[0035] A process for the preparation of a hydroperoxide functionalized rubber compound by the conversion of triplet state oxygen to singlet state oxygen in the presence of oxygen and a light-induced photoreductant. A dispersion of an unsaturated rubber component in a carrier solvent is introduced into a reactor containing a permeable catalyst bed comprising a light-induced photoreductant component supported on a particulate substrate component and passed through the catalyst bed. A gaseous oxidizing agent is passed through the catalyst bed in contact with the rubber-containing dispersion. The catalyst bed is irradiated with electromagnetic light radiation in the ultraviolet or visible light range at an intensity sufficient to convert triplet oxygen in the oxygenated rubber component to singlet oxygen. The oxygenated rubber component is then recovered from the reactor. The reactor can comprise a tubular outer shell and a tubular inner member having a permeable wall defining an annular space containing photoreductant-supported substrate material. The oxidizing agent is introduced into the inner member and radially dispersed outward from this member into contact with the supported photoreductant. The solvent rubber component is concurrently passed into contact with the catalyst bed.