Anthrone complexation with aliphatic amines in an aprotic medium

Article abstract of DOI:10.1134/S0036024413090203

Aromatic ketone (anthrone) complexation with aliphatic amines is studied by UV-Vis, ¹H, ¹H-¹H COSY NMR spectroscopy. It is found that the catalytic activity of aliphatic amine is observed in the reaction of anthrone oxidation by molecular oxygen in aprotic media due to the formation of intermolecular complexes consisting of two anthrone molecules and one aliphatic amine molecule.

Full text of DOI:10.1134/S0036024413090203

ISSN 0036ꢀ0244, Russian Journal of Physical Chemistry A, 2013, Vol. 87, No. 9, pp. 1470–1473. © Pleiades Publishing, Ltd., 2013.
Original Russian Text © A.A. Serdyuk, A.A. Abakumov, I.V. Kapitanov, M.G. Kasianczuk, I.A. Opeida, 2013, published in Zhurnal Fizicheskoi Khimii, 2013, Vol. 87, No. 9,
pp. 1477–11481.
CHEMICAL KINETICS
AND CATALYSIS
Anthrone Complexation with Aliphatic Amines in an Aprotic Medium
A. A. Serdyuk, A. A. Abakumov, I. V. Kapitanov, M. G. Kasianczuk, and I. A. Opeida
Litvinenko Institute of Physical Organic and Coal Chemistry, National Academy of Sciences of Ukraine,
Donetsk, 83001 Ukraine
eꢀmail: ann.serdyuk@rambler.ru
Received September 26, 2012
Abstract—Aromatic ketone (anthrone) complexation with aliphatic amines is studied by UV–Vis, 1H, 1H–
1H COSY NMR spectroscopy. It is found that the catalytic activity of aliphatic amine is observed in the reacꢀ
tion of anthrone oxidation by molecular oxygen in aprotic media due to the formation of intermolecular comꢀ
plexes consisting of two anthrone molecules and one aliphatic amine molecule.
Keywords: oxidation, catalysis, mechanism, anthrone, molecular complex, addition product to carbonyl
group.
DOI: 10.1134/S0036024413090203
INTRODUCTION
In this work, we consider in more detail one of its
stages, i.e., complexation.
Basic catalysis (particularly amine catalysis) is
actively used to promote oxidation by molecular oxyꢀ
gen [1]. In [2], we studied in detail the kinetic feaꢀ
tures (the effect of reagent concentrations, oxygen
pressure, and solvent nature) on aromatic ketone
(anthrone) oxidation by molecular oxygen, catalyzed
by amines in polar aprotic media. Based on our
The catalytic effect of amines in such processes can
manifest itself in two ways: one is the formation of
amine adducts from a substrate carbonyl group
(Scheme 1, A) [3]; the other is the formation of
molecular complexes between the substrate and amine
results, we proposed a mechanism for the process [2]. (Scheme 1, B) [4].
R
N
O
O
AI
(Imine
)
(Anthrone)
O
HO
NRR'
(
Anthraquinone)
[O]
HNRR'
+
AII
B
O
(Gemꢀaminoꢀalcohol)
OH
R
R'
N
R"
H
O
(
Anthrol)
O
(Bianthrone)
Scheme 1.
In this work, we studied the reaction of anthrone mation of anthraquinone and small amounts (1–3%)
oxidation by molecular oxygen, resulting in the forꢀ of bianthrone in aprotic media (dimethyl sulfoxide
1470

ANTHRONE COMPLEXATION WITH ALIPHATIC AMINES IN AN APROTIC MEDIUM
1471
(a)
3
2
1
9
8
7
6
5
4
1, ppm
3
2
1
(c)
0
f
(b)
6.8
7.2
7.6
8.0
8.4
8.8
0.5
1.0
1.5
2.0
2.5
3.0
3.5
O
O
8.8
8.4
8.0
ppm
7.6
7.2
6.8
3.6 3.2 2.8 2.4 2.0 1.6 1.2 0.8
ppm
1
Fig. 1. NMR spectra of anthrone in the presence of
n
ꢀbutylamine in DMSOꢀ
d
; (a) H NMR spectra of anthrone in the presence
6
of ꢀbutylamine; DMSOꢀ , 400 MHz: , immediately after mixing;
n
d
1
2
and
3, in 15 and 30 min after mixing of reagents; (b, c)
in the presence of nꢀbutylamine (400 MHz) in the regions of (b) aliꢀ
6
1
1
H– H COSY spectra of anthrone solution in DMSOꢀ
d
6
phatic protons and (c) aromatic protons.
(DMSO), acetonitrile). The mechanism of anthrone refractive index agreement with reference data. NMR
activation by aliphatic amines ( ꢀbutylamine, diethꢀ spectra were recorded using a BRUKER Avance II 400
n
ylamine, and triethylamine) was studied in greatest spectrometer (400 MHz); spectra in the ultraviolet and
detail via oneꢀdimensional (1H) and twoꢀdimenꢀ visible regions were recorded using a Genesys 10 S UVꢀ
sional (1H–1H COSY) NMR and UVꢀVis spectrosꢀ Vis (Thermo Electron Corp.) spectrophotometer. All
copy.
experiments were performed at 25°С.
EXPERIMENTAL
Anthrone (Aldrich, 97%), acetonitrile (Merck,
RESULTS AND DISCUSSION
Note that adducts can form with anthrone only priꢀ
≥
99.5%), and DMSOꢀd6 (Aldrich,
≥
99%) were used mary and secondary amines, yielding imines (Scheme 1,
without additional purification. ꢀButylamine, diethyꢀ A I) in the former case, and gemꢀaminoꢀalcohols (II)
n
lamine, and triethylamine were purified by distillation in the second case (Scheme 1, A II). The existence of
at atmospheric pressure. The purity was assessed by the catalytic activity of tertiary amines [5] allows the conꢀ
RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY A
Vol. 87
No. 9 2013

1472
SERDYUK et al.
(a)
D
3
4
10−
c
c
A = 2
Am = 0
×
2
1
c
A = 0
4
c
Am = 2 ×
10−
0
190
230
270
(b)
310
λ
, nm
Δ
D
0.4
0.3
0.2
0.1
0
0
0.2
0.4
0.6
0.8
1.0
cA c0
/
Fig. 2. Determination of the anthrone–amine complex stoichiometry via UV–Vis: (a) absorption spectra of the isomolar series
–4
of anthrone–triethylamine (2 × 10 mol/L) in acetonitrile at 298 K; (b) dependence of the optical density of the complex on the
solution’s composition (acetonitrile; 254 nm) at 298 K.
clusion that with anthrone, catalysis of the anthrone protons of a similar structure (see Figs. 1b and 1c) in
oxidation reaction cannot occur due only to adduct the range of 0.50–4.00 ppm, allows the conclusion
formation (AI, AII).
that they belong only to bianthrone. The unresolved
signals at 8.21, 7.94, 7.61, 7.52 ppm, and the signal at
4.46 ppm in the spectra of Fig. 1 correspond to
anthrone; the doublets at 8.44 and 7.84 ppm, the sinꢀ
glet at 7.68 ppm, and the triplets at 7.37 and 7.25 ppm
are due to anthrol. None of the impurities existing in
1
In series H of NMR spectra of solutions of mixꢀ
tures of both primary (Fig. 1a) and secondary amines
with anthrone in DMSOꢀd6, the signals at 6.8 (douꢀ
blet), 7.05 (multiplet), 7.25 (a multiplet partially overꢀ
lapped by the anthrol signal), and 8.55 ppm (doublet)
increased in the region of aromatic protons over time.
The presence of the corresponding cross peaks in 1H–
1H COSY spectra (Figs. 1b and 1c) gives grounds to
assert that these signals are associated with the same
compound. Based on our analysis of the multiplicity
and total peak intensity, this substance can be identiꢀ
the region of aliphatic protons (in cases of both nꢀ
butylamine and diethylamine) cannot be attributed to
protons of an adduct aliphatic fragment, as it is imposꢀ
sible to separate an appropriate set of cross peaks in
1H–1H COSY spectra (Fig. 1b).
Since no signals that could be attributed to adducts
fied either as one of the byꢀproducts of anthrone of primary and secondary amines formed by anthrone
(bianthrone) oxidation or as an amine adduct. Howꢀ carbonyl groups were detected, we may conclude with
ever, the presence of the same signals in the spectra of a high degree of probability that the catalytic effect of
anthrone solution in the presence of triethylamine, amines is associated only with the formation of
which cannot form adduct (AI, AII), and the lack of anthrone–amine molecular complexes. We detected
such signals, which could be attributed to aliphatic anthrone–triethylamine complexes in a nonpolar
RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY A
Vol. 87
No. 9 2013

ANTHRONE COMPLEXATION WITH ALIPHATIC AMINES IN AN APROTIC MEDIUM
1473
Isomolar anthroneꢀꢀamine series at λ = 254 nm
medium (cyclohexane) using UV–Vis spectroscopy in
[6]. In this work, we studied complexation in a polar
solvent (acetonitrile). The complex’s composition was
determined using the standard procedure, i.e., by anaꢀ
lyzing the isomolar series spectra by the Job method
(the total concentration of complex components in
solution is held constant while their ratio is varied;
Fig. 2a) [7]. The method assumes that the solution
contains two components (anthrone and amine) with
molar concentrations cА and cAm, respectively, which
form the АmAmn complex by the reaction
cА
×
103
cАm
×
103
xA
Δ
D
0.200
0.184
0.166
0.150
0.134
0.116
0.100
0.084
0.066
0.050
0.034
0.016
0
0
1
0
0.016
0.034
0.050
0.066
0.084
0.100
0.116
0.134
0.150
0.166
0.184
0.200
0.92
0.83
0.75
0.67
0.58
0.5
0.12
0.25
0.32
0.35
0.32
0.28
0.25
0.20
0.16
0.10
0.06
0
mA +
nAm = АmAmn.
(1)
0.42
0.33
0.25
0.17
0.08
0
The dependence of the complex’s content on the
solution’s composition has its maximum at a compoꢀ
nent ratio corresponding to stoichiometric coeffiꢀ
cients in the complexation equation (Fig. 2b). The
measure of the complex content in the solution is the
optical density at the wavelength corresponding to the
absorption band of the complex compound. Deconvoꢀ
lution of the measured spectra was performed to deterꢀ
mine the maximum of the complex absorption band
[8], and the spectra with a constant anthrone concenꢀ
tration and a gradually increasing amine concentraꢀ
tion were recorded. Analysis of the results made it posꢀ
sible to determine the wavelength (~254 nm) correꢀ
sponding to one of the absorption maxima of the
formed complex. Since both components of the sysꢀ
tem under study absorb at the same wavelength, the
Note: c and c
are the anthrone and amine concentrations,
Am
A
respectively, mol/L; x is the molar fraction of anthrone.
A
tic media is thus associated with the formation of
intermolecular complexes in ratio 2 : 1, rather than
with adducts formed from carbonyl groups. Substraꢀ
tum activation is most likely achieved by facilitating
the formation of the enol form (anthrol) in an aprotic
polar medium and the subsequent detachment of proꢀ
tons from the anthrol molecule.
measure of the complex content is the difference D
Δ
between the observed optical density and the one calꢀ
culated from the extinction coefficients and compoꢀ
nent concentrations,
REFERENCES
Δ
D
=
D
obs – (εАcА
+
εАmcAm
),
(2)
1. R. A. Sheldon, I. Arends, and U. Hanefeld, Green
Chemistry and Catalysis (Wiley, Weinheim, 2007).
2. A. A. Serdyuk, M. G. Kasianchuk, and I. A. Opeida,
where D is the optical density of the complex, Dobs is
Δ
the observed optical density, εА and εАm are the extincꢀ
tion coefficients of anthrone and amine, respectively.
Our data (table and Fig. 2) suggest that a complex
consisting of two anthrone molecules and one amine
molecule is formed in acetonitrile. These data are in
good agreement with the earlier results on the anthrone
oxidation kinetics catalyzed by amines: it was found
that the reaction orders for anthrone and amine were 1
and 0.5, respectively, indicating the involvement of the
anthrone–amine (2 : 1) complex in the proposed proꢀ
cess mechanism [2]. Estimating the stability of this
complex is an independent, rather complicated probꢀ
lem that will be solved in further studies.
Russ. J. Phys. Chem. A 84, 391 (2010).
3. X. Zhu, F. Tanaka, and R. A. Lerner, J. Am. Chem. Soc.
131, 18206 (2009).
4. S. Protti, A. Mezzetti, and J.ꢀP. Cornard, Chem. Phys.
Lett. 467, 88 (2008).
5. A. A. Serdyuk, M. G. Kasianchuk, I. A. Opeida, and
V. S. Tolkunov, Russ. J. Phys. Chem. A 83, 1094 (2011).
6. A. A. Serdyuk, M. G. Kasianchuk, I. V. Kapitanov, and
I. A. Opeida, Theor. Exp. Chem. 47, 129 (2011).
7. P. ForteꢀTavcer, Dyes Pigments 63, 181 (2004).
8. MouꢀYan Zou and R. Unbehauen, Meas. Sci. Technol.
6, 482 (1995).
The catalytic effect of aliphatic amines in the reacꢀ
tion of liquidꢀphase anthrone oxidation in polar aproꢀ
Translated by A. Kazantsev
RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY A
Vol. 87
No. 9 2013