The lower sulfur oxides are a group of
inorganic compounds
In chemistry, an inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds, that is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as '' inorganic chemi ...
with the formula S
mO
n, where 2m > n. These species are often unstable and thus rarely encountered in everyday life. They are significant intermediates in the combustion of elemental sulfur.
Some well characterized examples include
sulfur monoxide
Sulfur monoxide is an inorganic compound with formula . It is only found as a dilute gas phase. When concentrated or condensed, it converts to S2O2 ( disulfur dioxide). It has been detected in space but is rarely encountered intact otherwise.
St ...
(SO), its dimer S
2O
2, and a series of cyclic sulfur oxides, S
nO
x (x = 1, 2), based on cyclic S
n rings.
Interest in the lower sulfur oxides has increased because of the need to understand terrestrial atmospheric sulfur pollution and the finding that the extraterrestrial atmospheres of
Io, one of
Jupiter
Jupiter is the fifth planet from the Sun and the largest in the Solar System. It is a gas giant with a mass more than two and a half times that of all the other planets in the Solar System combined, but slightly less than one-thousand ...
's moons, and
Venus
Venus is the second planet from the Sun. It is sometimes called Earth's "sister" or "twin" planet as it is almost as large and has a similar composition. As an interior planet to Earth, Venus (like Mercury) appears in Earth's sky never f ...
contain significant amounts of sulfur oxides.
Some compounds reported by early workers such as the blue "sesquioxide", S
2O
3, formed by dissolving sulfur in liquid SO
3 appears to be a mixture of polysulfate salts of the S
42+ and S
82+ ions.
Sulfur monoxide, disulfur dioxide, disulfur monoxide
These species are well characterized in the gas phase, but they cannot be isolated as solids or liquids. Instead, when condensed, they undergo dimerization and oligomerization, usually yielding sulfur dioxide and elemental sulfur. At a few millibars pressure, the relative stabilities are S
2O > S
2O
2 > SO.
[ ]Sulfur monoxide
Sulfur monoxide is an inorganic compound with formula . It is only found as a dilute gas phase. When concentrated or condensed, it converts to S2O2 ( disulfur dioxide). It has been detected in space but is rarely encountered intact otherwise.
St ...
(SO) and its dimer (S2O2) have been trapped at low temperature. Disulfur dioxide (S2O2) is a dimer of sulfur monoxide. It has C2v structure (planar).
Disulfur monoxide (S2O) is an analogue of 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 ...
. Like SO2 as well as ozone
Ozone (), or trioxygen, is an inorganic molecule with the chemical formula . It is a pale blue gas with a distinctively pungent smell. It is an allotrope of oxygen that is much less stable than the diatomic allotrope , breaking down in the l ...
(O3), and trisulfur
The molecule, known as trisulfur, sulfur trimer, thiozone, or triatomic sulfur, is a cherry-red allotrope of sulfur. It comprises about 10% of vaporised sulfur at and . It has been observed at cryogenic temperatures as a solid. Under ordinary ...
(S3), it adopts a bent structure. The S-S bond length is 188.4 pm, the S-O bond is 146.5 pm and the SSO angle is 117.88°. The two dipole moment components are μa = 0.875 D and μb = 1.18 D. This species decomposes to give a polymeric sulfur oxides ("PSO's") with the approximate formula 3Osub>n. PSO's decompose at room temperature to elemental sulfur and SO2. PSO's have been proposed to be responsible for the colour of Io.
Trisulfur monoxide, S3O is an unstable molecule. It has been detected in the gas phase using neutralization-reionization mass spectrometry
Mass spectrometry (MS) is an analytical technique that is used to measure the mass-to-charge ratio of ions. The results are presented as a '' mass spectrum'', a plot of intensity as a function of the mass-to-charge ratio. Mass spectrometry is u ...
. Both cyclic and chain structures were found.
Cyclic SnOx (x = 1, 2)
A number of monoxides SnO are known where n = 5-10. The oxygen atom is exocyclic.trifluoroperoxyacetic acid
Trifluoroperacetic acid (trifluoroperoxyacetic acid, TFPAA) is an organofluorine compound, the peroxy acid analog of trifluoroacetic acid, with the condensed structural formula . It is a strong oxidizing agent for organic oxidation reactions, suc ...
:
References
{{reflist
Sulfur oxides
Interchalcogens