Thiosulfoxide
Encyclopedia
A thiosulfoxide is a chemical compound
containing a sulfur
to sulfur
double bond
of the type RR'S=S with R and R' both alkyl or aryl
residues. A 1982 review concluded that there was as yet no definitive evidence for the existence of stable thiosulfoxides which can be attributed to the double bond rule
which states that elements of period 3 and beyond do not form multiple bonds. The related sulfoxide
s of the type RR'S=O are very common. Many compounds containing a sulfur-sulfur double bond have been reported in the past although only a few verified classes of actually stable compounds exist, closely related to thiosulfoxides.
Sulfur sulfur double bonds can be stabilized with electron-withdrawing groups in so-called thionosulfites of the type RO(RO)S=S. These compounds can be prepared by reaction of diol
s with disulfur dichloride
. Sulfur halides such as disulfur dichloride
Cl-S-S-Cl can convert to the branched isomer
Cl2S=S. The related disulfur difluoride exists as an equilibrium mixture
with thiothionyl fluoride F2S=S thermodynamically more stable. These disulfide isomerizations are occasionally studied in silico
.
N-(Thiosulfinyl)amines of the type R-N=S=S are another group of stable compounds containing a S=S bond. The first such compound was prepared in 1974 reaction of the nitroso
compound N,N-dimethyl-p-nitrosoaniline with tetraphosphorus decasulfide. Heating to 200°C extrudes sulfur in this compound and forms the corresponding azo compound
. Disulfur monoxide S=S=O is stable at 20 °C for several days.
Occasionally thiosulfate
s are depicted as having a S=S unit but the sulfur-sulfur bond in it is in fact a single bond.
Chemical compound
A chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions. Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms that are held together...
containing a sulfur
Sulfur
Sulfur or sulphur is the chemical element with atomic number 16. In the periodic table it is represented by the symbol S. It is an abundant, multivalent non-metal. Under normal conditions, sulfur atoms form cyclic octatomic molecules with chemical formula S8. Elemental sulfur is a bright yellow...
to sulfur
Sulfur
Sulfur or sulphur is the chemical element with atomic number 16. In the periodic table it is represented by the symbol S. It is an abundant, multivalent non-metal. Under normal conditions, sulfur atoms form cyclic octatomic molecules with chemical formula S8. Elemental sulfur is a bright yellow...
double bond
Double bond
A double bond in chemistry is a chemical bond between two chemical elements involving four bonding electrons instead of the usual two. The most common double bond, that between two carbon atoms, can be found in alkenes. Many types of double bonds between two different elements exist, for example in...
of the type RR'S=S with R and R' both alkyl or aryl
Aryl
In the context of organic molecules, aryl refers to any functional group or substituent derived from an aromatic ring, be it phenyl, naphthyl, thienyl, indolyl, etc....
residues. A 1982 review concluded that there was as yet no definitive evidence for the existence of stable thiosulfoxides which can be attributed to the double bond rule
Double bond rule
The double bond rule states that chemical elements with a principal quantum numbergreater than 2 do not form multiple bonds with themselves or with other elements...
which states that elements of period 3 and beyond do not form multiple bonds. The related sulfoxide
Sulfoxide
A sulfoxide is a chemical compound containing a sulfinyl functional group attached to two carbon atoms. Sulfoxides can be considered as oxidized sulfides...
s of the type RR'S=O are very common. Many compounds containing a sulfur-sulfur double bond have been reported in the past although only a few verified classes of actually stable compounds exist, closely related to thiosulfoxides.
Sulfur sulfur double bonds can be stabilized with electron-withdrawing groups in so-called thionosulfites of the type RO(RO)S=S. These compounds can be prepared by reaction of diol
Diol
A diol or glycol is a chemical compound containing two hydroxyl groups A geminal diol has two hydroxyl groups bonded to the same atom...
s with disulfur dichloride
Disulfur dichloride
Disulfur dichloride is the chemical compound with the formula S2Cl2 . Some alternative names for this compound are sulfur monochloride , disulphur dichloride and sulphur monochloride...
. Sulfur halides such as disulfur dichloride
Disulfur dichloride
Disulfur dichloride is the chemical compound with the formula S2Cl2 . Some alternative names for this compound are sulfur monochloride , disulphur dichloride and sulphur monochloride...
Cl-S-S-Cl can convert to the branched isomer
Isomer
In chemistry, isomers are compounds with the same molecular formula but different structural formulas. Isomers do not necessarily share similar properties, unless they also have the same functional groups. There are many different classes of isomers, like stereoisomers, enantiomers, geometrical...
Cl2S=S. The related disulfur difluoride exists as an equilibrium mixture
Chemical equilibrium
In a chemical reaction, chemical equilibrium is the state in which the concentrations of the reactants and products have not yet changed with time. It occurs only in reversible reactions, and not in irreversible reactions. Usually, this state results when the forward reaction proceeds at the same...
with thiothionyl fluoride F2S=S thermodynamically more stable. These disulfide isomerizations are occasionally studied in silico
In silico
In silico is an expression used to mean "performed on computer or via computer simulation." The phrase was coined in 1989 as an analogy to the Latin phrases in vivo and in vitro which are commonly used in biology and refer to experiments done in living organisms and outside of living organisms,...
.
N-(Thiosulfinyl)amines of the type R-N=S=S are another group of stable compounds containing a S=S bond. The first such compound was prepared in 1974 reaction of the nitroso
Nitroso
Nitroso refers to a functional group in organic chemistry which has the general formula RNO. Nitroso compounds are a class of organic compounds containing the nitroso functional group, R−N=O....
compound N,N-dimethyl-p-nitrosoaniline with tetraphosphorus decasulfide. Heating to 200°C extrudes sulfur in this compound and forms the corresponding azo compound
Azo compound
Azo compounds are compounds bearing the functional group R-N=N-R', in which R and R' can be either aryl or alkyl. IUPAC defines azo compounds as: "Derivatives of diazene , HN=NH, wherein both hydrogens are substituted by hydrocarbyl groups, e.g. PhN=NPh azobenzene or diphenyldiazene." The more...
. Disulfur monoxide S=S=O is stable at 20 °C for several days.
Occasionally thiosulfate
Thiosulfate
Thiosulfate is an oxyanion of sulfur. The prefix thio indicates that thiosulfate ion is a sulfate ion with one oxygen replaced by a sulfur. Thiosulfate occurs naturally and is produced by certain biochemical processes...
s are depicted as having a S=S unit but the sulfur-sulfur bond in it is in fact a single bond.