Chlorophenoxyacetic acid

One of the economically most important areas in the control of plant processes is defoliation—the intentional removal of leaves. Large quantities of several chemicals currently are employed for this purpose, including magnesium chlorate and DEF (S,SyS-tributyl phosphor otrithioate), and the principal commercial value is for defoliation of cotton. Several synthetics such as 4-chlorophenoxyacetic acid and naphthalene-1-acetic acid are used to provide the opposite but related effect of retarding or limiting fruit drop in apples, stone fruits, and grapes. 

In several AT studies, pesticide levels in the Ebro were found to be high. Hildebrandt et al. [50] found a homogeneous contamination pattern from atrazine (and also from simazine from May 2000) in intensive Rioja cultivation areas throughout the Ebro. Nearer to the delta, Barata et al. [72] found high levels of bentazone, methyl-4-chlorophenoxyacetic acid, propanil, molinate and fenitrothion in water, while Kuster et al. [71] found low concentration levels of atrazine and simazine at the delta, but high levels of other pesticides used in rice cultivation. Importantly, Hildebrandt et al. [50] found that levels of pesticides in groundwater... 

Photolytic. Photolysis of 2,4-D in distilled water using mercury arc lamps (A, = 254 nm) or by natural sunlight yielded 2,4-dichlorophenol, 4-chlorocatechol, 2-hydroxy-4-chlorophenoxyacetic acid, 1,2,4-benzenetriol, and polymeric humic acids. The half-life for this reaction is 50 min (Crosby and Tutass, 1966). A half-life of 2 to 4 d was reported for 2,4-D in water irradiated at 356 nm (Baur and Bovey, 1974). 

Chlorophenoxyacetic acid, see 2,4-D 4-(4-Chlorophenoxy)aniline, see Chlnrnxiiron IV-(4 -Chlorophenoxy) phenyl-A -methylurea, see... 

Hydroxy-4-chlorophenoxyacetic acid, see 2,4-D 3 -Hydroxy-4 -chloropropionanilide, see Propanil Hydroxycinnamic acid, see Carbaryl... 

Crystal structures of the isostructural complexes [ZnfOH LJ (LH = phenoxyacetic acid or 4-chlorophenoxyacetic acid) have been reported, and the metal has been shown to be in a distorted octahedral Oe environment (108). 

Table 29. The effect of 2-methyl-4-chlorophenoxyacetic acid (I) and its silatranylmethyl ester (II) on the growth of cultures of plant tissues...

Common broadleaf weeds in turfgrasses, such as those listed in Table 19.1, are also controlled by other herbicides such as 2,4-D, dicamba, dichloroprop, 2-methyl-4-chlorophenoxyacetic acid (MCPA), mecoprop, clopyralid, and tri-clopyr, or combinations of these products (Bingham and Shaffran, 1982 Bingham et al., 1986 Coats et al., 1994 Johnson and Murphy, 1995 Murphy and Johnson, 1995). 

In recent years, scientists have found that many synthetic growth regulators will develop fruit in plants. The best of these are 4-chlorophenoxyacetic acid and 2-naphthoxyacetic acid. These chemicals are most effective on fruits that have many ovules, such as tomato, squash, egg-plant, and fig. They are usually rather ineffective, however, on peach, cherry, plum, and other stone fruits. Many fruits that can be set by such hormonal compounds also can be set by the gibberellins. In addition, gibberellins can set fruit in some species that do not respond to the other chemicals. 

Apart from the sorbents already mentioned in connection with HPTLC pre-coated layers, a micro-crystalline cellulose has also been produced in an average particle size and a narrow particle size distribution suitable for HPTLC (9.). HPTLC pre-coated plates cellulose P 254 s (E. Merck, Darmstadt), composed of this microcrystalline cellulose, were used to separate Trevespan 6058. This is a mixture of the substances ioxynil (3,5-diiodo-4-hydroxy-benzo-nitrile), flurenol (9-hydroxyfluorenecarboxylic acid) and MCPA (2-methyl-4-chlorophenoxyacetic acid). For comparison purposes Trevespan 6038 was also separated on HPTLC pre-coated plates silica gel 60 F 254 (E. Merck, Darmstadt). 

Boye B, Michaud PA, Marselli B, Dieng MM, Brillas E, Comninellis C (2002) Anodic oxidation of 4-chlorophenoxyacetic acid on synthetic boron-doped diamond electrodes. New Diamond Front Carbon Technol 12 63-72... 

Boye, B., Dieng, M. M. and Brillas, E. (2002) Degradation of herbicide 4-chlorophenoxyacetic acid by advanced electrochemical oxidation methods. Environ. Sci. Technol. 36, 3030-3035. 

Brillas, E., Boye, B. and Dieng, M. M. (2003) Peroxi-coagulation and photoperoxi-coagulation treatments of the herbicide 4-chlorophenoxyacetic acid in aqueous medium using an oxygen-diffusion cathode. J. Electrochem. Soc. 150, E148-E154. 

Fig. 19.16 TOC removal vs. consumed specific charge for the treatment of 100 cm3 of (open circle, filled circle) 194 mg dm-3 4-CPA (4-chlorophenoxyacetic acid), (open square, filled square) 200 mg dm 3 MCPA (4-chloro-2-methylphenoxyacetic acid), (open triangle, filled triangle) 230 mg dm 3 2,4-D, (open diamond, filled diamond) 266 mg dm-3 2,4,5-T solutions in 0.05 M Na2S04 + H2SO4 of pH 3.0 at 100 mA and at 35°C using a BDD/02 cell, open circle, open square, open triangle, open diamond) Anodic oxidation with electrogenerated H2O2, (filledcircle, filled square, filled triangle, filled diamond) electro-Fenton with 1 mM Fe2+ (Brillas et al. 2004b)...

Disposition in the Body. Readily absorbed after oral administration. About 85% of a dose is excreted in the urine as a glucuronide conjugate in 24 hours together with small amounts of unchanged drug, and the oxidised metabolites, 4-chlorophenoxylactic acid, 4-chlorophenoxyacetic acid and 4-chlorophenol. 

The mixture of cresols obtained from coal tar is called cresylic acid, an important technical product used as a disinfectant and in the manufacture of resins and tricresyl phosphate. Cresols are useful as raw materials for various chemical products, disinfectants, and synthetic resins. The isomer o-cresol is a starting material for the herbicides 4,6-dinitro-o-cresol and 2-methyl-4-chlorophenoxyacetic acid. The isomers w-cresol and p-cresol are used in phenol-formaldehyde resins and are converted to tricresyl phosphate (a plasticizer and gasoline additive) and to di-t-butyl cresols (antioxidants called BHT). 

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