Orthophenylene

Ortho-phenylene, also known as benzene-1,2-diamine or 1,2-diaminobenzene, is an organic compound with the chemical formula C6H4(NH2)2. It is one of three structural isomers of diaminobenzene, with the other two being meta-phenylene and para-phenylene. In ortho-phenylene, the two amino groups are attached to adjacent carbon atoms on the benzene ring.

This compound is typically encountered as a colorless to pale yellow crystalline solid. It is soluble in water and common organic solvents like ethanol and ether. Ortho-phenylene is a relatively weak base due to the electron-withdrawing nature of the benzene ring and the presence of two amino groups.

Ortho-phenylene serves as a valuable building block in organic synthesis. It is particularly important in the preparation of heterocyclic compounds. For instance, its reaction with diketones or alpha-halo ketones can lead to the formation of benzimidazoles, a class of compounds with significant pharmaceutical and material science applications. It is also used in the synthesis of quinoxalines and other nitrogen-containing heterocycles. Industrially, it can be produced by the reduction of 2-nitroaniline.