Disulfur Dichloride - Synthesis and Basic Properties

Synthesis and Basic Properties

Pure disulfur dichloride is a yellow liquid that smokes in air due to reaction with water:

2 S₂Cl₂ + 2 H₂O → SO₂ + 4 HCl + 3/8 S₈

It is synthesized by partial chlorination of elemental sulfur. The reaction takes place at usable rates at room temperature. In the laboratory, chlorine gas is led into a flask containing elemental sulfur. As disulfur dichloride is formed, the contents become a golden yellow liquid:

S₈ + 4 Cl₂ → 4 S₂Cl₂ ΔH = −58.2 kJ/mol

Excess chlorine gives sulfur dichloride which causes the liquid to become less yellow and more orange-red:

S₂Cl₂ + Cl₂ ↔ 2 SCl₂ ΔH = −40.6 kJ/mol

The reaction is reversible, and upon standing, SCl₂ releases chlorine to revert to the disulfur dichloride. Disulfur dichloride has the ability to dissolve large quantities of sulfur, which reflects in part the formation of polysulfanes:

S₂Cl₂ + n S → S_2+nCl₂

Pure disulfur dichloride is obtained by distilling the yellow-orange liquid over excess elemental sulfur.

S₂Cl₂ also arises from the chlorination of CS₂ as in the synthesis of thiophosgene.