Abstract Irradiation of the complex [(C 5 Me 4 H) 2 Ti (Ci (CH 3) 2] in an olefin as a solvent promotes stereospecific photoassisted isomerizations: olefins with terminal double bonds are rapidly isomerized into 2-alkenes with an E-configuration. Kinetic studies of hydrogen migration and of ZE isomerizations of disubstituted olefins have demonstrated the influence of substitution and of branching of the hydrocarbon chain on the course of the reaction. ...