A Simple Way of Synthesis of Bisethylthiopolymethylene Sulfides EtS(CH2S)nEt

Article abstract of DOI:10.1023/A:1014296411547

Two methods of synthesis of bisethylthiopolymethylene sulfides RS(CH2S)nR (R = Et, n >= 1) are developed. Both approaches are based on the reductive cleavage of the S-S bonds in diethyl polysulfides or a mixture of diethyl polysulfides with elementary sulfur by the system: hydrazine hydrate-base. Subsequent alkylation of the formed thiolate anions with dichloromethane leads to the formation of mixtures of oligomeric bisethylthiopolymethylene sulfides with a predominance of compounds with n = 1, 2.

Full text of DOI:10.1023/A:1014296411547

Russian Journal of General Chemistry, Vol. 71, No. 12, 2001, pp. 1929 1932. Translated from Zhurnal Obshchei Khimii, Vol. 71, No. 12, 2001,
pp. 2036 2039.
Original Russian Text Copyright
2001 by Russavskaya, Alekminskaya, Korchevin, Deryagina.
A Simple Way of Synthesis
of Bisethylthiopolymethylene Sulfides EtS(CH2S)nEt
N. V. Russavskaya, O. V. Alekminskaya, N. A. Korchevin, and E. N. Deryagina
Favorskii Irkutsk Institute of Chemistry, Siberian Division, Russian Academy of Sciences, Irkutsk, Russia
Received April 24, 2001
Abstract Two methods of synthesis of bisethylthiopolymethylene sulfides RS(CH2S) R (R = Et, n 1)
are developed. Both approaches are based on the reductive cleavage of the S S bonds in ndiethyl polysulfides
or a mixture of diethyl polysulfides with elementary sulfur by the system: hydrazine hydrate base. Subsequent
alkylation of the formed thiolate anions with dichloromethane leads to the formation of mixtures of oligomeric
bisethylthiopolymethylene sulfides with a predominance of compounds with n = 1, 2.
Compounds of the type RS(CH2S)nR (n 1) are
EtS
EtS + CH2Cl2
[EtSCH2Cl]
EtSCH2SEt
promising complexing agents and extractants of heavy
metals, dopes for oils and fuels upgrading their
antirust, anticuff, and anti-wear properties, as well as
intermediate products in organic synthesis [1, 2].
However, they are hardly available synthetically. Until
the present time only few bismethylthio polysulfides
MeS(CH2S)nMe (n 4) have been described [3]. They
were prepared in a low yield (not higher than 30%) in
several stages basing on such hardly available com-
pounds as methanethiol and bischloromethyl sulfide.
Cl
Cl
I
S2
Cl
[EtSCH2S ]
[EtSCH2SCH2S ]
CH2Cl2
Cl
CH2Cl2
Cl
S2
Cl
[EtSCH2SCH2Cl]
(2)
[EtSCH2SCH2SCl]
Cl
EtS
EtSCH2SCH2SEt
Now we propose two new approaches to the syn-
thesis of RS(CH2S)nR (n 1) with R = Et which are
based on the reductive cleavage of the S S bonds in
polysulfides and elementary sulfur.
II
S2
Cl
EtS
EtSCH2SCH2SCH2SEt
Cl
III
In method a as starting reagents we used Et2Sm,
where m = 3, 4. Their reduction with the system:
hydrazine hydrate base results in the formation of the
following products:
[EtSCH2SCH2SCH2S ], etc.
polysulfide. Diethyl polysulfides in reactions (1) and
(2) can be used not only in the individual state, but
also as a mixture of Et2S2, Et2S3, Et2S4, asf. The
average sulfur content of this mixture governs the m
value of the polysulfide. These mixtures are easily
prepared from elemental sulfur and alkyl halides in
basic reducing systems [4].
4Et2Sm + mN2H4 H2O + 4mNaOH
8EtSNa + 4(m 2)Na2S + mN2 + 5mH2O.
(1)
As it follows from the stoichiometry of reaction (1),
with m = 3 1 mol of S2 ions is formed for each 2 mol
of EtS anions, and with m = 4 per 2 mol of anions
S2 for 2 mol of anions EtS is formed.
Reaction of diethyl disulfide with dichloromethane
in accordance with Scheme (2) leads to the formation
of compound I, its content in the reaction mixture
may amount to as much as 82% of the reaction pro-
ducts. Increasing the m value to more than 2 results
in the appearance of compounds II, III and others
with different values of n (see table).
In the course of alkylation with dichloromethane
of the thiolate anions generated in reaction (1) the
following consequtive transformations presented in
Scheme (2) take place.
The formation of the mixture of products I III and
oligomers EtS(CH2S) Et with a hagher value of n is
controlled by the valnue of m in the starting diethyl
Method b of synthesis of oligomers EtS(CH2S) Et
is based on separate generation of anions EtS (by nthe
1070-3632/01/7112-1929$25.00 2001 MAIK Nauka/Interperiodica

1930
RUSSAVSKAYA et al.
Reaction conditions and yields of products EtS(CH2S)nEt
Composition of reaction products, as by GLC
oligomers
Starting
sulfur
reagents
Conversion
of Et2S2, %
Molar ratio of starting reagentsa
I
II
(n > 2)
Method a
Et2S2.5
Et2S3.1
Et2S2.5 : NaOH: CH2Cl2 = 1: 2.5: 1.5
Et2S3.1 : NaOH: CH2Cl2 = 1: 3.5: 2
80
75
37
28
14
22
12
18
Method b
Et2S2
Et2S2 :NaOH:CH2Cl2 = 1: 2: 1
98
68
87
88
82
34
40
26
Traces
26
18
Et2S2; S
Et2S2; S
Et2S2; S
Et2S2 :S:NaOH:CH2Cl2 = 1: 0.5: 4: 0.5
Et2S2 :S:NaOH:CH2Cl2 = 1: 0.5: 4: 0.5b
Et2S2 :S:NaOH:CH2Cl2 = 1: 1: 6: 1b
20
18
31
26
a
b
Hydrazine hydrate was used as a medium solvent. Separate preparation of solutions of sulfur and sodium ethanethiolate.
reductive activation of Et2S2 by the system: hydrazine
hydrate base) and anions S2 (with the use of re-
ductive activation of elementary sulfur).
fewer than 5 oligomers. The organic layers obtained
by the performance of synthesis by both methods
contain the starting Et2S2, despite the quantitative
proceeding of the reaction (3) (20 30% with the use
of method a and 10 15% in the case of method b). It
seems likely that Et2S2 is formed in the course of
reactions (2) (4) because of the presence of sulfur
both in the separate preparation of the ethyl thiolate
anion and the solution of sulfur (method b) and in the
reduction of diethyl polysulfides in the basic reductive
system. Dissolution of sulfur in the system: hydrazine
hydrate base, in addition to the formation of mono-
sulfide anions [reaction (4)], can also lead to the
generation of disulfide anions.
2Et2S2 + 4NaOH + N2H4 H2O
4EtSNa + N2 + 5H2O,
S8 + 16NaOH + 4N2H4 H2O
8Na2S + 4N2 + 20H2O.
(3)
(4)
Reaction mixtures prepared according to Schemes
(3) and (4) were combined and subjected to the reac-
tion with dichloromethane. The reaction proceeds by
Scheme (2), as in the case of the first method (see
table). However, synthesis of oligomers EtS(CH2S)nEt
with a high value of n by method b is more control-
lable. The necessity for the solutions of ethyl thiolate
and sodium sulfide to be prepared separately stems
from the fact that, when combined, sulfur and ethyl
thiolate react to produce diethyl disulfide, even in the
presence of such powerful reducing agent as hydrazine.
S8 + 8NaOH + 2N2H4 H2O
4Na2S2 + 2N2 + 10H2O.
(6)
Disulfide anions also can oxidize ethyl thiolate
anions into diethyl disulfide.
S22 + 2EtS
Et2S2 + S2 .
(7)
S8 + 2EtS
Et2S2 + S28 .
(5)
Under these conditions a major portion of diethyl
disulfide does not enter reaction (2).
In all cases 3,5-dithiaheptane (I) is formed with the
highest yield, because in the process termination of
the chain takes place. The highest yield of 3,5,7-tri-
thianonane (II) is achieved with the use in reaction (2)
of excess sulfur and methylene chloride.
By vacuum distillation of the products of reaction
(2) without the use of a superhigh vacuum only
compounds I, II can be isolated. Higher oligo-
mers appear to be unstable and decompose in the
course of distillation. The earlier described in the
literature oligomer RS(CH2S)nR (R = Me, n = 4) was
A careful analysis of the organic phase of the reac-
tion mixtures by means of GLC and GC-MS revealed
in some cases the formation in small proportions of
the following reaction products: EtSCH2SMe (IV)
( 1%) and EtSCH2SSEt (V) ( 3%). These compounds
are most likely the products of redox reactions pro-
ceeding in the used basic reductive system.
3
isolated at 10 mm Hg with the boiling point of 128
[3].
By means of GLC and GC-MS we fixed the forma-
tion by reaction (2) in appreciable amounts of no
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 71 No. 12 2001

A SIMPLE WAY OF SYNTHESIS
1931
dialkyl disulfides, and methylene chloride. Compound
I or mixtures of oligomers are prepared in one pre-
parative stage, and the oligomers can be separated by
high-vacuum distillation.
[H]
EtSCH2SCH2Cl
EtS + S22
EtSCH2SCH3,
HCl
IV
EtSS + S2 ,
EXPERIMENTAL
EtSCH2SCH2Cl + EtSS
EtSCH2SSEt.
V
The reactions progress and purity of the isolated
products were monitored by GLC on a LKhM-80-MD
chromatograph (column 2000 3 mm packed with 5%
of silicone XE-60 on Chromaton N-AW-HMDS),
carrier gas helium, linear programming of temperature
at a rate of 12 deg/min.
Isomeric compounds IV and Et2S2 differ in the
retention times in GLC analysis and the direction of
fragmentation in the mass spectra [in the scheme
given are the values of m/z (Irel, %)].
+
The GC-MS analyses were performed on a chro-
matomass spectrometer AHP-GC-MS-5972 (capillary
column 50 m 0.2 mm 0.5 m, PONA, carrier gas
helium, linear programming of temperature at a rate
of 12 deg/min).
CH3CH2SSCH2CH3
122 (100)
92 (85)
C2H6
SH
+
The NMR spectra were registered on a Bruker
DPX-400 spectrometer (400 MHz) in CDCl3 solutions
with HMDS as an internal reference.
28 (15)
CH3CH2SH
H2S
59 (20)
+
CH3CH2SCH2SCH3
122 (60)
C2H4
Bisethylthiopolymethylene sulfides EtS(CH2S)n
Et. a. Into a flask equipped with a stirrer, reflux
condenser, thermometer, and a dropping funnel an
appropriate amount of alkali was placed, hydrazine
hydrate was added as a solvent, and the mixture was
heated to 50 C. At this temperature diethyl disulfide
was added into the reaction mixture by portions. The
reaction mixture was kept for 1 h at 80 90 C, cooled,
and at 20 25 C dichlomethane was added by portions.
After the completion of alkylation the reaction mass
was kept at 60 70 C for 1 h, and cooled. The reaction
products were extracted with dichloromethane, the
extract was dried with CaCl2. The solvent was eva-
porated, and the residue was analyzed and subjected
to rectification in vacuo. The reaction conditions and
the results are presented in the table.
+
+
CH3SCH2SH
94 (5)
EtS
SCH3
61 (100)
75 (90)
(EtSCH2)+
HS
+
CH3S
47 (60)
45 (60)
H2
28 (40)
As the length of the oligomeric chain grows, the
intensity of the molecular ion peaks in the mass spec-
tra drops steeply. The intensity of the molecular ion
peak of compound I is 80%, and that of compound II
is 20%, while for compound V it is only 2%. In the
mass spectra of higher oligomers no peaks of mole-
cular ions is observed. However, the presence of the
fragmentation ions peaks 75 (EtSCH+2) (Irel 100%),
107 (EtSCH2S+) (Irel up to 30%), 121 (EtSCH2SCH+2),
and 153 (EtSCH2SCH2S+) support the conclusion that
higher oligomers EtS(CH2S)nEt are present in heavier
products of reactions (2).
3,5-Dithiaheptane (I) constitutes the major
portion of the fraction bp 75 90 C (40 mm). After
second distillation a practically pure product, bp 52 C
1
(3 mm) was isolated. H NMR spectrum, , ppm:
1.26 t (CH3), 2.65 q (SCH2C), 3.82 s (SCH2S).
The mixtures of oligomers EtS(CH2S)nEt obtained
by reaction (2) can be used without separation as
extractants of heavy metals and as sulfurizing agents
for oxide catalysts.
1
3,5,7-Trithianonane (II). bp 103 C (2 mm). H
NMR spectrum, , ppm: 1.25 t (CH3), 2.65 q
(SCH2C), 3.81 s (SCH2S), the ratio of intensities
3:2:2. With further rise in the distillation temperature
there is observed a profound decomposition of the still
It can be thus stated that the proposed ways of
preparation of oligomeric polymethylenesulfides
RS(CH2S)nR are characterized by the simplicity of
their accomplishment and are based on the use of
simple starting reagents, namely, elementary sulfur,
1
residue. In the H NMR spectrum of the residue in
the weak field there are found three singlet signals
4.02, 3.95, and 3.81 ppm with the ratio of intensities
of 1:2:5.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 71 No. 12 2001

1932
RUSSAVSKAYA et al.
b. A solution of sodium ethanethiolate was pre-
REFERENCES
pared by method , and then finely powdered sulfur
was added. The reaction mixture was kept for 1 h at
80 90 C, and then treated as described above for
method a.
1. Polucheniye i svoistva organicheskikh soedinenii sery
(Preparation and Properties of Organic Compounds of
Sulfur), Belen’kii, L.I., Ed., Moscow: Khimiya, 1998,
p. 557.
In the separate preparation of solutions of sulfur
and sodium ethanethiolate sulfur solution was pre-
pared by the procedure described in [4]. The obtained
solutions were placed into a common vessel, the
reaction mixture was kept for 1 h at 80 90 C, and
then treated as in method a. The reactions conditions
and the yields of oligomers are given in the table.
2. Kuliev, A.I., Khimiya i technologiya prisadok k maslam
i toplivam (Chemistry and Technology of Dopes for
Oils and Fuels), Leningrad: Khimiya, 1985, p. 312.
3. Feher, F. and Vogelbruch, K., Ber., 1958, vol. 91, no. 5,
p. 996.
ACKNOWLEDGMENTS
This study was performed under the financial
support of the Russian Foundation for Basic Research
(project no. 00-03-32810).
4. Korchevin, N.A., Turchaninova, L.P., Deryagina, E.N.,
and Voronkov, M.G., Zh. Obshch. Khim., 1989, vol. 59,
no. 8, p. 1785.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 71 No. 12 2001