2
50
CHOBAN et al.
However, conductometric study shows that in the
out in a temperature-controlled cell with a magnetic
stirrer at 298 K. The reactor was charged with the
required amount of a base crushed under argon, DMF
and DMSO (if necessary). The mixture was maintained
at the required temperature while stirring for 20 min,
and then the reactor was charged with hydrogen
peroxide. This time was registered as the reaction
beginning. The reaction was carried out while moni-
toring its kinetics by determining the amount of active
oxygen in the samples by iodometric technique. The
dimethyl sulfone accumulation was monitored by gas-
liquid chromatography with a Chrom-5 chromatograph
with a flame ionization detector. The glass column of
case of LiOH the introduction of hydrogen peroxide
practically does not change electrical conductivity of
the reaction medium (Fig. 4, curve 3), that is, the
process proceeds by a molecular pathway.
Thus, the nature of alkali affects considerably the
DMSO oxidation with hydrogen peroxide.
When KOH or LiOH are used as a base, the
limiting step is the formation of the salt MOOH.
Therewith, the KOOH salt formed on the alkali crystal
surface easily dissociate, due to large atomic radius of
the potassium cation. On the contrary, the LiOOH salt
is in nondissociated state due to the small atomic
radius of lithium cation. In the case of NaOH, the
formed NaOOH salt dissociates, but due to the smaller
atomic radius of sodium than potassium this process
occurs more slowly (or partially). The process of
dissolution–dissociation of the salt formed on the
surface of the crystal of base becomes the limiting
stage. Attention should be paid also to the higher
reactivity of LiOH than NaOH in the oxidation of
DMSO. We think this is due to the fact that the
dissolution of the LiOOH salt proceeds easier due to
occurrence of fewer molecules of DMSO in the
–
3
the chromatograph was of 3 m length and of 3×10 m
inner diameter, filled with the phase Cromaton-N
Super (0.16–0.22 mm) treated with 5% alcohol solution
of SE-30. Evaporator temperature 473 K, prog-
–
1
rammed rate of heating 12 K min . Carrier gas argon,
–
1
the inlet flow rate 40 ml min . Volume of the sample
1 µl. Measuring the electrical conductivity was carried
out using a P 577 circuit and a F 582 null indicator.
Used solvents were preliminarily purified according
to [14].
REFERENCES
+
coordination sphere of Li :
1
. Lee, Y., Lee, C., and Yoon, J., Water Res., 2004, vol. 10,
p. 2579.
LiOOH + HOOH + mS → mS…LiOOH…ООН. (10)
|
H
2
3
. Jones, C., USA Patent no. 6552231, 2003.
. Wu, J.J., Muruganandham, M., and Chen, S.H., J. Hazard.
Mater., 2007, vol. 149, p. 218.
Here m is the coordination number of lithium ion.
4
5
. Trofimov, B.A., Usp. Khim., 1981, vol. 4, no. 2, p. 248.
. Lyavinets, A.S., Abramyuk, I.S., and Choban, A.F., Zh.
Obshch. Khim., 2004, vol. 74, no. 7, p. 1157.
. Choban, A.F., Abramyuk, I.S., and Lyavinets, A.S., Zh.
Obshch. Khim., 2007, vol. 77, no. 12, p.1950.
. Rindich, N.O. and Lyavinets, O.S., Ukr. Khіm. Zh.,
Thus, the nature of the base significantly affects the
dimethyl sulfoxide oxidation with hydrogen peroxide
in DMF accelerating or decelerating the phase of the
salt formation. The alkali used in the oxidation of
DMSO with hydrogen peroxide can be arranged by
activity: KOH > LiOH > NaOH. Sodium hydroxide is
less active in the investigated reaction than sodium
tert-butoxide. In the case of NaOH or t-BuONa the
limiting step of the process is the formation of the
hydrogen peroxide sodium salt, while with KOH or
LiOH the process of DMSO oxidation with the
corresponding salt becomes the limiting one. In the
presence of KOH, NaOH or t-BuONa, the DMSO
oxidation proceeds by ionic mechanism, while with
LiOH a molecular mechanism is realized.
6
7
8
2
009, vol. 75, no. 8, p. 123.
. Lyavinets, A.S., Choban, A.F., and Chervinskii, K.A.,
Zh. Fiz. Khim., 1993, vol. 67, no. 7, p. 1364.
9. Choban, A.F. and Lyavinets, O.S., Ukr. Khim. Zh.,
997, vol. 63, no. 2, p. 117.
1
1
1
1
1
1
0. Lyavinets, A.S. and Marushchak, N.T., Zh. Obshch.
Khim., 2004, vol. 74, no. 6, p. 959.
1. Choban, A.F., Yurchuk, I.R., and Lyavinets, A.S., Zh.
Obshch. Khim.,2008, vol. 78, no. 11, p. 1838.
2. Lyavinets, A.S., Yurchuk, I.R., and Chervinskii, K.A.,
Zh. Fiz. Khim., 1998, vol. 72, no. 11, p. 1971.
3. Gutmann, V., Coordination Chemistry in Non-Aqueous
Solutions, Moscow: Mir, 1971.
4. Gordon, A.J. and Ford, R.A., The Chemist’s Com-
panion. A Handbook of Practical Data, Techniques and
References, New York: Wiley, 1972.
EXPERIMENTAL
The experiments on the DMSO oxidation with
hydrogen peroxide in the presence of bases was carried
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 82 No. 2 2012