[OH-].[Na+].[Cl:3][C:4]1[CH:16]=[C:15]([Cl:17])[C:14]([O:18][CH3:19])=[CH:13][C:5]=1[O:6][C@@H:7]([CH3:12])[C:8]([O:10]C)=[O:9].Cl>C(O)C>[Cl:3][C:4]1[CH:16]=[C:15]([Cl:17])[C:14]([O:18][CH3:19])=[CH:13][C:5]=1[O:6][C@@H:7]([CH3:12])[C:8]([OH:10])=[O:9]125 ml (0.125 mol) of 1M sodium hydroxide solution were added to a solution of 34.9 g (0.125 mol) of methyl (S)-2-(2,4-dichloro-5-methoxyphenoxy)-propionate in 200 ml of ethanol. The solution was stirred at room temperature for 40 minutes and then adjusted to pH 1 with 2M hydrochloric acid. Most of the solvent was evaporated and the residue was partitioned between 400 ml of ethyl acetate and 400 ml of water. The separated organic phase was dried over anhydrous magnesium sulphate and evaporated to give 32.4 g (97.7%) of (S)-2-(2,4-dichloro-5-methoxyphenoxy)-propionic acid as a white solid, m.p. 114°-115° C.
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