General procedure for the synthesis of 3-(4-methoxyphenoxy)propionic acid from 3-(4-methoxyphenoxy)propanenitrile: 945 g (5.34 mol, 1 equiv.) of a sample of 3-(4-methoxyphenoxy)propanenitrile was loaded into a 22 L round-bottomed flask fitted with an overhead stirrer, and 4 L of concentrated hydrochloric acid was added to the stirred solid under nitrogen protection. 2 L of water was added slowly and the reaction mixture was heated to 100 °C and kept for 3.5 h, at which point the completion of the reaction was confirmed by high performance liquid chromatography (HPLC) analysis. The reaction was cooled to 10 °C by adding ice to the reaction mixture. After drying, 920 g of crude 3-(4-methoxyphenoxy)propionic acid was obtained. The crude product was dissolved in 5 L of 6 wt% sodium carbonate aqueous solution (pH=9), 2 L of dichloromethane (DCM) was added to the reaction vessel, and after thorough stirring, the organic layer was separated and discarded with a dispensing funnel. The aqueous layer was refilled into a 22 L flask and the pH of the aqueous layer was carefully adjusted to 4.0 by slowly adding 6 M hydrochloric acid.The precipitated solid was filtered and dried in a vacuum oven to give 900 g of 3-(4-methoxyphenoxy)propionic acid as a white solid (yield: 86.04%).1H NMR (450 MHz, CDCl3): δ=2.78 (t, 2H; CH2COOH); 3.70 (s, 3H; OCH3); 4.18 (t, 2H; OCH2); 6.78 (m, 4H; Ar-H).13C NMR (112.5 MHz, CDCl3): δ=34.703 (CH2COOH); 55.925 (OCH3); 64.088 (OCH2); 114.855 (CH3OCCH); 115.984 (CH2OCCH); 152.723 (CH3OC); 154.302 (CH2OC); 177.386 (COOH).
