Acyclic allylic alcohols exhibit good selectivity as well. In these systems both A1,2 (steric interactions with vinyl) and A1,3 strain are considered. It has been shown that a dihedral angle of 120 best directs substrates which hydrogen bond with the directing group. This geometry allows for the peroxide to be properly positioned, as well as to allow minimal donation from the C-C pi into the C-O sigma star. This donation would lower the electron density of the alkene, and deactivate the reaction. However,vanadium complexes do not hydrogen bond with their substrates. Instead they coordinate with the alcohol. This means that a dihedral angle of 40 allows for ideal position of the peroxide sigma star orbital.