Sulfur dichloride explained

Sulfur dichloride is the chemical compound with the formula . This cherry-red liquid is the simplest sulfur chloride and one of the most common, and it is used as a precursor to organosulfur compounds. It is a highly corrosive and toxic substance, and it reacts on contact with water to form chlorine-containing acids.

Chlorination of sulfur

is produced by the chlorination of either elemental sulfur or disulfur dichloride.^[1] The process occurs in a series of steps, some of which are:

ΔH = −58.2 kJ/mol

ΔH = −40.6 kJ/molThe addition of to has been proposed to proceed via a mixed valence intermediate . undergoes even further chlorination to give , but this species is unstable at near room temperature. It is likely that several exist where n > 2.

Disulfur dichloride,, is the most common impurity in . Separation of from is possible via distillation with 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 in chemical synthesis

is used in organic synthesis. It adds to alkenes to give chloride-substituted thioethers. Illustrative is its addition to 1,5-cyclooctadiene to give a bicyclic thioether A well tested method for the production of the mustard gas bis(2-chloroethyl)sulfide, is the addition of ethylene to sulfur dichloride:^[2]

is also a precursor to several inorganic sulfur compounds. Treatment with fluoride salts gives via the decomposition of the intermediate sulfur difluoride. With, reacts to give "lower" sulfanes such as .

Reaction with ammonia affords sulfur nitrides related to . Treatment of with primary amines gives sulfur diimides. One example is di-t-butylsulfurdiimide.^[3]

Safety considerations

hydrolyzes with release of HCl. Old samples contain .

Notes and References

1. F. Fehér "Dichloromonosulfane" in Handbook of Preparative Inorganic Chemistry, 2nd Ed. Edited by G. Brauer, Academic Press, 1963, NY. Vol. 1. p. 370.
2. R. J. Cremlyn “An Introduction to Organosulfur Chemistry” John Wiley and Sons: Chichester (1996). .
3. 10.1002/anie.196701491. 4962859. New Methods of Preparative Organic Chemistry V: Organic Syntheses with Imides of Sulfur Dioxide. Angewandte Chemie International Edition in English. 6. 2. 149–167. 1967. Kresze. G.. Wucherpfennig. W..