Russian Chemical Bulletin, International Edition, Vol. 57, No. 11, pp. 2328—2331, November, 2008
2328
Oxidation of alcohols by chlorine dioxide in organic solvents
E. S. Ganieva, I. M. Ganiev, S. A. Grabovskiy, and N. N. Kabalnova
Institute of Organic Chemistry, Ufa Scientific Center of the Russian Academy of Sciences,
71 prosp. Oktyabrya, 450054 Ufa, Russian Federation.
Fax: +7 (347 2) 35 6066. Eꢀmail: oxboss@anrb.ru
The kinetics of oxidation of a series of alcohols (propanꢀ2ꢀol, 2ꢀmethylpropanꢀ1ꢀol, butanꢀ
1ꢀol, butanꢀ2ꢀol, 3ꢀmethylpentanꢀ1ꢀol, heptanꢀ4ꢀol, decanꢀ2ꢀol, cyclohexanol, borneol) by
chlorine dioxide in organic solvents was studied using spectrophotometry. The reaction is
described by the secondꢀorder rate equation w = k[ROH][ClO2]. The rate constants were
measured in the range of 10—60 °С, and the activation parameters of the processes
were calculated. The products were identified, and the yields were determined.
Key words: oxidation, chlorine dioxide, alcohols, rate constants, activation parameters.
metrically using the Brey method6 and spectrophotometrically.7
Potassium chlorate and oxalic acid (reagent grade) were purified
by recrystallization from water. Alcohols and solvents were
purified using known procedures.8,9
The kinetics of alcohol oxidation was studied spectroꢀ
photometrically detecting the consumption of chlorine dioxide
Chlorine dioxide finds wide use as a reagent for water
preparation and, hence, the oxidation involving chlorine
attracts attention of many researchers. The oxidation of
alcohols in an aqueous solution was studied for methanol,
propanꢀ2ꢀol, and glucose, which reacts at the —CH2OH
group to form the aldehyde or carboxy group.1—3 The
reaction rate constants depend on the pH of the solution.
They somewhat decrease in the interval pH 3.0—5.9 but
increase considerably with the further increase in pH to
6.7 due to the interaction of the RO– anion with chlorine
dioxide.1,2,4 The key step of the oxidation mechanism in
an aqueous solution is the transfer of the hydride ion.1,2,4
In the single work performed in the organic solvent, the
oxidation of mytrenol and transꢀverbenol was studied and
a possibility of synthesis of mytrenal, mytrenic acid,
and verbenone was shown.5
We studied the kinetic regularities for the reactions
of alcohols with chlorine dioxide in a series of organic
solvents. The following alcohols were chosen: propanꢀ2ꢀol
(1), 2ꢀmethylpropanꢀ1ꢀol (2), butanꢀ1ꢀol (3), butanꢀ2ꢀol (4),
3ꢀmethylpentanꢀ1ꢀol (5), heptanꢀ4ꢀol (6), decanꢀ2ꢀol (7),
cyclohexanol (8), and borneol (9). The oxidation was
carried out in nꢀC7H16, CCl4, C6H6, 1,4ꢀdioxane, C6H5Cl,
AcOEt, 1,2ꢀdichloroethane, and MeCN.
at λ
= 356 nm on a Specord M40 instrument (Carl Zeiss
max
Jena). A solution of the studied alcohol was placed in the working
quartz cell, and a solvent was poured in the reference cell.
The temperature of the cells were maintained at 10—60 °С in
the spectrophotometer chamber. Then a necessary amount of a
chlorine dioxide solution was added to the working cell, and the
change in the absorbance was monitored. The initial concentrations
of the oxidized substrates and chlorine dioxide were varied within
(0.1—10.0)•10–2 and (0.5—1.2)•10–3 mol L–1, respectively.
To study the oxygen effect on the kinetic regularities, the
argon or solution was O2 was purged through the solution, a
necessary amount of chlorine dioxide was added, and the kinetics
of its consumption was recorded.
The oxidation products were analyzed by GLC on a Chromꢀ5
instrument (column l = 3.5 m, d = 3 mm, 5% SEꢀ30 on
Chromatone) and by 1Н NMR on a Bruker AMꢀ300 spectroꢀ
meter with a frequency of 300 MHz using CDCl3 as solvent and
SiMe4 as standard. Benzene was used as a label for the quantiꢀ
tative determination of products.
The direct and inverse kinetic problems were solved by
numerical methods using the Kinetic System Solver (KSS)
program, version 4.10 (see Refs 10 and 11).
Experimental
Results and Discussion
Chlorine dioxide was obtained by the reaction of potassium
chlorate with oxalic acid in the presence of sulfuric acid.6 The
argon—ClO2 mixture was dehydrated by purging the flow through
the trap with P4O10 and then through the precooled to 0 °C
column with silica gel, where ClO2 was adsorbed. To prepare
solutions of ClO2, the column was heated in a thermostat to
30—35 °С and blown with argon into the trap with a solvent.
The ClO2 concentration in a solution was determined iodoꢀ
Reaction products. The reactions of alcohols 1—9 with
chlorine dioxide afford carbonyl compounds in good yields
(Table 1). In the case of 2ꢀmethylpropanꢀ1ꢀol (2) and
3ꢀmethylpentanꢀ1ꢀol (5), chlorinated products are formed,
which is due, most likely, to the formation of acids HClO
and HClO2 capable of chlorinating the oxidized substrates.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2283—2286, November, 2008.
1066ꢀ5285/08/5711ꢀ2328 © 2008 Springer Science+Business Media, Inc.