The elucidation of the sequence of transformations in compounds containing several reactive groups and the development of approaches to controlling the selectivity of the processes with their... Show moreThe elucidation of the sequence of transformations in compounds containing several reactive groups and the development of approaches to controlling the selectivity of the processes with their participation is of interest both from the theoretical and practical points of view. The article is devoted to the analysis of the kinetics of hydrogenation of 4-nitro-2'-hydroxy-5'-methylazobenzene in aqueous solution of 2-propanol with addition of sodium hydroxide on skeletal nickel at different initial amounts of the starting compound. An increase in the initial amount of 4-nitro-2'-hydroxy-5'-methylazobenzene leads to an increase in the rate of conversion of the nitro group in the starting compound and to a decrease in the rate of conversion of the azo-group. The effect of the introduced sodium hydroxide in the neutral solvent 2-propanol-water on the rate of conversion of the nitro and azo-groups to 4-nitro-2'-hydroxy-5'-methylazobenzene is consistent with the nature of the rate changes for the hydrogenation of individual compounds containing nitro and azo-groups, in the quality of which 4-nitroaniline and 4-amino-2'-hydroxy-5'-methylazobenzene were chosen. The results obtained do not contradict the notion of a parallel-sequential scheme of 4-nitro-2'-hydroxy-5'-methylazobenzene transformations. One of the directions involves the conversion of 4-nitro-2'-hydroxy-5'-methylazobenzene due to the hydrogenation of the azo-group to 4-nitroaniline and PC, and the second one is the conversion of 4-nitro-2'-hydroxy-5'-methylazobenzene through 4-amino-2'-hydroxy-5'-methylazobenzene due to the reduction of the nitro group. By the end of the reaction, all the intermediate compounds are restored to PC and 1,4-phenylenediamine. When sodium hydroxide is introduced into the neutral solvent 2-propanol-water, the effect of the direction providing the formation of 4-amino-2'-hydroxy-5'-methylazobenzene to the overall reaction rate increases. It was experimentally established that the amount of 4-amino-2'-hydroxy-5'-methylazobenzene during the hydrogenation of 4-nitro-2'-hydroxy-5'-methylazobenzene in the presence of sodium hydroxide increases by 15%, on the contrary, the amount of 4-nitroaniline decreases by 4 % in comparison with the neutral solvent. Show less
This manuscript reports the potential-dependent adsorption and deposition of cisplatin on polycrystalline gold electrode. It was found that this process is mediated by the adsorption of phosphate... Show moreThis manuscript reports the potential-dependent adsorption and deposition of cisplatin on polycrystalline gold electrode. It was found that this process is mediated by the adsorption of phosphate anions on the gold electrode and that the maximum coverage of Pt adsorbed is given by the maximum coverage of phosphate adsorbed at a given potential. The interaction of cisplatin with the phosphate groups was confirmed by in situ FTIR spectroscopy under external reflexion configuration. Quantitative analysis suggests that the stoichiometry of the phosphate species and the cisplatin adsorbed was 1:1. Moreover, the relationship between the charge of the Pt deposited and the charge of the electrochemical surface area of the Pt deposited on the gold electrodes indicates that 3D nanoclusters of a few atoms of Pt were formed over the gold electrode upon the electrochemical reduction of the adsorbed cisplatin.The Pt nanoclusters formed under these conditions were later evaluated for the oxidation of a monolayer of carbon monoxide. The Pt nanoclusters showed a high overpotential for the oxidation of the carbon monoxide monolayer and the high oxidation overpotential was attributed to the absence of adsorption sites for OH species on the Pt clusters: only at potentials where the OH species are adsorbed at the edge between the Pt nanocluster and the gold support, the oxidation of the carbon monoxide on the Pt nanoparticles takes place. Show less
A study of the kinetics of liquid phase hydrogenation of nitrobenzene, 4-nitrotoluene, 4-nitroaniline and 2-chloro-4-nitroaniline on supported palladium catalyst in aqueous solutions of 2-propanol... Show moreA study of the kinetics of liquid phase hydrogenation of nitrobenzene, 4-nitrotoluene, 4-nitroaniline and 2-chloro-4-nitroaniline on supported palladium catalyst in aqueous solutions of 2-propanol of different composition was carried out. The influence of the substituent on the value of the total amount of hydrogen absorbed during the reaction and the kinetics of the hydrogenation of substituted nitrobenzenes was discussed. It was found out that the reaction selectivity to 2-chloro-1,4-phenylenediamine decreases due to by-reaction dehalogenation. The degree of dehalogenation depends on the composition of solvent and may be approximately estimated by the values of the absorbed hydrogen volume during the reaction. Also, the presence of the donor-acceptor substituents is capable of exerting influence on the reaction rate of hydrogenation of the nitro compound. Show less
