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ethephon
Plant growth regulator
ethylene generator
NOMENCLATURE
Common name ethephon (ANSI, Canada); chorethephon (New Zealand)
IUPAC name 2-chloroethylphosphonic acid
Chemical Abstracts name (2-chloroethyl)phosphonic acid
CAS RN [16672-87-0] EEC no. 240-718-3
PHYSICAL CHEMISTRY
Mol. wt. 144.5 M.f. C2H6ClO3P Form Colourless solid; (tech. is a clear liquid). M.p. 74-75 ºC B.p. c. 265 ºC (decomp.) V.p. <0.01 mPa (20 ºC) KOW logP <-2.20 (25 ºC, unstated pH) Henry <1.55 ´ 10-9 Pa m3 mol-1 (calc.) S.g./density 1.409?.02 (20 ºC) (tech.) Solubility In water c. 1 kg/l (23 ºC). Readily soluble in methanol, ethanol, isopropanol, acetone, diethyl ether, and other polar organic solvents. Sparingly soluble in non-polar organic solvents such as benzene and toluene. Insoluble in kerosene and diesel oil. Stability Stable in aqueous solutions having pH <5; at higher pH, decomposition occurs with the liberation of ethylene; DT50 2.4 d (pH 7, 25 °C). Sensitive to u.v. irradiation. pKa pKa1 2.5, pKa2 7.2
COMMERCIALISATION
History Plant growth regulator introduced by Amchem Products Inc. (now Bayer CropScience). Patents US 3879188; US 3896163; US 3897486 Manufacturers Agrochem; Bayer CropScience; Cedar; Griffin; Sharda
APPLICATIONS
Mode of action Plant growth regulator with systemic properties. Penetrates into the plant tissues, and is decomposed to ethylene, which affects the growth processes. Uses To promote pre-harvest ripening in apples, currants, blackberries, blueberries, cranberries, morello cherries, citrus fruit, figs, tomatoes, sugar beet and fodder beet seed crops, coffee, capsicums, etc.; to accelerate post-harvest ripening in bananas, mangoes, and citrus fruit; to facilitate harvesting by loosening of the fruit in currants, gooseberries, cherries, and apples; to increase flower bud development in young apple trees; to prevent lodging in cereals, maize, and flax; to induce flowering of Bromeliads; to stimulate lateral branching in azaleas, geraniums, and roses; to shorten the stem length in forced daffodils; to induce flowering and regulate ripening in pineapples; to accelerate boll opening in cotton; to modify sex expression in cucumbers and squash; to increase fruit setting and yield in cucumbers; to improve the sturdiness of onion seed crops; to hasten the yellowing of mature tobacco leaves; to stimulate latex flow in rubber trees, and resin flow in pine trees; to stimulate early uniform hull split in walnuts; etc. Max. application rate per season 2.18 kg/ha for cotton, 0.72 kg/ha for cereals, 1.44 kg/ha for fruit. Formulation types EC; SL. Compatibility Incompatible with alkaline materials and with solutions containing metal ions, e.g. iron-, zinc-, copper-, and manganese-containing fungicides. Selected products: 'Agritrel' (Cequisa); 'Cerone' (Bayer CropScience); 'Coolmore' (Barclay); 'Eteroc' (Rocca); 'Ethrel' (Bayer CropScience); 'Super Boll' (Griffin); mixtures: 'Finish' (+ cyclanilide) (Bayer CropScience); 'Terpal' (+ mepiquat chloride) (BASF, DuPont, Bayer CropScience)
OTHER PRODUCTS
'Arvest' (Sipcam Phyteurop); 'Boll'd' (Agriliance); 'Charger' (Bayer CropScience); 'Cybele' (Sipcam Phyteurop); 'Etheverse' (Bayer CropScience); 'Ethio' (Agrochem); 'Florel' (Bayer CropScience); 'Halmstarker' (Stefes); 'Phosgrow' (Sabero); 'Pluck' (Cedar, Crystal); 'Prep' (Bayer CropScience); 'Spatial' (Stefes); 'Tomathrel' (Bayer CropScience); 'Vivax' (Bayer CropScience) mixtures: 'Banshee XL' (+ chlormequat chloride) (Barclay); 'Banshee' (+ mepiquat chloride) (Barclay); 'Concord' (+ imazaquin-ammonium+ chlormequat chloride) (BASF); 'CottonQuik' (+ urea sulfate) (Griffin); 'Cyclade' (+ mepiquat chloride+ chlormequat chloride) (BASF); 'EYK-2201' (+ urea sulfate) (Entek); 'Ranfor' (+ chlormequat chloride) (Calliope); 'Satellite' (+ imazaquin-ammonium+ chlormequat chloride) (BASF); 'Spatial Plus' (+ chlormequat chloride) (Stefes); 'Strate' (+ chlormequat chloride) (Bayer CropScience); 'Sypex' (+ chlormequat chloride) (BASF); 'Terpal C' (+ chlormequat chloride) (BASF); 'Terpitz' (+ mepiquat chloride) (Me2); 'Tycoon' (+ chlormequat chloride) (GreenCrop); 'Upgrade' (+ chlormequat chloride) (Bayer CropScience) Discontinued products: 'Bromoflor' * (Rhône-Poulenc); 'Ibis' * (Rhône-Poulenc); 'Stantion' * (Aventis); 'Cepha' * (GAF); 'Etherfon' * (Productos OSA); 'Stance' * (Stefes)
ANALYSIS
Product analysis by measuring the ethylene, or phosphate ion, produced on treatment with concentrated alkali (CIPAC Handbook, 1998, H, 165). Residues determined by conversion to the dimethyl ester, measured by glc with NPD or FPD (Pestic. Anal. Man., Vol. II; Anal. Methods Residues Pestic., 1988, Part II; W. P. Cochrane, J. Assoc. Off. Anal. Chem., 1976, 59, 617).
MAMMALIAN TOXICOLOGY
Reviews FAO/WHO 80 (see part 2 of the Bibliography). G. Hennighausen et al., Pharmazie, 32, 181 (1977). Oral Acute oral LD50 for rats 3030 mg/kg (tech.). Skin and eye Acute percutaneous LD50 for rabbits 1560 mg/kg (tech.). Irritating to skin and eyes. Inhalation LC50 (4 h) for rats 4.52 mg/l (tech.). NOEL (2 y) for rats 3000 ppm diet. ADI (JMPR) 0.05 mg/kg b.w. [1997]. Toxicity class WHO (a.i.) U; EPA (formulation) I (tech.) EC classification Xn; R20/21| C; R34| R52, R53: for preparations containing ³25%, C; R20/21, R34: for 25%>concn.³10%,C; R34: for 10%>concn.³5%, Xi; R36/37/38
ECOTOXICOLOGY
Birds Acute oral LD50 for bobwhite quail 1072 mg/kg (tech.). Dietary LC50 (8 d) for bobwhite quail >5000 ppm in diet (tech.). Fish LC50 (96 h) for carp >140, rainbow trout 720 mg/l (tech.). Daphnia EC50 (48 h) 1000 mg/l (tech.). Algae EC50 (24-48 h) for Chlorella vulgaris 32 mg/l. Other aquatic spp. Low toxicity. Bees Harmless to bees. Worms Not toxic to earthworms.
ENVIRONMENTAL FATE
Animals In animals, ethephon is rapidly excreted intact via the urine, and as ethylene via the expired air. Plants In plants, ethephon rapidly undergoes degradation to ethylene. Soil/Environment Rapidly degraded in soil, and low mobility; unlikely to leach.
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