The oxidation of 6-hydroxydopamine in aqueous solution. Part 1. The formation of three metastable quinones at low pH†
作者:Guy N. L. Jameson、Andrei B. Kudryavtsev、Wolfgang Linert
DOI:10.1039/b007912j
日期:——
1H and 13C NMR investigations have been carried out in order to elucidate the products of oxidation of 6-hydroxydopamine [5-(2-aminoethyl)benzene-1,2,4-triol, protonated form H3LH+]. Stopped-flow, NMR kinetic experiments, and quantum mechanical calculations were employed as additional aids to the interpretation of the results. Evidence is provided that, at low pH, three quinones are produced that are in metastable equilibrium, namely the p- (pQ), o- (oQ), and triketo-quinones (tQ). Results obtained with sodium periodate and iron(III) are compared and discussed. At higher pHs (>2.5) the quinones reach rapid equilibrium because they start to deprotonate, all giving rise to the same species (Q−), which is the only species detectable above a pH of about 6 and which is stable over a large pH range.
为了阐明6-羟基多巴胺 [5-(2-氨乙基)苯-1,2,4-三醇,质子化形式H3LH+] 氧化反应的产物,进行了1H和13C NMR研究。采用停流、NMR动力学实验和量子力学计算作为结果解释的辅助工具。提供的证据表明,在低pH下,产生了三种在亚稳态平衡中的醌,即对位醌(pQ)、邻位醌(oQ)和三酮醌(tQ)。比较和讨论了使用过量钠和三价铁获得的结果。在较高pH值(>2.5)下,醌迅速达到平衡,因为它们开始去质子化,最终都生成相同的物种(Q−),这是唯一在pH约为6以上可以检测到的物种,并且在较大的pH范围内稳定。