Simazine

Simazine is an herbicide of the triazine class. The compound is used to control broad-leaved weeds and annual grasses.
Simazine's HRAC classification is Group C1, Group C, Group 5, as it inhibits photosynthesis at photosystem II.

Preparation

Simazine may be prepared from cyanuric chloride and a concentrated solution of ethyl amine in water. The reaction is highly exothermic and is therefore best carried out below 10 °C.
Cyanuric chloride decomposes at high temperatures into hydrogen chloride and hydrogen cyanide, both of which are highly toxic by inhalation.

Properties and uses

Simazine is an off-white crystalline compound which is sparingly soluble in water. It is a member of the triazine-derivative herbicides, and was widely used as a residual non-selective herbicide, but is now banned in European Union states. Like atrazine, a related triazine herbicide, it acts by inhibiting photosynthesis. It remains active in the soil for two to seven months or longer after application.