The photochemistry of p-nitrobenzyl derivatives 610 has been studied in aqueous solution as a function of pH, using product analysis, UVvis spectrophotometry, and laser flash photolysis (LFP). The compounds were chosen with the aim of further exploring the propensity of these systems to give rise to α-hydroxy-p-nitrobenzyl carbanions on photolysis, and to study their mechanisms of subsequent reaction. α-Hydroxy-substituted carbanions are anions that cannot be readily formed using thermal routes but which are believed to have some interesting chemistry. Three methods were employed for photogenerating these carbanions: (i) decarboxylation; (ii) retro-Aldol reaction; and (iii) carbon acid deprotonation. All three methods proved to be successful using the p-nitrobenzyl chromophore. Photogenerated α-hydroxy-p-nitrobenzyl carbanions react via disproportionation, giving rise to oxidized and reduced products; simple protonation of the anion was undetectable.Key words: photodecarboxylation, nitrobenzyl carbanions, photoredox, nitroaromatic compounds, excited-state carbon acids.
对p-硝基苯甲基衍生物6-10在水溶液中的光化学作用进行了研究,作为pH值的函数,使用产物分析、紫外-可见分光光度法和激光闪光光解(LFP)。选择这些化合物的目的是进一步探索这些体系产生α-羟基-p-硝基苯甲基负离子的倾向,并研究它们后续反应的机制。α-羟基取代的负离子是一类不能通过热路线容易形成的负离子,但据信具有一些有趣的化学性质。用于光生成这些负离子的三种方法包括:(i)脱羧反应;(ii)逆Aldol反应;和(iii)碳酸脱质子化。所有三种方法都证明在p-硝基苯甲基色团中是成功的。光生成的α-羟基-p-硝基苯甲基负离子通过不均化反应,产生氧化和还原产物;负离子的简单质子化是不可检测的。关键词:光脱羧、硝基苯甲基负离子、光氧化还原、硝基芳香化合物、激发态碳酸。