Chemical Properties
Crystalline Solid
Uses
Auxin-type herbicide.
Production Methods
Quinmerac is commercially produced through a multi-step synthesis starting with the Skraup reaction of 3-amino-4-chlorobenzoic acid with glycerol and sulfuric acid to form 8-chloroquinoline-3-carboxylic acid, followed by selective nucleophilic substitution of the 8-chloro group with methanethiol under basic conditions to yield 8-(methylthio)quinoline-3-carboxylic acid, which is then oxidised with hydrogen peroxide or peracid to the corresponding methylsulfonyl derivative, quinmerac.
Definition
ChEBI: A quinolinemonocarboxylic acid that is quinoline-8-carboxylic acid carrying additional methyl and chloro substituents at positions 3 and 7 respectively. A residual herbicide used to control broad-leaved weeds on a range of crops including cereals, rape and
beet.
Mechanism of action
Selective. Absorbed by roots, synthetic auxin
Environmental Fate
In the field, the DT
50 of quinmerac
may range from 3 to 33 days. Losses due to volatilization
are negligible. Soil moisture conditions greatly influence
quinmerac persistence by moderating microbial degradation
and soil leaching. Quinmerac is only slightly adsorbed
to the soil.
Metabolism
Chemical. Quinmerac is stable to heat, light, and in
aqueous solutions with pH values between 3 and 9.
Plant. The degradation and metabolic pathways of
quinmerac have not been extensively studied. In plants,
oxidation of the 3-methyl group to the alcohol and
hydroxylation at the 2-quinoline position are the major
metabolism reactions (56). These quinmerac metabolites
are subsequently conjugated to carbohydrates. The
quantity of quinmerac metabolized varies among species,
ranging from 5% to 80% (56).
Soil. In the soil, degradation of quinmerac was similar
to that observed in plants, resulting in the same
oxygenated and hydroxylated metabolites.
Toxicity evaluation
Quinmerac is excreted in the urine
of mammals and appears to remain primarily unmodified.
The acute oral LD
50 in rat is >5000 mg/kg.
