Simultaneous degradation of nitroaromatic compounds TNT,RDX, atrazine,and simazine by Pseudomonas putida HK‐6 in bench‐scale bioreactors

BACKGROUND: Environmental contamination by nitroaromatic compounds such as 2,4,6‐trinitrotoluene (TNT), hexahydro‐1,3,5‐trinitro‐1,3,5‐s‐triazine (RDX), atrazine, and/or simazine (TRAS) generated as waste from military and agricultural activities is a serious worldwide problem. Microbiological treatment of these compounds is an attractive method because many explosives and herbicides are biodegradable and the process can be made cost‐effective. We explored the feasibility of using cultures of Pseudomonas putida HK‐6 for simultaneous degradation of TRAS with the aim of microbial application in wastewater treatment in bench‐scale bioreactors. RESULTS: Experiments were conducted to study the effects of supplemental carbons, nitrogens, and Tween‐80 on the degradation of Ps. putida HK‐6 in media containing TRAS as target substrate(s). The most effective TRAS degradation was shown in the presence of molasses. Addition of nitrogen sources produced a delayed effect for the target substrate(s). Tween‐80 enhanced the degradation of target substrate(s). Simultaneous degradation of these compounds proceeded to completion within the given period. CONCLUSIONS: Ps. putida HK‐6 was capable of growth with TRAS, and the effects of supplements on TRAS degradation and simultaneous TRAS degradation were evaluated in bench‐scale bioreactors. The results of this study have practical applications in the processes of industrial waste stream treatment where the disposal of TRAS may be problematic. Copyright © 2008 Society of Chemical Industry     

硝基芳烃对黑头呆鱼毒性的DFT研究

对35种硝基芳烃化合物进行DFT-B3LYP/6-311G**水平全优化计算。据所得量子化学参数和标题化合物的辛醇/水分配系数(IgK_OW)建立硝基芳烃对黑头呆鱼毒性(-IgLC₅₀)的QSAR模型,采用内部及外部双重验证的办法深入分析和检验模型的稳健性。最佳模型的复相关系数（R²）,去一法（LOO）交互检验复相关系数(R²_cv),外部预测样本复相关系数(R²_ext)分别为0.975,0.970和0.904,故所建立QSAR模型的稳定性和预测能力良好。结果表明:硝基芳烃化合物的毒性主要由分子最低空轨道能(E_LUMO)、硝基静电荷(Q_NO2)、氢原子所带的最高正电荷（Q_H⁺）及辛醇/水分配系数决定。苯环上取代基的类型、数目和取代位置直接影响到标题化合物的毒性大小,强吸电子基如硝基会使化合物毒性增强,且邻对位硝基取代的毒性高于间位取代;相反,给电子基团氨基的存在则会使化合物的毒性降低。总之,硝基是这类化合物致毒的主要基团,将硝基包覆或还原为氨基应为此类化合物解毒的重要途径。     

含芘的超支化介孔聚合物的合成及对硝基芳烃的荧光传感性能

合成了以金刚烷为核心,以二苯乙炔基芘为连接臂的超支化聚合物P。金刚烷的三维立体结构及分子骨架的刚性结构特点,赋予了聚合物多孔的结构特点。研究结果表明,聚合物P具有均匀的狭缝孔道结构,其孔径多分布在10 nm左右,属于介孔材料。此外还合成了共聚单体二苯乙炔基芘(M)用于对比研究其光学性质及对硝基芳烃的荧光猝灭性能。聚合物P与单体M相比具有更大的Stokes位移,二者在含有三硝基甲苯(TNT)的溶液中,其平衡时的猝灭率几乎相同。然而二者在相同条件下制备的旋涂膜在二硝基甲苯(DNT)饱和蒸汽中,当达到猝灭平衡时,聚合物P的猝灭率为82%,而化合物M的猝灭率仅为22%。说明聚合物P多孔的特点使其透气性大大提高。以不同浓度的聚合物溶液制备出一系列厚度不同的薄膜,发现随着薄膜厚度的增加,荧光峰发生红移,但在DNT饱和蒸汽中的猝灭率变化不大。这种介孔的结构特点在一定程度上克服了旋涂膜传感器的猝灭率对厚度的依赖性。     

微波促进氟代脱硝合成含氟芳香族化合物

在微波加热下,以硝基芳烃为反应底物,以喷雾干燥氟化钾为氟化试剂,以四苯基溴化鏻-四乙二醇二甲醚为催化剂,以邻苯二甲酰氯为NO2-捕捉剂,在二甲亚砜溶剂中经氟代脱硝反应合成一系列含氟芳香族化合物。该反应反应时间短(10min～2h),氟代产物收率和选择性分别可达20.1%～91.9%和46.1%～94.0%,均好于相同条件下常规加热的收率和选择性。     

A formula for assessing the relative severity of population crises

Historical crises are dealt with in terms of the number of people involved, the incidence of mortality, and their duration. By first an empirical approach and then by reasoning based on social psychology a formula is produced that enables one to compare the severity of historical crises.     

Rapid Hydrogenation of Aromatic Nitro Compounds in Supercritical Carbon Dioxide: Mechanistic Implications via Experimental and Theoretical Investigations

An exceptionally rapid hydrogenation of nitrobenzene to aniline [TOF=252,000 h⁻¹] over palladium containing MCM‐41 (Pd/MCM‐41) with excellent yield of >99% can be achieved in supercritical carbon dioxide at 50 °C and a hydrogen pressure of 2.5 MPa. It has been observed that this promising method preferred a single phase between liquid substrate and carbon dioxide‐hydrogen system. The ascendancy of the supercritical carbon dioxide medium is established in comparison with the conventional organic solvent and solvent‐less conditions. Changes in the reaction parameters such as carbon dioxide and hydrogen pressure, temperature and the reaction time do not affect the selectivity. A combined experimental and theoretical study has elucidated the mechanism under the studied reaction condition because experimental observations revealed a direct conversion of nitrobenzene to aniline. However, density functional theory (DFT) calculation shows that the direct conversion is energetically unfavourable; hence, a stepwise mechanism has been proposed. Theoretical predictions and experimental observations suggested that the rate‐limiting step of nitrobenzene conversion is different from that of the liquid phase hydrogenation. This catalytic process can also be successfully extended to the hydrogenation of other aromatic nitro compounds with different substituents. Easy separation of the liquid product from catalyst and the use of an environmentally friendly solvent make this procedure a viable and an attractive green chemical process.     

N-烷基芳胺合成的研究进展

N-烷基芳胺是非常重要的有机原料和精细化工中间体,广泛应用于染料、塑料、医药和农药等领域。介绍了芳胺与烷基化试剂如卤代烃、羰基化合物、醇等进行的取代烷基化反应合成N-烷基芳胺的反应机理及烷基化工艺;重点阐述了以芳香硝基化合物为原料一锅法合成N-烷基芳胺的生产工艺,分别讨论了以羰基化合物、腈、醇作为烷基化试剂的优劣,认为以醇为烷基化试剂的反应条件温和、不需要添加任何配体,具有较好的应用前景。指出开发适合以醇为烷基化试剂的选择性高的催化剂是以后的研究方向。     

N‐Arylamides from Selenium‐Catalyzed Reactions of Nitroaromatics and Amides in the Presence of Carbon Monoxide and Mixed Organic Bases

N‐Arylamides were exclusively obtained in moderate to good yields from selenium‐catalyzed reactions of nitroaromatics with amides in the presence of CO and mixed organic bases Et₃N and DBU.     

Liquid‐Liquid‐Liquid Phase Transfer Catalysis: A Novel and Green Concept for Selective Reduction of Substituted Nitroaromatics

The selective reduction of nitroaromatics to the corresponding amines is an important transformation since many aromatic amines exhibit biological activities and find a multitude of industrial applications, being intermediates for the synthesis of dyes, pharmaceuticals and agrochemicals. A variety of nitroaromatics dissolved in organic solvents was reduced by using aqueous sodium sulfide, and tetrabutylammonium bromide (TBAB) as the phase transfer catalyst by choosing appropriate concentrations which resulted in three immiscible liquid phases. Compared to L‐L PTC, the L‐L‐L PTC offers much higher rates of reaction, better selectivities and repeated use of catalyst. The selectivities for the desired products were 100%.     

Reduction of nitroaromatics with poly(vinylpyridine) complexes of palladium(II) and platinum(II)

Palladium(II) and platinum(II) anchored to 2- and 4-vinylpyridine polymers of different molecular weights were used for the dihydrogen reduction of various nitroaromatics and benzaldehyde in ethanol at 50°C. Palladium(II) complexes were far more effective than their platinum(II) analogues and the activity decreased with increasing molecular weights of the polymers. The nitroaromatics were selectively and almost completely reduced to the corresponding anilines. During reduction, the orange palladium(II) complexes changed to voluminous green precipitates, which could be used repeatedly and preserved for a long time without any loss of activity. A rate equation of the type: rate = K[Cat] [H₂] has been derived and a reduction mechanism has been proposed on the basis of experimental results and kinetic data.