Abstract

Spectrophotometry has been used to examine the kinetics of Np(V) disproportionation in HCOOH solutions containing H₂O and HClO₄ at temperatures of 20–45°C. The reaction rate is described in the initial portion by the equation –d[Np(V)]/dt = k[Np(V)]². The rate constant k sharply grows with increasing [HClO₄] (order n = 3.5) and with decreasing content of H₂O (n = –2.30. The appearing Np(VI) is slowly reduced to Np(V) by formic acid. The activation energy of the disproportionation reaction is 54 kJ mol^–1. The mechanism includes the elimination of an H₂O molecule from the H⁺_aq ion and addition of a proton to NpO₂⁺. The protonated Np(V) ions form a dimer which is an activated complex. The H transfer in this complex yields Np(IV) and Np(VI).

中文翻译：

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Np（V）在含H 2 O和HClO 4的HCOOH溶液中的行为

摘要

分光光度法已被用于检查在20–45°C的温度下，含有H ₂ O和HClO _4的HCOOH溶液中Np（V）歧化的动力学。反应速率在开始部分用等式–d [Np（V）] / d t = k [Np（V）] ^2来描述。速率常数k随着[HClO ₄ ]的增加（n = 3.5的阶数）和H ₂ O含量的减少（n = –2.30 ）而急剧增加。出现的Np（VI）会被甲酸缓慢还原为Np（V）。歧化反应的活化能为54 kJ mol ^–1，其机理包括消除HH ⁺_{水溶液中的2} O分子，向NpO ₂ ⁺添加质子。质子化的Np（V）离子形成一个二聚体，它是一种活化的复合物。在该络合物中的H转移产生Np（IV）和Np（VI）。