2,4-D

Herbicide

HRAC  O WSSA  4; aryloxyalkanoic 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 0.7-0.8  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 

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.  Compatibility Compatibility depends upon the particular formulation. 

CERTIFICATE OF ANALYSIS