Sulfur dioxide (SO2) is a toxic gas responsible for the odor of burnt matches and is released naturally by volcanic activity. It is produced as a by-product of copper extraction and the burning of sulfur-bearing fossil fuels. SO2 is a bent molecule with C2v symmetry point group, with a bond order of 1.5. The sulfur–oxygen bond has a bond order of 1.5, and its oxidation state is +4 and a formal charge of +1.
Sulfur dioxide is found on Earth in very small concentrations in the atmosphere at about 15 ppb. On other planets, it can be found in various concentrations, with Venus being the most significant, where it reacts with water to form clouds of sulfuric acid. This contributes to global warming and has been implicated as a key agent in the warming of early Mars. On both Venus and Mars, its primary source is thought to be volcanic.
The atmosphere of Io, a natural satellite of Jupiter, is 90% sulfur dioxide, and trace amounts are thought to also exist in the atmosphere of Jupiter. The James Webb Space Telescope has observed the presence of sulfur dioxide on the exoplanet WASP-39b, where it is formed through photochemistry in the planet's atmosphere. As an ice, it is thought to exist in abundance on the Galilean moons—as subliming ice or frost on the trailing hemisphere of Io, and in the crust and mantle of Europa, Ganymede, and Callisto, possibly also in liquid form and readily reacting with water.
Production of sulfur dioxide is primarily produced for sulfuric acid manufacture. In 1979, 23.6 million metric tons (26 million U.S. short tons) of sulfur dioxide were used in this way, compared with 150,000 metric tons (165,347 U.S. short tons) used for other purposes. Most sulfur dioxide is produced by the combustion of elemental sulfur or roasting pyrite and other sulfide ores in air.
Combustion routes for sulfur dioxide include burning of sulfur or burning materials that contain sulfur, liquified sulfur, hydrogen sulfide, organosulfur compounds, roasting of sulfide ores such as pyrite, sphalerite, and cinnabar, and the reduction of higher oxides. The largest source of sulfur dioxide, volcanic eruptions, can release millions of tons of SO2.
Reactions for sulfur dioxide include the action of aqueous bases on sulfur dioxide, the reduction of sulfur dioxide by halogens to give sulfuryl halides, and the Claus process, which is conducted on a large scale in oil refineries.
The CAS Number of Sulfur Dioxide is 7446-09-5
The Molecular Formula of Sulfur Dioxide is O2S
The Molecular Mass of Sulfur Dioxide is 64.07
The SMILES Notation of Sulfur Dioxide is O=S=O
The InChI Notation of Sulfur Dioxide is InChI=1S/O2S/c1-3-2