Russian Journal of Organic Chemistry, Vol. 38, No. 6, 2002, pp. 905 906. Translated from Zhurnal Organicheskoi Khimii, Vol. 38, No. 6, 2002,
pp. 946 947.
Original Russian Text Copyright
,
2002 by Opeida, Kas yanchuk.
SHORT
COMMUNICATIONS
Oxidation of Anthrone with Oxygen in DMSO
I. A. Opeida and M. G. Kas,yanchuk
Litvinenko Institute of Physical Organic Chemistry, National Academy of Sciences of the Ukraine,
Donetsk, 83114 Ukraine
Received July 10, 2001
Relatively weak CH-acids (pKa < 30), as fluor-
enes, indenes, dihydroanthracenes and other poly-
cyclic compounds, were formerly shown [1, 2] to
undergo oxidation with molecular oxygen in the
presence of strong bases (benzyltrimethylammonium,
potassium tert-butylate, complexes of alkali metal
hydroxides with crown ethers) in aprotic solvents
(DMSO and DMF).
Identification of reaction products was carried out
by IR spectroscopy (from samples pelleted with KBr)
and H NMR spectroscopy in solutions in DMSO-d6.
1
The IR spectrum was in complete agreement with that
of a sample of anthraquinone of the chemically
pure grade and was distinguished from the IR spec-
trum of anthrone of the chemically pure grade by
1
the presence of absorption bands at 1580, 1330 cm
and by the absence of bands at 1480, 1460, 1450,
We established that 10-hydro-9-ketoanthracene
(anthrone) in DMSO solution was readily oxidized
with molecular oxygen to anthraquinone in virtually
quantitative yield in the absence of strong bases.
1
1
1400, 1150, 960 cm . The H NMR spectrum of the
oxidation product was identical to that of anthra-
quinone sample, , ppm: 7.9 m, 8.2 m. whereas in
the spectrum of anthrone appeared signals at , ppm:
4.3 s, 7.6 m, 8.2 d.
The oxidation kinetics was monitored by the
volume of oxygen consumed on a device described in
[3]. The reaction was studied in the temperature range
25 70 C, anthrone concentrations were varied within
the limits 0.01 0.08 mol l 1, partial pressure of
oxygen in all runs was 760 mm Hg, solvent DMSO.
Analysis of the reaction mixture for hydroper-
oxide content performed by TLC procedure [4]
showed the lack of peroxy compounds. The bright
red color of the reaction mixture at the early stage of
the reaction suggested carbanion formation. The
addition of an initiator (azoisobutyronitrile) or an
inhibitor (hydroquinone) did not affect the reaction
course. These facts testify to the ionic character of
the reaction.
Under the reaction conditions used an intense
consumption of molecular oxygen was observed. The
kinetic curves attain stationary consumption rate. This
fact permitted calculation of the maximum oxygen
consumption from the value of the limiting consump-
tion. The maximum consumption thus determined
amounted approximately to 1 mole of oxygen per
1 mole of substrate. Thus the overall equation of the
process is as follows.
It was shown experimentally that the reaction
occurred also at lower temperature (10 C) in mixtures
of DMSO with acetonitrile, thus in solvents of lower
polarity than that of DMSO.
The ease of oxidation of a C H bond in the
compound under study under the chosen conditions
may be due as we presume to two causes: relatively
high acidity of anthrone as compared with the other
alkylarenes facilitating carbanion formation, and
1
high enthalpy of the reaction ( 72 kcal mol ) (the
calculation of reaction enthalpy was carried out
by PMS procedure with the use of MOPAC soft-
ware).
1070-4280/01/3806-905$27.00 2002 MAIK Nauka/Interperiodica
Opeida
