2-Methyl-4-Chlorophenoxyacetic Acid (MCPA)

MCPA is a powerful, selective, widely used phenoxy herbicide. The pure compound is a brown-colored powder. Because it is inexpensive, MCPA is used in various chemical applications. Its carboxylic acid group allows the formation of conjugated complexes with metals. The acid functionality makes MCPA a versatile synthetic intermediate for more complex derivatives. Templeman and Foster were searching for compounds with similar or greater selective activity than 1-naphthaleneacetic acid in inhibiting the growth of weeds while not adversely affecting the growth of cereal grains.  MCPA is used as an herbicide, generally as its salt or esterified forms. Used thus, it controls broadleaf weeds, including thistle and dock, in cereal crops and pasture. It is selective for plants with broad leaves, and this includes most deciduous trees. Clovers are tolerant at moderate application levels.