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本文研究了水—醇(如甲醇、乙醇和正丙醇等)混合溶剂中[Co(N_3)(NH_3)_5]~(2+)与 Fe(Ⅱ)间电子转移反应。其表观速度常数 k_(app)随甲醇、乙醇和正丙醇的摩尔分数X 醇增大(即随混合溶剂介电常数的减小)和酸浓度的增大而增大。反应速度与酸浓度的依存关系,可用[Co(N_3)(NH_3)_5]~(2+)的配体 N_3~-的质子化作用和由此而产生的特殊酸催化作用阐明.[Co(N_3)(NH_3)_5]~(2+)还原反应的表观速度常数 k_(app)可表示为:k_(app)=k_HK_H[H_3O~+]由特殊酸催化而使[Co(N_3)(NH_3)_5]~(2+)被还原反应加速,可认为电子转移是反应的速控步骤。
In this paper, the electron transfer reactions between [Co (N_3) (NH_3) _5] ~ (2+) and Fe (Ⅱ) in water-alcohol mixtures such as methanol, ethanol and n-propanol were studied. The apparent velocity constant k_app increases with the increase of the mole fraction of methanol, ethanol and n-propanol, that is, with the increase of the dielectric constant of mixed solvents and the increase of acid concentration. The dependence of the reaction rate on the acidity can be explained by the protonation of the N_3 ~ [Co (N_3) (NH_3) _5] ~ (2+) ligand and the resulting special acid catalysis [Co The apparent velocity constant k_ (app) of the reduction reaction of N_3) (NH_3) _5] 2+ can be expressed as: k_app = k_HK_H [H_3O ~ +] NH_3) _5] ~ (2+) is accelerated by the reduction reaction, which can be considered electron transfer reaction rate control step.