A. Krotov, O. Lefedova, L. Antina
2003
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Journal
Russian Journal of Physical Chemistry A
Abstract
The kinetics of liquid-phase hydrogenation of 4-aminoazobenzene was studied in aqueous and aqueous-alcoholic solvents of various compositions including solvents with acetic acid and sodium hydroxide admixtures. Experiments showed that the rate of azo group hydrogenation substantially changed under the action of solvents. The introduction of the acid sharply increased reaction rates, whereas, when sodium hydroxide was introduced, the process acquired a stage character and the observed hydrogenation rates decreased. Changes in the rate of the reaction were found to depend on solvation interactions in solutions evidenced by hypso- and bathochromic shifts of the absorption maxima of 4-aminoazobenzene in solvents of various compositions. The experimental data were used to calculate the activation energies of hydrogenation of 4-amino-azobenzene in the solvents under investigation. The possibility of controlling the rate and selectivity of liquid-phase hydrogenation of azo compounds by varying the composition of solvents was grounded.