Mandal Subrata, Kazmi Najam H, Sayre Lawrence M
Department of Chemistry, Case Western Reserve University, Cleveland, OH 44106, USA.
Arch Biochem Biophys. 2005 Mar 1;435(1):21-31. doi: 10.1016/j.abb.2004.11.025.
Transition metal-mediated oxidation of hydroquinones is an important physiologic reaction, and copper(II) effectively catalyzes the reaction in phosphate-buffered saline (PBS). Studies reported herein in phosphate buffer alone demonstrate that copper(II) is an ineffective catalyst in the absence of coordinating ligands, but that 1,10-phenanthroline and histamine facilitate the copper(II)-mediated oxidation of hydroquinone and its 2,5- and 2,6-di-tert-butyl analogs to the corresponding benzoquinones. The high concentration of chloride in PBS is the key element that allows copper(II) to work in this system. Although the bis-bathocuproine disulfonate complex of Cu(II), (BC)(2)Cu(II), is a strong stoichiometric oxidant, stoichiometric amounts of copper(II) in the presence of ligands other than BC oxidize hydroquinones very slowly under anaerobic conditions. Thus, the rapid copper(II)-catalyzed reaction operating aerobically does not involve a simple ping-pong reduction of copper(II) to copper(I) by hydroquinone and reoxidation of copper(I) by O(2).
对苯二酚的过渡金属介导氧化是一种重要的生理反应，铜（II）能在磷酸盐缓冲盐水（PBS）中有效催化该反应。本文仅在磷酸盐缓冲液中进行的研究表明，在没有配位配体的情况下，铜（II）是一种无效的催化剂，但1,10 - 菲咯啉和组胺能促进铜（II）介导的对苯二酚及其2,5 - 和2,6 - 二叔丁基类似物氧化为相应的苯醌。PBS中高浓度的氯离子是使铜（II）能在该体系中发挥作用的关键因素。尽管铜（II）的双（邻二氮菲）二磺酸络合物（BC）₂Cu（II）是一种强化学计量氧化剂，但在厌氧条件下，除BC之外的配体存在时，化学计量的铜（II）氧化对苯二酚的速度非常慢。因此，有氧条件下快速的铜（II）催化反应并不涉及对苯二酚将铜（II）简单地乒乓还原为铜（I）以及氧气将铜（I）再氧化的过程。
