Isomerization of polyunsaturated non-aromatic compounds

Process for obtaining an all-E retinoid compound or a mixture of all-E retinoid compounds of formula 1

• with R being selected from the group of moieties consisting of CH2—OH, CHO, CH2—OR2, COOH, COOR3,
• with R2 being (C═O)-alkyl,
• with R3 being alkyl;
• with alkyl being selected from the group consisting of methyl, ethyl, propyl, isopropyl, butyl, 2-butyl, sec-butyl, isobutyl, tert-butyl;
• comprising the reaction steps:
• feeding a retinoid compound of formula 2
• or a retinoid compound of formula 3
• or a retinoid compound of formula 4
• or a retinoid compound of formula 5
• or a mixture of at least two of retinoid compounds 2 to 5, or a mixture of at least one of retinoid compounds 2 to 5 and retinoid compound of formula 1,
• an organic solvent and a photosensitizer into a reaction device,
• irradiating the thus obtained reaction mixture by means of a filter-free, electroluminescent lighting device emitting monochromatic light,
• at least 90% of the power of said monochromatic light and at most 100% of said power being emitted in the range from 460 nm to 580 nm;
• wherein only a distinct portion of the reaction mixture is irradiated.