Abstract <p>The free-radical chlorination of three cycloarenes (indane, tetralin, and indene) in heterophase systems upon chlorine generation in an aqueous solution through sequential additions of potassium permanganate to hydrochloric acid is considered. This method enables the controlled formation of chlorination products containing the minimal number of chlorine atoms in a molecule compared to reactions in homogeneous systems, and thus improves the identification of these products and more highly chlorinated ones. This feature also improves the reliability of the identification of chlorocycloarenes by mass spectra and gas-chromatographic retention indices when reference data are limited. Chlorination of indene predominantly yields dimeric products. Oxidation of cycloarenes by permanganic acid HMnO₄ proceeds in parallel with the free-radical chlorination and predominantly yields phthalonic (<i>ortho</i>-(HO₂C)−C₆H₄−COCO₂H) and phthalic acids. These products do not interfere with the determination of chlorinated derivatives because they do not present in the organic phase and are accumulated mainly in the aqueous phase.</p>