Chemically, it is a halogenated triazine; compared with atrazine (1958 inv., Geigy lab) and simazine, it has a tert-butyl group −[C−(CH3)3] in place of the isopropyl −[CH−(CH3)2] and ethyl group, respectively.

[1][2] The sim-azine molecule with 2 ethyl groups is symmetric and flat (excepting its equal NH−C2H5 ends).

The threefold substituted triazines have resonance of the free (non-bonding,

-) electron pairs, resulting in equivalent mesomeric structures.

Simazine remains active in the soil for 2 to 7 months or longer after application.