Plant 2,4-dichlorophenol

In addition to the use of 2,4-dichlorophenol in the synthesis of 2,4-D herbicides (acid 2,4-D, acid 2,4-DP, acid 2,4-DB), it is also found in the selective post-emergence herbicide, diclofop-methyl [51338-27-3] (61) and as a selective pre-emergence herbicide, oxadia2on [19666-30-9] (62). A postemergence herbicide is appHed between the emergence of a seedling and the maturity of a crop plant. 

Plant uptake is one of several routes by which an organic contaminant can enter man s food chain. The amount of uptake depends on plant species, concentration, depth of placement, soil type, temperature, moisture, and many other parameters. Translocation of the absorbed material into various plant parts will determine the degree of man s exposure—i.e., whether the material moves to an edible portion of the plant. Past experience with nonpolar chlorinated pesticides suggested optimal uptake conditions are achieved when the chemical is placed in a soil with low adsorptive capacity e.g., a sand), evenly distributed throughout the soil profile, and with oil producing plants. Plant experiments were conducted with one set of parameters that would be optimal for uptake and translocation. The uptake of two dioxins and one phenol (2,4-dichlorophenol (DCP)) from one soil was measured in soybean and oats (7). The application rates were DCP = 0.07 ppm, DCDD 0.10 ppm, and TCDD = 0.06 ppm. The specific activity of the com-... 

Next, we attempted to deal with translocation of foliar-applied TCDD. Labeled dioxins were applied to the center leaflet of the first trifoliate leaf of 3-week-old soybean plants and the first leaf blade of 12-day-old oat plants. All compounds were applied in an aqueous surfactant solution (Tween 80) to enhance leaf adsorption and to keep the water insoluble dioxins in solution. Plants were harvested 2, 7, 14, and 21 days after treatment, dissected into treated and untreated parts, and analyzed separately. Neither dioxin nor chlorophenol was translocated from the treated leaf. A rapid loss of the dichlorodioxin and dichlorophenol occurred from the leaf surface. This loss may have resulted from volatilization. Very little TCDD was lost from soybean leaves while a gradual loss (38% in 21 days) did occur from oat leaves. 

Several facts have emerged from our studies with 2,7-DCDD and 2,3,7,8-TCDD. They are not biosynthesized by condensation of chloro-phenols in soils, and they are not photoproducts of 2,4-dichlorophenol. They do not leach into the soil profile and consequently pose no threat to groundwater, and they are not taken up by plants from minute residues likely to occur in soils. Photodecomposition is insignificant on dry soil surfaces but is probably important in water. Dichlorodibenzo-p-dioxin is lost by volatilization, but TCDD is probably involatile. These compounds are not translocated within the plant from foliar application, and they are degraded in the soil. 

In a cohort study of workers in two Danish chemical plants (Lynge, 1985), potential exposure to 2,4,5-trichlorophenol occurred between 1951 and 1959, when small amounts were produced or purchased to make 2,4,5-T. No overall increase in cancer incidence rate was observed, but there were significantly increased risks of soft-tissue sarcoma and lung cancer in certain subcohorts. [The Working Group noted that 2,4-dichlorophenol is an intermediate in the production of 2,4-D, which was produced by the larger of the two plants.]... 

Gimenez J, Curco D, Queral MA. Photocatalytic treatment of phenol and 2,4-dichlorophenol in a solar plant in the way to scaling-up. Catal Today 1999 54 229-243. 

Dichlorophenol, hexagonal ndls (from benz), mp 43° bp 2o6-08°at 753 mm press, vol with steam forms some unstable salts most important use is in the manuf of 2,4" D (2,4-dichlorophenoxyacetic acid), a powecful plant-growth regulator (Refs 2 6) 2,5-Dichlorophenol, crysts (from benz), mp 59° bp 209 11° volatile with steam of no coml importance (Refs 3 6) 2,6 Dichlorophenol, crysts (from petr eth), mp 66-68°, bp 220°, volatile with steam no Coml application (Refs 4 8c 6) 3,4 f it hloropkenol, ndls (from petr eth) mp 64-66°, bp 145-46° volatile with steam no coml utility (Refs 5 6)... 

Dichlorophenol, hexagonal ndls (from benz), mp 43°, bp 206-08° at 753 mm press, vol with steam forms some unstable salts most important use is in the manuf of 2,4 D (2,4-dichlorophenoxyacetic acid), a powerful plant-growth regulator (Refs 2 6)... 

TABLE 1. Photosynthetic electron-transport reactions in Cu-sufficient and Cu-deficient pea plants. Values in brackets are % of +Cu control MV, methylviologen asc, ascorbate DCIP, dichlorophenol indo-... 

Another important plant protection agent based on 2,4-dichlorophenol is di-clofop-methyl, which is produced via the intermediate nitrofen (from 2,4-dichloro-phenol and p-nitrochlorobenzene) by reduction of the nitro group, diazotization, and hydrolysis of the diazonium salt to yield the phenol with subsequent reaction with 2-chloropropionic acid methyl ester. 

TLC has been used to determine ascorbic acid in foods, pharmaceutical preparations, and biological fluids. Paper chromatography was used to separate ascorbic and dehydroascorbic acid in plant extracts, and the spots were visualized using 2,5-dichlorophenol indophenol (Bui-Nguyen, 1985). This procedure is probably applicable to TLC on cellulose. 

In pharmaceutical preparations and fruit juices, ascorbic acid is readily separated from other compounds by TLC on silica gel and quantified directly by absorption at 254 nm. Serum and plasma may be deproteinized with twice its volume of methanol or ethanol. Various ascorbic acid compounds in plant extracts and foods have been separated on cellulose layers and detected by spraying with 2,S dichlorophenol indophenol (36). Heulandite, a natural zeolite (particle size 45 p) has successfully been employed as an adsorbent and ascorbic acid and other hydrophilic vitamins have separated within 5 cm by ascending chromatography in dimethylformamide (37). HPTLC and OPLC methods have been developed to improve the separation of ascorbic acid from other water soluble vitamins, with mixed success (11). 

Only one plant (Edmonton) manufactures chlorinated phenols in Canada (Jones, 1981). The installation can produce up to 1800 and 450 metric tons of pentachlorophenol and 2,3,4,6-tetrachlorophenol per year, respectively. Although 2,4-dichlorophenol was formerly produced at the site, no other chlorinated phenol has been manufactured in Canada. Imports of chlorinated phenols into Canada have increased from 558 to 625 metric tons between 1976 and 1980. 

The solid line (Fig. 4) is the spectrum of a large standard composite of representative plant product. Although it is not apparent in this spectrum, many plant batches show as unknown impurity absorption at 11.3 n. It is, therefore, impossible to use the 11.07 band of 2,5-dichlorophenol for the analysis. The 12.58 n absorption is coincident with a 2,3,6-trichlorophenol band. However, with proper correction for the 2,3,6 interference, accurate values for the 2,5-dichlorophenol were obtained. Calculation with reference to the pure 2,4,5-trichlorophenol spectrum gives... 

Very highly purified 2,4,5-trichlorophenol is somewhat difHcult to prepare. To use it routinely for a standard in this analysis would involve considerable effort to maintain a supply. We, therefore, use as a standard a composite sample of plant material, the spectrum of which appears in Fig. 4. By calculation with reference to the spectrum of pure 2,4,5-trichlorophenol, this standard was found to contain 0.713% 2,3,6-tri- and 0.143% 2,5-dichlorophenol. Calculation with reference to the standard spectrum gives... 

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