110
SHARIPOV
crystallized from water, and dried in a water-jet-pump
vacuum. The resulting DMSF is a colorless crystalline
substance readily soluble in organic solvents; purity
99.8%, mp 109 C, bp 238 C.
10 h, 88%. After oxidation for 5 h at 80 C, the con-
tent of TMSF was as high as 99%. The optimal oxida-
tion temperature is 80 90 C. To attain a high yield of
TMSF, H O should be taken in a 35% excess. The
2
2
product obtained by oxidation of TMSO under these
conditions is an aqueous solution containing 35 40%
TMSF, 60 50% water, and 4 7% impurities. Tetra-
methylene sulfone is infinitely miscible with water,
forms no binary azeotrope with water, and strongly
differs from water in the boiling point. However,
TMSF cannot be isolated from the oxidation products
by common distillation, since it is thermally unstable
and starts to decompose at temperatures above 170 C,
forming in the presence of oxygen acidic compounds
and condensation products. According to analyses, the
oxidation product always contaions residual H O ,
Found, %: C 25.59; H 6.36; S 34.02.
C2H6O2S. Calculated, %: C 25.53; H 6.38; S 34.04.
Oxidation of TMS to tetramethylene sulfoxide
(TMSO) was studied at 20, 40, and 60 C (Table 3).
These data show that, after oxidation for 1 h at 20 C,
the content of DMSO in the dehydrated oxidation
products was 94%, and after oxidation for 3 h it
reached 97%. The content of TMSO after oxidation
for 1 h at 60 C was 98%. Thus, oxidation of TMS to
TMSO occurs with a high rate. At all the examined
temperatures, the formation of TMSO is virtually
complete in 1 3 h. Oxidation occurs in a two-phase
system and is accompanied by a large heat release in
a short time. The reaction mixture undergoes autocata-
lytic self-heating, which results in intense decompo-
sition of excess H O . Therefore, H O was added
2
2
which promotes decomposition of TMSF in the course
of distillation to acetic and sulfuric acids. Therefore,
prior to distillation, the oxidation product was treated
with 6% aqueous alkali to decompose H O , after
2
2
which it was fractionated on a 2 3-TP batch distilla-
tion column; the temperature in the still was 100 C,
and the residual pressure, 20 mm Hg. TMSF was iso-
lated from the oxidation product in 96% yield and was
99.7% pure.
2
2
2 2
gradually to maintain its optimal concentration in the
mixture in the course of the process.
The oxidation product obtained by oxidation of
TMS under the above conditions is a single-phase
transparent colorless aqueous solution. To isolate
We also examined the possibility of recovering
TMSF from the oxidation product by extraction with
organic solvents. The extractant should selectively
recover TMSF with minimal extraction of impurities;
it should be sparingly soluble in water and should
also meet such general requirements as availability,
stability under regeneration conditions, and low cost
[9]. The best suited are aromatic hydrocarbons, in
particular, benzene. Study of the phase equilibria
showed that, in extraction of TMSF from the oxida-
tion product with benzene, the separation of TMSF
from impurities is fairly efficient; the impurities most-
ly remain in the aqueous phase. Under the optimal
extraction conditions (benzene : oxidation product
weight ratio 2.4 : 1, 25 C, six extraction steps), the
recovery of TMSF from the oxidation product is 94
96%. Distillation of benzene from the extract was per-
formed at 200 mm Hg. The energy consumption for
distillation of benzene from the extract is much less
than that for distillation of water from the oxidation
product (because of considerably higher heat capacity
and heat of vaporization of water).
TMSO, the oxidation product was treated with MnO
2
to remove residual H O , heated at reduced pressure
2
2
(30 40 mm Hg) to remove water (bath temperature
40 50 C), and vacuum-distilled (bath temperature
140 160 C, vapor temperature 85 100 C, residual
pressure 3 5 mm Hg).
Tetramethylene sulfoxide is thermally unstable. Its
loss in the course of distillation was evaluated from
the decrease in the content of sulfoxide sulfur. The
average loss of sulfoxide sulfur is 3%, which corre-
sponds to 10% loss of TMSO. Under the optimal con-
ditions, the yield of TMSO is 89 91%. The purity of
the distilled product is 99.6%, bp 45 C (3 mm Hg),
20
20
n
1.5203, d 1.1816.
D
4
Found, %: C 45.72; H 7.83; S 30.5.
C4H8OS. Calculated, %: C 46.1; H 7.7; S 30.8.
Oxidation of TMSO to tetramethylene sulfone
(TMSF) was performed at 60, 70, 80, 90, and 100 C
(Table 4). The reaction occurs in the homogeneous
system with a lower heat effect and at a lower rate
than oxidation of TMS to TMSO. After oxidation for
8 h at 60 C, the content of TMSF in the dehydrated
oxidation product was 60%, and after oxidation for
Tetramethylene sulfone obtained by this procedure
is a colorless hygroscopic solid (at room temperature)
with pleasant odor, soluble in water, ethanol, benzene,
acetone, and other organic solvents; the product purity
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 76 No. 1 2003