2-chloroethylphosphonic acid

(2-chloroethyl)phosphonic acid

C₂H₆ClO₃P

Colourless solid; (tech. is a clear liquid).

74-75 ℃

c. 265 ℃ (decomp.)

<0.01 mPa (20 ℃)

1.409

In water c. 1 kg/l (23 ℃). 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.

Stable in aqueous solutions having pH <5; at higher pH, decomposition occurs with the liberation of ethylene; DT5₀ 2.4 d (pH 7, 25 ℃). Sensitive to u.v. irradiation.

<1.55 ×10^-9 Pa m³ mol^-1 (calc.)

<-2.20 (25 ℃,

pKa₁ 2.5, pKa₂ 7.2

Plant growth regulator with systemic properties. Penetrates into the plant tissues, and is decomposed to ethylene, which affects the growth processes.

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.

Incompatible with alkaline materials and with solutions containing metal ions, e.g. iron^-, zinc^-, copper^-, and manganese^-containing fungicides

FAO/WHO 80 (see part 2 of the Bibliography). G. Hennighausen et al., Pharmazie, 32, 181 (1977).

Acute oral LD₅₀ for rats 3030 mg/kg (tech.).

Acute percutaneous LD₅₀ for rabbits 1560 mg/kg (tech.). Irritating to skin and eyes.

LC₅₀ (4 h) for rats 4.52 mg/l (tech.).

(2 y) for rats 3000 ppm diet.

(JMPR) 0.05 mg/kg b.w. [1997].

WHO (a.i.) U; EPA (formulation) I (tech.)

Acute oral LD₅₀ for bobwhite quail 1072 mg/kg (tech.). Dietary LC₅₀ (8 d) for bobwhite quail >5000 ppm in diet (tech.).

LC₅₀ (96 h) for carp >140, rainbow trout 720 mg/l (tech.).

EC₅₀ (48 h) 1000 mg/l (tech.).

EC₅₀ (24-48 h) for Chlorella vulgaris 32 mg/l.

Not toxic to earthworms

In plants, ethephon rapidly undergoes degradation to ethylene.

In animals, ethephon is rapidly excreted intact via the urine, and as ethylene via the expired air.

Rapidly degraded in soil, and low mobility; unlikely to leach. 

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).