SULFUR MONOBROMIDE

Sulfur monobromide is a dark red, oily liquid which does not wet glass. M.p. -46°C; dissociates on heating into the elements and therefore can be distilled without decomposition only in high vacuum, d. (20℃) 2.629 In H2O, hydrolyzes to HBr, SO2 and S. Soluble in CS2, CCl4and C6H6.

The procedure is based on that described by Ruff and Winterfield. Thus, 94 ml. of Br2 is slowly added to 119 g of S (recrystallized from CS2) in a dry 500-ml pressure flask capable of withstanding 20 atm of internal pressure. (If proper precautions are observed, a beer bottle can be used.) The mixture is heated for two hours on a steam bath. The dark-red liquid product is distilled at 0.1 mm. The first cut contains primarily unreacted Br2; the main fraction distilling between 46 and 48℃ is pure S2Br2, while crystalline S remains in the distillation flask.The yield averages 80%.