Direct Irradiation of Phenol and <i>Para</i>-Substituted Phenols with a Laser Pulse (266 nm) in Homogeneous and Micro-heterogeneous Media. A Time-Resolved Spectroscopy Study
作者:Gastón Siano、Stefano Crespi、Sergio M. Bonesi
DOI:10.1021/acs.joc.0c02031
日期:2020.11.6
Direct irradiation of para-substituted phenols under N2 atmosphere in homogeneous (cyclohexane, acetonitrile, and methanol) and micellar (SDS) solution was investigated by means of time-resolved spectroscopy. After a laser pulse (266 nm), two transient species were formed, viz. the para-substituted phenol radical-cations and the corresponding phenoxy radicals. The radical-cations showed a broad absorption
通过时间分辨光谱法研究了N 2气氛下均相(环己烷,乙腈和甲醇)和胶束(SDS)溶液中对位取代的苯酚的直接辐照。在激光脉冲(266 nm)之后,形成了两个瞬态物质,即。的对位取代的酚自由基阳离子和相应的苯氧自由基。自由基阳离子在390至460 nm之间显示出较宽的吸收带,而苯氧基自由基在320 nm和400–410 nm处具有两个特征带。自由基阳离子的去质子化速率常数(k H)为10 5 s –1和苯氧基自由基的反应速率常数(kR)的阶数为10 9 –10 10 M –1 ·s –1。所述ķ ħ速率常数给出了良好的线性相关性哈米特具有正斜率表明吸电子取代基增强自由基阳离子的酸度。的结合常数(ķ b的的)对位还测量了用表面活性剂取代的酚,NOESY实验表明酚位于胶束的疏水核中。最后,计算计算提供了瞬态的预测吸收光谱,并且在这些物种的较低吸收带的理论能量和实验能量之间获得了良好的线性相关性。