Formation of diphenyl sulfoxide and diphenyl sulfide via the aluminum chloride-facilitated electrophilic aromatic substitution of benzene with thionyl chloride, and a novel reduction of sulfur (IV) to sulfur (II)

Article abstract of DOI:10.1080/10426501003733849

The aluminum chloride (AlCl₃)-facilitated electrophilic aromatic substitution (EAS) reaction of benzene (PhH) with thionyl chloride (SOCl ₂) in the molar ratio of PhH:SOCl₂:AlCl₃ = 2:1:1 was studied under different conditions. At about 70C, adding granular AlCl₃ (equimolar to SOCl₂) piecewise to a 2:1 mixture of PhH and SOCl₂ led to formation of a highly pure (99.9%) sole product of diphenyl sulfoxide (Ph₂SO) in an isolated yield of 85% after aqueous workup. It represents a simple and very efficient synthesis of Ph ₂SO, an important fundamental organic reagent. At about 0C, adding PhH (twice the molar quantity of SOCl₂) to a 1:1 mixture of SOCl ₂ and AlCl₃ gave both diphenyl sulfide Ph₂S (yield: 37%) and Ph₂SO (yield: 27%) after aqueous workup, together with a small amount of S-phenyl benzenesulfonothioate PhSO₂SPh (yield: about 5%) and a trace amount of diphenyl sulfone (Ph₂SO ₂). A possible mechanism has been proposed to account for formation of all these products, especially for the formation of Ph₂S [S (II)] from SOCl₂ [S (IV)], which involves a novel reduction of sulfur in the course of the EAS reaction. Taylor & Francis Group, LLC.

Full text of DOI:10.1080/10426501003733849

Phosphorus, Sulfur, and Silicon, 185:2535–2542, 2010
Copyright ꢀC Taylor & Francis Group, LLC
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426501003733849
FORMATION OF DIPHENYL SULFOXIDE AND DIPHENYL
SULFIDE VIA THE ALUMINUM CHLORIDE–FACILITATED
ELECTROPHILIC AROMATIC SUBSTITUTION OF
BENZENE WITH THIONYL CHLORIDE, AND A NOVEL
REDUCTION OF SULFUR (IV) TO SULFUR (II)
Xiaoping Sun, David Haas, Kayanna Sayre, and Donald Weller
Department of Natural Science and Mathematics, University of Charleston,
Charleston, West Virginia, USA
The aluminum chloride (AlCl3)–facilitated electrophilic aromatic substitution (EAS) reac-
tion of benzene (PhH) with thionyl chloride (SOCl2) in the molar ratio of PhH:SOCl2:AlCl3
= 2:1:1 was studied under different conditions. At about 70◦C, adding granular AlCl3
(equimolar to SOCl2) piecewise to a 2:1 mixture of PhH and SOCl2 led to formation of a
highly pure (99.9%) sole product of diphenyl sulfoxide (Ph2SO) in an isolated yield of 85%
after aqueous workup. It represents a simple and very efficient synthesis of Ph2SO, an im-
portant fundamental organic reagent. At about 0◦C, adding PhH (twice the molar quantity
of SOCl2) to a 1:1 mixture of SOCl2 and AlCl3 gave both diphenyl sulfide Ph2S (yield: 37%)
and Ph2SO (yield: 27%) after aqueous workup, together with a small amount of S-phenyl
benzenesulfonothioate PhSO2SPh (yield: about 5%) and a trace amount of diphenyl sulfone
(Ph2SO2). A possible mechanism has been proposed to account for formation of all these
products, especially for the formation of Ph2S [S (II)] from SOCl2 [S (IV)], which involves
a novel reduction of sulfur in the course of the EAS reaction.
Keywords Diphenyl sulfide; diphenyl sulfoxide; EAS; reduction; sulfur; thionyl chloride
INTRODUCTION
Diphenyl sulfoxide (Ph2SO) and diphenyl sulfide (Ph2S) are important reagents in
organic synthesis.1,2 Ph2S is commonly synthesized by the reaction of benzene (PhH) with
disulfur dichloride (S2Cl2) in the presence of anhydrous aluminum chloride (AlCl3).3 It
gives a good yield, but the method is complex and tedious. Ph2SO, on the other hand, is
usually made by catalytic oxidation of Ph2S.4,5 The preparation often suffers with overoxi-
dation to the diphenyl sulfone (Ph2SO2) side product. In order to overcome this difficulty,
a different method was developed by the reaction of Ph2S with sulfuryl chloride (SO2Cl2),
which gives moderate yield of Ph2SO after crystallization.6 In this article, we report a sim-
ple synthesis of Ph2SO by the AlCl3-catalyzed Friedel–Crafts reaction of PhH with thionyl
chloride (SOCl2). Upon mild heating (70◦C) and by optimizing the manner of mixing
Received 21 January 2010; accepted 25 February 2010.
Address correspondence to Xiaoping Sun, Department of Natural Science and Mathematics, University of
Charleston, Charleston, WV 25304, USA. E-mail: xiaopingsun@ucwv.edu
2535

2536
X. SUN ET AL.
the starting materials, this reaction (after aqueous workup) has led to efficient formation
of highly pure Ph2SO (99.9%) as a sole product in an isolated yield of 85%. Olah and
Nishimura7 have studied the AlCl3-catalyzed electrophilic aromatic substitution (EAS) re-
actions of benzene and toluene with arenesulfonyl chlorides (ArSOCl), which is analogous
to SOCl2. The reactions gave various aryl sulfoxides at 25◦C. However, no study of the
AlCl3-catalyzed EAS reactions of arenes including benzene and toluene with SOCl2 had
been reported prior to our current work. Among other things, to our surprise, when the
reaction was performed at 0◦C and the manner of mixing the starting materials was altered,
Ph2S was formed as a major product in a significant yield. Clearly, formation of Ph2S [S
(II)] in the reaction of PhH with SOCl2 [S (IV)] in the presence of AlCl3 was accompanied
by reduction of sulfur, which is the electrophilic center for the EAS reaction. Such an
aromatic C–H bond functionalization is unprecedented. The current study of reaction of
benzene with thionyl chloride aided by aluminum chloride is of significance in both organic
synthesis and mechanisms.
RESULTS AND DISCUSSION
Benzene has been shown to undergo general extensive EAS reactions with chlorine,
alkyl chlorides, and acyl chlorides in the presence of AlCl3 giving chlorobenzene, alkylben-
zenes, and aromatic ketones, respectively.8,9 Similar to the above EAS reactions, especially
analogous to the reactions of acyl chlorides (RCOCl), SOCl2 was initially expected to
undergo double consecutive EAS (Fiedel–Crafts) reactions with PhH in the presence of
AlCl3 as a catalyst to give Ph2SO as shown below when the starting materials were mixed
in the molar ratio of PhH:SOCl2:AlCl3 = 2:1:1.
AlCl3
2PhH + SOCl2 −−−−−−−→ Ph2SO + 2HCl
(Rxn1)
However, only under carefully selected and controlled conditions did this reaction give a
sole product Ph2SO as shown in Rxn. (1). In many other cases, depending on the tem-
perature and the manner in which the starting materials were actually mixed, this reaction
was shown (Table I) to usually give several products, including Ph2SO, Ph2S, S-phenyl
benzenesulfonothioate (PhSO2SPh), and Ph2SO2, in various yields. A possible mechanism
has been proposed to account for formation of all these products (Figure 1).
Formation of Ph2SO via Approach (A)
When granular AlCl3 (equimolar to SOCl2) was added in aliquots (piecewise) to a
2:1 (molar ratio) mixture of PhH and SOCl2 at about 70◦C, the reaction gave a highly
pure (99.9%) sole product of Ph2SO [Rxn. (1)] in an isolated yield of 85% after aqueous
workup. The high yield and outstanding purity of the Ph2SO product indicated that the
reaction followed the double consecutive EAS mechanism under the applied conditions.
First, as established previously,10,11 SOCl2 and AlCl3 combined to form a Cl2SO-AlCl3
zwitterionic adduct via an O→Al coordination bond (Figure 1). After the Cl2SO-AlCl3
adduct completed an EAS reaction with the first benzene molecule, the intermediate product
(PhSOCl-AlCl3) was immediately attacked by a second benzene molecule (Approach A),
exclusively effecting another EAS reaction to give Ph2SO. The postulated approaches (B)
and (C) did not occur. When SOCl2 (equimolar to AlCl3) was added in aliquots (dropwise)
to a 2:1 (molar ratio) mixture of PhH and AlCl3 at about 25◦C, the reaction also gave a pure

FORMATION OF DIPHENYL SULFOXIDE AND DIPHENYL SULFIDE
2537
Table I Product distribution (after aqueous workup) for reaction of benzene (PhH) and thionyl chloride (SOCl2)
in the presence of aluminum chloride (AlCl3) with the molar ratio of PhH:SOCl2:AlCl3 = 2:1:1 under different
conditions
Temp
(◦C)
Ph2SO
(yield)
Ph2S
(yield)
Ph2SO2SPh
(yield)
Ph2SO2
(yield)
Manner of mixing
70
25
25
25
0
AlCl3 added piecewise to the PhH-SOCl2 85% (isolated) 0%
mixture
0%
0%
AlCl3 added piecewise to the PhH-SOCl2 75% (GC)
3% (GC) 5% (GC)
Trace amount
0%
mixture
SOCl2 added dropwise to the PhH-AlCl3
78% (isolated) 0% 0%
mixture
PhH poured at once into the SOCl2-AlCl3 52% (GC)
mixture
AlCl3 added piecewise to the PhH-SOCl2 75% (GC)
mixture
22% (GC) 5% (GC)
5% (GC) 5% (GC)
6% (GC) 5% (GC)
37% (GC) 5% (GC)
Trace amount
Trace amount
Trace amount
Trace amount
0
SOCl2 added dropwise to the PhH-AlCl3
mixture
72% (GC)
0
PhH poured at once into the SOCl2-AlCl3 27% (GC)
mixture
(99%) sole product of Ph2SO [Rxn. (1)] in an isolated yield of 78% after aqueous workup.
The results again indicated almost exclusive double consecutive EAS reactions of benzene
with the Cl2SO-AlCl3 adduct via approach (A). Approaches (B) and (C) essentially did
not take place. In each of these cases, because AlCl3 or SOCl2 was added in aliquots, the
Cl2SO-AlCl3 adduct was in deficit relative to the quantity of benzene during the overall
reaction. As a result, the first EAS product (PhSOCl-AlCl3) remained at low concentration.
Therefore, the postulated intramolecular (unimolecular) and intermolecular (bimolecular)
auto-redox processes (B and C, respectively) would reasonably be thought to be too slow to
actually take place. Instead, after PhSOCl-AlCl3 was produced from the first EAS reaction,
it was immediately attacked by the excessive benzene (Approach A) exclusively to give
Ph2SO as a sole product.
Traditionally, Ph2SO has been made by catalytic oxidation of Ph2S.4,5 Ph2S is com-
monly prepared by reaction of benzene with S2Cl2 in the presence of AlCl3.3 In this work,
a more direct, simpler, and perhaps more efficient route to the synthesis of a high yield
of Ph2SO has been developed via the EAS reaction of benzene with SOCl2 catalyzed by
AlCl3. Because of the simplicity of the reaction mechanism, side reactions only took place
to a very minimal extent (indicated by the green color but removed readily by aqueous
workup), and high purity of Ph2SO has been produced without any further purification
process.
At lower temperatures such as 25◦C and 0◦C (Table I), when AlCl3 was added
piecewise to a PhH:SOCl2 = 2:1 mixture, the reactions gave small amounts of Ph2S
(yield: 3–5%], PhSO2SPh (yield: about 5%), and Ph2SO2 (trace amount) in addition to
the major product Ph2SO (yield: about 75%). When SOCl2 was added dropwise to a
PhH:AlCl3 = 1:1 mixture at 0◦C, essentially, the same situation was found. All this indicated
(Figure 1) that higher temperatures favor approach (A), leading to formation of Ph2SO,
while lower temperatures favor approaches (B) and (C), leading to formation of Ph2S and
PhSO2SPh.

2538
X. SUN ET AL.
-
AlCl3
:O:
+
O
(Cl2SO_AlCl3)
S
AlCl3
+
Cl
H
Cl
S
Cl
Cl
-
-
AlCl3
AlCl3
+
O
:
O:
-
H
AlCl3
+
O
S
EAS
Cl
Cl
S
+
Ph
Cl
S
-
HCl
(PhSOCl_AlCl3)
Cl
Cl
+
(PhH)
-
-
AlCl3
+
O
AlCl3
+
O
O
S
PhH, EAS
HCl
H2O
(A)
(B)
(C)
S
S
Ph
Cl
-
Ph
Ph
Ph
Ph
(Ph2SO)
Or
Cl
Cl
Cl
Cl
-
Al
Al
+
O
O
S
-
Al(OH)Cl2
EAS
Cl
S
Auto-redox
Cl2
S
Ph
Ph
Ph
Cl
Ph
H
-
(Ph2S)
S (II)
S (IV)
Or
-
-
-
AlCl3
AlCl3
AlCl3
+
O
+
O
+
O
S
S
S
Auto-redox
S
Cl
Cl
+
Ph
Ph
Cl
Cl
Ph
Ph
+
O
-
+
AlCl3
S (IV)
S (IV)
S (VI)
(i)
S (II)
EAS
-
Cl2 (ii)
-
AlCl3
PhH
(work-up)
H2O
O
O
S
Ph
S
Ph
S
Ph
Ph
O
O
(PhSO2Ph)
(PhSO2SPh)
A trace amount
Figure 1 Proposed mechanism for the aluminum chloride (AlCl3)–facilitated electrophilic aromatic substitution
of benzene (PhH) with thionyl chloride (SOCl2), possibly giving several products.

FORMATION OF DIPHENYL SULFOXIDE AND DIPHENYL SULFIDE
2539
Formation of Ph2S via a Possible Auto-Redox Process (Approach B)
Since under certain conditions and at relatively low temperatures reaction of PhH
with SOCl2 in a 2:1 molar ratio in the presence of AlCl3 led to formation of Ph2S in
various yields in addition to Ph2SO (Table I), attempted preparation of Ph2S by a simple
EAS reaction of benzene with SOCl2 by the aid of AlCl3 was performed at about 0◦C.
Having found that maintaining the Cl2SO-AlCl3 adduct (Figure 1) in deficit relative to the
quantity of benzene facilitates approach (A) (formation of Ph2SO), but disfavors approach
(B) (formation of Ph2S), an opposite manner of mixing the starting materials was employed.
PhH (twice the molar quantity of SOCl2) was poured all at once into a 1:1 (molar ratio)
mixture of SOCl2 and AlCl3 at about 0◦C. The reaction led to formation of both Ph2S (yield:
37%) and Ph2SO (yield: 27%) after an aqueous workup. In addition, a minor amount of
PhSO2SPh (yield: about 5%) and a trace amount of Ph2SO2 were formed.
0◦C
H2O
2PhH+SOCl2 +AlCl3 −−−→ −−−→Ph2S + Ph2SO + PhSO2SPh + PhSO2Ph (Rxn2)
37% 27% about 5% trace amount
It is interesting to notice that formation of Ph2S containing S (II), a major product of
Rxn. (2) in a significant yield, from SOCl2 containing S (IV) involved a reduction process
in the sulfur atom, while no reducing agent was added to the reaction system. We believe
that the first EAS product (PhSOCl-AlCl3), after being formed, might undergo a major
fast intramolecular auto-redox reaction (approach B) eventually giving Ph2S (Figure 1) in
addition to forming Ph2SO via approach (A). An Al–Cl bond in PhSOCl-AlCl3 (the first
EAS product) can reasonably be a chloride (Cl−) donor (nucleophilic). The S–Cl chlorine
atom is apparently activated by the electronegative sulfoxide (S O) group, possibly being
electrophilic and readily attacked by the Al–Cl chloride to give Cl2. Formation of Cl2 in the
reaction was experimentally identified.12 S (IV) was in turn reduced to S (II). In this reaction,
because benzene was added all at once to a 1:1 SOCl2–AlCl3 mixture, the concentration
of PhSOCl-AlCl3 was relatively high. Approach (B) could possibly take place rapidly as
a major process to give Ph2S. In this process, high affinity of aluminum to oxygen was
believed to aid cleavage of the S–O bond (removal of oxygen from sulfur), facilitating a
second EAS reaction. Concurrently, approach (A) also took place to a substantial extent
giving Ph2SO.
When the reaction was performed at 25◦C in the same manner, the product distribution
(52% Ph2SO, 22% Ph2S, and 5% PhSO2SPh) indicates (Figure 1) a substantial increase in
the ratio of Ph2SO:Ph2S relative to that at 0◦C (37% Ph2SO and 27% Ph2S). The results
demonstrate that at 25◦C, approach (A) became the major process and approaches (B) and
(C) were minor processes.
A postulated minor intermolecular auto-redox (oxygen exchange) process between
two PhSOCl-AlCl3 molecules (approach C) has been proposed (Figure 1) to account for the
formation of a small amount of PhSO2SPh and a trace amount of Ph2SO2. The postulated
S (VI) species was believed to be reasonably responsible for the formation of Ph2SO2
via an EAS reaction with benzene. p-Toluenesulfonyl chloride [analogous to the S (VI)
species] has been previously shown to undergo aluminum chloride–catalyzed EAS reactions
with benzene and toluene giving sulfone (analogous to Ph2SO2) products.13 On the other
hand, identification of Ph2SO2 as a reaction product supported formation of the S (VI)
species in the course of the reaction. The combination of the S (VI) and S (II) species
(sulfonothioesterification) might possibly be responsible for formation of PhSO2SPh.

2540
X. SUN ET AL.
EXPERIMENTAL
Chemical Reagents
Thionyl chloride (SOCl2) (purified) from J.T. Baker Chemical Company was used.
Benzene (PhH) (99.9%) was obtained from Sigma Aldrich. Granular anhydrous aluminum
chloride (AlCl3) (99%, extra pure) and both the authentic diphenyl sulfoxide (Ph2SO) (98%)
and diphenyl sulfide (Ph2S) (99%) reagents (GC-MS standards) were obtained from Acros
Organics. Anhydrous sodium sulfate (99.5%, drying agent) and dichloromethane (99.9%,
the solvent for GC-MS samples) were both purchased from Fisher Scientific Company.
The GC-MS Measurements
Reaction products were identified and quantified using a Varian CP-3800 gas
chromatograph–Varian Saturn 2200 mass spectrometer. Reaction products and samples
of Ph2S and Ph2SO reagents were prepared in an approximate 1% (m/m) dilution in
dichloromethane. One µL of this solution was injected onto a Chrompack CP-SIL 8-CB 30
m × 0.25 mm capillary column using a He carrier gas of 1.0 mL/min, a 1/100 injection split
ratio, and a temperature ramp of 150◦C to 240◦C (10◦C/min). All chemical compounds
were eluted in 10 min. For individual samples of the authentic Ph2S and Ph2SO reagents, a
single major peak (over 99%) was identified for each with only a few very low peaks found
less than 1%, indicating the purity of each of the authentic reagents and thermal stability
for Ph2S and Ph2SO at the analysis temperature. The mass spectra of Ph2S and Ph2SO were
consistent with fragmentation patterns available from a NIST database on the instrument.
The retention times and mass spectra of Ph2S and Ph2SO identified by GC-MS in the sam-
ples of various reaction products were found to be consistent with those of the authentic
Ph2S and Ph2SO reagents measured under the same conditions. In the samples of reaction
products, which contained both Ph2S and Ph2SO, their percentages were determined by
comparing the related GC peak areas with those of a sample made up with known contents
of Ph2S and Ph2SO using the authentic reagents. In some experiments, small amounts
of diphenylsulfone (Ph2SO2) and S-phenyl benzenesulfonothioate (PhSO2SPh) were also
determined by comparison of their mass spectra with those on the available NIST database.
Synthesis of Diphenyl Sulfoxide (Ph2SO) by Friedel–Crafts Reactions
Method (1). To an approximately 2:1 (molar ratio) liquid mixture of PhH (2.00 g,
25.6 mmol) and SOCl2 (1.45 g, 12.2 mmol), which had been maintained at about 70◦C using
a hot-water bath, granular AlCl3 (1.63 g, 12.2 mmol) was added in aliquots (piecewise)
as follows (experiment performed in a fumehood): First, one piece of AlCl3 was added to
the PhH–SOCl2 mixture, and gas (HCl) bubbles started to form immediately. The piece of
AlCl3 was crushed using a stirring rod. When most of the piece of AlCl3 had dissolved and
bubbling occurred very slowly, another piece of AlCl3 was added. Each piece of AlCl3 was
crushed before the next piece was added. All the AlCl3 granules were eventually added
at 70◦C into the PhH–SOCl2 mixture piece by piece. In the beginning of the reaction, the
solution was light green. It turned dark green as the reaction went to completion, which was
indicated by ceasing of bubbling after all the AlCl3 had been added. Then water (40 mL)
was poured into the reaction mixture, and the green color disappeared. This was followed
by addition of diethyl ether (20 mL). All the contents were transferred into a separatory
funnel and shaken well to assure the organic product being fully extracted into the ether

FORMATION OF DIPHENYL SULFOXIDE AND DIPHENYL SULFIDE
2541
phase. The ether and water phases were separated. The water phase was extracted by diethyl
ether (20 mL) again. Then all the ether solutions were combined and dried by anhydrous
sodium sulfate. The dried ether solution was filtered off. The diethyl ether was evaporated.
A white crystalline product Ph2SO (2.10 g, 10.4 mmol) was received in an isolated yield
of 85%. The product was characterized by GC-MS, showing that it only contained a sole
compound Ph2SO with a purity of 99.9%.14
The reactions were also performed at room and ice-water temperatures (about 25◦C
and 0◦C, respectively) by mixing the starting materials PhH:SOCl2:AlCl3 = 2:1:1 (molar
ratio) in the same manner. GC-MS showed that the product (after aqueous work-up) from
each experiment contained Ph2SO (Yield: about 75%), the major component, and Ph2S
(yield: 3–5%], PhSO2SPh (yield: about 5%), and (Ph2SO2) (trace amount), the minor
components.
Method (2). Synthesis of Ph2SO was also performed under modified conditions
as follows: With constant stirring, SOCl2 (1.75 g, 14.7 mmol) was added in aliquots
(dropwise) to an approximately 2:1 (molar ratio) mixture of PhH (2.41g, 30.9 mmol) and
AlCl3 (1.96 g, 14.7 mmol) at about 25◦C. The reaction took place quickly, as indicated
by bubbling as above. After all the SOCl2 was added, the reaction went to completion,
which was indicated by cessation of bubbling. Then aqueous workup was performed as
above. Eventually, a white crystalline product Ph2SO (2.30 g, 11.4 mmol) was received
in an isolated yield of 78%. GC-MS showed that the product contained essentially a sole
compound Ph2SO with the purity of 99%.14
For a reaction performed at 0◦C in the same manner, GC-MS showed that the product
contained Ph2SO (yield: 72%) as the major component and Ph2S (yield: 6%), PhSO2SPh
(yield: about 5%), and Ph2SO2 (trace amount) as the minor components.
Attempted Synthesis of Diphenyl Sulfide (Ph2S) by AlCl3-Facilitated
Reaction of PhH and SOCl2
PhH (2.36 g, 30.2 mmol) was poured all at once into a 1:1 (molar ratio) mixture of
SOCl2 (1.71 g, 14.4 mmol) and AlCl3 (1.92 g, 14.4 mmol), which had been maintained
at about 0◦C using an ice-water bath. The contents were stirred at 0◦C. The reaction took
place quickly, indicated by bubbling as above. After the reaction went to completion, which
was indicated by cessation of bubbling, an aqueous workup was performed as above. The
ether solvent was allowed to evaporate completely. A very slightly yellow liquid (1.76 g)
was received. The product was determined by GC-MS to contain Ph2S (yield: 37%) and
Ph2SO (yield: 27%).15 In addition, a small amount of PhSO2SPh (yield: about 5%) and a
trace amount of PhSO2Ph were identified by GC-MS.
For a reaction performed at 25◦C in the same manner, GC-MS showed that the product
contained Ph2SO (yield: 52%) as the major component and Ph2S (yield: 22%), PhSO2SPh
(yield: about 5%), and PhSO2Ph (trace amount) as the minor components.
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2542
X. SUN ET AL.
6. E. D. Savin and V. I. Nedelkin, Russ. Chem. Bull., 45, 2668–2669 (1996).
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Vol’pin, Russ. Chem. Bull., 45, 1056 (1996).
12. The gas that evolved in such a reaction performed at 0◦C with the molar ratio of PhH:SOCl2:AlCl3
= 2:1:1 was tested by a wet mixture of starch and potassium iodide (KI). The color turned dark
blue immediately, indicating formation of chlorine (Cl2) in the reaction.
13. F. P. DeHaan, P. Y. Ahn, C. R. Kemnitz, S. K. Ma, J. Na, B. R. Patel, R. M. Ruiz, and R. M.
Villahermosa, Int. J. Chem. Kinet., 30, 367 (1998).
14. Purity of the Ph2SO product was determined by comparison of the Ph2SO peak area to the tiny
impurity (Ph2S) peak area. No other impurities were found in GC-MS.
15. The molar ratio of Ph2S:Ph2SO in the isolated product (1.76 g) was determined to be 1.4:1 by
comparison of the related GC peak areas. Ph2S (37%) and Ph2SO (27%), the percent yields
based on the quantity of SOCl2, were determined according to the total quantity of the isolated
product (1.76 g) and the Ph2S:Ph2SO molar ratio (1.4:1) in the product. By comparison of the
PhSO2SPh GC peak area with that for Ph2SO, the yield of PhSO2SPh in this and all the other
samples containing it was estimated to be about 5%.

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