Catalysis by bromide ions

Br ions inhibit the oxidation of alcohols if the latter do not contain H202. However, in the presence of H202, 2-propanol oxidation is accelerated by Br [89], as the latter induces decomposition of H202 leading to free radical formation. The rate of initiation by reaction of Br with H202 is [89] 

Decomposition of hydroxyperoxides to free radicals is also accelerated by bromide ions [90], The reaction of hydroperoxide with Br is second order, in contrast to that of hydrogen peroxide, i.e. 

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The orientation of addition of iodine chloride to butadiyne, however, corresponds to an electrophilic attack. A study of the kinetics of bromination of various mono- and dialkyl-substituted butadiynes has been interpreted in terms of an electrophilic mechanism . The observed rates increased with increasing inductive electron-releasing power of the substituents. However, the effects are small, and under the conditions used (two-fold excess of hydrocarbon) it seems likely that significant polybromination occurred . Marked catalysis by bromide ion was observed and interpreted in terms of electrophilic attack by bromine on a complex of acetylene with Br ... 

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