MCPA ‘Methoxone

MCPA Methoxone (4-chloro-o-tolyloxy) acetic acid... 

MCPA, l-methyl-A-chlorophenoxyacetic acid, Methoxone, CgH ClOj. Made by chlorination of o-cresol followed by reaction with chloroethanoic acid. While crystals, m.p. 118-119 C. As usually obtained, crude MCPA contains both 4- (60%) and 6- (40%) chloro-isomers, and is a light brown solid. Selective weedkiller. 

METAXONE METHOXONE (2-METEm 4-CHLOROPHENOXY)ACETIC ACID, SODIUM SALT 2M-4KH SODIUM SALT 2M-4X Na MCPA PHENOXYLENE SODIUM (4-CHLORO-2-METHYL-PHENOXY)ACETATE SODIUM MCPA SYS 67ME... 

Among the numerous discoveries that we owe to botanists and pharmacognosts are the development of tryptophan metabolites, and especially indolylacetic acid. This compound acts as growth hormone in plants. Para-chlorinated phenoxyacetic acids (MCPA or methoxone 2,4-D or chloroxone) are mimics of indolylacetic acid (bioisostery) and show similar phytohormonal properties at high doses they serve as weeders. Ring-chlorinated phenoxyacetic acids were later introduced in molecules as varied as meclofenoxate (cerebral metabohsm), clofibrate (Upid metabolism) and ethacrynic acid (diuretic). 

Methoxcide, see Methoxychlor Methoxo, see Methoxychlor Methoxone, see MCPA... 

The two most used herbicides in this class are 2-methyl-4-chlorophen-oxyacetic acid (4.55) (MCPA or Methoxone )> and 2,4-dichlorophen-oxyacetic acid (2,4-D, or Chloroxone ). The use of 2,4,5-trichlorophen-oxyacetic acid has been suspended, because the usual process of manufacture contaminates it with a teratogenic dioxin (6.51). Tests carried out on 30 annual weeds that normally impoverish cereal crops showed that, by choosing the right compound and applying it at the right time, almost all the weeds can be killed. It is not known why cereals are relatively unaffected. In some experiments cereals were made to absorb as much of the phenoxyacetic acids as the weeds do (normally they absorb less), but the cereals remained unharmed (Wood, Wolfe and Irving, 1947). On the whole, dicotyledons are killed and monocotyledons survive, but there are striking exceptions. Thus onions (monocotyledons) are susceptible to the phenoxyacetic acids, whereas chickweed and cleavers (dicotyledons) are resistant because they have an enzyme that removes the side-chain. 

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