High-temperature synthesis of thiophene from bis(2-chloroethyl) sulfide

Article abstract of DOI:10.1007/s11178-005-0260-5

Gas-phase reaction of bis(2-chloroethyl) sulfide (Yperite) with acetylene at 550-700°C leads to formation of thiophene in 45% yield, the conversion of the initial sulfide being complete. The yield of thiophene reaches 63-68% in the thermolysis of a mixture of acetylene, bis(2-chloroethyl) sulfide, and lower organic disulfides.

Full text of DOI:10.1007/s11178-005-0260-5

Russian Journal of Organic Chemistry, Vol. 41, No. 6, 2005, pp. 891–893. Translated from Zhurnal Organicheskoi Khimii, Vol. 41, No. 6, 2005,
pp. 910–912.
Original Russian Text Copyright © 2005 by Voronkov, Levanova, Sukhomazova, Russavskaya, Deryagina, Korchevin.
High-Temperature Synthesis of Thiophene
from Bis(2-chloroethyl) Sulfide
M. G. Voronkov, E. P. Levanova, E. N. Sukhomazova, N. V. Russavskaya,
E. N. Deryagina, and N. A. Korchevin
Favorskii Irkutsk Institute of Chemistry, Siberian Division, Russian Academy of Sciences,
ul. Favorskogo 1, Irkutsk, 664033 Russia
fax: +7(3952)511926; e-mail: papern@inoch.irk.ru
Received June 5, 2004
Abstract—Gas-phase reaction of bis(2-chloroethyl) sulfide (Yperite) with acetylene at 550–700°C leads to
formation of thiophene in 45% yield, the conversion of the initial sulfide being complete. The yield of
thiophene reaches 63–68% in the thermolysis of a mixture of acetylene, bis(2-chloroethyl) sulfide, and lower
organic disulfides.
Thiophene is a thermodynamically stable aromatic
compound. It is formed as a result of thermal trans-
formations of a number of sulfur-containing com-
pounds, e.g., dimethyl and diethyl sulfides and disul-
fides [1, 2], dibutyl polysulfides [3, 4], divinyl sulfide
[5], bis(2-chloroethyl) sulfide, etc., and their joint
thermolysis with acetylene [6–8]. Taking into account
that thiophene is widely used in organic synthesis [9],
development of new practical and economic methods
for preparation of thiophene is an important problem.
For this purpose, convenient starting materials may
be bis(2-chloroethyl) sulfide (Yperite) and “disulfide
oil” (a mixture of lower dialkyl disulfides). Therefore,
we examined in detail gas-phase thermolysis of bis-
(2-chloroethyl) sulfide (I) and found that thiophene
can be obtained therefrom in a high yield. Yperite is
a chemical weapon [10], and utilization of its reserves
is important from the ecological viewpoint.
We also showed (cf. [6]) that the conversion of
sulfide I and the yield of thiophene considerably in-
crease when the thermolysis of I is performed in the
presence of acetylene at 550–700°C. Here, the conver-
sion of sulfide I and the yield of thiophene depend not
only on the temperature but also on the sulfide-to-
acetylene ratio (run nos. 6–11). The optimal conditions
for the synthesis of thiophene (II) are as follows:
temperature 650–700°C, sulfide I-to-acetylene ratio
1:2. The yield of thiophene reaches 45%, the conver-
sion of I being 100% (run nos. 8, 9). According to
the GLC and GC–MS data, bithienyls (a mixture of
isomers), thienothiophenes (a mixture of isomers),
benzothiophene, benzene, toluene, and carbon disul-
fide are formed as by-products. The overall yield of
sulfur-containing compounds does not exceed 10%.
The gas phase contains hydrogen chloride, C1–C4
hydrocarbons, and hydrogen sulfide.
Thermolysis of sulfide I was not studied in detail
previously. It was shown that bis(2-chloroethyl) sul-
fide (I) completely decomposes above 500°C; how-
ever, the structure of the decomposition products was
not discussed [6, 10]. We found that thermolysis of
sulfide I in a flow reactor at 400–600°C (contact time
20–30 s) is characterized by a conversion of no more
than 30% and that thiophene (II) is thus formed in
5–10% yield (calculated on the initial sulfide). The
process is accompanied by strong tarring (see table,
run nos. 1–5).
(ClCH2CH2)2S
+
HC CH
I
Δ
+
2HCl
+
H2C CH2
S
II
The mechanism of formation of thiophene by
thermolysis of organosulfur compounds and their joint
thermolysis with acetylene was thoroughly discussed
in [1, 5–8, 11]. It includes initial generation of vinyl-
1070-4280/05/4106-0891 © 2005 Pleiades Publishing, Inc.

VORONKOV et al.
892
High-temperature reactions of bis(2-chloroethyl) sulfide (I)
and yields of thiophene
amount of tars. Acetylene effectively binds vinylsul-
fanyl radicals, thus accelerating thermal decomposition
of sulfide I with formation of thermodynamically
stable thiophene. When the concentration of acetylene
in the system decreases, the conversion of I does not
attain 100% even at 700°C (run no. 10).
Run Molar ratio Tempera- Conversion
Yield
no. I : C2H2 : R2S2 ture, °C
of I, %
of II,a %
b
01
02
03
04
05
06
07
08
09
10
11
12
13
14
400
450
500
550
600
550
600
650
700
700
650
650
650
700
006
05
06
06
10
08
53
48
45
43
38
47
63
68
65
b
b
b
b
013
019
025
030
083
098
100
100
084
096
100
100
100
·
2H2C CHS
II
–H2S
III
The yield of thiophene appreciably increases when
the thermolysis of sulfide I and acetylene is performed
in the presence of lower organic disulfides, dimethyl
disulfide or a mixture of dimethyl and diethyl disul-
fides (disulfide oil) which is a waste product in the
processing of sulfur-rich natural gases [8]. In these
experiments (run nos. 12–14), the yield of thiophene
reaches 68% (650–700°C, 100% conversion of I)
provided that one molecule of I and one disulfide
molecule react with acetylene to form two thiophene
molecules. Among by-products, only the yields of
carbon disulfide and thienothiophenes increase.
1 : 2c
1 : 2c
1 : 2c
1 : 2c
1 : 1c
1 : 3c
1 : 3 : 1d
1 : 3 : 1e
1 : 3 : 1e
The larger yield of thiophene in the reaction of
sulfide I with acetylene in the presence of disulfide is
favored by both additional generation of vinylsulfanyl
radicals and increase in their stability in the presence
of hydrogen sulfide arising from thermolysis of di-
sulfides.
a
b
c
d
e
Calculated on the initial sulfide I.
Neither acetylene nor polysulfides were added.
Joint pyrolysis of sulfide I with acetylene.
R = Me.
R2S2 was a 1 : 1 mixture of dimethyl and diethyl disulfide
(“disulfide oil”).
Thus, joint thermolysis of bis(2-chloroethyl) sulfide
(I) with acetylene gives 45% of thiophene, whereas in
the presence of disulfides the yield of thiophene in-
creases to 68%. Thiophene is readily separated from
the condensed products by distillation. It is isolated in
a sufficiently pure form and can be brought into further
syntheses. The proposed procedures for the synthesis
of thiophene attract practical interest from the view-
point of utilization of bis(2-chloroethyl) sulfide and
disulfide oil as large-scale waste product.
sulfanyl radicals (III) from sulfur-containing sub-
strates. In the absence of chemical traps, radicals III
undergo mainly profound decomposition. Acetylene
binds vinylsulfanyl radicals to produce thiophene, thus
preventing their decomposition [11]. Sulfide I is
capable of yielding radicals III via elimination of
hydrogen chloride and subsequent decomposition of
divinyl sulfide.
EXPERIMENTAL
Δ
I
H2C CHSCH2CH2Cl
–HCl
Liquid initial compounds and thermolysis products
were analyzed by gas–liquid chromatography on
an LKhM 8MD-2 instrument equipped with a 2000×
3-mm column (stationary phase 5% XE-60, linear oven
temperature programming at a rate of 12 deg/min),
carrier gas helium). The liquid products were addi-
tionally analyzed by GC–MS using an LKB-2091-152
instrument (SE-54 capillary column, injector tem-
perature 300°C, oven temperature programming at
8 deg/min, energy of ionizing electrons 70 eV, carrier
gas helium). The gaseous products were analyzed on
·
H
·
·
H2C CHS
+
CH2CH2Cl
H2C CH2
–HCl
III
HC CH
III
II
·
–H
In the absence of acetylene, the concentration of
radicals III is low; therefore, their condensation con-
tributes little to the formation of thiophene. Thermol-
ysis of sulfide I produces mainly a considerable
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 41 No. 6 2005

HIGH-TEMPERATURE SYNTHESIS OF THIOPHENE
893
a KhL-6 chromatograph (7.5-m column packed with
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a liquid product mixture was collected. It contained
1.73 g of thiophene, 0.12 g of benzothiophene, 0.22 g
of thienothiophenes, 0.09 g of isomeric bithienyls,
0.09 g of carbon disulfide, 0.25 g of benzene, and 0.4 g
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isolated by distillation. A fraction with bp 80–82°C
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and acetylene was carried out in a similar way.
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RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 41 No. 6 2005