Abstract
Hypobromous acid reacts with allyl bromide in water in the presence of perchloric acid to give 2,3-dibromopropan-1-ol (79%) and 1,3-dibromopropan-2-ol (21%). An isotope dilution experiment indicated that no other product was formed in significant amount. When the reaction was carried out with allyl [82Br] bromide, the resulting 2,3-dibromopropanol contained 29 ± 1% of its radioactivity in the 2-position. When the bromine labelling was reversed, i.e., [82Br]hypobromous acid was added to inactive allyl bromide, the 3-position was labelled to the extent of 30 ± 1%. This value, which is taken as a measure of the allylic bromine rearrangement, was reduced to 25% when the reaction was carried out in 40% dioxan–water. These results, together with earlier work on the corresponding chloro- and chlorobromo-systems, are discussed in terms of participation by neighbouring halogen groups in the intermediate carbonium ions.
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