Abstract: This invention concerns an improved process for preparing monocarboxylated derivatives of cyclododecatriene by the catalytic addition of carbon monoxide using certain homogeneous, experimentally selected, three component, ligand-stabilized, platinum(II) or palladium(II)-Group IVB metal halide catalyst compositions.Optionally, in the case of certain ligand-stabilized, platinum(II) halide-Group IVB metal halide catalyst complexes, the above carboxylated reaction mixture containing alkyl cyclododecadiene carboxylate can be purged of carbon monoxide, hydrogen can be passed into the reaction mixture, the reaction mixture pressurized in a hydrogen atmosphere and the carbon-to-carbon double bonds in said alkyl cyclododecadiene carboxylate intermediate reduced.