MCPA 4-Chloro-2-methylphenoxyacetic

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]... 

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)...

The analysis of pesticides in samples of high color content needs the optimization of cleanup parameters. Carrots, spinach, and apple extracts were extracted with acetone, partitioned into methylene chloride, and finally purified on a mixed adsorbent column (Table 1). The loadability of the TLC plates and the effectiveness of this cleanup method were tested not only by GLC but by TLC as well (23). TLC can be used as a detection method, as a test of the cleanup (see above), and furthermore can be applied as a cleanup procedure (16). In MCPA (4-chloro-2-methylphenoxyacetic acid) analysis the recovery data showed that TLC cleanup was as effective as H20-toluene partitioning. 

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. 

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. 

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

It is prepared by the condensation of 4-chloro-o-cresol with sodium mono-chloroacetate in alkaline aqueous solution. As the isomeric 6-chloro-o-cresol is always present as an impurity in 4-chIoro-o-cresol, the crude MCPA also contains isomeric 6-chloro-3-methylphenoxyacetic acid. 

Alkyl substitution on the ring increases only the activity of chlorophenoxy acids. In practice, only 4-chloro-2-methylphenoxyacetic acid derivatives (MCPA, MCPP anc MCPB) are used in agriculture. Of the trisubstituted products, the structural analogue of 2,4,5-T — 2,4-dichloro-5-methylphenoxyacetic acid has considerable activity. 

The chlorophenoxyalkanoic acids constitute yet another economically important group of halogenated aromatic hydrocarbons. They are widely used as herbicides to control dicotyledonous weeds. The most important of them are 2,4-D and its propionic and butyric acid homologs, 4-chloro> 2-methylphenoxyacetic acid (MCPA), and 2,4,5>trichlorophenoxyacetic add (2,4,5-T). In all the cases studied, aerobic biodegradation proceeds by removal of the aliphatic side chain with the formation of the corresponding chlorinated phenoL Thus, formation of 2,4 chlorophenol from both 2,4-D and 4-(2,4-dichlorophenoxy)-butyric acid, 4-chloro-o-cresol from MCPA, and 2,4,5-trichlorophenol from 2,4,5-T has been... 

Chloro-l-methyletltyl)ether, see Bis(2-chloroisopropyl)ether 4-Chloro-2-methylphenoxyacetic acid, see MCPA... 

Abbott et al. [1] have separated six herbicides, e. g., 2,4-, 2,4,5-T and 4-chloro-2-methylphenoxyacetic acid (MCPA), 2,2-dichloropropionic acid (dalapon) in the S-chamber on mixed layers of sihca gel G-kiesel-guhr G (2 + 3) liquid paraffin-benzene-acetic acid-cyclohexane (4 + H + 8 + 77) was the solvent. It has been possible also to detect herbicide residues in extracts of soil and water, using TLC. 

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