Although ethers resist hydrolysis, they are cleaved by hydrobromic acid and hydroiodic acid. Hydrogen chloride cleaves ethers only slowly. Methyl ethers typically afford methyl halides:
:ROCH + HBr → CHBr + ROH
These reactions proceed via onium intermediates, i.e. [RO(H)CH]Br.
Some ethers undergo rapid cleavage with boron tribromide (even aluminium chloride is used in some cases) to give the alkyl bromide. Depending on the substituents, some ethers can be cleaved with a variety of reagents, e.g. strong base.
Despite these difficulties the chemical paper pulping processes are based on cleavage of ether bonds in the lignin.