4- Methylphenoxyacetic acid

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.

Faulkner JK, D Woodcock (1965) Fungal detoxication. Part VII. Metabolism of 2,4-dichlorophenoxyacetic and 4-chloro-2-methylphenoxyacetic acids by Aspergillus niger. J Chem Soc 1187-1191. 

Phenoxyacids (PA) have been widely used as herbicides in agriculture, forestry, and, to a lesser extent, garden activities. The principal products are represented by 2,4-D (2,4-dichlorophenoxyacetic acid) 2,4,5-T (2,4,5-trichlo-rophenoxyacetic acid) and MCPA (4-chloro, 2-methylphenoxyacetic acid) (Stevens and Sumner, 1991). 2,4,5-T has been banned in many countries for a long time because of contamination of the commercial formulations of 2,4,5-T by 2,3,7,8-tetrachlorodibenzodioxin. At present, dioxin contamination of these formulations has been reduced to very low concentrations. 

MCPA (4-Chloro-2-methylphenoxyacetic acid) and MCPB (4-chloro-2-methylphenoxybutyric acid)... 

Fig. 9.72Structures of MCPA(4-chloro-2-methylphenoxyacetic acid (I)), its metabolites 4-chloro-o-cresol (II), 5-chloro-3-methyl catechol (III), 4-chloro-2-methyl muconic acid (IV), reagent pentafluorobenzyl bromide (V), and the derivatives VI-VIII from l-lll Source Reproduced with permission from the American Chemical Society [155]... 

Soderquist, C.J. and Crosby, D.G. Dissipation of 4-chloro-2-methylphenoxyacetic acid (MCPA) in a rice field. Pestle. Sci, 6(l) 17-33, 1975. 

Steenson, T.I. and Walker, N. The pathway of breakdown of 2,4-dichloro- and 4-chloro-2-methylphenoxyacetic acid by bacteria, J. Gen. Microbiol, 16 146-155,1957. 

Table 26. The effect of 2-methylphenoxyacetic acid and its silatranylmethyl ester on the growth of cultures of plant tissues...

Silatranylmethyl ester has a higher auxin activity with respect to the culture of soya tissue than free 2-methylphenoxyacetic acid. At the same time, it has a low activity with respect to tobacco and potato cultures. 1-Silatranylesterof 4-chlorophenoxyacetic... 

Pozo, O., E. Pitarch, J.V. Sancho, and F. Hernandez (2001). Determination of the herbicide 4-chloro-2-methylphenoxyacetic acid and its main metabolite, 4-chloro-2-methylphenol in water and soil by liquid chromatography-electrospray tandem mass spectrometry. J. Chromatogr. A, 923 75-85. 

Agemian and Chau [190] have reported a method for determining low levels of 4-chloro-2-methylphenoxyacetic acid and 4-(4-chloro-2-methylphenoxy)-butyric acid in non saline and waste waters by derivatisation with pentafluorobenzyl bromide. The increased sensitivity of the pentafluorobenzyl esters of these two herbicides over the 2-chloroethyl methyl esters as well as their longer retention times make pentafluoro-benzyl bromide the preferred reagent. 

Virtanen, M., Hattula, M.L., Arstila, A.U. (1979) Behavior and fate of 4-chloro-2-methylphenoxyacetic acid (MCPA) and 2,6-dichloro-o-cresol as studied in an aquatic-terrestrial model ecosystem. Chemosphere 8, 431. 

Photosensitization for the removal of certain pollutants in photolytic processes can contribute significantly to the degradation rate. Thus, Simmons and Zepp [88] observed increases of up to 26 times of the photodegradation rates of nitroaromatic compounds due to the action of natural or commercial humic substances with solar irradiation. In another work [89], the herbicide 4-chloro-2-methylphenoxyacetic acid (MCPA) was irradiated in water with 300 nm light in the presence of different photosensitizers. This compound, which does not photolyze directly at this wavelength, could be degraded more than 95% in 5 hr when riboflavin was used as photosensitizer. 

Soley J, Vicente M, Clapes P, Esplugas S. Kinetic study of 4-chloro-2-methylphenoxyacetic acid photodegradation. Ind Eng Chem Prod Res Dev 1986 25 645-649. 

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)...

Boye, B., Brillas, E. and Dieng, M. M. (2003a) Electrochemical degradation of the herbicide 4-chloro-2-methylphenoxyacetic acid in aqueous medium by peroxi-coagulation and photoperoxi-coagulation. J. Electroanal. Chem. 540, 25-34. 

The relation between these discrepancies and the nature of the substituents (Table II) can be attributed to electronic effects (112). Similar discrepancies have been observed in systems where steric effects are present, e.g., 2-methylphenoxyacetic acid is... 

MCPA. (2-methyl-4-chlorophenoxyacetic acid 4-chloro-2-methylphenoxyacetic acid). 

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