Sulfur dichloride
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| Names | |||
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| IUPAC names
Sulfur dichloride
Sulfur(II) chloride Dichlorosulfane | |||
| Other names
Sulphur chloride
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| Identifiers | |||
3D model (JSmol)
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| ECHA InfoCard | 100.031.014 | ||
| EC Number |
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| RTECS number |
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| UN number | 1828 | ||
CompTox Dashboard (EPA)
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| Properties | |||
| SCl2 | |||
| Molar mass | 102.97 g mol−1 | ||
| Appearance | red liquid with pungent odour | ||
| Density | 1.621 g cm−3, liquid | ||
| Melting point | −121.0 °C (−185.8 °F; 152.2 K) | ||
| Boiling point | 59 °C (138 °F; 332 K) | ||
| hydrolysis | |||
Refractive index (nD)
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1.5570 | ||
| Structure | |||
| C2v | |||
| Bent | |||
| Hazards | |||
| NFPA 704 (fire diamond) | |||
| 234 °C (453 °F; 507 K) | |||
| Related compounds | |||
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Sulfur dichloride is the chemical compound with the formula SCl2. This cherry-red liquid is the simplest sulfur chloride and one of the most common. It is used as a precursor to organosulfur compounds.[1]
Chlorination of sulfur
SCl2 is produced by the chlorination of either elemental sulfur or disulfur dichloride.[2] The process occurs in a series of steps, some of which are:
- S8 + 4 Cl2 → 4 S2Cl2; ΔH = −58.2 kJ/mol
- S2Cl2 + Cl2 → 2 SCl2; ΔH = −40.6 kJ/mol
The addition of Cl2 to S2Cl2 has been proposed to proceed via a mixed valence intermediate Cl3S-SCl. SCl2 undergoes even further chlorination to give SCl4, but this species is unstable at near room temperature. It is likely that several SxCl2 exist where x > 2.
Disulfur dichloride, S2Cl2, is the most common impurity in SCl2. Separation of SCl2 from S2Cl2 is possible via distillation with PCl3 to form an azeotrope of 99% purity, however sulfur dichloride loses chlorine slowly at room temperature and reverts to disulfur dichloride. Pure samples may be stored in sealed glass ampules which develop a slight positive pressure of chlorine, halting the decomposition.
Use of SCl2 in chemical synthesis
- SCl2 is used in organic synthesis. It adds to alkenes to give chloride-substituted thioethers. Illustrative applications are its addition to 1,5-cyclooctadiene to give a bicyclic thioether[3] and ethylene to give sulfur mustard S(CH2CH2Cl)2.[4]
SCl2 is also a precursor to several inorganic sulfur compounds. Treatment with fluoride salts gives SF4. Reaction with ammonia affords sulfur nitrides related to S4N4. With H2S, SCl2 reacts to give "lower" sulfanes such as S3H2.
Safety considerations
SCl2 hydrolyzes with release of HCl. Old samples contain Cl2.
References
- ^ Schmidt, M.; Siebert, W. "Sulphur" Comprehensive Inorganic Chemistry Vol. 2, ed. A.F. Trotman-Dickenson. 1973.
- ^ F. Fehér "Dichloromonosulfane" in Handbook of Preparative Inorganic Chemistry, 2nd Ed. Edited by G. Brauer, Academic Press, 1963, NY. Vol. 1. p. 370.
- ^ Bishop, Roger (1992). "9-Thiabicyclo[3.3.1]nonane-2,6-dione". Organic Syntheses. 70: 120; Collected Volumes, vol. 9, p. 692.
- ^ R. J. Cremlyn “An Introduction to Organosulfur Chemistry” John Wiley and Sons: Chichester (1996). ISBN 0-471-95512-4.