2,4-Dichlorophenoxyacetic acid,CAS 94-75-7

2,4-D (2,4-Dichlorophenoxyacetic acid) is a selective systemic herbicide for the control of broad-leaved weeds. 2,4-D acts as a plant hormone, causing uncontrolled growth in the meristematic tissues. 2,4-D inhibits DNA and protein synthesis and thereby prevents normal plant growth and development[1].

2,4-Dichlorophenoxy)acetic acid Use and Manufacturing
Methods of Manufacturing
Using phenol as the raw material, condensation with chloroacetic acid followed by chlorination, or chlorination followed by condensation with chloroacetic acid can produce products. Condensation first followed by chlorination process. Phenol was placed in the reaction kettle, heated and melted, followed by 2.2 times (molar ratio) sodium hydroxide and 1.2 times (molar ratio) chloroacetic acid, and reacted at 100~110℃ for 30min . After the reactant was cooled, it was neutralized with hydrochloric acid to precipitate phenoxyacetic acid with a yield of 82% or more. Phenoxyacetic acid is slowly fed with 1.4-1.6 times (molar ratio) chlorine gas at 65~90℃, the chlorinated product is 2, 4-dichlorophenoxyacetic acid, and the yield is 89%. The process of chlorination first followed by condensation puts the molten phenol in a chlorinator and passes chlorine at 45-65°C for about 8-9 hours. When the relative density of the reaction material reaches 1.406 (40°C), the chlorination reaction ends. Add 30% sodium hydroxide solution while the reaction is hot. After heating to boiling, add sodium chloroacetate solution dropwise and reflux for 4~5h. After a little cold, neutralize with 30% hydrochloric acid to Ph value 1-3. Add benzene while hot, and separate the organic layer. After cooling, white crystals are precipitated, and the finished product is obtained by suction filtration and drying.
Uses
Herbicide. Used to increase latex output of old rubber trees.2,4-Dichlorophenoxyacetic acid is often formulated as various forms of inorganic salts or esters. 2,4-D was first registered as a herbicide in 1948, and its annual production was estimated at 52–67 million lb in 1990. The primary use of 2,4-D is for control of broadleaf weeds, and as such, it is used for a large spectrum of applications in agriculture, forestry, and lawn care. 2,4-D also is used along right-ofways, on rangelands, parks, and in aquatic environments.2,4-D is one of the most widely used herbicides. It is a chlorine-substituted phenoxyacetic acid herbicide used for postemergence control of annual and perennial broad-leaved weeds in fruits, vegetables, turfs and ornamentals.Exposure to this chemical may arisein the garden, farm, or plantation setting,where it is sprayed for weed control andto enhance the plant growth. Its residueshave been detected in soils, sediments, andgroundwater, as well as in tissues of corals(Crockett et al. 1986; Glynn et al. 1984).