Structural Effects on the OH−-Promoted Fragmentation of Methoxy-Substituted 1-Arylalkanol Radical Cations in Aqueous Solution: The Role of Oxygen Acidity
作者:Enrico Baciocchi、Massimo Bietti、Maria Francesca Gerini、Laura Manduchi、Michela Salamone、Steen Steenken
DOI:10.1002/1521-3765(20010401)7:7<1408::aid-chem1408>3.0.co;2-m
日期:2001.4.1
corresponding cumyl alcohol radical cations; this suggests a mechanism in which a key role is played by the oxygen acidity as well as by the strength of the scissile C-C bond: a radical zwitterion is formed which undergoes a rate-determining C-C bond cleavage, coupled with the intramolecular ET. Finally, oxygen acidity also determines the reactivity of the radical cations of 2-(3,4-dimethoxyphenyl)ethanol
动力学和产物研究,由OH诱导,H 2 O由一些二和三甲氧基取代的1-芳基烷醇(ArCH(OH)R * +)以及2-和3-(3, 4-二甲氧基苯基)链烷醇已经通过使用脉冲-和γ-辐解技术进行。在1-芳基链烷醇体系中,自由基阳离子3,4-(MeO)2C6H3CH2-OH * +的分解速率比其甲基醚的分解速率高两个数量级。这表明侧链OH基团在衰变过程中的关键作用(氧酸度)。但是,与该α-非氘代对应物相比,该自由基阳离子具有相当大的氘动力学同位素效应(3.7)。提出了一种机制,其中快速的OH去质子化导致自由基两性离子,然后进行速率确定的1,2-H移位,偶联至侧链至环的分子内电子转移(ET)步骤。该概念也将重要的作用归因于该ET的能量屏障,该能量屏障应取决于环中正电荷的稳定性,并因此取决于甲氧基的数量和位置。在相似的实验基础上,对于2,5-(MeO)2C6H3CH2OH * +提出了与3,4-(MeO)2C6H3CH2OH