2.4.5- Trichlorophenoxyacetic

Abbreviations ABA = abscisic acid 2,4-D = 2,4-dichlorophenoxyacetic acid DNP = 2,4-dinitrophenol GA3 = gibberellic acid IAA = indole-3-acetic acid IB A = indole-3-butyric acid NAA = naphthalene-1-acetic acid NPA = naphthylphthalamic acid PEP = phos-phoenolpyruvate 2,3,5-T = 2,3,5-trichlorophenoxyacetic acid TIBA = 2,3,5-triiodoben-zoic acid. 

Alkanes can be simultaneously chlorinated and chlorosulfonated. This commercially useful reaction has been appHed to polyethylene (201—203). Aromatics can be chlorinated on the ring, and in the presence of a free-radical initiator alkylaromatic compounds can be chlorinated selectively in the side chain. King chlorination can be selective. A patent shows chlorination of 2,5-di- to 2,4,5-trichlorophenoxyacetic acid free of the toxic... 

Figure 13.11 Column-switcliing RPLC trace of a surface water sample spiked with eight chlorophenoxyacid herbicides at the 0.5 p-g 1 level 1, 2,4-dichlorophenoxyacetic acid 2, 4-chloro-2-methylphenoxyacetic acid 3, 2-(2,4-diclilorophenoxy) propanoic acid 4, 2-(4-cliloro-2-methylphenoxy) propanoic acid 5, 2,4,5-trichlorophenoxyacetic acid 6, 4-(2,4-dichlorophenoxy) butanoic acid 7, 4-(4-chloro-2-methylphenoxy) butanoic acid 8, 2-(2,4,5-tiichlorophenoxy) propionic acid. Reprinted from Analytica Chimica Acta, 283, J. V. Sancho-Llopis et al., Rapid method for the determination of eight chlorophenoxy acid residues in environmental water samples using off-line solid-phase extraction and on-line selective precolumn switcliing , pp. 287-296, copyright 1993, with permission from Elsevier Science.

ENDOR and ESEEM studies of phthalate dioxygenase (PDO) (7, 84), benzene dioxygenase (85), 2-halobenzoate 1,2-dioxygenase (86), 2,4,5-trichlorophenoxyacetate monooxygenase (86a), spinach bef complex (8), and the bci complexes from Rhodobacter capsulatus (7, 84) and in bovine mitochondrial membranes (87) (Fig. 16) have identified two nitrogen nuclei coupled to the [2Fe-2S] cluster with isotropic N... 

PDO, phthalate dioxygenase BDO, benzene dioxygenase 2,4,5-T-MO, 2,4,5-trichlorophenoxyacetate monooxygenase UHDBT, undecyUiydroxybenzothiazole. 

Cl4-DBpD) may occur in trace amounts in the herbicide, 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) (I, 2). Radiolabeled preparations of this dioxin are needed to facilitate studies of its degradation chemistry, metabolism, and mode of action. 

TJesticides derived from chlorinated phenols (Table I) are among the most prominent of those currently in worldwide use. Several major herbicides have been applied in large quantities in subtropical locations. Cahfornia used more than 1,200,000 pounds of 2,4-dichlorophenoxyacetic acid (2,4-D) and its derivatives in 1970 (I) Hawaii consumed some 465,000 pounds of pentachlorophenol (PCP) in 1968 (2), and the amount of combined butyl esters of 2,4-D and 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) released in one area of Cambodia during two months of 1969 was estimated to exceed 77,000 pounds (3). 

TAetection of the highly potent impurity, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in the herbicide 2,4,5-trichlorophenoxyacetic acid (2,4,5-T), necessitated an environmental assessment of the impact of this contaminate. Information was rapidly needed on movement, persistence, and plant uptake to determine whether low concentrations reaching plants, soils, and water posed any threat to man and his environment. Because of the extreme toxicity of TCDD, utmost precautions were taken to reduce or minimize the risk of exposure to laboratory personnel. Synthesis of uniformly labeled C-TCDD by Muelder and Shadoff (I) greatly facilitated TCDD detection in soil and plant experiments. For unlabeled experiments it seemed wise to use only small quantities of diluted solutions in situations where decontamination was feasible and to rely on the sensitivity afforded by electron capture gas chromatography... 

Tetrachlorodibenzo-p-dioxin (TCDD) is a contaminant in 2,4,5- trichlorophenoxyacetic acid (2,4,5-T) which may occur in the manufacturing process. Before 1971 some samples of 2,4,5-T contained from 2-50 ppm TCDD (i) in the technical acid. Highest concentrations of TCDD occurred before 1968. 

Daubaras DL, CD Hershberger, K Kitano, AM Chakrabarty (1995) Sequence analysis of a gene cluster involved in metabolism of 2,4,5-trichlorophenoxyacetic acid by Burkholderia cepacia ACHOO. Appl Environ Microbiol 61 1279-1289. 

Daubaras DL, K Saido, AM Chakrabarty (1996) Purification of hydroxyquinol 1,2-dioxygenase and maley-lacetate reductase the lower pathway of 2,4,5-trichlorophenoxyacetic acid metabolism by Burkholderia cepacia ACllOO. Appl Environ Microbiol 62 4276-4279. 

Haugland RA, DJ Schlemm, RP Lyons, PR Sferra, AM Chakrabarty (1990) Degradation of the chlorinated phenoxyacetate herbicides 2,4-dichlorophenoxyacetic acid and 2,4,5-trichlorophenoxyacetic acid by pure and mixed bacterial cultures. Appl Environ Microbiol 56 1357-1362. 

So far as the author is aware, the first statement of the herbicidal action of 2,4-dichlorophenoxyacetic acid, made in the United States, was in a publication by Hamner and Tukey (14) in 1944. They sprayed 2,4-dichlorophenoxyacetic acid and 2,4,5-trichlorophenoxyacetic acid on bindweed and obtained a complete kill down to the root tips. At about the same time Hamner and Tukey (13) and Marth and Mitchell (24) demonstrated the effect of 2,4-dichlorophenoxyacetic acid as a differential herbicide on lawns. All plants growing on the lawns (except the grasses) were destroyed with apparently no noticeable ill effect on the grasses. 

Kraus and Mitchell have published an interesting paper (20) on the effects of a variety of substances including 2,4-dichlorophenoxyacetic acid and 2,4,5-trichlorophenoxyacetic acid on plant growth their experiments were carried out in 1943. 

Shadoff, L.A., R.A. Hummel, L. Lamparski, and J.H. Davidson. 1977. A search for 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in an environment exposed annually to 2,4,5-trichlorophenoxyacetic acid ester (2,4,5-T) herbicides. Bull. Environ. Contam. Toxicol. 18 478-485. 

Many pesticides are moderate to weak acids. Strong acid pollutants are fully ionised at ambient pH. Examples include trifluoroacetic and chloroacetic acids, whose use as herbicides has been banned but which still occur as solvent degradation products [16], or the pesticide 2,4,5-trichlorophenoxyacetic acid (P 2.83). 

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