Preparation method of p-chlorophenoxyacetic acid_Kain Industrial Additive

Background and overview^[1]

P-chlorophenoxyacetic acid is an intermediate of the central nervous system stimulant drug meclofenac and is also a plant growth regulator. p-Chlorophenoxyacetic acid is a systemic, highly efficient and multi-functional plant growth regulator that can promote biosynthesis and biotransfer in plants. It can not only prevent flower and fruit drop, improve fruit setting rate, increase fruit growth speed, and promote early growth. When mature, it can also achieve the purpose of improving plant quality. At the same time, it also acts as a herbicide. It is mainly used in tomatoes, grapes, vegetables, etc. It can improve the yield and quality of crops and has great practical value. Moreover, this product is easily soluble in water and has no residue on crops, fruits and seeds. It is currently one of the most promising growth regulators.

Liquid Chromatography Analysis^[2]

Quantitative analysis method for the determination of p-chlorophenoxyacetic acid using high performance liquid chromatography, using methanol + water as the mobile phase, RP-18 chromatographic column, detection wavelength 254nm, and external standard method for quantification. The recovery rate of this method ranges from 98.6% to 102.3%, the standard deviation is 0.198, and the coefficient of variation is 1.83%. p-Chlorophenoxyacetic acid is well separated, the operation is simple and practical, and the quantitative analysis results are accurate and stable.

Preparation method^[1]

Using phenoxyacetic acid, concentrated hydrochloric acid and 36.05% hydrogen peroxide as raw materials, they react under the catalysis of ferric chloride to generate p-chlorophenoxyacetic acid. The reaction equation is:

In a reaction device equipped with an electric stirrer, reflux condenser, thermometer, constant pressure funnel, and 250mL four-necked flask, add 7.0g phenoxyacetic acid and 35mL glacial acetic acid. Stir to dissolve the phenoxyacetic acid. Weigh. Add 64 mg ferric chloride to the four-necked flask, slowly add 25 mL concentrated hydrochloric acid dropwise. Heat the solution to 65°C in a water bath, and slowly add 15 mL 36.05% hydrogen peroxide dropwise. Since the reaction is an exothermic reaction, the dropping speed must be controlled. And keep the water bath temperature at 60~65℃. When the solution turns reddish brown, end the reaction, cool, crystallize, filter and dry. The crude yield of the product reaches 90%. Wash with a solution of ethanol:water = 1:3 , recrystallization, weighing.