The kinetics of the aluminium bromide catalyzed isomerization of I -propyl bromide corresponds to a nucleophilic displacement of the aliphatic bromine contained in the monomeric and dimeric complexes of the alkyl bromide with aluminium bromide, (1-C3H7BrAlBr3) and (1-C3H7BrAl2Br6), and the antiparallell dipole pair of the dimeric complexes. The initial rate analysis of the isomerization process shows that parallel mixed dipole pairs of the monomeric and dimeric complexes, (1-C3H7Br center dot AlBr2 delta+ AlBr4 delta-)center dot(1-C3H7 Delta+Br center dot AlBr3 Delta-) and (1-C3H7 Delta+Br center dot AlBr3 Delta-)center dot(1-C3H7Br center dot AlBr2 delta+ AlBr4 delta-), could also take part in the isomerization process. The kinetics of the process is investigated and the conclusion is that the isomerization does not require the mixed parallel dipole pairs for the reaction. (C) 2007 Elsevier B.V. All rights reserved.