2,4-dichlorophenoxyacetic acid 2,4-dichlorophenoxyacetic acid 2,4-dichlorophenoxyacetic acid is an organic compound with the chemical formula c8h6cl2o3 which is usually referred to by its iso common name 2,4-d. it is a systemic herbicide which kills most broadleaf weeds by causing uncontrolled growth in them but most grasses such as cereals, lawn turf, and grassland are relatively unaffected. 2,4-dichlorophenoxyacetic acid names preferred iupac name (2,4-dichlorophenoxy)acetic acid other names 2,4-d identifiers cas number 94-75-7 y 3d model (jsmol) interactive image chebi chebi:28854 y chembl chembl367623 y chemspider 1441 y echa infocard 100.002.147 kegg c03664 y pubchem cid 1486 unii 2577aq9262 y comptox dashboard (epa) dtxsid0020442 inchi inchi=1s/c8h6cl2o3/c9-5-1-2-7(6(10)3-5)13-4-8(11)12/h1-3h,4h2,(h,11,12) ykey: ovskikfhrzpjss-uhfffaoysa-n yinchi=1/c8h6cl2o3/c9-5-1-2-7(6(10)3-5)13-4-8(11)12/h1-3h,4h2,(h,11,12)key: ovskikfhrzpjss-uhfffaoyam smiles clc1cc(cl)ccc1occ(=o)o properties chemical formula c8h6cl2o3 molar mass 221.04 g/mol appearance white to yellow powder melting point 140.5 °c (284.9 °f; 413.6 k) boiling point 160 °c (320 °f; 433 k) 0.4 mm hg solubility in water 900 mg/l hazards ghs labelling: pictograms hazard statements h302, h317, h318, h335, h412 precautionary statements p261, p273, p280, p305+p351+p338 flash point nonflammable lethal dose or concentration (ld, lc): ld50 (median dose) 500 mg/kg (oral, hamster) 100 mg/kg (oral, dog) 347 mg/kg (oral, mouse) 699 mg/kg (oral, rat) niosh (us health exposure limits): pel (permissible) twa 10 mg/m3 rel (recommended) twa 10 mg/m3 idlh (immediate danger) 100 mg/m3 safety data sheet (sds) icsc 0033 related compounds related compounds 2,4,5-t, dichlorprop except where otherwise noted, data are given for materials in their standard state (at 25 °c , 100 kpa). infobox references 2,4-d is one of the oldest and most widely available herbicides and defoliants in the world, having been commercially available since 1945, and is now produced by many chemical companies since the patent on it has long since expired. it can be found in numerous commercial lawn herbicide mixtures, and is widely used as a weedkiller on cereal crops, pastures, and orchards. over 1,500 herbicide products contain 2,4-d as an active ingredient. history the discovery of 2,4-d as well as the similar hormone herbicides 2,4,5-t, and mcpa occurred during world war ii and was a case of multiple discovery by four groups working independently under wartime secrecy in the united kingdom and the united states: william g. templeman and associates at imperial chemical industries (ici) in the uk; philip s. nutman and associates at rothamsted research in the uk; franklin d. jones and associates at the american chemical paint company; and ezra kraus, john w. mitchell, and associates at the university of chicago and the united states department of agriculture. all four groups were subject to wartime secrecy laws and did not follow the usual procedures of publication and patent disclosure. in december 1942, following a meeting at the ministry of agriculture the rothamsted and ici workers pooled resources and nutman moved to jealott's hill to join the ici effort. the first scientific publication describing the 2,4-d structure and plant growth regulating activity was by percy w. zimmerman and albert e. hitchcock at the boyce thompson institute, who were not the original inventors. the precise sequence of early 2,4-d discovery events and publications has been discussed. william templeman found that when indole-3-acetic acid (iaa), the naturally occurring auxin, was used at high concentrations, it could stop plant growth. in 1940, he published his finding that iaa killed broadleaf plants within a cereal field. mcpa was discovered at about that time by his ici group.: sec 7.1 in the usa, a similar search for an acid with a longer half life, i.e., a metabolically and environmentally more stable compound, led to 2,4-dichlorophenoxyacetic acid (2,4-d) and 2,4,5-trichlorophenoxyacetic acid (2,4,5-t), both phenoxy herbicides and analogs of iaa. robert pokorny, an industrial chemist for the c.b. dolge company in westport, connecticut, published their synthesis in 1941. all the novel auxins were developed as part of a clandestine wartime effort to create chemical warfare agents and / or selective herbicides; although 2,4-d was not used this way during the war.: sec 7.1 britain and the united states were looking for a chemical to starve germany and japan into submission by killing their potato and rice crops, but 2,4-d was found to be ineffective for that purpose, because both crops tolerate it. within a year after the war ended, 2,4-d was commercially released as an herbicide to control broadleaf weeds in grain crops such as rice and wheat, and in the 1950s it was registered in the united states to control size and enhance skin color in potatoes without affecting yields. the first publication of 2,4-d's use as a selective herbicide came in 1944. the ability of 2,4-d to control broadleaf weeds in turf was documented soon thereafter, in 1944. starting in 1945, the american chemical paint company brought 2,4-d to market as an herbicide called "weedone". it revolutionized weed control, as it was the first compound that, at low doses, could selectively control dicotyledons (broadleaf plants), but not most monocotyledons — narrowleaf crops, such as wheat, maize (corn), rice, and similar cereal grass crops. at a time when labor was scarce and the need for increased food production was large, it literally "replaced the hoe".: sec 7.1 2,4-d is one of the ingredients in agent orange, an herbicide that was widely used during the malayan emergency and the vietnam war. however, 2,3,7,8-tetrachlorodibenzodioxin (tcdd), a contaminant in the production of another ingredient in agent orange, 2,4,5-t, was the cause of the adverse health effects associated with agent orange. in the 2000s, dow agrosciences developed a new choline salt version of 2,4-d (2,4-d choline) that dow included in its "enlist duo" herbicide along with glyphosate and an agent that reduces drift; the choline salt form of 2,4-d is less volatile than 2,4-d. manufacture 2,4-d is a member of the phenoxy family of herbicides. 2,4-d is manufactured from chloroacetic acid and 2,4-dichlorophenol, which is itself produced by chlorination of phenol. alternatively, it is produced by the chlorination of phenoxyacetic acid. the production processes may create several contaminants including di-, tri-, and tetrachlorodibenzo-p-dioxin isomers and n-nitrosamines, as well as monochlorophenol. containers of 2-4 d herbicide, ca. 1947 mode of action 2,4-d acts by mimicking the action of the plant growth hormone auxin, which results in uncontrolled growth and eventually death in susceptible plants. it is absorbed through the leaves and is translocated to the meristems of the plant. uncontrolled, unsustainable growth ensues, causing stem curl-over, leaf withering, and eventual plant death. 2,4-d is typically applied as an amine salt, but more potent ester versions exist, as well. effect of 2-4-d foliar application on lantana applications 2,4-d is primarily used as a selective herbicide which kills many terrestrial and aquatic broadleaf weeds, but not grasses. as it was discovered in the 1940s, a patent no longer governs the manufacture and sale of 2,4-d, and any company is free to produce it. thus, it is sold in various formulations under a wide variety of brand names. 2,4-d can be found in commercial lawn herbicide mixtures, which often contain other active ingredients including mecoprop and dicamba. over 1,500 herbicide products contain 2,4-d as an active ingredient. estimated use of 2,4-d in the usa to 2019 a wide variety of different sectors uses products containing 2,4-d to kill weeds and unwanted vegetation. in agriculture, it was the first herbicide found to be capable of selectively killing weeds but not crops. it has been used since 1945 to control broad-leafed weeds in pastures, orchards, and cereal crops such as corn, oats, rice, and wheat. cereals, in particular, have excellent tolerance to 2,4-d when it is applied before planting. 2,4-d is the cheapest way for farmers to control winter annual weeds by spraying in the fall, often at the lowest recommended rate. this is particularly effective before planting beans, peas, lentils, and chickpeas. the estimated use of 2,4-d in us agriculture is mapped by the us geological survey. in 2019, the latest date for which figures are available, this reached 45,000,000 pounds (20,000,000 kg) annually. in domestic lawn and garden maintenance, 2,4-d is commonly used for weed control in lawns and other turf. it is used to kill unwanted weeds such as dandelions, plantain, clover, and chickweed. in forestry, it is used for stump treatment, trunk injection, and selective control of brush in conifer forests. along roadways, railways, and power lines, it is used to control weeds and brush which might interfere with safe operation and damage equipment. along waterways, it is used to control aquatic weeds that might interfere with boating, fishing, and swimming or clog irrigation and hydroelectric equipment. it is often used by government agencies to control the spread of invasive, noxious, and non-native weed species and prevent them from crowding out native species, and also to control many poisonous weeds such as poison ivy and poison oak.: 35–36 a 2010 monitoring study conducted in the us and canada found that "current exposures to 2,4-d are below applicable exposure guidance values." 2,4-d has been used in laboratories for plant research as a supplement in plant cell culture media such as ms medium since at least 1962. 2,4-d is used in plant cell cultures as a dedifferentiation (callus induction) hormone. it is classified as an auxin plant hormone derivative. health effects