Allylic rearrangement
An allylic rearrangement or allylic shift is an organic chemical reaction in which reaction at a center vicinal to a double bond causes the double bond to shift to an adjacent pair of atoms: It is encountered in both nucleophilic and electrophilic substitution, although it is usually suppressed relative to non-allylic substitution. For example, reaction of 1-chloro-2-butene with sodium hydroxide gives 2-buten-1-ol and 3-buten-2-ol: In the similar substitution of 1-chloro-3-methyl-2-butene, the secondary 2-methyl-3-buten-2-ol is produced in a yield of 85%, while that for the primary 3-methyl-2-buten-1-ol is 15%.