Octasulfur

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Octasulfur
Stereo, skeletal formula of octathiocane
Spacefill model of octathiocane
Ball and stick model of octathiocane
Sample of pulverised octasulfur
Names
Systematic IUPAC name
Octathiocane[1]
Identifiers
10544-50-0 YesY
ChEBI CHEBI:29385
ChEMBL ChEMBL1235452 YesY
ChemSpider 59726 YesY
2973
Jmol 3D model Interactive image
MeSH Cyclooctasulfur
PubChem 66348
Properties
S8
Molar mass 256.48 g·mol−1
Appearance Vivid, yellow, translucent crystals
Density 2.07 g cm−3
Melting point 119 °C; 246 °F; 392 K
Boiling point 159 °C; 318 °F; 432 K (decomposes)
log P 6.117
Thermochemistry
32 J·mol−1·K−1[2]
0 kJ·mol−1[2]
Related compounds
Related compounds
Hexathiane
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Octasulfur is an inorganic chemical with the chemical formula S
8
. It is a yellow solid, and is odourless and tasteless. It is the most common allotrope of sulfur. It is a major industrial chemical that occurs widely in nature.[3]

Nomenclature[edit]

The name octasulfur is the most commonly used; the preferred IUPAC name is cyclo-octasulfur. The compound is systematically named octathiocane, and cyclo-octasulfur. It is also the final member of the thiocane heterocylic series, where every carbon is substituted with a sulfur atom.

Structure[edit]

Main article: Allotropes of sulfur

The compound adopts a crown conformation with D4d point group symmetry. The S–S bond lengths are equal, at about 2.05 Å. Octasulfur crystallizes in three distinct polymorphs: rhombohedral, and two monoclinic forms, of which only two are stable at standard conditions. The rhombohedral crystal form is the accepted standard. The remaining polymorph is only stable between 96 and 115 °C at 100 kPa. Octasulfur forms several allotropes: α-Sulfur, β-sulfur, γ-sulfur, λ-sulfur.

λ-Sulfur is the liquid form of octasulfur, from which γ-sulfur can be crystallised by quenching. If λ-sulfur is crystallised slowly, it will revert to β-sulfur. Since it must have been heated over 115 °C, neither crystallised β-sulfur or γ-sulfur will be pure. The only known method of obtaining pure γ-sulfur is by crystallising from solution.

Octasulfur easily forms large crystals, which are typically yellow and are somewhat translucent.

Production and reactions[edit]

Main article: sulfur

It is typically not produced as S8 per se. It is the main (99%) component of elemental sulfur, which is recovered from volcanic sources and is a major product of the Claus Process, associated with petroleum refineries.

See also[edit]

References[edit]

  1. ^ "cyclooctasulfur (CHEBI:29385)". Chemical Entities of Biological Interest. UK: European Bioinformatics Institute. Main. 
  2. ^ a b Zumdahl, Steven S. (2009). Chemical Principles 6th Ed. Houghton Mifflin Company. p. A23. ISBN 0-618-94690-X. 
  3. ^ Steudel, R., "Homocyclic Sulfur Molecules", Topics Curr. Chem. 1982, 102, 149.