Pulse radiolytic one-electron oxidation of some dihydroxy-substituted anthraquinones
作者:Haridas Pal、Dipak K. Palit、Tulsi Mukherjee、Jai P. Mittal
DOI:10.1039/ft9928800681
日期:——
The spectroscopic characteristics and the kinetic parameters associated with the transients formed on one-electron oxidation of quinizarin (1,4-dihydroxy-9, 10-anthraquinone), quinizarin 2- and 6-sulfonates, 1,5-dihydroxy-9, 10-anthraquinone and 1,8-dihydroxy-9, 10-anthraquinone have been studied by pulse radiolysis and kinetic spectrophotometric techniques, using OH˙, O˙–, N3˙, Br˙–2 and ˙CH2CHO as the oxidising radicals. The pKa and the disproportionation equilibria of the semi-oxidised quinones have been studied for the water-soluble sulfonates. In contrast to the complex decay of the semi-oxidised naphthazarin (5,8-dihydroxy-1,4-naphtho-quinone), the semi-oxidised anthraquinone derivatives decay by simple second-order kinetics. The pKa values of the latter are also much higher (ca. 8) compared to the former (ca. <4). The differences observed are attributed to the loss in symmetry in the free radical structures of the semi-oxidised anthraquinone derivatives.
通过脉冲辐射分析和动力学分光光度法,研究了喹吖啶(1,4-二羟基-9,10-蒽醌)、喹吖啶 2-和 6-磺酸盐、1,4-二羟基-9,10-蒽醌和 1,8-二羟基-9,10-蒽醌单电子氧化时形成的瞬态相关光谱特征和动力学参数、以 OH˙、O˙-、N3˙、Br˙-2 和 ˙CH2CHO 为氧化自由基,通过脉冲辐射分解和动力学分光光度法研究了喹吖啶(1,4-二羟基-9,10-蒽醌)、喹吖啶 2-和 6-磺酸盐、1,5-二羟基-9,10-蒽醌和 1,8-二羟基-9,10-蒽醌的氧化过程。研究了水溶性磺酸盐半氧化醌的 pKa 和歧化平衡。与半氧化萘甲萘醌(5,8-二羟基-1,4-萘醌)的复杂衰变不同,半氧化蒽醌衍生物的衰变采用简单的二阶动力学。后者的 pKa 值(约 8)也远高于前者(约 <4)。观察到的差异归因于半氧化蒽醌衍生物的自由基结构失去了对称性。