Terbuthylazine

Terbuthylazine is a selective herbicide that belongs to the triazine class of chemicals. It is primarily used in the control of broadleaf weeds and grasses in crops such as maize, sorghum, and sugarcane.

Chemical Structure and Properties

Terbuthylazine is a symmetrical triazine herbicide, with the chemical formula C9H16ClN5. It is a white crystalline solid at room temperature, with a melting point of 175-176°C. It is slightly soluble in water and readily soluble in most organic solvents.

Mode of Action

Terbuthylazine acts by inhibiting photosynthesis in target plants. It specifically inhibits the photosystem II (PSII) enzyme, which is essential for the conversion of light energy into chemical energy during photosynthesis. This inhibition leads to the death of the plant.

Usage and Application

Terbuthylazine is applied pre-emergence or early post-emergence. The rate of application depends on the crop and the weed species to be controlled. It is often used in combination with other herbicides to broaden the spectrum of weed control and to prevent the development of herbicide resistance.

Environmental Impact

Terbuthylazine is moderately persistent in the soil, with a half-life of 30-60 days. It has a low potential for bioaccumulation but can leach to groundwater in certain soil types. It is toxic to aquatic organisms and non-target plants.

Health Effects

Exposure to terbuthylazine can cause irritation to the eyes, skin, and respiratory tract. Long-term exposure can lead to liver and kidney damage. It is classified as a Category 3 carcinogen by the European Chemicals Agency (ECHA).

Regulation

In the European Union, the use of terbuthylazine is regulated under the Pesticides Regulation (EC) No 1107/2009. It is approved for use in certain crops under specific conditions.

See Also

• Atrazine
• Simazine
• Photosystem II inhibitors

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