物理化学学报 >> 1987, Vol. 3 >> Issue (04): 368-374.doi: 10.3866/PKU.WHXB19870407

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光透薄层光谱电化学法研究紫脲酸铵电还原过程

董绍俊; 宋士华; 程广金   

  1. 中国科学院长春应用化学研究所
  • 收稿日期:1986-01-27 修回日期:1986-07-20 发布日期:1987-08-15
  • 通讯作者: 董绍俊

STUDIES ON THE REDUCTION OF MUREXIDE BY OPTICALLY TRANSPARENT THIN-LAYER SPECTROELECTROCHEMISTRY

Dong Shaojun; Song Shihua; Cheng Guanjing   

  1. Changchun Institute of Applied Chemistry; Academia Sinica; China
  • Received:1986-01-27 Revised:1986-07-20 Published:1987-08-15
  • Contact: Dong Shaojun

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摘要： 采用金网橱光透薄层电解池, 配合紫外可见光谱技术现场监测了有机染料紫脲酸铵的电还原过程。用光透薄层光谱电化学方法测定了紫脲酸铵在pH5.0醋酸盐缓冲溶液中的式电极电位和电子转移数。薄层循环伏安法和薄层光谱电化学法研究表明, 紫脲酸铵在金网栅电极上的还原为双电子转移不可逆过程, pH<8时, 还原产物双巴比士亚胺进一步分解为尿咪和巴比士酸。用双电位跃-计时吸收谱法研究了双巴比士亚胺在不同pH缓冲溶液中的分解动力学过程, 测定了拟-级反应动力学常数。

Abstract: The reduction process of murexide (or ammoniumm purpurate) has been inves- tigated at gold minigrid electrode in optically transparent thin-layer cell, using UV-VIS spectroscopy technique. From the experimental results of thin-layer cyclic voltammograms of murexide (or purpurate ion) in different pH system and UV-VIS spectra from the reduction of purpurate ion obtained in situ by spectro- electrochemistry, it was found that the reduction of purpurate ion is a two electron transfer irreversible process, accompanied with a subsequent chemical reaction at pH<8 in which the reduction product, dibarbituylamine decomposed into uramil and barbituric acid. In addition, the formal potential, E~0′ and electron transfer number, n were calculated from spectra at different potentials. Double potentialstep chronoabsorptometry was employed for measuring the decomposition rate constant of dibarbituylamine. The pseudo-firstorder rate constants at pH4.0, 5.0, 5.5 and 6.4 were 6.6, 5.0, 3.4 and 2.6×10~(-4) s~(-1), respectively.