|
2,4-D
Herbicide
HRAC O WSSA 4; phenoxycarboxylic acid
NOMENCLATURE
2,4-D
Common name: 2,4-D (BSI, E-ISO, (m) F-ISO, WSSA); 2,4-PA (JMAF)
IUPAC name: (2,4-dichlorophenoxy)acetic acid
Chemical Abstracts name: (2,4-dichlorophenoxy)acetic acid
CAS RN: [94-75-7]
EEC no:. 202-361-1
Development codes: L208 (Marks)
PHYSICAL CHEMISTRY
2,4-D
Composition: Tech. is ³96% pure.
Mol. wt.: 221.0
M.f.: C8H6Cl2O3
Form: Colourless powder, with a slight phenolic odour.
M.p.: 140.5 ºC
V.p.： 1.86 ´ 10-2 mPa (25 °C, OECD 104)
KOW： logP = 2.58-2.83 (pH 1), 0.04-0.33 (pH 5)
Henry：1.32 ´ 10-5 Pa m3 mol-1 (calc.)
S.g./density： 1.508 (20 °C)
Solubility： In water 311 (pH 1), 20 031 (pH 5), 23 180 (pH 7), 34 196 (pH 9) (all in mg/l, 25 °C). In ethanol 1250, diethyl ether 243, heptane 1.1, toluene 6.7, xylene 5.8 (all in g/kg, 20 ºC); in octanol 120 g/l (25 °C). Insoluble in petroleum oils. Mono-n-butylamine salt: In water 18 g/l (30 ºC).
Stability： 2,4-D is a strong acid, and forms water-soluble salts with alkali metals and amines. Hard water leads to precipitation of the calcium and magnesium salts, but a sequestering agent is included in formulations to prevent this. Photolytic DT50 (simulated sunlight) 7.5 d.
pKa：2.73
COMMERCIALISATION
History: The potent effects of its salts on plant growth were first described by P. W. Zimmerman & A. E. Hitchcock (Contrib. Boyce Thompson Inst., 1942, 12, 321), and its early history is covered in The Hormone Weedkillers, C. Kirby (1980).
Manufacturers: Agrochem; Ancom; Atanor; Atul; CAC; Crompton; Crystal; Dow AgroSciences; Krishi Rasayan; Marks; Nitrokémia; Nufarm GmbH; Nufarm Ltd; Nufarm UK; Proficol; Sannong; Sharda; Sundat; United Phosphorus
APPLICATIONS
Biochemistry: Synthetic auxin (acting like indolylacetic acid).
Mode of action: Selective systemic herbicide. Salts are readily absorbed by the roots, whilst esters are readily absorbed by the foliage. Translocation occurs, with accumulation principally at the meristematic regions of shoots and roots. Acts as a growth inhibitor.
Uses: Post-emergence control of annual and perennial broad-leaved weeds in cereals, maize, sorghum, grassland, established turf, grass seed crops, orchards (pome fruit and stone fruit), cranberries, asparagus, sugar cane, rice, forestry, and on non-crop land (including areas adjacent to water), at 0.28-2.3 kg/ha. Control of broad-leaved aquatic weeds. The isopropyl ester can also be used as a plant growth regulator to prevent premature fruit fall in citrus fruit. Phytotoxicity Phytotoxic to most broad-leaved crops, especially cotton, vines, tomatoes, ornamentals, fruit trees, oilseed rape and beet.
Formulation types: EC; GR; SP; SL.
2,4-D
Compatibility: Compatibility depends upon the particular formulation.
Selected products: 'Agricorn D' (FCC); 'Capri' (Makhteshim-Agan); 'Damine' (Agriphar); 'Deferon' (Milenia); 'Dikamin' (Nitrokémia); 'Dymec' (PBI/Gordon); 'Kay-D' (mixture of sodium and amine salts with ethyl ester) (Krishi Rasayan); 'Palormone' (Unicrop); 'U 46 D' (BASF); 'Weedtox' (Aimco); 'Yerbisol' (amine salt) (Ingeniería Industrial);
mixtures: 'Novermone' (+ dichlorprop) (Nufarm SA); 'Rogue' (+ butachlor) (Monsanto)
OTHER PRODUCTS
2,4-D
'Amicide' (Nufarm Ltd); 'BEE-4' (Dow AgroSciences); 'Crisalamina' (Crystal); 'Crisamina' (Crystal); 'Dacamine' (GB Biosciences); 'Dicotox' (Bayer CropScience); 'Diserbone E 54' (ester) (Chemia); 'Dormone' (Bayer CropScience); 'Easel' (Nufarm UK); 'Estercide' (Nufarm Ltd); 'Hedonal' (Bayer CropScience); 'Herbamine' (Agrochem); 'Herbifen Super' (Atanor); 'King' (ester) (Chemiplant); 'Maton' (Headland); 'Mortal' (CAS); 'Novertex' (Nufarm SA); 'Patonok' (Pato); 'Ragox' (ester) (Nufarm UK); 'Statesman' (Dow AgroSciences); 'Syford' (Vitax); 'Weedar' (Bayer CropScience, Sedagri, Nufarm SA); 'Weedkiller 4D' (Dow AgroSciences); 'Weedone 2D' (Nufarm SA) mixtures: 'Atladox HI' (+ picloram) (Nomix-Chipman); 'Campaign' (+ glyphosate-isopropylammonium) (2,4-D also as isopropylamine salt) (Monsanto); 'Certrol DS' (+ ioxynil octanoate) (Nufarm SA); 'Combatran' (+ picloram-triisopropanolammonium) (2,4-D also as triisopropanolammonium salt) (Dow AgroSciences); 'Curtail' (+ clopyralid-olamine) (2,4-D as triisopropanolammonium salt) (Dow AgroSciences); 'Drago 3.4' (+ flufenacet) (Bayer CropScience); 'Esteron 638' (+ 2,4-D-butotyl) (Dow AgroSciences); 'Flash' (+ picloram-triisopropanolammonium) (2,4-D also as triisopropanolammonium salt) (Dow AgroSciences); 'Glymix' (+ glyphosate-isopropylammonium) (2,4-D as the triisopropylammonium salt) (Dow AgroSciences); 'Grazon P+D' (+ picloram-triisopropanolammonium) (2,4-D also as triisopropanolammonium salt) (Dow AgroSciences); 'Hat-Trick' (+ glyphosate) (Ancom); 'Holster' (+ dicamba+ fluroxypyr) (SumiAgro); 'KambaMaster' (+ dicamba) (Nufarm Americas); 'Kuron M' (+ picloram-triisopropanolammonium) (2,4-D also as triisopropanolammonium salt) (Dow AgroSciences); 'Landmaster' (+ glyphosate-isopropylammonium) (2,4-D also as isopropylamine salt) (Monsanto); 'Lonpar' (+ clopyralid-olamine+ MCPA) (2,4-D and MCPA as amine salts) (Dow AgroSciences); 'New Estermone' (+ dicamba) (Vitax); 'Nox-D' (+ propanil) (Crystal); 'Nu-Shot' (+ dicamba+ triclopyr) (Nufarm UK); 'Pasture MD' (+ dicamba+ metsulfuron-methyl) (Nufarm Americas); 'Pathway' (+ picloram) (Dow AgroSciences); 'Phenoxy 088' (+ 2,4-D-butotyl) (Agriliance); 'Polo' (+ MCPA) (Headland); 'RT Master' (+ glyphosate-isopropylammonium) (2,4-D as the triisopropylammonium salt) (Monsanto); 'Sound' (+ metosulam) (Dow AgroSciences, Bayer CropScience); 'Supertox' (+ mecoprop) (Bayer CropScience); 'Sydex' (+ mecoprop-P) (Vitax); 'Top Gun' (+ metribuzin) (Platte); 'Tordon 101' (+ picloram) (Dow AgroSciences); 'Tordon RTU' (+ picloram) (as triisopropylammonium salts) (Dow AgroSciences); 'UPL Camppex' (+ dichlorprop+ MCPA+ mecoprop-P) (United Phosphorus); 'Weedone 638 Solventless' (+ 2,4-D-2-ethylhexyl) (Nufarm Ltd); 'Weedone 638' (+ 2,4-D-butotyl) (Nufarm Ltd); 'Weedone DPC Amine' (+ dichlorprop-dimethylammonium) (2,4-D as triisopropanolammonium salt) (Nufarm Ltd); 'Weedone' (+ dichlorprop) (Nufarm SA); 'Xrm-5202 Premium' (+ clopyralid+ triclopyr-triethylammonium) (2,4-D and clopyralid as triisopropanolammonium salts) (Riverdale) Discontinued products: 'Destox' * (MTM); 'For-ester' * (Vitax); 'Herbifen' * (Compania Quimica) mixtures: 'Broadshot' * (+ dicamba+ triclopyr) (Cyanamid); 'Broadstrike Post' * (+ clopyralid+ flumetsulam) (Dow AgroSciences); 'Camppex' * (+ dichlorprop+ MCPA+ mecoprop) (United Phosphorus Ltd); 'Cleanrun' * (+ mecoprop) (Zeneca); 'Scorpion III' * (+ clopyralid+ flumetsulam) (Dow AgroSciences); 'SWK 333' * (+ dicamba) (Keychem); 'Sydex' * (+ mecoprop) (Vitax); 'Weed and Brushkiller' * (+ dicamba+ mecoprop) (Vitax)
ANALYSIS
Product analysis of 2,4-D, salts, esters and mixed combination products by acid-base titration, by glc (CIPAC Handbook, 1985, 1C, 2060, 2257; 1994, F, 292-319; Herbicides 1977, pp. 6-21), by rplc (AOAC Methods, 17th Ed., 971.07, 976.03, 978.05, 984.07; CIPAC Handbook, 1985, 1C, 2060; 1988, D, 51), by hplc (ibid., 1983, 1757), or by i.r. spectrometry (ibid., 1998, H, 131). Free phenol impurity determined by glc (CIPAC Handbook, 1994, F, 197), hplc (ibid., 1994, F, 362) or electrochemically (ibid., 1994, F, 368). Residues determined by glc of derivatives (Pestic. Anal. Man., 1979, I, 201-D; Anal. Methods Pestic. Plant Growth Regul., 1972, 6, 630) or by hplc (M. Meier et al.,Fresenius Z. Anal. Chem.,1989, 334, 235). In drinking water, by conversion to methyl ester with diazomethane, then glc with ECD (AOAC Methods, 17th Ed., 992.32).
MAMMALIAN TOXICOLOGY
Reviews: FAO/WHO 77, 79, 80, 82, 92 (see part 2 of the Bibliography). Toxicity and hazards to man, domestic animals and wildlife have been reviewed (J. M. Way, Residue Rev., 1969, 26, 37). IARC ref. 15, 41; Suppl. 7
Class: chlorophenoxy herbicides classified as 2B, based on epidemiology of production. More recent evidence (M. Kogevinas et al., Am. J. Epidemiol., 145(12), 1061 (1997)) relates this to dioxin contamination of early production. Not relevant to current processes.
2,4-D
Oral: Acute oral LD50 for rats 639-764, mice 138 mg/kg.
Skin and eye: Acute percutaneous LD50 for rats >1600, rabbits >2400 mg/kg. Skin and eye irritant (rabbits). A skin sensitiser (guinea pigs).
Inhalation: LC50 (24 h) for rats >1.79 mg/l.
NOEL: (2 y) for rats and mice 5 mg/kg b.w.; (1 y) for dogs 1 mg/kg b.w.
ADI: (JMPR) 0.01 mg/kg b.w. [2001, 1997]; 0.01 mg/kg b.w. [1996] (sum of 2,4-D and its salts and esters, as 2,4-D); [EEC] 0.05 mg/kg b.w. (2001).
Water GV: 30 mg/l (based on ADI).
Toxicity class: WHO (a.i.) II; EPA (formulation) II
EC classification: Xn; R22| Xi; R37, R41| R43| R52, R53: (for salts Xn; R22| Xi; R41| R43| N; R51, R53; for esters Xn; R22| R43| N; R50, R53)
ECOTOXICOLOGY
2,4-D
Birds: Acute oral LD50 for wild ducks >1000, Japanese quail 668, pigeons 668, pheasants 472 mg/kg. LC50 (96 h) for mallard ducks >5620 mg/l.
Fish: Some formulations (e.g. esters) are toxic to fish, whilst others are not. LC50 (96 h) for rainbow trout >100 mg/l.
Daphnia: LC50 (21 d) 235 mg/l.
Algae: EC50 (5 d) for Selenastrum capricornutum 33.2 mg/l.
Other aquatic spp.: EC50 (14 d) for Lemna gibba 0.58 mg/l.
Bees: Not toxic to bees; LD50 (oral) 104.5 mg/bee.
Worms: LC50 (7 d) 860 mg/kg; NOEC (14 d) 100 g/kg.
Other beneficial spp.: Harmless to Trichogramma cacoeciae, Poecilus cupreus, Aleochara bilineata.
ENVIRONMENTAL FATE
2,4-D:
EHC: 29 (WHO, 1984), 84 (WHO, 1989). EHC 84 concludes that, when used as recommended, 2,4-D does not appear to produce direct toxic effects on any animal species. Animals In rats, following oral administration, elimination is rapid, and mainly as the unchanged substance. Following single doses of up to 10 mg/kg, excretion is almost complete after 24 hours, although, with higher doses, complete elimination takes longer. The maximum concentration in organs is reached after c. 12 hours.
Plants: In plants, metabolism involves hydroxylation, decarboxylation, cleavage of the acid side-chain, and ring opening.
Soil/Environment: In soil, microbial degradation involves hydroxylation, decarboxylation, cleavage of the acid side-chain, and ring opening. Half-life in soil <7 d. Koc c. 60. For a review of environmental aspects of 2,4-D, see Environmental Health Criteria 84 (WHO, 1989). Rapid degradation in the soil prevents significant downward movement under normal conditions.
|