Process for the Production of Anethole

A mixture of 432 g (4 mols) of anisole and 4 g of concentrated H3P04 was heated to 150° C. in a reaction vessel equipped with a stirrer, metering unit and descending condenser. After the afore mentioned temperature had been reached, 58 g (1 mol) of propionaldehyde were added through the metering unit over a period of 1.5 hours and, at the same time, the water of reaction formed distilled off. On completion of the addition, the upper phase of the reaction mixture was decanted from the phosphoric acid precipitated and the excess anisole removed from the reaction mixture by distillation, leaving 251.8 g of condensation product consisting of p,p -, o,p - and o,o -l,l-dimethoxy diphenyl propane. The yield amounted to 98.4%, based on the propionaldehyde used. 

For splitting, 100 g of 1,1-dimethoxy diphenyl propane from the condensation stage (a) were heated to 200° C. in a distillation apparatus fitted with a Claisen attachment, followed by the addition of 0.5 g of concentrated phosphoric acid. The products formed during the splitting reaction distilled off over a period of 15 minutes at about 5 to 30 Torn According to analysis by gas chromatography, the distillate (95.5 g) contained 32.7 g of unsplit 1,1-dimethoxy diphenyl propane, 24.1 g of ira .9-p-anethole, 9.1 g of trans-o- and cns-p-anethole and 1.2 g of p-propyl anisole, corresponding to a yield of 91.4% of anetholes, based on reacted condensate. 

Pure /ran.s-p-anethole was obtained from the product of splitting by fractional distillation b.p. 110° (L/10 Torn 

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