Thionyl bromide is the chemical compound SOBr2. It is less stable and less widely used than its chloride analogue, thionyl chloride. It is prepared by the action of hydrogen bromide on thionyl chloride, a characteristic reaction where a stronger acid is converted to a weaker acid: SOCl2 + 2 HBr → SOBr2 + 2 HCl Thionyl bromide will convert alcohols to alkyl bromides and can be used for brominations of certain α,β-unsaturated carbonyl compounds. It may occasionally be used as a solvent.