Effect of individual solvents on the rates of hydrogenization for substituted nitro-, azo-, and nitroazobenzenes on skeletal nickel

The effect the nature of a solvent has on the rate of hydrogenation is studied for azobenzene, 4-amino-2'-hydroxy-5'-methylazobenzene, 2-hydroxymethyl-2'-hydroxy-5'-methylazobenzene, nitrobenzene, 4-nitroaniline, 4-nitro-2'-5'-methylazobenzene and 2-nitro-2'-hydroxy-5'-methylazobenzene on skeletal nickel in toluene, 2-propanol and DMFA. It is noted that having objective concepts concerning ways of selectively controlling the transformation staging of substituted nitro-, azobenzenes and compounds simultaneously containing two reaction groups under conditions of hydrogenation is extremely important from both theoretical and practical points of view. It is found that moving from toluene to DMFA results in a different change in the observed rates of nitro and azo group hydrogenation and alters the selectivity of the reaction during 4-nitro-2'-hydroxy-5'-methylazobenzene and 2-nitro-2'-hydroxy-5 '–methylazobenzene hydrogenation.