Disulfur dichloride is the
inorganic compound of
sulfur
Sulfur (or sulphur in British English) is a chemical element with the symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms form cyclic octatomic molecules with a chemical formul ...
and
chlorine
Chlorine is a chemical element with the symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate between them. Chlorine i ...
with the
formula
In science, a formula is a concise way of expressing information symbolically, as in a mathematical formula or a ''chemical formula''. The informal use of the term ''formula'' in science refers to the general construct of a relationship betwe ...
S
2Cl
2.
Some alternative names for this compound are ''sulfur monochloride'' (the name implied by its
empirical formula, SCl), ''disulphur dichloride'' (British English Spelling) and ''sulphur monochloride'' (British English Spelling). S
2Cl
2 has the structure implied by the formula Cl−S−S−Cl, wherein the angle between the Cl
a−S−S and S−S−Cl
b planes is 90°. This structure is referred to as ''gauche'', and is akin to that for
H2O2. A rare
isomer of S
2Cl
2 is S=SCl
2; this isomer forms transiently when S
2Cl
2 is exposed to UV-radiation (see
thiosulfoxides).
Synthesis, basic properties, reactions
Pure disulfur dichloride is a yellow liquid that "smokes" in moist air due to reaction with water. An idealized (but complicated) equation is:
:16 S
2Cl
2 + 16 H
2O → 8 SO
2 + 32 HCl + 3
S8
It is produced by partial chlorination of elemental sulfur. The reaction proceeds at usable rates at room temperature. In the laboratory, chlorine gas is led into a flask containing elemental sulfur. As disulfur dichloride is formed, the contents become a golden yellow liquid:
[F. Fehér "Dichlorodisulfane" in ''Handbook of Preparative Inorganic Chemistry'', 2nd Ed. Edited by G. Brauer, Academic Press, 1963, NY. Vol. 1. p. 371.]
:S
8 + 4 Cl
2 → 4 S
2Cl
2, ''ΔH'' = −58.2 kJ/mol
Excess chlorine produces
sulfur dichloride, which causes the liquid to become less yellow and more orange-red:
:S
2Cl
2 + Cl
2 ↔ 2 SCl
2, ''ΔH'' = −40.6 kJ/mol
The reaction is reversible, and upon standing, SCl
2 releases chlorine to revert to the disulfur dichloride. Disulfur dichloride has the ability to dissolve large quantities of sulfur, which reflects in part the formation of
polysulfane
A polysulfane is a chemical compound of formula , where ''n'' > 1 (although disulfane () is sometimes excluded). Polysulfanes consist of unbranched chains of sulfur atoms terminated with hydrogen atoms. Compounds containing 2 – 8 concatenated ...
s:
:S
2Cl
2 + n S → S
2+nCl
2
Disulfur dichloride can be purified by distillation from excess elemental sulfur.
S
2Cl
2 also arises from the chlorination of
CS2 as in the synthesis of
thiophosgene
Thiophosgene is a red liquid with the formula . It is a molecule with trigonal planar geometry. There are two reactive C–Cl bonds that allow it to be used in diverse organic syntheses.
Preparation
is prepared in a two-step process from carbon ...
.
Reactions
S
2Cl
2 hydrolyze
Hydrolysis (; ) is any chemical reaction in which a molecule of water breaks one or more chemical bonds. The term is used broadly for substitution, elimination, and solvation reactions in which water is the nucleophile.
Biological hydrolysis i ...
s to
sulfur dioxide
Sulfur dioxide (IUPAC-recommended spelling) or sulphur dioxide (traditional Commonwealth English) is the chemical compound with the formula . It is a toxic gas responsible for the odor of burnt matches. It is released naturally by volcanic a ...
and elemental sulfur. When treated with hydrogen sulfide, polysulfanes are formed as indicated in the following idealized formula:
:2 H
2S + S
2Cl
2 → H
2S
4 + 2 HCl
It reacts with ammonia to give
heptasulfur imide
Heptasulfur imide is the inorganic compound with the formula . It is a pale yellow solid that is, like elemental sulfur, highly soluble in carbon disulfide. The compound, which is only of academic interest, is representative of a family of sulfur i ...
(S
7NH) and related S−N rings S
8−x(NH)
x (x = 2, 3).
Applications
S
2Cl
2 has been used to introduce C−S bonds. In the presence of
aluminium chloride (AlCl
3), S
2Cl
2 reacts with benzene to give diphenyl sulfide:
:S
2Cl
2 + 2 C
6H
6 → (C
6H
5)
2S + 2 HCl + 1/8 S
8
Aniline
Aniline is an organic compound with the formula C6 H5 NH2. Consisting of a phenyl group attached to an amino group, aniline is the simplest aromatic amine. It is an industrially significant commodity chemical, as well as a versatile starti ...
s (1) react with S
2Cl
2 in the presence of NaOH to give 1,2,3-benzodithiazolium salts (2) (
Herz reaction The Herz reaction, named after the chemist Richard Herz, is the chemical conversion of an aniline-derivative (1) to a so-called Herz salt (2) with disulfur dichloride, followed by hydrolysis of this Herz salt (2) to the corresponding sodium thiola ...
) which can be transformed into ''ortho''-aminothiophenolates (3), these species are precursors to
thioindigo
Thioindigo is an organosulfur compound that is used to dye polyester fabric. A synthetic dye, thioindigo is related to the plant-derived dye indigo, replacing two NH groups with two sulfur atoms to create a shade of pink.
Thioindigo is generate ...
dyes.
:
It is also used to prepare
sulfur mustard
Mustard gas or sulfur mustard is a chemical compound belonging to a family of cytotoxic and blister agents known as mustard agents. The name ''mustard gas'' is technically incorrect: the substance, when dispersed, is often not actually a gas, ...
, commonly known as "mustard gas", by reaction with ethylene at 60 °C (the Levinstein process):
:S
2Cl
2 + 2 C
2H
4 → (ClC
2H
4)
2S + 1/8 S
8
Other uses of S
2Cl
2 include the manufacture of sulfur dyes, insecticides, and synthetic rubbers. It is also used in cold vulcanization of rubbers, as polymerization catalyst for vegetable oils and for hardening soft woods.
Safety and regulation
This substance is listed in Schedule 3 Part B – Precursor Chemicals of the Chemical Weapons Convention (CWC). Facilities that produce and/or process and/or consume Scheduled chemicals may be subject to control, reporting mechanisms and inspection by the OPCW (Organisation for the Prohibition of Chemical Weapons).
References
{{Chlorides
Disulfides
Sulfur chlorides