Anethol Refinement

A mixture of 324 g (3 mols) of anisole and 4 g of concentrated H3P04 was heated to 150° C. in a 500 mL. capacity reaction vessel equipped with a thermometer, stirrer and dropping funnel. After the above-mentioned temperature had been reached, 64 g (0.432 mol) of o-anethole (2-methoxy-propen-l-yl benzene) were introduced into the thoroughly stirred anisole/phosphoric acid mixture over a period of 1 hour, followed by stirring for 1 hour at the same temperature. The excess anisole was then distilled off at 50° C./5 Torr, leaving 110 g of a condensation product consisting predominantly of the o,p -isomers of 1,1-dimethoxy diphenyl propane. The yield was substantially quantitative. 

For splitting, the condensate was heated to 200.° C. in the presence of the phosphoric acid left in the condensate. The products of splitting formed, anisole and the o-p-anetholes, distil off over a period of 10 minutes at 10 Torr. 

Distillation of 55 g of 1,1-dimethoxy diphenyl propane gave 17.8 g of a distillate which contained 14% of ra s-p-anethole according to analysis by gas chromatography. 24.2 g of condensate were recovered. 

The Example illustrates that o-anethole can be converted by the process according to the invention into rans-p-anethole. 

Source Bauer 1977 Wagner (1952) for a review of anethole production. 

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Bernhagen, W. Springer, H Verfahren zur Herstellung von Dimethylbenzylcarbinol und Dimethylbenzylcarbinylformiat 1982 EP 44514 Bibb, C. H. Process of Refining Anethol 1936 US 2,052,745 Boehringer Ingelheim l-Phenyl-2-Amino Ethanes and Derivatives 1970 GB 1,192,223... 

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