The synthesis of polymeric sulfides by reaction of dihaloalkanes with sodium sulfide

Article abstract of DOI:10.1080/17415993.2011.616589

Several poly(alkylene sulfide)s have been synthesized in excellent yields from reactions of α,ω-dibromo- and/or α,ω- dichloroalkanes with sodium sulfide nonahydrate under reflux conditions. The procedure is general, simple and convenient for the production of various poly(alkylene sulfide)s and the way reaction parameters influence the properties of the polymers formed has been examined.

Full text of DOI:10.1080/17415993.2011.616589

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The synthesis of polymeric sulfides by
reaction of dihaloalkanes with sodium
sulfide
Keith Smith a , Gamal A. El-Hiti a & Ali J. Al-Zuhairi a
a School of Chemistry , Cardiff University , Main Building, Park
Place, Cardiff , CF10 3AT , UK
Published online: 05 Oct 2011.
To cite this article: Keith Smith , Gamal A. El-Hiti & Ali J. Al-Zuhairi (2011) The synthesis of
polymeric sulfides by reaction of dihaloalkanes with sodium sulfide, Journal of Sulfur Chemistry,
32:6, 521-531, DOI: 10.1080/17415993.2011.616589
To link to this article: http://dx.doi.org/10.1080/17415993.2011.616589
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Journal of Sulfur Chemistry
Vol. 32, No. 6, December 2011, 521–531
The synthesis of polymeric sulfides by reaction of dihaloalkanes
with sodium sulfide
Keith Smith*, Gamal A. El-Hiti† and Ali J. Al-Zuhairi
School of Chemistry, Cardiff University, Main Building, Park Place, Cardiff CF10 3AT, UK
(Received 20 July 2011; final version received 18 August 2011)
Several poly(alkylene sulfide)s have been synthesized in excellent yields from reactions of α,ω-dibromo-
and/or α,ω-dichloroalkanes with sodium sulfide nonahydrate under reflux conditions. The procedure is
general, simple and convenient for the production of various poly(alkylene sulfide)s and the way reaction
parameters influence the properties of the polymers formed has been examined.
Reflux
X(CH2)nX
+
Na2S.9H2O
X(CH2)nS[(CH2)nS]y(CH2)nX
1–24 h
X = Br, Cl; n = 1–10; y = 1–42
Keywords: polymeric sulfides; polycondensation; dihaloalkanes; sodium sulfide; synthesis
1. Introduction
Poly(alkylene sulfide)s are important polymers and their applications have been reviewed recently
(1). They possess excellent thermal stability, weatherability, solvent resistance and oil resistance
(2–4) and hence are widely used in coatings, adhesives, sealants, insulators and other applica-
tions (5–8). Also, poly(alkylene sulfide)s find application in vulcanizing rubbers (9). Moreover,
poly(alkylene sulfide)–AgNO3 electrolytes show interesting conductivities (10). Therefore, the
syntheses of such polymers are always of interest.
Poly(alkylene sulfide)s are usually prepared by one of four major methods: polymerization of
episulfides; reactions of dithiols with carbonyl compounds; addition of dithiols to diolefins; and
reactions of dithiols with dihalides. The first two obviously apply to only very specific types of
polymeric sulfides (containing a two-carbon or one-carbon spacer group, respectively), while the
other two methods are not simple to operate and require the availability of appropriate dithiols.
Other problems may also arise. For example, in the episulfide polymerization, the presence of
disulfide impurities results in the poor control over molecular weight distribution; therefore, work
*Corresponding author. Email: smithk13@cardiff.ac.uk
†Permanent address: Chemistry Department, Faculty of Science, Tanta University, Tanta 31527, Egypt.
ISSN 1741-5993 print/ISSN 1741-6000 online
© 2011 Taylor & Francis
http://dx.doi.org/10.1080/17415993.2011.616589
http://www.tandfonline.com

522 K. Smith et al.
carried out by Wang etal. (11) was aimed at minimizing the presence of disulfides and optimizing
synthesis procedures.
In the view of the above problems and also on grounds of convenience and cheapness, a method
involving a direct reaction of a metal sulfide with a dihaloalkane would have obvious attrac-
tions. Early workers prepared poly(alkylene sulfide)s from dihaloalkanes and potassium sulfide;
however, they used only 1,2-dihaloethenes and the polymeric materials obtained were poorly
characterized (12). Later, the reaction of dichloromethane (DCM) with sodium sulfide nonahy-
drate was shown to form tetrathiocane first, but treatment of this with BF3 gave poly(methylene
sulfide), which was obtained as an insoluble polymer (13). In 1974, Landini and Rolla (14) demon-
strated that excellent yields of simple dialkyl sulfides can be obtained from sodium sulfide and
monohaloalkanes using a phase-transfer catalysis technique. Related reactions of sodium dithio-
lates with their corresponding dihalides gave polymers, with some cyclic oligomers also formed
(15), and Imai etal. (16) reported that a phase–transfer catalyst could be used to assist in the
synthesis of such poly(alkylene sulfide)s. Subsequently, the same group reported the preparation
of higher molecular weight poly(alkylene sulfide)s from dibromoalkanes having relatively long
spacer groups (8–11 carbon atoms) by reaction with 1 M aqueous sodium sulfide solution in the
presence of quaternary ammonium or phosphonium salts (4 mol %) under a nitrogen atmosphere
at 100◦C for 24 h (17). The yields of polymers were good (86–99% depending on the type of cat-
alyst used). However, application of the process on only a small scale (1–2 g) and with a restricted
range of dibromoalkanes, together with the need for a catalyst, a long reaction time and use of
an inert atmosphere, limits the attractiveness of the process; also the factors that influence the
process are not clear.
As a part of our own interest in the synthesis of sulfur-containing compounds (18), we have
examined the reaction of dibromoalkanes and dichloroalkanes with sodium sulfide in more detail.
We have been able to produce a range of polymers simply from reactions of dihaloalkanes with
cheap sodium sulfide nonahydrate by use of reflux conditions in the absence of a catalyst or
additional solvent. The process has been applied to dihaloalkanes with spacer lengths from 1 to
10carbons and generally givesexcellentyields. Inthispaper, wereport thehigh-yieldingsyntheses
of a range of such poly(alkylene sulfide)s. Very recently, we have synthesized a range of borane
adducts derived from such polymeric sulfides as new hydroborating and reducing reagents, which
might well be suitable for large scale industrial application (19).
2. Results and discussion
Initial experiments were conducted in which mixtures of dibromomethane and various quantities
of sodium sulfide nonahydrate (1.0–1.5 mole equivalents) were heated under reflux for various
times with efficient stirring (Scheme 1; n = 1). The mixtures became very viscous and on cooling
to room temperature produced solids, which were filtered, washed with water and dried to give
the polymeric material 1 in high yield. The yield of 1 was 95% when the reaction time was 4 h
and the molar ratio of Na2S·9H2O to dibromomethane was 1.5:1.
Reflux
Br(CH2)nBr
+
Na2S.9H2O
Br(CH2)nS[(CH2)nS]y(CH2)nBr
1–6 h
1–10
n =1–10; y = 3–42
Scheme 1. Synthesis of poly(alkylene sulfide)s 1–10 from polycondensation of dibromoalkanes
with Na2S·9H2O.

Journal of Sulfur Chemistry 523
The solubility of polymeric material 1 was poor in organic solvents and we were unable to
run the 1H NMR spectrum or gel permeation chromatography (GPC) analysis for such material.
Therefore, our attention was next turned to the investigation of the synthesis of other polymeric
materials in which various α,ω-dibromoalkanes having different spacer group chain lengths from
2 to 10 carbons were used (Scheme 1). The molar ratio of Na2S·9H2O:dibromoalkane was kept
at 1.5:1 but the reaction time was varied for each dibromoalkane in order to provide high yields
of polymeric material. Table 1 gives the reaction times, yields, melting points, average molecular
1
weights calculated by GPC and the average number of repeating units calculated from the H
NMR spectrum for poly(alkylene sulfide)s 1–10. No NMR spectroscopy or GPC analysis was
carried out for 2 since that material, like 1, was highly insoluble in organic solvents.
The average molecular weights calculated by GPC were usually higher than those calculated
based on the number of repeating units calculated from the ratio of end-groups CH2Br to internal
CH2SCH2 units in the 1H NMR spectra. In some cases, this may be because of the presence of
significant quantities of disulfide impurities, which lead to additional NMR signals that are not
taken into account in the calculations. Another factor may be because polystyrene was used as the
GPC standard rather than a polymeric sulfide. However, the trends in molecular weights derived
from GPC analysis were consistent with the trends in the number of repeating units calculated
based on 1H NMR spectra.
As can be seen from Table 1, the reaction is simple, general, accommodates various spacer chain
lengths varying from 1 to 10 and usually provides high yields (90–100%) of the polymeric sul-
fides. The reaction involves no solvent and employs inexpensive starting materials. This therefore
represents a very useful general method for the synthesis of poly(alkylene sulfide)s.
However, the yield of polymeric sulfide 4 was very low (11%) under the conditions tried. In this
case, tetrahydrothiophene (11; Figure 1) was obtained in 78% yield due to the rapid cyclization on
reactionof1,4-dibromobutanewithsodiumsulfide. Noattemptsweremadetotrytofindconditions
under which the yield of 4 could be increased. It has been reported previously that the reaction
of 1,4-dibromobutane in chloroform with sodium sulfide nonahydrate in water in the presence
of a phase–transfer catalyst under nitrogen gave 11 in 42% yield, but no polymeric material of
the structure 4 was reported in that case (20). In contrast, 1,2-dithiane (12) was produced in 80%
yield from the reaction of 1,4-dibromobutane with sodium sulfide in the presence of sulfur and
Table 1. Synthesis of poly(alkylene sulfide)s 1–10 from reactions of 1,n-dibromoalkanes and sodium
sulfide nonahydrate according to Scheme 1.a
Melting
Approximate number of
Polymer
n
Time (h)
point (◦C)
Yield (%)b
Mnc
repeating units (y)d
1e
2e
3
4
5
6
7
8
9
1
2
3
4
5
6
7
8
9
4
1
4
6
4
4
5
5
5
5
225–230
185–186
55–57
65–68
70–75
70–77
78–85
58–64
70–76
70–78
95
100
100
15f
94
100
90
97
Not known
Not known
4546
5939
3921
4068
4308
1201
2082
Notknown
Notknown
24
43
33
33
33
3
92
95
5
5
10
10
1700
Notes: aA mixture of dibromoalkane (0.10 mmol) and Na2S·9H2O (36.0 g, 0.15 mmol) was heated under reflux in an oil
bath set at 140–160◦C for the indicated reaction time.
bYield based on an assumed empirical formula for the product of (CH2)nS.
cThe average molecular weight calculated by GPC.
dCalculated from the 1H NMR spectrum by comparison of the integrations of the CH2Br and CH2SCH2 signals.
eThe polymeric material was highly insoluble in solvents.
f Tetrahydrothiophene (11; Figure 1) was produced in 78% yield.

524 K. Smith et al.
S
S
S
11
12
Figure 1. Structures of tetrahydrothiophene (11) and 1,2-dithiane (12).
didecyldimethylammonium bromide, as a phase–transfer catalyst, at 30◦C for 4 h in a mixture of
water and chloroform (21). In our current reaction, the preferential formation of 11 accounts for
the low yield of 4. No evidence was found to suggest the formation of a significant amount of 12
during the reaction.
The NMR spectra of polymeric sulfides 8–10 (n = 8–10) showed the prevalence of short-chain
polymers in which the calculated average numbers of repeating units were in the range of 3–5,
compared with averages of 24–43 repeating units in cases where n was less than 8. We therefore
varied the reaction time and the quantity of sodium sulfide in an attempt to increase the chain
length of polymeric sulfide 8 and to see what effect these parameters have on the chain length and
physical properties (e.g. melting point) of the polymer. Initially, the reaction of 1,8-dibromooctane
(1 mole equivalent) with sodium sulfide nonahydrate (1.5 mole equivalents) was conducted under
reflux conditions and the reaction time was varied (2–24 h). The results obtained are recorded in
Table 2.
The results (Table 2) show that the chain length (y) increases with increasing reaction time up
to a reaction period of around 16 h, by which time the average number of repeating units (y) was
ca. 20. Also, the yield and the melting point of the polymeric material 8 increased in line with the
chain length as the reaction period increased. The reaction conducted for the shortest period (2 h)
produced a low yield (30%) of the material that contained a calculated average of only two sulfur
atoms per molecule (Scheme 1; y = 1). It is likely that the low cross-solubility of water with both
the longer-chain dibromides and with the corresponding intermediate thiolates is responsible for
the longer time taken in these cases for the polymer chain length to reach the higher values.
We also investigated reactions of 1,8-dibromooctane with various quantities of sodium sulfide
(1.0–2.5 mole equivalents) under reflux conditions for a fixed period of 5 h and the results obtained
are shown in Table 3.
Increasing the quantity of sodium sulfide resulted in a longer chain length over the fixed 5 h
reaction period, but there were still only approximately eight repeating units when 2.5 mole
equivalents of sodium sulfide were used. Also, the use of 1.2 mole equivalents for a longer period
(24 h) provided polymeric sulfide 8 with only approximately six repeating units. Clearly, at least
1.5 mole equivalents of sodium sulfide and a prolonged reaction time are important for obtaining
a longer-chain polymer.
Table 2. Effect of reaction time on the chain length of 8 according to Scheme 1.a
Melting
Approximate number of
Time (h)
point (◦C)
Yield (%)b
repeating units (y)c
2
5
Slurry
58–64
30
97
1
3
8
16
24
80–85
110–118
110–118
96
100
100
13
20
20
Notes: aA mixture of 1,8-dibromooctane (27.0 g, 0.10 mol) and Na2S·9H2O (36.0 g, 0.15 mmol) was
heated under reflux in an oil bath set at 140–160◦C for the indicated reaction time.
bYield based on an assumed empirical formula for the product of (CH2)nS.
cCalculated from the 1H NMR spectrum by comparison of the integrations of the CH2Br and
CH2SCH2 signals.

Journal of Sulfur Chemistry 525
Table 3. Effect of quantities of Na2S·9H2O on the average chain length of 8.a
Na2S·9H2O
Melting
Approximate number of
(mole equivalent)
point (◦C)
Yield (%)b
repeating units (y)c
1.0
1.2
1.5
1.7
2.0
2.5
Slurry
52–60
58–64
75–79
75–79
78–85
25
57
97
92
92
98
1d
2d
3
6
6
8
Notes: aA mixture of 1,8-dibromooctane (27.0 g, 0.10 mmol) and Na2S·9H2O was heated under
reflux in an oil bath set at 140–160◦C for 5 h.
bYield based on an assumed empirical formula for the product of (CH2)nS.
cCalculated from the 1H NMR spectrum by comparison of the integrations of the CH2Br and
CH2SCH2 signals.
dThe number of repeating units (y) may be a little higher than reported due to the presence of a
significant proportion of disulfide.
Attention was next turned to the use of various dichloroalkanes with sodium sulfide nonahydrate
to produce the polymeric sulfides 13–17 (Scheme 2). These reactions were significantly slower
than those using dibromides and therefore required longer reaction times to provide good yields
of polymers. In the early experiments, the NMR peaks assumed to arise from disulfides were more
prominent in the products than had been observed with the dibromides. In the case of reaction of
1,6-dichlorohexane with sodium sulfide nonahydrate (1.5 mole equivalents) for 48 h, the product
mixture was treated with methanol and most of the polymeric material (16) precipitated and was
collectedbyfiltration.Thefiltratewasthencooledto0◦Candmore 16 separatedout.Thetotalyield
of 16 was around 60%. The filtrate was then concentrated under reduced pressure to give a 40%
yield of the material that was mainly the cyclic disulfide 1,2-dithiocane (18; Figure 2), identical
in all respects to the authentic material produced from the oxidation of 1,6-hexanedithiol with
bromine (22). It is believed that compound 18 resulted from oxidation in air of 1,6-hexanedithiol
formed in situ from 1,6-dichlorohexane under the conditions used.
The yield of 16 was higher when the quantity of sodium sulfide nonahydrate was increased to
2.5 mole equivalents, but 18 was still evident in the 1H NMR spectrum of the product mixture,
albeit in low proportion. Several attempts were made in order to find conditions under which 18
Reflux
Cl(CH2)nCl
+
Na2S.9H2O
Cl(CH2)nS[(CH2)nS]y(CH2)nCl
8–24 h
13–17
n = 2, 4, 5, 6 and 8; y = 2–23
Scheme2. Synthesisofpoly(alkylenesulfide)s13–17frompolycondensationofdichloroalkanes
and Na2S·9H2O.
S
S
18
Figure 2. Structure of 1,2-dithiocane (18).

526 K. Smith et al.
could be eliminated. However, carrying out the reaction under an inert atmosphere or the use of
KI as a catalyst for the nucleophilic substitution reaction had little effect on the yield of 16 or
the proportion of 18 formed. In the course of these investigations, it was noticed that a volatile
material, believed to contain 1,6-hexanedithiol, evaporated from the reaction mixture and after
condensation ran down the wall of the flask rather than dripping back directly into the reaction
mixture. It was felt that the liquid dithiol might be re-evaporating on contact with the hot walls of
the flask before it got back into the reaction mixture, thereby preventing its reaction with further
chloroalkyl-terminated polymer in the flask and also increasing the likelihood of its oxidation to
18. In order to minimize this problem, a condenser with a long drip-tip, which would allow the
condensed material back into the reaction mixture more efficiently, was employed. The use of
such a condenser improved the yield of 16 and also reduced the amount of 18 to a trace. Such a
condenser was therefore used for further investigations.
A series of experiments was conducted in which the conditions of the reaction were varied in
an attempt to produce the corresponding polymeric sulfides 13–17 in high yields. The optimum
yields were obtained when a larger quantity of sodium sulfide nonahydrate (2.5 mole equivalents)
was used for a longer reaction time (8–24 h, Table 4) than was the case for the corresponding
dibromoalkanes (1–6 h). The NMR spectra of 14–17 showed the presence of only very low
proportions of peaks thought to be due to disulfides.
As can be seen from Table 4, the reaction is general and usually provides high yields of the
polymeric sulfides. However, the reactions were slower than those involving the use of dibro-
moalkanes (Table 1) and gave shorter-chain polymers. Again, the yield of polymeric sulfide 14
was low (19%) due to the formation of tetrahydrothiophene (11; Figure 1) in high yield (75%).
It is clear that poly(alkylene sulfide)s can generally be synthesized efficiently in high yields from
either dibromo- or dichloroalkanes by reactions with sodium sulfide. However, longer reaction
times and/or greater quantities of sodium sulfide are required with dichloroalkanes in order to
achieve comparable chain lengths.
For the polymers with the very short spacer groups (one or two methylene units), there was an
issue of lack of solubility of the polymers produced under all the conditions tried. Several attempts
were therefore made to synthesize a soluble polymeric material of structure similar to 2 or 13 to
widen the scope of application for such polymeric materials. It was thought that the low solubility
might be caused by longer chain lengths and that shorter chain lengths could be encouraged
by the addition of a monohaloalkane to terminate the polymeric chains. Therefore, mixtures
of 1,2-dichloroethane (0.6 mole equivalents), a haloalkane (1-bromobutane, 2-bromopropane,
1-chlorobutane or 2-chlorobutane; 0.4 mole equivalent) and sodium sulfide nonahydrate (1.5 mole
Table 4. Synthesis of polymers 13–17 from dichloroalkanes according to Scheme 2.a
Melting
Approximate number of
Polymer
n
Time (h)
point (◦C)
Yield (%)b
Mnc
repeating units (y)d
13e
14
15
16
17
2
4
5
6
8
8
24
14
14
14
185–186
68–70
70–75
72–76
60–66
91
19f
85
97
90
Not known
5243
2726
2727
1229
Not known
47
25
13
3g
Notes: aA mixture of dichloroalkane (0.10 mol) and Na2S·9H2O (60.0 g, 0.25 mol) was heated under reflux in an oil
bath set at 140–160◦C for the indicated reaction time.
bYield based on an assumed empirical formula for the product of (CH2)nS.
cThe average molecular weight calculated by GPC.
dCalculated from the 1H NMR spectrum by comparison of the integrations of the CH2Br and CH2SCH2 signals.
eThe polymeric material is highly insoluble in most solvents.
f Tetrahydrothiophene (11; Figure 1) was produced in 75% yield.
gThe calculated number of repeating units is less accurate due to the presence of a significant quantity of disulfide.

Journal of Sulfur Chemistry 527
Reflux
12 h
Cl(CH2)2Cl
+
RX
+
Na2S.9H2O
RS[(CH2)2S]yR
19-22
R = n-Bu, iso-Bu, iso-Pr; X = Br, Cl; y = 3–8
Scheme 3. Synthesis of poly(alkylene sulfide)s 19–22 from polycondensation of
1,2-dichloroethane and Na2S·9H2O in the presence of haloalkanes.
Figure 3. Total yields of polymeric materials 19–22 obtained from polycondensation of 1,2-dichloroethane and
Na2S·9H2O in the presence of haloalkanes under reflux conditions.
equivalents) was refluxed for 12 h (Scheme 3). The polymeric materials produced (19–22) were
treated with DCM and the residual solids (longer-chain polymers) were removed by filtration. The
DCM was removed under reduced pressure from the filtrate to give the shorter-chain polymers
as white solids. The total yield of the polymeric materials 19–22 are shown in Figure 3. The 1H
NMR spectra of the shorter-chain polymers indicated that the number of repeating units (y) was
in the range of 3–8. The low solubility of the residual solid polymers meant that it was difficult to
obtain molecular weight data, but it is assumed that the average chain lengths of such materials
were significantly greater.
It is clear from Figure 3 that the total yields of polymeric materials 19–22 were high. In general,
the yields of the short-chain polymeric materials using monobromoalkanes to terminate the chains
were higher than those obtained with monochloroalkanes. Alkyl bromides tend to terminate the
polymerization reaction faster than alkyl chlorides, and as a result, the proportions of short-chain
oligomers are higher and the average chain lengths of such oligomers are lower (y = 3–5 with the
bromides compared with y = 5–8 with the chlorides). Also, the yield of short-chain polymeric
materials using 1-bromobutane was higher than that obtained with 2-bromopropane (Figure 3).
This arises because the rate of nucleophilic substitution of primary alkyl halides is higher than
that of secondary ones in these reactions (23).
The melting points of the short-chain polymeric materials prepared using primary alkyl halides
were in the range of 70–72◦C, while, the melting points of the corresponding ones obtained with
secondary alkyl halides were a bit lower (64–68◦C).

528 K. Smith et al.
3. Conclusions
A general method for the synthesis of symmetrical poly(alkylene sulfide)s has been developed
based on reactions of α,ω-dihaloalkanes of different spacer lengths with cheap sodium sulfide non-
ahydrate, in the absence of any added solvent, base or catalyst. The process is simple, general and
convenient and provides excellent yields of polymer sulfides. Dibromoalkanes react faster than
dichloroalkanes and under comparable conditions provide polymers with greater average chain
lengths and molecular weights. The chain lengths of the polymeric materials can be increased
by increasing the reaction time and/or the quantity of sodium sulfide. On the other hand, chain
lengths are reduced by the addition of monohaloalkanes. Consequently, the properties of the poly-
meric materials obtained can be controlled to a large extent by judicious choice of dihaloalkane,
haloalkane terminating agent (if any), reactant proportions and reaction time.
4. Experimental
4.1. General
Melting point determinations were performed by the open capillary method using a Gallenkamp
melting point apparatus and are reported uncorrected. 1H and 13C NMR spectra were recorded on
a Bruker AV500 spectrometer operating at 500 MHz for 1H and 125 MHz for 13C measurements.
Chemical shifts are reported relative to TMS and coupling constants J are in Hz and have been
rounded to the nearest whole number. Assignments of signals are based on coupling patterns
and expected chemical shift values and have not been rigorously confirmed. Signals with similar
characteristics might be interchanged. GPC was carried out using a GPC MAX variable loop
equipped with two KF-805L SHODEX columns in CHCl3, with a RI (VE3580) detector using a
GPC MAX pump operating at a flow rate of 1 ml/min. Calibration was achieved using a series
of Viscotek polystyrene standards up to Mw = 9.4 × 105. Microanalyses were performed by
Warwick analytical service at the University of Warwick. Chemicals were obtained from Aldrich
Chemical Company and used without further purification.
4.2. Typical experimental procedure for the synthesis of polymeric sulfides 1–10
Dibromoalkane (100 mmol) and sodium sulfide nonahydrate (36.0 g, 150 mmol) were placed in
a 1 l round-bottom flask that contained a magnetic bar. The flask was equipped with a water
condenser and placed in an oil bath set at 140–160◦C. The mixture was heated under reflux for
1–6 h with vigorous stirring, by which time a very viscous material resulted. Water (ca. 30 ml) was
added to the hot reaction mixture, which was then poured into a clean beaker and vigorously stirred
before being left to cool to room temperature. The solid mass was then collected by filtration,
washed thoroughly with water (3 × 30 ml) and dried at 50◦C under reduced pressure to give a
white powdery solid. The physical properties and NMR spectroscopic data of 1–10 are presented
in Tables 1 and 5, respectively.
4.3. Typical experimental procedure for the synthesis of polymeric sulfides 13–17
The procedure was similar to that described for the formation of polymers 1–10 but using a
mixture of dichloroalkane (0.10 mol) and sodium sulfide nonahydrate (60.0 g, 0.25 mol) heated
under reflux for 8–24 h in a bath set at 140–160◦C. Also, a condenser with a long drip-tip was
used to minimize disulfide formation. The physical properties and NMR spectroscopic data of
13–17 are presented in Tables 4 and 5, respectively.

Journal of Sulfur Chemistry 529
Table 5. NMR spectra for polymeric sulfides 3–10, 14–17 and 19–22.a
NMR (δ, ppm; CDCl3)b
Polymer
1H NMR (500 MHz)
13C NMR (125 MHz)c
3
1.90 (m, 2 H, CH2CH2S), 2.65 (t, J = 7 Hz, 4 H, CH2S), 29.5 (CH2CH2S), 32.6 (CH2S), 37.6 (CH2SS)
2.80 (t, J = 7 Hz, 0.166 H, CH2SS), 3.35 (t, J = 7 Hz,
0.166 H, CH2Br)
4
5
6
7
1.70 (m, 4 H, CH2CH2S), 2.45 (t, J = 7 Hz, 4 H, CH2S), 28.4 (CH2CH2S), 32.4 (CH2S)
2.65 (t, J = 7 Hz, 0.372 H, CH2SS), 3.35 (t, J = 7 Hz,
0.093 H, CH2Br)
1.40 (m, 2 H, CH2CH2CH2S), 1.50 (m, 4 H, CH2CH2S), 28.4 (CH2CH2CH2S), 29.5 (CH2CH2S), 32.4
2.45 (t, J = 7 Hz, 4 H, CH2S), 2.60 (t, J = 7 Hz, 0.24 H, (CH2S), 38.8 (CH2SS)
CH2SS), 3.35 (t, J = 7 Hz, 0.12 H, CH2Br)
1.35 (m, 4 H, CH2CH2CH2S), 1.50 (m, 4 H, CH2CH2S), 28.4 (CH2CH2CH2S), 29.5 (CH2CH2S), 32.4
2.45 (t, J = 7 Hz, 4 H, CH2S), 3.35 (t, J = 7 Hz, 0.12 H, (CH2S)
CH2Br)
1.20–1.35 (m, 6 H, CH2CH2CH2CH2S and
CH2CH2CH2S), 1.50 (m, 4 H, CH2CH2S), 2.45
(t, J = 7 Hz, 4 H, CH2S), 2.60 (t, J = 7 Hz, 0.89 H,
CH2SS), 3.35 (t, J = 7 Hz, 0.12 H, CH2Br)
1.27–1.45 (m, 8 H, CH2CH2CH2CH2S), 1.50 (m, 4 H,
CH2CH2CH2S), 2.45 (t, J = 7 Hz, 4 H, CH2S), 2.65 (t,
J = 7 Hz, 0.42 H, CH2SS), 3.35 (t, J = 7 Hz, 0.20 H,
CH2Br)
28.1 (CH2CH2CH2CH2S), 29.1
(CH2CH2CH2S), 29.6 (CH2CH2S), 32.1
(CH2S), 39.0 (CH2SS)
8d
9
28.6 (CH2CH2CH2CH2S), 29.4
(CH2CH2CH2S), 29.7 (CH2CH2S), 32.2
(CH2S)
1.16–1.40 (m, 10 H, CH2CH2CH2CH2CH2S and
CH2CH2CH2CH2S), 1.50 (m, 4 H, CH2CH2S), 2.45 (t,
28.9 (CH2CH2CH2CH2CH2S), 29.2
(CH2CH2CH2CH2S), 29.4 (CH2CH2CH2S),
J = 7 Hz, 4 H, CH2S), 2.60 (t, J = 7 Hz, 0.8 H, CH2SS), 29.7 (CH2CH2S), 32.2 (CH2S), 34.0 (CH2Br),
3.35 (t, J = 7 Hz, 0.8 H, CH2Br) 39.5 (CH2SS)
1.17–1.25 (m, 8 H, CH2CH2CH2CH2CH2S), 1.27–1.40 28.9 (CH2CH2CH2CH2CH2S), 29.2
(m, 4 H, CH2CH2CH2S), 1.50 (m, 4 H, CH2CH2S), (CH2CH2CH2CH2S), 29.5 (CH2CH2CH2S),
2.45 (t, J = 7 Hz, 4 H, CH2S), 2.61 (t, J = 7 Hz, 0.27 H, 29.7 (CH2CH2S), 32.2 (CH2S), 34.2 (CH2Br),
39.5 (CH2SS)
10
CH2SS), 3.35 (t, J = 7 Hz, 0.86 H, CH2Br)
14
15
16
17
1.90 (m, 4 H, CH2CH2S), 2.65 (t, J = 7 Hz, 4 H, CH2S), 28.4 (CH2CH2S), 32.4 (CH2S), 38.5 (CH2SS)
2.65 (t, J = 7 Hz, 0.344 H, CH2SS), 3.50 (t, J = 7 Hz,
0.086 H, CH2Cl)
1.40 (m, 2 H, CH2CH2CH2S), 1.50 (m, 4 H, CH2CH2S), 28.4 (CH2CH2CH2S), 29.5 (CH2CH2S), 32.4
2.45 (t, J = 7 Hz, 4 H, CH2S), 2.60 (t, J = 7 Hz,
(CH2S)
0.416 H, CH2SS), 3.50 (t, J = 7 Hz, 0.157 H, CH2Cl)
1.35 (m, 4 H, CH2CH2CH2S), 1.50 (m, 4 H, CH2CH2S), 28.4 (CH2CH2CH2S), 29.5 (CH2CH2S), 32.4
2.45 (t, J = 7 Hz, 4 H, CH2S), 2.60 (t, J = 7 Hz,
0.393 H, CH2SS), 3.50 (t, J = 7 Hz, 0.304 H, CH2Cl)
1.20–1.42 (m, 8 H, CH2CH2CH2CH2S), 1.50 (m, 4 H,
CH2CH2CH2S), 2.45 (t, J = 7 Hz, 4 H, CH2S), 2.60 (t,
J = 7 Hz, 0.834 H, CH2SS), 3.50 (t, J = 7 Hz, 1.57 H,
CH2Cl)
(CH2S), 38.5 (CH2SS), 44.5 (CH2Cl)
28.6 (CH2CH2CH2CH2S), 29.4
(CH2CH2CH2S), 29.7 (CH2CH2S), 32.2
(CH2S), 39.0 (CH2SS), 45.0 (CH2Cl)
19
0.95 (t, J = 7 Hz, 1.27 H, CH3CH2CH2CH2S), 1.45
(m, 0.85 H, CH3CH2CH2CH2S), 1.61 (m, 0.85 H,
CH3CH2CH2CH2S), 2.55 (t, 0.85 H, J = 7 Hz,
CH3CH2CH2CH2S), 2.80 (s, 4 H, CH2S)
13.6 (CH3CH2CH2CH2S), 22.1
(CH3CH2CH2CH2S), 29.3
(CH3CH2CH2CH2S), 31.0
(CH3CH2CH2CH2S), 32.4 (CH2S).
23.5 [CH(CH3)2S], 32.4 [CH(CH3)2S], 35.1
(CH2S)
13.6 (CH3CH2CH2CH2S), 22.1
(CH3CH2CH2CH2S), 29.3
20
21
1.20 [d, J = 7 Hz, 4 H, CH(CH3)2S], 2.71 (s, 4 H,
CH2S), 2.90 [m, 0.67 H, CH(CH3)2S]
0.95 (t, J = 7 Hz, 1.27 H, CH3CH2CH2CH2S), 1.45
(m, 0.85 H, CH3CH2CH2CH2S), 1.61 (m, 0.85 H,
CH3CH2CH2CH2S), 2.55 (t, J = 7 Hz, 0.85 H,
CH3CH2CH2CH2S), 2.80 (s, 4 H, CH2S)
(CH3CH2CH2CH2S), 31.0
(CH3CH2CH2CH2S), 32.4 (CH2S)
22
0.95 (t, J = 7 Hz, 0.70 H, CH3CH2), 1.22 (d, J = 7 Hz,
22.9 (CH3CH2), 30.8 [CH2CH(CH3)S], 32.4
0.70 H, CH3CHS), 1.50 (m, 0.47 H, CH3CH2), 2.70 (m, (CH3CHS), 35.1 (CH2S)
0.23 H, CH3CHS), 2.85 (s, 4 H, CH2S)
Notes: aPolymeric sulfides 1, 2 and 13 were highly insoluble in most solvents and no NMR spectra were recorded.
bCH2X (X = Br, Cl) represents the terminal CH2 of the polymer and the CH2SS represents the disulfide. The term CH2S refers to signals
next to sulfide sulfur, CH2SCH2.
cIn some cases, the signals for the CH2X and the CH2SS were not noticeable.
dNMR for the polymeric material 8 obtained when the reaction time was 16 h.

530 K. Smith et al.
4.4. Typical experimental procedure for the synthesis of short-chain polymeric sulfides
18–21
A mixture of 1,2-dichloroethane (5.8 g, 60 mmol), haloalkane (40 mmol) and sodium sulfide non-
ahydrate (36.0 g, 150 mmol) was heated under reflux with efficient stirring for 12 h in a silicon oil
bath set at 140–160◦C. The reaction mixture was allowed to cool and then water (30 ml) was added.
The solid was removed by filtration and washed thoroughly with water (3 × 30 ml) and dried to
give a white solid. The solid was treated with DCM (30 ml) and the insoluble solid was removed
by filtration to give the longer-chain polymers. The DCM was removed under reduced pressure
from the filtrate to give the shorter-chain polymers as white solids. The NMR spectroscopic data
of the short-chain polymers 19–22 are presented in Table 5.
4.5. Tetrahydrothiophene (11)
A mixture of 1,4-dibromobutane or 1,4-dichlorobutane (100 mmol) and sodium sulfide nonahy-
drate (150–250 mmol) was heated under reflux for 6–24 h. The mixture was cooled and DCM
(50 ml) was added. The layers were separated and the organic layer was dried (MgSO4) and
concentrated under reduced pressure. Diethyl ether (30 ml) was added to precipitate the poly-
meric material 4 or 14. The solid was filtered and washed with diethyl ether (30 ml). The filtrates
were combined and the solvent was removed under reduced pressure to give tetrahydrothiophene
1
(11) in 75–78% yield. H NMR (500 MHz, CDCl3), δ (ppm): 2.76 (t, J = 6 Hz, 4 H, CH2S),
1.87 (t, J = 6 Hz, 4 H, CH2CH2S); 13C NMR (125 MHz, CDCl3), δ (ppm): 31.8 (CH2S), 31.0
(CH2CH2S); EI-MS (m/z, %): 88 (M+, 88), 60 ([M – S]+, 100); HRMS (EI): calcd for C4H8S
(M), 88.0347; found, 88.0343.
4.6. 1,2-Dithiocane (18)
Compound 18 was produced in around 40% yield as a side product from the reaction of
1,6-dichlorohexane with sodium sulfide nonahydrate along with the polymeric material 16. Also,
it was produced in 87% yield by oxidation of 1,6hexanedithiol with bromine according to the liter-
ature procedure (22). 1H NMR (500 MHz, CDCl3), δ (ppm): 3.35 (t, J = 7 Hz, 4 H, CH2SS), 1.65
(m, 4 H, CH2CH2SS), 1.30 (m, 4 H, CH2CH2CH2SS); 13C NMR (125 MHz, CDCl3), δ (ppm):
38.9 (CH2SS), 29.1 (CH2CH2SS), 27.5 (CH2CH2CH2SS); EI-MS (m/z, %): 148 (M+, 37), 116
([M – S]+, 25), 101 (20), 87 (100), 84 ([M – 2 S]+, 25); HRMS (EI): calcd for C6H12S2 (M),
148.0380; found, 148.0376.
Acknowledgements
The authors thank the Iraqi Government and Cardiff University for financial support.
References
(1) Vo, C.D.; Kilcher, G.; Tirelli, N. Macromol. Rapid Commun. 2009, 30, 299–315.
(2) Ellerstein, S. Handbook of Polymer, 3rd ed.; Wiley-Interscience: New York, 1985.
(3) Lee, T.C.P. In Properties and Applications of Elastomeric Polysulfides; Dolbey, R., Ed.; Rapra Technology Ltd.:
Shrewsbury, 1999; Vol. 9.
(4) Mahon, A.; Kemp, T.J.; Coates, R.J. Polym. Degrad. Stabil. 1998, 62, 15–24.
(5) Lee, C.; Chang, T.C.; Huang, Y.-H. US Patent, 5432257, 1995.
(6) Tobolsky, A.V. The Chemistry of Sulfides; Wiley-Interscience: New York, 1968.
(7) Bahh, C.A.; Baah, J.I.; Gianadda, P.; Fisher, C. Mater. Des. 2000, 21, 211–215.
(8) Lucke, H. ALIPS – Aliphatic Polysulfides; Hüthig and Wepf: Basel, 1994.

Journal of Sulfur Chemistry 531
(9) Fettes, E.M.; Jorczak, J.S.; Panek, J.R. Ind. Eng. Chem. 1954, 46, 1539–1541.
(10) Clancy, S.; Shriver, D.F.; Ochrymowycz, L.A. Macromolecules 1986, 19, 606–611.
(11) Wang, L.; Kilcher, G.; Tirelli, N. Macromol. Chem. Phys. 2009, 210, 447–456.
(12) (a) Crafts, J.M. Justus Liebigs Ann. Zhem. 1862, 124, 110–114; (b) Meyer, V. Ber. Dtsch. Chem. Ges. 1886, 19,
3259–3266.
(13) Russo, M.; Mortillaro, L.; De Cecchi, C.; Valle, G.; Mammi, M. J. Polym. Lett. Ed. 1965, 3, 501–504.
(14) Landini, D.; Rolla, F. Synthesis 1974, 565–566.
(15) Montaudo, G.; Puglisi, C.; Scamporrino, E.; Vitalini, D. Macromolecules 1986, 19, 2689–2692.
(16) Imai, Y.; Kato, A.; Ii, M.; Ueda, M. J. Polym. Sci. Polym. Lett. Ed. 1979, 17, 579–583.
(17) Ueda, M.; Oishi, Y.; Sakai, N. Macromolecules 1982, 15, 248–251.
(18) See for example: (a) Metwally, M.A.; Khalifa, M.E.; El-Hiti, G.A. J. Sulfur Chem. 2010, 31, 205–229; (b) Smith, K.;
Barratt, M.L. J. Org. Chem. 2007, 72, 1031–1034; (c) Smith, K.; El-Hiti, G.A.; Hegazy, A.S. J. Sulfur Chem. 2005,
26, 121–131; (d) Smith, K.; El-Hiti, G.A.; Mahgoub, S.A. Synthesis 2003, 2345–2348; (e) El-Hiti, G.A. Sulfur Rep.
2001, 22, 217–250; (f) Smith, K.; Tzimas, M.; Brown, C.M.; Payne, K. Sulfur Lett. 1999, 22, 89–101; (g) Smith,
K.; Tzimas, M.; Brown, C.M.; Payne, K. Sulfur Lett. 1999, 22, 103–123; (h) Smith, K.; Shukla A.P.; Matthews, I.
Sulfur Lett. 1996, 20, 121–137; (i) Smith, K.; Hou, D. J. Org. Chem. 1996, 61, 1530–1532; (j) Smith, K.; Anderson,
D.; Matthews, I. J. Org. Chem. 1996, 61, 662–665; (k) Abdel-Megeed, M.F.; Aly, Y.L.; Saleh, M.A.; Abdo, I.M.;
El-Hiti, G.A.; Smith, K. Sulfur Lett. 1995, 19, 129–140; (l) Smith, K.; Tzimas, M. J. Chem. Soc. Perkin Trans. 1995,
1, 2381–2382; (m) Smith, K.;Anderson, D.; Matthews, I. Sulfur Lett. 1995, 18, 79–95; (n) Smith, K.; Lindsay, C.M.;
Morris, I.K.; Matthews, I.; Pritchard, G.J. Sulfur Lett. 1994, 17, 197–216.
(19) Smith, K.; Balakit, A.A.; Pardasani, R.T.; El-Hiti, G.A. J. Sulfur Chem. 2011, 32, 287–295.
(20) Sundarrajan, S.; Srinivasan, K.S.V. Macromol. Rapid Commun. 2004, 25, 1406–1409.
(21) Sonavane, S.U.; Chidambaram, M.; Khalil, S.; Almog, J.; Sasson, Y. Tetrahedron Lett. 2008, 49, 520–522.
(22) Ali, M.; McDermott, M. Tetrahedron Lett. 2002, 43, 6271–6273.
(23) Clayden, J.; Greeves, N.; Warren, S.; Wothers, P. Organic Chemistry; Oxford University Press: Oxford, UK, 2001.