Diffusion of Photochemically Generated Intermediate Radicals in Water-Ethanol Mixed Solvents
Diffusion of Photochemically Generated Intermediate Radicals in Water-Ethanol Mixed Solvents
复制标题
光化学产生的中间自由基在水-乙醇混合溶剂中的扩散
DOI：
10.1021/jp9803743
复制
发表时间：
1998
影响因子：
2.9
通讯作者：
M. Terazima
中科院分区：
文献类型：
--
作者：
K. Okamoto;N. Hirota;M. Terazima
用瞬态光栅（TG）方法研究了苯醌（BQ）和苯乙酮（AP）在乙醇-水混合溶剂中光诱导夺氢反应产生的中间自由基的扩散过程.通过向溶液中加入氢氧化钠（NaOH）或硫酸（H2SO 4）选择性地产生电中性自由基和阴离子自由基。中间物种和自由基的化学稳定性进行了监测的瞬态吸收和时间分辨EPR方法。同时测定了自由基和母体分子的扩散常数D。在任何溶剂混合物中，阴离子自由基的D与中性自由基的D相似。中性和阴离子自由基（DR）在乙醇中的D值远小于母体分子（DP）的D值（BQ的DP/DR = 2.8，AP的DP/DR = 2.1），而随着溶剂中水含量的增加，DP值逐渐接近DR值（BQ和QP在90%水溶液中的DP/DR = 1.3，AP在乙醇中的DP/DR = 2.1）。
Diffusion processes of intermediate radicals created by the photoinduced hydrogen abstraction reactions of benzoquinone (BQ) and acetophenone (AP) in ethanol−water mixed solvents are studied by using the transient grating (TG) method. The electrically neutral radicals and the anion radicals are created selectively by adding sodium hydroxide (NaOH) or sulfuric acid (H2SO4) to the solutions. The intermediate species and the chemical stability of the radicals were monitored by the transient absorption and time-resolved EPR methods. The diffusion constants (D) of the radicals and the parent molecules are determined simultaneously. D of the anion radicals are similar to those of the neutral radicals in any mixtures of the solvents. D of the neutral and anion radicals (DR) are much smaller than those of the parent molecule (DP) in ethanol (DP/DR ∼ 2.8 for BQ and DP/DR ∼ 2.1 for AP in ethanol), while DP become closer to DR with increasing water content in the solvent (DP/DR ∼ 1.3 for BQ and QP in 90% water solut...