Kinetics of the electrochemical oxidation of 1,1-bis-hydroperoxy-4- methylcyclohexane on platinum

Article abstract of DOI:10.1134/S0036024413030333

The electrochemical synthesis of 3,12-dimethyl-7,8,15,16-tetraoxadispiro[5. 2.5.2]hexadecane (1,2,4,5-tetraoxane) from 1,1-bis-hydroperoxy-4- methylcyclohexane on platinum electrode in a cell with separated and unseparated cathode and anode space in an aprotic solvent is conducted. The kinetics of electrochemical oxidation of 1,1-bis(hydroperoxy)-4-methylcyclohexane is studied. The current yield of the reaction is determined.

Full text of DOI:10.1134/S0036024413030333

ISSN 0036ꢀ0244, Russian Journal of Physical Chemistry A, 2013, Vol. 87, No. 3, pp. 397–400. © Pleiades Publishing, Ltd., 2013.
Original Russian Text © M.D. Vedenyapina, A.P. Simakova, M.M. Platonov, A.O. Terent’ev, A.M. Skundin, A.A. Vedenyapin, 2013, published in Zhurnal Fizicheskoi Khimii, 2013,
Vol. 87, No. 3, pp. 418–421.
CHEMICAL KINETICS
AND CATALYSIS
Kinetics of the Electrochemical Oxidation
of 1,1ꢀBisꢀhydroperoxyꢀ4ꢀmethylcyclohexane on Platinum
M. D. Vedenyapinaa, A. P. Simakovaa, M. M. Platonova,
A. O. Terent’eva, A. M. Skundinb, and A. A. Vedenyapina
aZelinskii Institute of Organic Chemistry, Russian Academy of Science, Moscow, Russia
bFrumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Science, Moscow, Russia
eꢀmail: mvedenyapina@yandex.ru
Received March 11, 2012
Abstract—The electrochemical synthesis of 3,12ꢀdimethylꢀ7,8,15,16ꢀtetraoxadispiro[5.2.5.2]hexadecane
(1,2,4,5ꢀtetraoxane) from 1,1ꢀbisꢀhydroperoxyꢀ4ꢀmethylcyclohexane on platinum electrode in a cell with
separated and unseparated cathode and anode space in an aprotic solvent is conducted. The kinetics of elecꢀ
trochemical oxidation of 1,1ꢀbis(hydroperoxy)ꢀ4ꢀmethylcyclohexane is studied. The current yield of the
reaction is determined.
Keywords: 1,1ꢀbisꢀhydroperoxyꢀ4ꢀmethylcyclohexane, electrochemical synthesis, 1,2,4,5ꢀtetraoxane, platiꢀ
num electrode, cyclic voltammetry.
DOI: 10.1134/S0036024413030333
INTRODUCTION
EXPERIMENTAL
Initial compound
1
was obtained via the reaction of
Over the last two decades, organic peroxides have
been attracting the attention of chemists and researchꢀ
ers in the development of medicinal preparations due
to the high antimalarial [1, 2] and antitumor [3] activꢀ
ity found for these compounds. To date, tetraoxanes,
ozonides, and trioxanes having activity comparable to
or surpassing that of natural peroxide artemisinin have
been obtained [4].
4ꢀmethylcyclohexanone with hydrogen peroxide [7].
A 1% LiClO4 (Acros) solution in acetonitrile was used
as our background electrolyte. To conduct our prelimꢀ
inary synthesis, 600 mg of
of the background electrolyte, while 10 mg of
dissolved in 10 mL of the background electrolyte to
perform the electroanalytical and kinetics experiꢀ
ments. Preliminary electrolysis was performed in the
galvanostatic (50 mA) and potentiostatic modes in a
twoꢀelectrode glass cell with and without a Kꢀ40 ionꢀ
exchange membrane. Platinum plates with surface
areas of 10 cm2 were used as electrodes in our prelimꢀ
inary experiments, while platinum plates with surface
areas of 1 cm2 were used for our electroanalytical meaꢀ
surements (working and auxiliary electrodes). Elecꢀ
trochemical measurements were conducted relative to
1
were dissolved in 150 mL
were
1
Geminal bisꢀhydroperoxides are initial reagents in
the synthesis of peroxides with antimalarial and antiꢀ
tumor activity. Moreover, they are of interest as initiaꢀ
tors of radical polymerization [5] and as initial comꢀ
pounds in the synthesis of esters [6]. The reactivity and
other properties of geminal bisꢀhydroperoxides have
been actively studied in the last five years after conveꢀ
nient and accessible methods for their synthesis were
developed [7].
a
(
silver/silver chloride reference electrode
AgCl КCl(sat)).
Cyclic voltammograms (CVAs) were recorded
Ag
|
|
The electrochemistry of organic peroxides attracts
attention in developing methods for their analysis with
the aim of investigating the mechanisms of O–O moiꢀ
ety reduction, and when studying structures having
antimalarial activity [8–10].
using a computerꢀcontrolled IPCꢀCompact potenꢀ
tiostat.
Acetonitrile was distilled over phosphorus pentoxꢀ
ide. Lithium perchlorate was used without additional
purification.
In [11], we studied the electrosynthesis of 1,2,4,5ꢀ
tetraoxane (
cyclohexane (
2
) from 1,1ꢀbisꢀhydroperoxyꢀ4ꢀmethylꢀ
Samples were collected and analyzed by means of
thin layer chromatography (TLC) in the electrooxidaꢀ
1) under membraneꢀfree conditions.
The aim of this work is to study the kinetics of this
reaction and of the electrochemical behavior of initial
tion of
lished based on the disappearance of a spot correꢀ
sponding to the initial . After the completion of elecꢀ
1. The completion of electrolysis was estabꢀ
compound
1
and product
2.
1
397

398
VEDENYAPINA et al.
the disappearance of spot of
1 in TLC was observed.
I, mА
Analysis of the isolated product by NMR showed that
tetraoxane was formed as a product in both cases. No
byꢀproducts were detected. This agrees with the data
of [11] and corresponds to the electrooxidation of the
6
initial compound into 2 according to the reaction:
HOO OOH
O
O
O
O
4
2
–4e
2
CH3CN, LiClO4
1
(1)
(2)
Compound
2 was isolated in amounts of 314–
341 mg from the reaction mass, corresponding to a
reaction yield of 68–72% expressed in the weight of
isolated product regardless of in which cell (separated
or unseparated) the electrolysis was conducted.
10
To determine the depth to which the reaction of
oxidation of
1 into 2 proceeded, the kinetics of this
0
reaction before extraction of the product was studied
under potentiostatic conditions in a threeꢀelectrode
cell. In this experiment, electrolysis was conducted at
working electrode potential Е = 2.0 V for 6 h with conꢀ
500
1000
1500
2000
, mV
trol over the electrolysis current. The experiment was
interrupted each 30 min, and CVAs were recorded at
potential sweep rate of 100 mV/s. The whole experiꢀ
ment was thus split into 12 separate experiments. As
can be seen from Fig. 1, the appearance of CVAs varꢀ
ied continuously in the course of electrolysis. Neither
anodic nor cathodic branches of the CVAs of the initial
E
Fig. 1. Change in the cyclic voltammograms of 1,1ꢀbisꢀ
hydroperoxyꢀ4ꢀmethylcyclohexane on a Pt anode during
electrolysis in the potentiostatic mode; 1–10 are the numꢀ
bers of our experiments.
1
have maxima. During electrolysis, however, the forꢀ
mation of results in the emergence of two peaks: an
anodic one at = 1.35 V and a cathodic one at
0.85 V (Fig. 1).
A monotonous decline in the value of electrolysis
current at = 2.0 V and an increase in the peak curꢀ
rents belonging to are observed during the oxidation
of . The appearance of the CVAs does not change
after 5 h of electrolysis, indicating the end of the oxiꢀ
dation of . This is also confirmed by the spot belongꢀ
ing to completely disappearing in the same time of
trolysis, acetonitrile was evaporated on a rotary
evaporator to yield 3–4 mL of solution to which
15 mL of water were added, followed by extraction
with five portions of diethyl ether (5 mL each time).
The combined extracts were washed with water (5 mL)
and dried over Na2SO4. The ether was then evapoꢀ
rated, and the residue was purified via column chroꢀ
matography on SiO2. The product was analyzed by
means of NMR spectroscopy and TLC using the preꢀ
liminarily prepared reference.
2
Е
Е =
Е
2
1
1
1
1
The H NMR spectra were recorded on a Bruker
electrolysis, according to TLC of the reaction mixture.
Moreover, the CVAs obtained for electrolysis product
AMꢀ300 spectrometer (CDCl3 was used as a solvent).
Silufol UVꢀ254 plates were used for TLC; column
chromatography was performed on silica gel 63–
200 mesh (Acros) using a mixture of petroleum ether
and ethyl acetate (20 : 1) as an eluent.
1
and those recorded for tetraoxane obtained by
counter synthesis [11] are identical, which also indiꢀ
cates the completion of the process within 5 hours of
electrolysis and the formation of 2 as a single product.
A sample of
2 was synthesized according to the proꢀ
The dependence of electrolysis current on the
duration of the experiment (Fig. 2) shows that the
electrolysis current fell substantially over time in each
experiment and with respect to each preceding experꢀ
iment as well. It can be seen from Fig. 2 that the initial
cedure described in [12]. The melting point of the samꢀ
1
ple was 69.5–71
spectrum (300.13 MHz,
= 6.4 Hz) and 1.08–1.99 (m, 18H, CH2, CH).
°C
(mp 71–72°C [4]). The H NMR
δ
, ppm) was 0.91 (d, 6H, CH3,
J
current of oxidation for 1 in each experiment and the
charge passing through the cell in the experiment and
equal to the area enclosed by the kinetics curve both
1 in diminish continuously in the course of electrolysis.
RESULTS AND DISCUSSION
Preliminary experiments on the oxidation of
galvanostatic mode in a cell with separated and unsepꢀ The current fell to zero after 5 h of electrolysis, and an
arated cathode and anode space were performed until electric charge equal to 11.99 C was passed through
RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY A
Vol. 87
No. 3 2013

KINETICS OF THE ELECTROCHEMICAL OXIDATION
, mА
399
I
, mА
I
6
5
4
3
2
1
0
1
0
1
1
10
v
= 0.2 V/s
0.01 V/s
−
500
1000
1500
t, s
0
1000
2000
, mV
E
Fig. 2. Kinetics of electochemical oxidation of 1,1ꢀbisꢀ
hydroperoxyꢀ4ꢀmethylcyclohexane on a Pt anode in the
potentiostatic mode; 1–10 are the numbers of our experiꢀ
ments.
Fig. 3. Cyclic voltammograms for the product of the elecꢀ
tochemical oxidation of in an acetonitrile solution on a
Pt anode. The electrode potential scanning rates were
0.01, 0.025, 0.050, 0.075, 0.1, 0.125, 0.150, 0.175 V/s.
1
the cell during this time. Calculations using the chemꢀ quent complete disappearance of the anodic and
ical equation shows that an electric charge equal to cathodic peaks on our CVAs.
11.91 C is required for the complete oxidation of
Figure 3 shows CVAs of
scanning rates (
anodic peak (Ip, a) and the current of the cathodic peak
Iр, с) grow linearly with an increase in . The straightꢀ
line dependence of Ip, a and Ip, c on indicates that
participates in the reaction of redox pair formation
while in the adsorbed state. The Laviron equation [13]
2
at different potential
10 mg of
amount of electricity required for the complete oxidaꢀ
tion of and the amount of electricity calculated from
the experimental data, it follows that the reaction proꢀ
ceeds with a current yield of no less than 99%. The relꢀ
atively moderate values of the product yield (no more
than 72%) obtained in the preparative experiments
were due only to losses of the product at the stage of its
isolation from the reaction mass.
1 into 2. From the ratio of the calculated
v
). It turns out that the values of the
1
(
v
v
2
defining the dependence of Ip, а on
Ip,a nFQ /4RT
is the potential scanning rate,
v
is applicable here:
=
v
,
Comparison of CVAs of
2 (Fig. 3) and CVAs of 1
where
v
Q
is the electric
is the Faraꢀ
shows that the first differ from the second not only in
the presence of anodic and cathodic peaks but also in
charge required for trioxane adsorption,
F
day number equal to 96485 C/mol,
stant equal to 8.315 J/(mol K), and
R
Т
is the gas conꢀ
is the absolute
the highest value of anodic current for
potential value = 2.0 V being considerably lower
than that for . The latter indicates the stability of
toward anodic oxidation, as was already shown above.
It seems that peaks in the region of potentials
2 in CVAs at the
E
temperature (K) of the experiment. From the experiꢀ
mental data for the range of values of the potential
1
2
scanning rate = 0.025–0.1 V/s, it was found that n =
v
E
=
0.88. Keeping in mind the measurement error, we may
therefore assume that the formation of the redox pair
by tetraoxane proceeds with the transfer of one elecꢀ
tron. Considering the possibility of interaction
between the unshared electron pair of the peroxide
bridge and the metal cations resulting complex formaꢀ
tion [15], it is reasonable to assume that the formation
0.85–1.35 V correspond to a redox pair being formed
on the surface of platinum electrode. The interrelation
of the values of the anodic peak at
and the cathodic peak at = 0.85–0.90 V (Fig. 3) can
be seen from the narrowing of the potential scanning
interval to = 0.0–1.5 V, = 0.0–1.4 V, and = 0.0–
E = 1.20–1.35 V
E
E
E
E
1.0 V resulting in the simultaneous drop and subseꢀ of a surface complex between tetraoxane and platinum
RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY A
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400
VEDENYAPINA et al.
accompanied by the transfer of one electron occurs in
this case:
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ACKNOWLEDGMENTS
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This work was supported by the RF Ministry of
Education and Science, project no. 11.519.11.2038.
RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY A
Vol. 87
No. 3 2013