Sulfur monoxide

Sulfur monoxide

Names
IUPAC name Sulfur monoxide
Systematic IUPAC name Oxidosulfur
Identifiers
CAS Number	13827-32-2 N
3D model (Jmol)	Interactive image
Beilstein Reference	7577656
ChEBI	CHEBI:45822 Y
ChemSpider	102805 Y
Gmelin Reference	666
MeSH	sulfur+monoxide
PubChem CID	114845
InChI InChI=1S/OS/c1-2 Y Key: XTQHKBHJIVJGKJ-UHFFFAOYSA-N Y InChI=1/OS/c1-2 Key: XTQHKBHJIVJGKJ-UHFFFAOYAK
SMILES O=S
Properties
Chemical formula	SO
Molar mass	48.064 g mol−1
Appearance	Colourless gas
Solubility in water	Reacts
log P	0.155
Thermochemistry
Std molar entropy (So298)	221.94 J K−1 mol−1
Std enthalpy of formation (ΔfHo298)	5.01 kJ mol−1
Related compounds
Related compounds	Triplet oxygen
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N  (what is YN ?)
Infobox references

Sulfur monoxide is an inorganic compound with formula SO. 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.

The SO molecule has a triplet ground state similar to O₂, i.e. each molecule has two unpaired electrons. The S−O bond length of 148.1 pm is similar to that found in lower sulfur oxides (e.g. S₈O, S−O = 148 pm) but is longer than the S−O bond in gaseous S₂O (146 pm), SO₂ (143.1 pm) and SO₃ (142 pm).

The molecule is excited with near infrared radiation to the singlet state (with no unpaired electrons). The singlet state is believed to be more reactive than the ground state triplet state, in the same way that singlet oxygen is more reactive than the triplet oxygen.

Production of SO as a reagent in organic syntheses has centred on using compounds that "extrude" SO. Examples include the decomposition of the relatively simple molecule thiirane 1-oxide: as well as more complex examples, such as a trisulfide oxide, C₁₀H₆S₃O,

The SO molecule is thermodynamically unstable, converting initially to S₂O₂. SO inserts into alkenes, alkynes and dienes producing molecules with three membered rings containing sulfur.

In the laboratory sulfur monoxide can be produced by treating sulfur dioxide with sulfur vapour in a glow discharge. It has been detected in single bubble sonoluminescence of concentrated sulfuric acid containing some dissolved noble gas.

A chemiluminescence detector for sulfur has been reported that is based on the reactions: