Yield:-

Reaction Conditions:

Stage #1:phthalic anhydride with sodium chlorate;sodium hydroxide in water at 28 - 30; for 17 h;
Stage #2: with hydrogenchloride in water; pH=Ca. 5.5 at 30;

Steps:

1
In a four-necked flask equipped with a thermometer, a stirrer, a dropping device and a reflux device, 550 g of water was added, 250 g of phthalic anhydride was added with stirring, and then 1,325 g of sodium hypochlorite (10% concentration, 1% free base (based on NaOH)) was added dropwise. And 110g of liquid alkali (32% concentration). Control the dripping acceleration, keep the temperature at 28 -30 , prevent punching, and the dropping time is about 17 hours. After the dropwise addition, the pH value is adjusted to about 5.5 with about 40 g of hydrochloric acid (30% concentration), and the temperature is maintained at about 30 ° C for 0.5 to 1.0 hour, and the crude 4-chlorophthalic acid monosodium salt is obtained by filtration, and the filter cake is ready for use.Add 400 g of water to a three-necked flask equipped with a thermometer, a stirrer and a reflux device, add the above-mentioned filtered filter cake with stirring, heat up to 90 ° C, keep it for 1-2 hours, then lower to about 30 ° C, filter to obtain a refined product 4-chlorophthalic acid monosodium salt filter cake, the filter cake is ready for use.

References:

Shanghai Guchuang Chemical New Materials Co., Ltd.;Liu Shaohua CN110563678, 2019, A Location in patent:Paragraph 0021-0022; 0027