Disulfur

Disulfur
IUPAC name Disulfur
Other names Diatomic sulfur Sulfur Sulfur dimer
Identifiers
CAS number	23550-45-0 Y
PubChem	5460602
ChemSpider	4574100 Y
ChEBI	CHEBI:29387 Y
Gmelin Reference	753
Jmol-3D images	Image 1
SMILES [S][S]
InChI InChI=1S/S2/c1-2 Y Key: MAHNFPMIPQKPPI-UHFFFAOYSA-N Y
Properties
Molecular formula	S2
Molar mass	64.13 g mol−1
Exact mass	63.944141380 g mol-1
Dipole moment	0 D
Thermochemistry
Std enthalpy of formation ΔfHo298	128.60 kJ mol-1
Standard molar entropy So298	228.17 kJ K-1 mol-1
Specific heat capacity, C	32.51 kJ K-1 mol-1
Related compounds
Related compounds	Triplet oxygen
Y (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Disulfur is the diatomic molecule with the formula S₂.^[1] It is analogous to the dioxygen molecule but rarely occurs at room temperature. This violet gas is commonly generated by heating sulfur above 720 °C and comprises 99% of vapor species at low pressure (1 mm Hg) at 530 °C. S₂ is one of minor components of the atmosphere of Io’s, which is dominantly composed of SO₂.^[2] Diatomic molecules are common containing C, O, N and F, but for heavier elements they are often only stable at high temperatures.

Production

Disulfur results when an atmosphere of COS is irradiated with UV light using a mercury photosensitizer or when CS₂, H₂S₂, S₂Cl₂ or C₂H₄S are photolyzed. Singlet S₂ is also formed when sulfur compounds such as H₂S, PSF₃ or COS are photolyzed. S₂ can be generated by heating various organosulfur precursors.^[3]

Properties

S₂ exists in the triplet state like O₂, i.e. both are diradicals. It has S-S double bond length of 189 pm, much shorter than the S-S single bonds in S₈, which are 206 pm. In its Raman spectrum, the S-S vibrational band is observed at 715 cm⁻¹.^[4] The corresponding vibrational band of O-O is found at 1122 cm⁻¹. The S-S bond energy is 265 kJ/mol compared to 498 kJ/mol for O₂.

Sulfur has a large number of allotropes, perhaps as many as thirty. Their specific properties are distinguishable by various types of spectroscopy. The only stable form of sulfur at normal condition is S₈.^[5]

References

1. ^ B. Eckert. R. Steudel “Solid Sulfur Allotropes”, Topic in Current Chemistry (2003) volume 231, pages 1-79. doi:10. 1007/b12110B.
2. ^ Emmanuel Lellouch "Io’S Atmosphere and Surface-Atmosphere Interactions", LESIA, Observatoire de Paris, F-92195 Meudon. doi:10.1 007/s11214-005-1957-z
3. ^ Sylvie L. Tardif, Andrzej Z. Rys, Charles B. Abrams, Imad A. Abu-Yousef, Pierre B. F. Leste-Lasserre, Erwin K. V. Schultz, and David N. Harpp “Recent Chemistry of the Chalcogen Diatomics” Terrahedron, Vol. 53, No 36, pp. 12225-12236. doi:10.1016/S0040-4020(97)00555-3
4. ^ B. Eckert, Ralf Steudel “Molecular Spectra of Sulfur Molecules and Solid Sulfur Allotropes”, Topics in Current Chemistry (2003) volume 231, pages 31–98. doi:10.1007/b13181
5. ^ A. F. Holleman, N. Wiberg. Inorganic Chemistry. Academic Press; Berlin ; New York : De Gruyter, 2001.ISBN 0-12-352651-5.