Thionyl bromide is the chemical compound SOBr₂. It is less stable and less widely used than its

chloride The term chloride refers to a compound or molecule that contains either a chlorine anion (), which is a negatively charged chlorine atom, or a non-charged chlorine atom covalently bonded to the rest of the molecule by a single bond (). The pr ...

analogue,

thionyl chloride Thionyl chloride is an inorganic compound with the chemical formula . It is a moderately Volatility (chemistry), volatile, colourless liquid with an unpleasant acrid odour. Thionyl chloride is primarily used as a Halogenation, chlorinating reagen ...

, but engages in similar reactions.

Chemistry

It is prepared by the action of

hydrogen bromide Hydrogen bromide is the inorganic compound with the formula . It is a hydrogen halide consisting of hydrogen and bromine. A colorless gas, it dissolves in water, forming hydrobromic acid, which is saturated at 68.85% HBr by weight at room temper ...

on thionyl chloride, although the corresponding reaction at higher pH (i.e. alkali bromides) proceeds only with difficulty: :SOCl₂ + 2 HBr → SOBr₂ + 2 HCl Phosphorus trichlorodibromide (but not phosphorus pentabromide!) converts

sulfur dioxide Sulfur dioxide (IUPAC-recommended spelling) or sulphur dioxide (traditional Commonwealth English) is the chemical compound with the formula . It is a colorless gas with a pungent smell that is responsible for the odor of burnt matches. It is r ...

to thionyl bromide. Thionyl chlorobromide appears to be a key intermediate in these syntheses, but has not been isolated. Thionyl bromide will convert

alcohol Alcohol may refer to: Common uses * Alcohol (chemistry), a class of compounds * Ethanol, one of several alcohols, commonly known as alcohol in everyday life ** Alcohol (drug), intoxicant found in alcoholic beverages ** Alcoholic beverage, an alco ...

s to alkyl bromides and carboxylic acids to acyl bromides. Unlike with thionyl chloride, stoichiometric bases are problematic activating agents, because free bromide anions decompose thionyl bromide to tribromide,

, and

sulfur Sulfur ( American spelling and the preferred IUPAC name) or sulphur ( Commonwealth spelling) is a chemical element; it has symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms ...

. It can be used for brominations of certain α,β-unsaturated carbonyl compounds. It may occasionally be used as a solvent.

Safety

SOBr₂ hydrolyzes readily in air to release dangerous fumes of

and

. :SOBr₂ + H₂O → SO₂ + 2 HBr Decomposition to

bromine Bromine is a chemical element; it has chemical symbol, symbol Br and atomic number 35. It is a volatile red-brown liquid at room temperature that evaporates readily to form a similarly coloured vapour. Its properties are intermediate between th ...

and

sulfur monoxide Sulfur monoxide is an inorganic compound with formula . It is only found as a dilute gas phase. When concentrated or condensed, it converts to S2O2 ( disulfur dioxide). It has been detected in space but is rarely encountered intact otherwise. St ...

does not occur except at elevated temperatures.

References

Sulfur oxohalides Oxobromides Thionyl compounds Sulfur(IV) compounds Inorganic solvents {{inorganic-compound-stub