Reactions of thiols and organic sulfides with hydrogen in the presence of iron powder

Article abstract of DOI:10.1007/s11172-006-0435-4

Previously unknown reduction of thiols to hydrocarbons and H₂S with hydrogen formed by the interaction of powdered iron with dilute HCl was found.

Full text of DOI:10.1007/s11172-006-0435-4

Russian Chemical Bulletin, International Edition, Vol. 55, No. 8, pp. 1433—1435, August, 2006
1433
Reactions of thiols and organic sulfides with hydrogen
in the presence of iron powder
G. F. Pavelko
A. V. Topchiev Institute of Petrochemical Synthesis, Russian Academy of Sciences,
2
9 Leninsky prosp., 119991 Moscow, Russian Federation.
Eꢀmail: pavelko@ips.ac.ru
Previously unknown reduction of thiols to hydrocarbons and H S with hydrogen formed by
2
the interaction of powdered iron with dilute HCl was found.
Key words: thiols, organic sulfides, disulfides, trisulfides, hydrogen, iron.
Organic disulfides in a mixture of chlorohydrocarbons
are efficient additives to mineral oils that decrease friction
and attrition wear of steel surfaces. As a result of the
3 times increased the yield of H S by 2.8 times (cf. enꢀ
2
tries 12 and 14). When thiol 1d is reduced with the iron
powder preliminarily wetted with water, the yield of H2S
decreases by 3.5 times (cf. entries 18 and 19).
boundary friction they decompose to evolve H S and HCl,
2
respectively, and the mobile hydrogen atom in hydrocarꢀ
Unlike disulfide 3a containing nꢀbutyl radicals, steriꢀ
cally hindered disulfide 3b is not reduced with hydrogen,
bons reacts with air oxygen to form H O. Therefore, it
2
was of interest to reveal whether thiols and organic sulꢀ
fides, disulfides, and trisulfides can be reduced to H2S
with hydrogen formed by the reaction of HCl with iron.
In the present work, we studied the reduction of thiols
and wetting Fe with water decreases the yield of H S in
2
the case of reduction of thiol 1d. Therefore, it can be
assumed that only the molecules adsorbed on the Fe surꢀ
face are reduced. In this case, organic disulfides are reꢀ
duced with hydrogen to thiols, which then interact with
the Fe surface purified from oxides using the chemical
method. In fact, the formation of soꢀcalled "selfꢀassembled
monolayers" of Fe thiolates already at 100—150 K was
found in numerous works (see, e.g., Refs 1 and 2) on the
interaction of thiols with the surface of Fe single crystals
under ultrahighꢀvacuum conditions. At 256—298 K iron
thiolates decompose to form FeS and the corresponding
saturated or unsaturated hydrocarbons.
(
RSH) 1a—e, sulfides (R S) 2d,e, disulfides (R S ) 3a—e,
2 2 2
t
trisulfides (R S ) 4a,b (R = Bu (a), Bu (b), Dd (doꢀ
2
3
decyl, c), Bn (d), and Ph (e)), and Oꢀcontaining iron
thiolates C H Fe O S (5) and C H Fe O S (6) with
1
0
24
2
6
14 16
3
7 2
hydrogen.
Results and Discussion
The results of quantitative determination of H S are
2
3
presented in Table 1. It is seen that monosulfides 2d,e and
sterically hindered disulfide 3b are not reduced with hydroꢀ
In the previous work, we have shown that in the
reaction with the powder of reduced iron thiols 1d,e form
iron dithiolates (IDT) at room temperature, and thiol 1e
exceeds thiol 1d in reactivity, which is undoubtedly reꢀ
lated to a higher acidity of thiol 1e compared to thiol 1d.
It is found in the present work that these thiols, when
gen to H S. For the reduction of sterically hindered trisulꢀ
2
fide 4b, the yield of H S is by 15 times lower than that for
2
the reduction of trisulfide 4a (cf. entries 5 and 10) conꢀ
taining unbranched butyl radicals. Upon the addition of
pentane, the yield of H S during the reduction of thiols
reduced with hydrogen, form mostly H S (cf. entries 17,
2
2
1
a,b decreases, which is caused, most likely, by the reꢀ
18, 24, and 25); however, thiol 1d exceeds thiol 1e
in reactivity, which is caused, most likely, by the higher
nucleophilicity of thiol 1d compared to thiol 1e
(see Ref. 4).
To compare amenability of hydrogen reduction of the
C—S bond in IDT and disulfides, we synthesized and
reduced Oꢀcontaining thiolates 5 and 6.
moval of thiols with volatile pentane from the reaction
mixture. The improvement of conditions for contact of
powdered iron with reduced compounds in a pentane
solution exerts virtually no effect on the yield of H2S
during the reduction of thiols 1c—e and disulfide 3a
(
cf. entries 12 and 13, 17 and 18, 24 and 25, 3 and 4). For
the reduction of disulfide 3d and trisulfides 4a and 4b, the
The IDT samples are very sensitive to O . In the indiꢀ
2
yield of H S increases by 5.8, 2.1, and 3 times, respecꢀ
tively (cf. entries 21 and 22, 5 and 6, 10 and 11). When
thiol 1c is reduced, the increase in the Fe : 1c ratio by
vidual state some of them are reduced with ignition and,
hence, Oꢀcontaining thiolates 5 and 6, which are more
stable in open air, were used for reduction with hydrogen.
2
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1380—1382, August, 2006.
066ꢀ5285/06/5508ꢀ1433 © 2006 Springer Science+Business Media, Inc.
1

1434
Russ.Chem.Bull., Int.Ed., Vol. 55, No. 8, August, 2006
G. F. Pavelko
Table 1. Yields of H S in the reduction of organosulfur comꢀ
pounds (OSC)
where R = Alk, Bn, or Ph; (Fe) is the Fe powder on
which thiols are chemisorbed. When thiol 1d is reduced
2
n
with hydrogen evolved upon the interaction of Na with
Entry
OSC
mOSC
Condiꢀ
V b
/mL
Yield
5
anhydrous EtOH, H S and dibenzyl are formed, indicatꢀ
tionsa
2
/
g
of H S (%)
2
ing a possibility of another reduction mechanism.
1
2
3
4
5
6
7
8
9
BuSH (1a)c
1a
0.1076
0.1021
0.1028
0.1020
0.1015
0.1001
0.1009
0.1000
0.1011
0.1002
0.1005
0.0997
0.1011
0.1051
0.1013
0.1017
0.1003
0.1022
0.1001
0.0979
0.1014
0.0993
0.1010
0.1011
0.1108
0.1009
0.0999
+
–
+
–
+
–
+
–
+
+
–
+
–
+
+
–
+
–
–
+
+
–
–
+
–
–
+
2.3
4.1
1.1
1.0
1.8
0.5
0.6
9.1
4.3
0.3
1.6
0.0
0.6
0.2
1.9
1.9
5.4
1.6
8.3
37.1
35.8
10.5
0.0
4.1
0.7
36.7
5.9
5.4
0.0
2.9
The quantitative determination of H S formed by the
2
reduction of thiols and disulfides with hydrogen showed
that the reduction of compounds 1a,b,d,e and 3a,d begins
already at room temperature, and the initial reduction of
compounds 1c and 3c,e is observed only after heating the
initial mixture of the reactants.
The formation of hydrocarbons, in particular, toluene
upon the reduction of thiol 1d, was confirmed by GLC.
Thus, the earlier unknown reaction of reduction of
Bu S (3a)
2
2
3a
1.4
Bu S (4a)
26.3
12.4
0.6
3.5
0.0
1.8
0.7
1.8
1.9
5.6
1.6
4.4
59.8
57.5
16.9
0.0
6.8
1.2
2
3
4a
t
c
Bu SH (1b)
1b
t
Bu S (3b)
2
2
t
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
Bu S (4b)
2
3
4b
thiols to hydrocarbons and H S with hydrogen formed
2
DdSH (1c)
upon the interaction of dilute HCl with the Fe powder
was found.
1c
1c
d
Dd S (3c)
2
2
Experimental
5
BnSH (1d)
1d
1d
Identification of PhCH formed upon the formation of comꢀ
e
3
pound 1d was carried out on a ‹‹Chromꢀ4 chromatograph (glass
column 2.5 m×3 mm, Chromaton NꢀAW + 15% Apieson L,
Bn S (2d)
2
Bn S (3d)
2
2
1
60 °C, carrier gas He).
3d
6
The FTꢀIR spectrum of Oꢀcontaining thiolate 6 was reꢀ
corded on a Magnaꢀ750 instrument (Nicolet).
Compounds 1a—e, 2d,e, and 3a (highꢀpurity grade) were
additionally purified by fractional distillation using Fe (special
purity grade 6ꢀ2). Reactants 3b—e and 4a,b were synthesized by
known methods.6
29.4
10.6
10.7
0.0
PhSH (1e)
1e
Ph S (2e)
2
Ph S (3e)
5.3
2
2
a
Reduction of compounds 1a—e, 2d—e, 3a—e, and 4a,b. The
reaction was carried out in a device consisting of a 100ꢀmL
conic flask equipped with a reflux condenser, a dropping funnel,
Sign "+" means that the solvent (pentane) was preliminarily
added to the reaction mixture and then evaporated in vacuo;
"
b
–" indicates that no solvent was added.
and tubes for gas supply and removal. The H S that formed was
Volume of a 0.01 М solution of I2.
Pentane was not evaporated in vacuo.
A weighed sample of the Fe powder was 3 g; in all other
2
c
displaced with argon and absorbed by a 10% solution of CdCl2.
Powdered Fe (1.00 g), a compound under study (0.1 g), and
pentane (1 mL) were placed in the flask. The mixture was slightly
stirred for 1—2 min, the solvent (except for experiments with
thiols 1a,b) was evaporated in vacuo, after which the flask was
connected to the reflux condenser, and argon was passed through
the device (50 mL min– ). Hydrochloric acid (40 mL) diluted
with water (1 : 1) was added to the dropping funnel, and in
10 min the rate of passing argon was decreased to 10—15 gas
bubbles per min, after which the acid was added to the flask.
Hydrogen began to evolve at room temperature but the reaction
mixture was slightly heated to accelerate the evolution. After all
the Fe dissolved, the flask content was heated to boiling
d
entries, 1 g.
e
Water (1 mL) was first added to the Fe powder, then the
reduced compound was added, and finally dilute HCl was added.
1
As can be seen from the data in Table 1, Oꢀcontaining
thiolates 5 and 6 form more H S than disulfides 3c,d
2
(
cf. entries 15 and 16, 22 and 23) containing similar
radicals.
The reduction of thiols with hydrogen formed by the
interaction of the iron powder with dilute HCl can be
presented, most likely, by the following schemes:
(
2—3 min). Heating was stopped, the rate of bubbled argon was
increased, and the gas was continued to pass for 30 min more.
A precipitate of CdS was separated by filtration through a folded
paper filter and washed first with distilled water and then
Fe + 2 HCl
FeCl + H ,
2 2
R—SH + (Fe)n
R—S—(Fe) —H,
n
with EtOH. The amount of evolved H S in the decomposition of
2
R—S—(Fe) —H + H2
(Fe) + R—H + H S
CdS with concentrated HCl was determined iodometrically usꢀ
n
n
2
ing titrated 0.01 N solutions of I and Na S O (see Ref. 7).
2
2
2
3
or, taking into account published data,2
OꢀContaining thiolate 5. Weighed samples of FeCl •2H O
2 2
(
(
0.30 g, 1.8 mmol), compound 1c (1.00 g, 4.9 mmol), and Et N
0.7 mL, 5.0 mmol) were dissolved in 25, 15, and 10 mL of
3
R—S—(Fe) —H
FeS + (Fe)n–1 + R—H,
FeCl + H S,
n
FeS + 2 HCl
EtOH, respectively. Each solution was refluxed under Ar atmoꢀ
2
2

Reduction of thiols with hydrogen
Russ.Chem.Bull., Int.Ed., Vol. 55, No. 8, August, 2006
1435
sphere and sealed. All the three solutions were placed in a box
filled with Ar and mixed in a 100ꢀmL flask, which was hermetiꢀ
cally closed. The reaction mixture was magnetically stirred
for 1 h. Next day iron bis(dodecanethiolate) that formed was
filtered off in air with suction through a porous glass filter. The
precipitate was washed with EtOH and benzene and dried
in vacuo. A dark green oxygenꢀcontaining amorphous substance
was obtained. Found (%): C, 29.90; H, 6.14; Fe, 31.97; S, 8.03.
C H Fe O S. Calculated (%): C, 31.27; H, 6.30; Fe, 29.08;
added to the mixture. The mixture was stirred, the solvent was
evaporated in vacuo, several drops of dilute (1 : 1) HCl was
added to the residue, and a filter paper wetted with a 1% aqueꢀ
ous solution of AgNO was immediately introduced. If hydrogen
3
did not begin to evolve at room temperature, the mixture was
heated. The indicator paper became dark brown or black in
5—10 s. The indicator paper placed in a gaseous medium of
two—three drops of thiols 1b, 1d, and 1e gains light pink, light
brown, and light yellow colors, respectively. Thiol 1а and disulꢀ
fides impart no color to the indicator paper. (The filter paper
that was not stored in open air under laboratory conditions
should be used in the experiments).
10
24
2
6
S, 8.35. The oxygen content depends on the duration of filtraꢀ
tion and washing. Dry Oꢀcontaining thiolate 5 in open air is
oxidized within several days to disulfide 3c and Fe O and turns
2
3
brown.
OꢀContaining thiolate 6 was synthesized similarly to
thiolate 5. Its element composition is variable. Being in the dry
state in open air and in water, the substance remains unchanged
without color change for many years. Found (%): C, 30.75;
H, 3.20; Fe, 31.57; S, 12.25. C H Fe O S . Calculated (%):
References
1
. L. Cheng, S. L. Bernasek, and A. B. Bocarsly, Langmuir,
995, 7, 1807.
2. J. D. Batteas, T. S. Rufael, and C. M. Friend, Langmuir,
999, 15, 2391.
. G. F. Pavelko, Izv. Akad. Nauk, Ser. Khim., 2006, 1383 [Russ.
Chem. Bull., Int. Ed., 2006, 55, 1436].
1
14
16
3
7 2
–
1
C, 31.85; H, 3.05; Fe, 31.73; S, 12.14. FTꢀIR, ν/cm : 258, 324,
1
3
1
40, 478, 697, 764, 915, 1029, 1066, 1193, 1216, 1419, 1452,
494, 1599, 2853, 2923, 3026, 3060, 3083, 3383. When anhydrous
3
FeCl and absolute EtOH are used for the synthesis of 6, the
2
–
1
4. S. Oae, Khimiya Organicheskikh Soedinenii Sery [Chemistry of
Organic Sulfur Compounds], Khimiya, Moscow, 1975, p. 66
spectrum contains no broad absorption band at 3383 cm
.
Thermal decomposition of Oꢀcontaining thiolates 5 and 6.
Wet compound 5 (0.2 g) or dry compound 6 (0.10 g) was placed
in a device for sublimation and gradually heated to 300 °C in a
vacuum <1 Torr. Several drops of dilute (1 : 1) HCl were added
to the residue after decomposition, which was placed in a 10ꢀmL
(
Russ. Transl. from Japanese).
5
6
. C. G. Moses and E. E. Reid, J. Am. Chem. Soc., 1926, 48, 776.
. Methoden der Organischen Chemie, Houben—Weil, Georg
Thieme Verlag, Stuttgart, 1955, B. 9, 1337 S.
. Metody Issledovaniya Neftei i Nefteproduktov [Methods of Inꢀ
vestigation of Petroleum and Petrochemicals], Collection of
Works, Ed. L. A. Potolovskii, Gostoptekhizdat, Moscow, 1955,
p. 264 (in Russian).
7
tube. A filter paper wetted with a 1% solution of AgNO was
3
introduced into the tube. In both experiments, the filter paper
blackened immediately, indicating that compounds 5 and 6 conꢀ
tain the Fe—SDd and Fe—SBn thiolate bonds.
Procedure of qualitative reaction to H S. Two—three drops
2
of the liquid (or 0.02 g of solid) tested substance were placed in a
narrow tube. In the latter case, several drops of pentane were
Received July 25, 2005;
in revised form July 21, 2006