Synthesis
In a 1000ml three-necked flask, add 33g of sublimed sulfur, 96.5ml of 3-methoxyacetophenone (V), and 92ml of morpholine, and reflux for 15 hours with mechanical stirring. Cool to about 30°C, and add a mixed solution prepared from 350ml of glacial acetic acid, 105ml of distilled water, and 70ml of concentrated sulfuric acid with mechanical stirring, and continue reflux for 5.5 hours. Pour the reaction mixture into ice water (400g ice + 100ml water), and stir mechanically until a yellowish-brown solid precipitates (add crushed ice if necessary), then rapidly cool and filter under ice bath conditions.
The solid was dissolved in 300 ml of 20% sodium hydroxide aqueous solution, filtered, and the brown insoluble matter was added to 100 ml of 20% sodium hydroxide aqueous solution and heated under reflux for half an hour, then filtered while hot. The filtrates were combined, and 10 g of activated powdered activated carbon was added and refluxed for half an hour for decolorization. The mixture was then filtered. 15 g of Raney Ni was added as a catalyst and refluxed and stirred for 2 hours to remove the reacted Ni. Another 15 g of Raney Ni was added and refluxed for 2 hours. The mixture was filtered, and the filtrate was acidified to pH 1-2 with 2N hydrochloric acid under ice bath and mechanical stirring to obtain a feathery white precipitate. This precipitate was placed under ice bath for half an hour, filtered, and dried to obtain 58 g of 3-Methoxyphenylacetic acid, with a yield of 49.8% and a melting point of 68-71℃.
Purification Methods
Crystallise the acid from H2O, or aqueous EtOH. The S-benzylisothiuronium salt has m 160-161o (from EtOH). [Beilstein 10 I 82, 10 III 428, 10 IV 541.]
