氧的p型孤对电子对抗氧化剂苯氧自由基的稳定作用

用ＡＭ１方法计算了几种甲氧基苯酚的ΔＨＯＦ值，以此为理论指标探讨了甲氧基氧的ｐ型孤对电子对苯氧自由基的稳定作用。发现ｐ型孤对电子对邻、对位苯氧自由基的稳定作用较强，对间位自由基没有稳定作用，呈现出明显的位置效应。同时ｐ型孤对电子轨道的扭转对稳定作用有较大影响。当轨道与苯环平面垂直时，稳定作用最强，而当轨道与苯环平面平行时，稳定作用最弱。最后将上述结果用于黄酮类抗氧化剂和维生素Ｅ，阐明了许多实验现象。

木质素光降解机理研究进展

从木质素模型及原本木质素2个方面综述木质素光降解的研究现状。木质素模型研究表明,光降解是典型的自由基反应,主要通过游离酚途径、羰游基途径和苯甲酰甲基芳醚途径反应,苯氧自由基是光化学反应的重要中间产物。木质素光降解是个氧化过程,伴随着碳的氧化态升高、非共轭羰基减少、共轭羰基增加,大分子木质素发生解聚,最终形成对醌、邻醌等发色基团及苯甲酸、苯甲醛等可溶性小分子酚类化合物,木质素含量明显降低。木质素光化学反应的机理研究中,木质素模型和原本木质素存在一定差距,分子和细胞水平上的深入研究将是未来的发展方向。

漆酶改性高木素含量的硫酸盐浆,提高纸的强度特性——在没食子酸的条件下用漆酶处理

在高-K(91)硫酸盐浆中,漆酶与没食子酸发生化学反应。与未处理的试样相比,处理后的耐破、抗张、湿强分别增加34%、20%和72%。而漆酶对全漂浆没有大的影响,这就表明木素是对纤维处理的主要对象。结果表明纸页强度的提高是由于纤维间氢键结合的改善和产生苯氧自由基缩合作用的结果。

Mixed hetero-/homogeneous TiO_(2)/N-hydroxyimide photocatalysis in visible-light-induced controllable benzylic oxidation by molecular oxygen

Homogeneous and heterogeneous types of catalysis are frequently considered as separate disciplines or even opposed to each other.In the present work,a new type of mixed het-ero-/homogeneous catalysis was demonstrated for the case of selective alkylarene oxidation by molecular oxygen.The proposed catalytic system consists of two widely available components:N-hydroxyphthalimide(NHPI,a homogeneous organocatalyst for free-radical chain reactions)and nanosized TiO_(2)(heterogeneous UV-active photoredox catalyst).The interaction of NHPI with TiO_(2) allows for a shift from UV to visible light photoredox activity and generation of phthalimide-N-oxyl(PINO)radicals that diffuse into the solution where NHPI/PINO-catalyzed free-radical chain reaction can proceed without the additional light input providing a fundamental increase in energy efficiency.The NHPI/TiO_(2) ratio controls the selectivity of oxidation affording preferential formation of hydroperoxide or ketone from alkylarene.

Selective aerobic oxidation promoted by highly efficient multi-nitroxy organocatalysts

Selective oxidation with molecular oxygen as the sole oxidant under mild conditions is of crucialimportance for the long‐term sustainable exploitation of available feedstocks and the formation ofrequired intermediates for organic synthesis and industrial processes.Among the developed oxidationprotocols,innovative strategies using hydroxyimide organocatalysts in combination with metallicor metal‐free cocatalysts have attracted much attention because of the good activities andselectivities of such catalysts in the oxo functionalization of hydrocarbons.This method is based onthe reaction using N‐hydroxyphthalimide,which was first reported by Ishii’s group in the1990s.Although the important and wide‐ranging applications of such catalysts have been summarizedrecently,there are no reviews that focus solely on oxidation strategies using multi‐nitroxy organocatalysts,which have interesting properties and high reactivities.This review covers the concisesynthetic methods and mechanistic profiles of known multi‐nitroxy organocatalysts and summarizessignificant advances in their use in efficient aerobic oxidation.Based on a combination of experimentaland theoretical results,guidelines for the future rational design of multi‐nitroxy organocatalystsare proposed,and the properties of various model multi‐nitroxy organocatalysts are predicted.The present overview of the advantages,limitations,and potential applications of multi‐nitroxyorganocatalysts can provide useful tools for researchers in the field of selective oxidation.

Detection of OH Radical in the Photodissociation of p-Aminobenzoic Acid at 266 nm

Photodissociation of p-aminobenzoic acid at 266 nm was investigated by probing the nascent OH photoproduct employing the laser-induced fluorescence technique. It was found that the nascent OH radical was vibrationally cold and its rotational state distribution conformed to be a Boltzmann behavior, characterized by a rotational temperature of 1040±110 K. The rotational energy of OH was determined to be 8.78±0.84 kJ/mol. Between the two spinorbit states of OH, ^2Ⅱ3/2 and ^2Ⅱ1/2, the former was found to be preferentially populated. The distribution of the II（A＇） state for the A-doublet was dominant. Finally, a probable mechanism for the formation of OH produced from the photodissociation of p-aminobenzoic acid is discussed.

Degradation of diphenyl chlorophosphate by using ozone

Diphenyl chlorophosphate （DPCP）, which acts as a simulant of nerve warfare agent, is decontaminated by ozone in this study. Experimental results show that DPCP can be degraded rapidly by ozone. In the optimum working conditions, 99% 50 mg/L DPCP are degraded in 16min, and 30% total organic carbon of the solution is reduced. The free radical accelerant, Fe2＋, and inhibitors, 2-propanol and tert-butanol significantly influence the degradation efficiency of DPCP, therefore, free radical is the most important oxidant for the DPCP degradation reaction in this system. Ozone can be decomposed to hydroxyl radical, which would attack DPCP to start the degradation reaction. Furthermore, parts of DPCP would be mineralized, and degradation of toluene probably is the controlling step of the mineralization of DPCP. Finally, the reaction pathways are predicted for the degradation of DPCP by ozone.

Degradation of p-nitrotoluene by O_3/H_2O_2 process and oxidation mechanism

The degradation of p-nitrotoluene by O3/H2O2 process in a bubble contact column was investigated. Effects of the molar ratio of hydrogen peroxide to ozone,pH value and t-butanol on the oxidation process were discussed. It was found that the proper H2O2/O3 molar ratio for the degradation of p-nitrotoluene was around 0.6, different pH values and the presence of t-butanol highly influenced the removal efficiency of p-nitrotoluene. 5-methyl-2-nitrophenol, 2-methyl-5-nitrophenol, (4-nitrophenyl) methanol, 5-(hydroxymethyl)-2-nitro phenol, acetic acid, 2-methylpropane diacid and 2-(hydroxylmethyl)propane diacid were identified as degradation intermediates and products through GC-MS. Radical reaction mechanism and degradation pathway were proposed based on the results of experiments. It is deduced that the benzene ring of p-nitrotoluene can be only destroyed by hydroxyl radicals through a polyhydroxy intermediate pathway. Then unstable polyhydroxy intermediates can be oxidized to different acids with low molecular weight rapidly.