Concentration Effects in the Hydrogenation of 4-Nitro-2′-Hydroxy-5′-Methylazobenzene over Skeletal Nickel in an Aqueous 2-Propanol Solution

Abstract

The kinetics of hydrogenation of 4-nitro-2′-hydroxy-5′-methylazobenzene in aqueous 2-propanol solution over the skeletal nickel is investigated at different initial concentrations. It is established that the hydrogenation of 4-nitro-2′-hydroxy-5′-methylazobenzene over a skeletal nickel in azeotropic aqueous 2-propanol solution proceeds via two parallel pathways at both low and high initial concentrations. It is shown that increasing the initial concentration of the hydrogenated compound above its level of solubility raises the rate of azo group transformation in 4-nitro-2′-hydroxy-5′-methylazobenzene, while the content of 4-amino-2′- hydroxy-5′-methylazobenzene does not change in the hydrogenate and is not accumulated in the bulk of solution.