Selective systemic herbicide absorbed through the roots and foliage, with rapid translocation both acropetally and basipetally.
Metsulfuron-methyl
Herbicide
HRAC B WSSA 2; sulfonylurea
NOMENCLATURE
Chemical Abstracts name methyl 2-[[[[(4-methoxy-6-methyl-1,3,5-triazin-2-yl)amino]carbonyl]amino]sulfonyl]benzoate
CAS RN [74223-64-6]
PHYSICAL CHEMISTRY
Mol. wt. 381.4
M.f. C14H15N5O6S
Form Colourless crystals; (tech., off-white solid, with a faint ester-like odour).
M.p. 158 ºC
V.p. 3.3 ´ 10-7 mPa (25 ºC)
KOW logP = -1.74 (pH 7)
Henry 2.3 ´ 10-10 Pa m3 mol-1 (calc.)
S.g./density 1.47
Solubility In water 0.55 (pH 5), 2.79 (pH 7), 213 (pH 9) (all in g/l, 25 ºC). In hexane 0.00079, xylene 0.58, ethanol 2.3, methanol 7.3, acetone 36, dichloromethane 121 (all in g/l, 20 ºC).
Stability Stable in air up to c. 140 ºC. Hydrolysis DT50 (25 °C), 22 d (pH 5), stable (pH 7 and 9).
pKa 3.3
APPLICATIONS
Biochemistry Branched chain amino acid synthesis (ALS or AHAS) inhibitor. Acts by inhibiting biosynthesis of the essential amino acids valine and isoleucine, hence stopping cell division and plant growth. Selectivity derives from rapid metabolism in the crop. Metabolic basis of selectivity in sulfonylureas reviewed (M. K. Koeppe & H. M. Brown, Agro-Food-Industry, 6, 9-14 (1995)).
Mode of action Selective systemic herbicide absorbed through the roots and foliage, with rapid translocation both acropetally and basipetally. Susceptible plants cease growth almost immediately after post-emergence treatment, and are killed in 7-21 days. Surfactants increase the activity of metsulfuron-methyl on certain broad-leaved weeds.
Metsulfuron-methyl 95%TC
