1: With chromium(VI) oxide; sulfuric acid in water T=5 - 15°C; 0.25 h; 2: (2-methoxy-5-trifluoromethylphenyl)-phenylmethanol in water; acetone T=20 - 25°C; 1.23333 h; 3: With sodium hydrogencarbonate; isopropyl alcohol more than 3 stages;