Diquat

Diquat is a contact herbicide that produces desiccation and defoliation most often available as the dibromide, diquat dibromide. Brand names for this formulation include Aquacide, Dextrone, Preeglone, Deiquat, Spectracide, Detrone, Reglone, Reglon, Reglox, Tribune, Ortho-Diquat, Weedtrine-D, Weedol 2 and, in combination with glyphosate, Resolva.

Diquat is a non-selective herbicide that acts quickly to damage only those parts of the plant to which it is applied. It has been used in pre-harvest crop desiccation. It bonds strongly to mineral and organic particles in soil and water where it remains without significant degradation for years. However, bound to clays diquat is biologically inactive at concentrations typically observed in agricultural soils.

Diquat dibromide is moderately toxic. It may be fatal to humans if swallowed, inhaled, or absorbed through the skin in large quantities.

Production

Pyridine is oxidatively coupled to 2,2'-bipyridine over a heated Raney nickel catalyst. The ethylene bridge is formed by the reaction with 1,2-dibromoethane: