Review in Synthesis and Biological Activities of Azo Compounds

In this research, we deal with azo compounds, which are organic compounds that contain in their structure one or more active groups, that are the bridge azo groups (-N=N-), which can bind with the alpha group, giving the formula (R-N=N-R) and they are called aliphatic azo compounds, and if associated with an aromatic group (Ar-N=N-Ar), they are called aromatic azo compounds . We classified the azo compounds according to the groups attached to their ends (which included aliphatic compounds and aromatic compounds) the second class according to the number of azo groups (mono-, di-, tri-, and poly-azo), and the third class according to the type of rings associated with the azo groups (homocyclic azo compounds and heterocyclic azo compounds) . Methods for preparing azo compounds were indicated, including two methods: The direct method (which includes the reduction of aromatic nitro compounds in the presence of zinc, and this method is used in the preparation of the corresponding azobenzene compounds) or the indirect method, which includes two steps in this type of reaction. The first step is the nitrogenation reaction and the second step is the coupling reaction . Reference was also made to the preparation of diazonium salts through the reaction of primary amines with nitrous acid, which was prepared simultaneously from the reaction of sodium nitrite with mineral acid, at a low temperature between (0-5 °C) because nitrous acid dissociates quickly, and we discussed the resonant forms of diazonium salts .