Reaction of Alcohols with Phosphorus Tribromide

Analogous to their reaction with thionyl chloride, reaction of alcohols with phosphorus tribromide followed by hydrobromic acid results in the replacement of the hydroxyl group of the alcohol with bromine, forming the alkyl bromide product. This mechanism does not, like dehydrohalogenation, pass through a carbocation intermediate. Therefore, rearrangement cannot occur in this reaction. A carboxylic acids can be converted to an acyl bromide with this reaction.