Cl[C:2]1[CH:7]=[CH:6][CH:5]=[C:4]([Cl:8])[CH:3]=1.[Al+3].[Cl-:10].[Cl-].[Cl-].[CH:13](Cl)([CH3:15])[CH3:14].Cl.C(O)C(O)C>>[Cl:10][C:3]1[C:4]([Cl:8])=[C:5]([CH:13]([CH3:15])[CH3:14])[CH:6]=[CH:7][CH:2]=1A 2 liter autoclave was charged with 1,470 g (10.0 mols of 85% strength m-dichlorobenzene (15% of p-dichlorobenzene) and 133 g (1.0 mol) of AlCl3. 413 g (5.0 mols) of isopropyl chloride were pumped in at room temperature with stirring in the course of 35 minutes during which the resulting HCl pressure was maintained at 5 bar by continuously blowing off. 15.2 g (0.2 mol) of 1,2-propanediol were added to the final 150 ml of isopropyl chloride to be pumped in, and were pumped in together with the isopropyl chloride. After the addition by pumping was complete, the autoclave was raised to 50° C. while the pressure was again maintained at a constant 5 bar by blowing off. Stirring was continued for 10 hours at 50° C./5 bar of HCl pressure. After the reaction had ended, the autoclave was cooled down, the pressure was let off, and the contents were sucked out on to 2 liters of ice-water, for hydrolysis. Stirring was continued until the mixture had become colorless, and the organic phase was then separated from the aqueous phase in a separating funnel. The subsequent distillation in a 40 cm silver-jacketed column packed with 4 mm Raschig glass rings produced a dichlorocumene mixture which passed over at 102-103° C./18 bar and consisted of 10.8% of 2,5-, 21.6% of 2,4- and 67.5% of 3,5-dichlorocumene. The yield was 84.6% of theory. 53.25% of the feed m/p-dichlorobenzene mixture was recovered (782.8 g), having a composition of 84.86% of m- and 15.14% of p-dichlorobenzene. The further conversion to 3,5-dichloro-α-methylstyrene was carried out as in Example 1.
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