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.
is produced by the chlorination of either elemental sulfur or disulfur dichloride. The process occurs in a series of steps, some of which are:
The 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 a common impurity in . Separation of from is possible via distillation with to form an azeotrope of 99% purity. Sulfur dichloride loses chlorine slowly at room temperature, converting to disulfur dichloride and eventually higher sulfanes. Pure samples may be stored in sealed glass ampules which develop a slight positive pressure of chlorine, halting the decomposition.
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:
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 . oxidizes to .
Reaction with ammonia affords sulfur nitrides related to . Treatment of with primary amines gives sulfur diimides. One example is di-t-butylsulfurdiimide.
hydrolyzes with release of HCl. Old samples contain .