Triazine herbicides are broad-spectrum herbicides with the basic chemical structure of above. The IUPAC Name is 6-chloro-1,3,5-triazine-2,4-diamine, wherein X = Cl, OCH3, SCH3, etc; R1, R2, R3 = H, lower alkyl or alkenyl group; R4 = low alkyl or alkenyl group.
They are classified as persistent organic compounds because they resist chemical and biological degradation. Triazines appear to be selective herbicides to fight against an extensive range of weeds in crops such as corn, millet, sugarcane, or sorghum, including turfs, such as golf courses and residential lawns. They are applied either early pre-plant, preemergence, or post-emergence, being efficient in weeds prevention. The metabolic pathways of triazine herbicides are well-known through chromatography and spectral analysis.
Triazine herbicides are used as selective weedkillers. Their toxicity is exerted on the chlorophyll. They produce the breakdown in the electron transportation throughout photosynthesis, which would cause nitrate accumulation and an increased oxidative damage to photosynthetic tissues. The main symptom due to this herbicide is chlorosis, the leaf edge becomes yellow, and the whole plant dies. The herbicide does not work in darkness. Thus, the degree of toxicity is directly related to light intensity.
Atrazine, (2-chloro-4-ethylamino-6-isopropyl-amino-s-triazine), is the triazine herbicide that has the greatest yield. It is a white crystalline compound which results from the reaction of ethylamine and isopropylamine with cyanuric acid chloride. Atrazine is usually applied in a water spray before the weed emerges.
The appearance of weeds that have developed a tolerance to triazines is an increasing problem encountered in agriculture. Sometimes the tolerance is almost complete.