M;
3
3
(
3) NaVO , c = 5 10 mol/l; and (4) 0.1 N HClO (sup-
3
4
porting electrolyte).
Unfortunately, the presence of hydrogen peroxide
made it impossible to monitor the reaction kinetics,
for clearly defined waves of products II+III and IV
were obscured by the wave of H O , so that they
2
2
could be measured only after complete transformation
of hydrogen peroxide (Fig. 3, curve 4). Our attempts
to terminate the process at an intermediate stage by
adding compounds reacting with H O were unsuc-
2
2
cessful. Such compounds as SO , hydrazine, and
2
hydroxylamine, which promote fast decomposition of
hydrogen peroxide, either were reduced in the range
of potentials to be measured or reacted with 2-furalde-
hyde and its oxidation products. Taking into account
that the wave of compound I was observed during
the reaction only in the presence of excess substrate
with respect to H O , our further study included two
Fig. 2. Polarographic curves for (1) 0.1 N HClO (sup-
4
porting electrolyte); (2) 0.1 N HClO containing 4.84
4
4
1
1
4
0
0
mol/l of H O ; (3) 0.1 N HClO containing 5
2 2 4
3
mol/l of 2-furaldehyde; (4) 0.1 N HClO containing
.84 10 mol/l of H O and 5 10 mol/l of 2-furalde-
hyde; (5) 0.1 N HClO containing 4.84 10 mol/l of H O ;
and (6) 0.1 N HClO containing 4.84 10 mol/l of H O
4
4
3
2
2
2
2
3
series of experiments. In the first series of experi-
ments solutions with constant concentrations of 2-fur-
4
2
2
3
4
2
2
3
and 5 10 mol/l of 2-furaldehyde.
aldehyde and NaVO and variable concentration of
3
hydrogen peroxide (0 4 mol per mole of I) in 0.1 N
HClO were prepared and were left to stand until
indicate fast formation of a primary reaction product
by 2-furaldehyde and hydrogen peroxide; such product
may be known 2-furaldehyde hydroxyhydroperoxide
4
hydrogen peroxide was consumed completely. In the
second experiment series, the concentration of sodium
vanadate was varied in the range from 0 to 0.4 mol
per mole of 2-furaldehyde, the concentrations of I
(
VI) [7]. On addition of an equimolar amount of H O2
a single wave is observed with a different shape
Fig. 2, plot 6), indicating a considerable interaction
2
and H O being constant. Polarograms of these solu-
(
2
2
between the reactants; however, in the absence of
vanadium compound, this interaction does not result
in appreciable formation of products II IV over
a period of 7 days.
tions were measured when the reactions were com-
plete. Figures 4 and 5 show the dependences of 2-fur-
aldehyde consumption and yields of products II+III
and IV on the concentration of H O .
2
2
Addition of NaVO to a mixture of compound I
As follows from Fig. 4, the conversion of 2-fural-
dehyde (I) and the yield of cis- -formylacrylic acid
(II+III) depend on the amount of hydrogen peroxide
3
and H O strongly accelerates the process. Figure 3
2
2
shows that even on mixing the components (2-furalde-
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 37 No. 9 2001

POLAROGRAPHIC STUDY OF REACTIONS
1315
added (curves 3 and 4). With a large deficit of the
oxidant, the yield of II+III is close to quantitative
calculated on the reacted 2-furaldehyde, the fraction
(
of I consumed for formation of complex with vana-
dium ions, acid IV, and a small amount of uniden-
tified polarographically inactive product VII being
subtracted; curve 5). When the ratio H O 2-furalde-
2
2
hyde is close to 0.2, the yield of II+III falls down
to 75 80%. On further raising the concentration of
hydrogen peroxide, the consumption of 2-furaldehyde
and accumulation of acid II+III are accompanied
by oxidation of the latter at an appreciable rate. As
a result, the yield of II+III (calculated on the reacted
2
-furaldehyde) notably decreases as excess of H O2
2
increases. With a threefold excess of H O , 2-furalde-
2
2
hyde (I) is oxidized comletely, and in the presence
of 4 equiv of H O , product II+III also disappears.
Figure 5 shows that at the initial parts of plots 1 6
the conversion of I is proportional to the catalyst
2
2
Fig. 3. Polarographic curves for (1) 0.1 N HClO contain-
4
3
3
ing 4.8 10 mol/l of H O and 5 10 mol/l of NaVO3;
2
2
3
(
2) 0.1 N HClO containing 4.8 10 mol/l of H O , 5
4
2
2
3
3
concentration; in the range of NaVO concentrations
3
10 mol/l of NaVO , and 5 10 mol/l of 2-furaldehyde
3
about 0.04 0.2 mol per mole of 2-furaldehyde, the
conversion of I slightly decreases; and it sharply
3 min after mixing the components; (3) the same as 2 1 h
after mixing; and (4) the same as 2 after complete consum-
increases as the concentration of NaVO further rises.
ption of H O .
2 2
3
Therefore, plots 1 6 are third-order curves. The yield
of cis- -formylacrylic acid (II + III) (plots 1 6)
increases as the concentration of sodium vanadate
changes from 0 to 0.2 mol per mole of 2-furaldehyde.
On further raising the NaVO concentration, the yield
3
of II+III falls down to zero due to its oxidation to
polarographically inactive saturated acids.
Our results led us to presume that 2-furaldehyde,
hydrogen peroxide, and sodium vanadate, taken at
a ratio close to 5:1:1, form a stable intermediate
complex which ensures selective oxidation of I to
-formylacrylic acid (II+III) with a small admixture
of acid IV. Increased amount of NaVO is likely
3
to promote wasteful decomposition of H O and more
2
2
intense oxidation of II+III. Raising the concentration
Scheme 2.
(
(
(
(
(
(
(
1)
2)
3)
4)
5)
6)
7)
Fig. 4. Effect of hydrogen peroxide concentration on the
conversion of 2-furaldehyde (I) and the yields of polaro-
graphically detectable products: (1) unidentified product;
(
(
2) acid IV; (3) 2-furaldehyde (I); (4) -formylacrylic acid
II+III); and (5) ratio of the yield of II+III and the
amount of oxidized 2-furaldehyde. Reaction conditions:
.1 N HClO ; initial concentrations, M: 2-furaldehyde,
0
4
3
4
5 10 ; NaVO , 5.4 10 ; H O , 0 0.02.
3
2
2
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 37 No. 9 2001

1
316
STRIZHOV et al.
of hydrogen peroxide increases not only the degree
of oxidation of II+III but also the contribution of
On the basis of the above experimental data, we
propose a mechanism for the oxidation of 2-furalde-
concurrent transformation of 2-furaldehyde to succinic hyde with hydrogen peroxide in the presence of
acid and 2,5-dihydro-2-furanone [1, 6].
sodium vanadate, shown in Scheme 2.
It is known that at pH < 2 vanadium(V) ions exist
+
2
mainly as hydrated VO cations [8] which are capable
of coordinating 2-furaldehyde molecules [9] [see
Eqs. (1) (3) in Scheme 2]. On addition of hydrogen
peroxide peroxo compounds of quinquevalent vana-
dium are quickly formed [Eqs. (4) and (5)]; their
structure depends on the concentration of H O . When
2
2
the amount of the latter is insufficient with respect to
+
NaVO , monoperoxo complex VO(O ) (VIII) is
3
2
mainly formed in acid medium; at a H O /V(V) ratio
2
2
of greater than 2, diperoxo complex VO(O ) (IX)
2
2
is obtained [10]. Our previous results in combination
with published data [9, 11, 12] led us to presume that
under optimal conditions, i.e., at a I H O NaVO
2
2
3
ratio of about 5:1:1, the formation of intermediate
VIII is responsible for highest efficiency and selec-
tivity of the process. The predominant formation of
VIII is also indicated by a weak red color of the
reaction mixtures ( max 450 nm) [13]. The reaction of
2
-furaldehyde with intermediate VIII gives complex
X whose possible structure is shown below. Complex
X decomposes into products II IV through inter-
mediate formation of organic peroxides [14] [Eq. (6)].
Complex V reacts with hydrogen peroxide to give
a peroxo complex which cannot be distinguished from
intermediate X by polarography. That complex also
decomposes with formation of products II IV. The
low yield of maleic acid IV and its weak dependence
on the yield of II+III suggests that in the system
under study acid IV is formed via concurrent trans-
formation of 2-furaldehyde rather than as a result of
oxidation of -formylacrylic acid (II + III). This
assumption is consistent with the other data [14, 15].
EXPERIMENTAL
Polarographic studies were performed in a cell
placed in a temperature-controlled unit. The potentials
were measured with the aid of a dropping mercury
electrode relative to a standard calomel electrode.
The polarograms were recorded using a PLS-1 elec-
tronic polarograph. Experiments were carried out in
Fig. 5. Plots (1 6 ) of the conversion of 2-furaldehyde
and (1 6) the yield of acid II+III versus concentrations
of NaVO and hydrogen peroxide. Concentration of H O ,
3
2
2
mole per mole of 2-furaldehyde: (1, 1 ) 0.05; (2, 2 ) 0.1;
3, 3 ) 0.15; (4, 4 ) 0.2; (5, 5 ) 0.25; (6, 6 ) 0.5.
(
0.1 N HClO with an initial 2-furaldehyde concentra-
4
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 37 No. 9 2001

POLAROGRAPHIC STUDY OF REACTIONS
1317
tion cinit of (1.8 5.0) 10 3 M at 25 0.2 C; the
capillary parameters were as follows: m = 2.01 mg/s,
5. Stradyn’, Ya.P. and Teraud, V.V., Izv. Akad. Nauk
Latv. SSR, Ser. Khim., 1964, no. 2, pp. 169 179.
t1 = 3.41 s. Dissolved oxygen was removed by
purging with nitrogen.
6.
Oganova, O.A., Cand. Sci. (Chem.) Dissertation,
Krasnodar, 2000.
The initial concentration of hydrogen peroxide was
varied from 0 to 4 mol per mole of 2-furaldehyde, and
7. Kul’nevich, V.G. and Badovskaya, L.A., Usp. Khim.,
1975, vol. 44, no. 7, pp. 1256 1279.
of NaVO , from 0 to 0.4 mol per mole of I. Solutions
3
8. Vol’nov, I.I., Peroksokompleksy vanadiya, niobiya
i tantala (Peroxo Complexes of Vanadium, Niobium,
and Tantalum), Moscow: Nauka, 1987.
of HClO , H O , and NaVO were prepared from
4
2
2
3
chemically pure reagents using distilled water. Pure
cis- -formylacrylic acid was synthesized by the proce-
dure reported in [2]. Products II IV were identified
by adding standard solutions of authentic samples to
the polarographic cell prior to the end of the reaction.
9
.
Virtanen, P.O.I. and Puutio, M., Finn. Chim. Lett.,
981, no. 1, pp. 49 50.
1
1
1
0. Butler, A., Claque, M.J., and Meister, G.E., Chem.
Rev., 1994, vol. 94, no. 3, pp. 625 638.
1. Poskonin, V.V., Badovskaya, L.A., and Povaro-
va, L.V., Khim. Geterotsikl. Soedin., 1998, no. 7,
pp. 893 897.
REFERENCES
1
2
.
.
Poskonin, V.V. and Badovskaya, L.A., Khim. Getero-
tsikl. Soedin., 1991, no. 11, pp. 1462 1468.
1
1
2. Poskonin, V.V. and Badovskaya, L.A., Khim. Getero-
tsikl. Soedin., 1998, no. 6, pp. 742 747.
Poskonin, V.V., Badovskaya, L.A., Gavrilova, S.P.,
and Kul’nevich, V.G., Zh. Org. Khim., 1989, vol. 25,
no. 8, pp. 1701 1706.
3. Muzgin, V.I., Khamzina, L.B., and Zolotavin, V.B.,
Analiticheskaya khimiya vanadiya (Analytical Chem-
istry of Vanadium), Moscow: Nauka, 1981.
3
4
.
.
Kuzovnikova, I.A., Badovskaya, L.A., Tur’yan, Ya.I.,
and Kul’nevich, V.G., Khim. Geterotsikl. Soedin.,
14. Poskonin, V.V. and Badovskaya, L.A., Khim. Getero-
tsikl. Soedin., 1991, no. 11, pp. 1462 1467.
1
974, no. 6, pp. 737 742.
Kuzovnikova, I.A., Badovskaya, L.A., Tur’yan, Ya.I.,
and Kul’nevich, V.G., Zh. Anal. Khim., 1989, vol. 34,
no. 7, pp. 1349 1353.
15. Poskonin, V.V., Badovskaya, L.A., and Povaro-
va, L.V., Khim. Geterotsikl. Soedin., 1998, no. 8,
pp. 1047 1054.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 37 No. 9 2001