新型多功能三溴三聚氰胺催化剂催化醇甲酰化和乙酰化反应(英文)

Tribromo melamine has been found to be an efficient and green organocatalyst for the acetylation and formylation reactions of alcohols with acetic anhydride and ethyl formate at room temperature and under mild reaction conditions.     

可重复使用的新型催化剂的合成、表征及在绿色条件下催化Suzuki和Heck反应:锚合在磁性纳米多孔的MCM-41上Pd(0)希夫碱络合物

将Pd希夫碱络合物固定在磁性的MCM-41表面上,做为环境友好且可循环使用的新型多相纳米催化剂,并采用红外光谱、振动探针式磁强计、能量散射谱、透射电镜、扫描电镜、热重、电感耦合等离子体发射光谱和X-射线衍射等对其进行了全面的表征.然后将该催化剂用于以PEG为绿色溶剂的一步法Suzuki和Heck合成反应中,均以较高收率得到目标产物.该法主要优点为反应时间短、反应条件绿色友好、操作简便、无需使用有毒的有机溶剂、催化剂使用量低,且底物适用性广.更为重要的是,通过外部磁场即可方便地将催化剂从反应混合物中分离出来,可重复使用数次而活性和稳定性未见明显下降.     

Square-shaped beam generated by phase shifted bounded square zone plate

A novel diffractive element is presented which is made through lateral phase shifted square zone plate bounded along horizontal and vertical axes via two perpendicular rectangle windows, respectively. We demonstrate that under a given condition the element is able to produce a square light beam at the focal plane. We have also elaborated that the produced square beam can be simply manipulated by an appropriate combination of the phase shifting parameter and bounded width. Experimental works verify the simulation results.     

Biodiesel production in the presence of heterogeneous catalyst of alumina: Study of kinetics and thermodynamics

In the current research, biodiesel production was investigated in the presence of solid catalysts of K₂CO₃/Al₂O₃ by transesterification of rapeseed oil. The specifications of produced fatty acid methyl esters like viscosity and flash point were studied, and it was noted that they complied with the requirements of ASTM D6751. In addition, the kinetic and thermodynamic parameters were explored considering the temperature changes between 318.15 and 348.15 K. Mass transfer resistance (external diffusion or internal diffusion) over the catalyst was neglected with regard to theWeisz-Prater criterion and Mears criterion. The kinetic models containing Eley-Rideal, Langmuir-Hinshelwood, pseudo–first-order, pseudo–second-order, and α-order models were investigated. Corrected Akaike information criterion was utilized to find the best model fitted with the experimental data. The greatest illustration for the K₂CO₃/Al₂O₃-catalyzed reaction was the nonlinear model with an order of α = 1.287 and the activation energy of 12.12 kJ/mol. Using transition state theory (Eyring-Polanyi equation), the activation Gibbs free energy, activation enthalpy, and activation entropy were calculated at different temperatures. The equilibrium thermodynamic properties depicted that this process is endothermic and spontaneous toward biodiesel production and tends to be irreversible.     

Preparation of aromatic nitriles via direct oxidative conversion of benzyl alcohols,aldehydes and amines with pentylpyridinium tribromide in aqueous NH4OAc

Pentylpyridinium tribromide and aqueous ammonium acetate was used for the rapid oxidative conversion of benzyl alcohols, benzaldehydes and benzyl amines to the corresponding benzonitriles in good to excellent yields. This simple, mild and one-pot system provides easy workup and separation of the products.     

Sulfamic Acid–Catalyzed Oxidation of Sulfides to Sulfoxides and Sulfones Using H2O2: Green and Chemoselective Method

A mild, efficient, green, and selective oxidation method of sulfides to sulfoxides or sulfones using H₂O₂ in the presence of catalytic amounts of sulfamic acid has been developed. Various substituted sulfides having functional groups such as alcohol, ester, and aldehyde are successfully and selectively oxidized without affecting the sensitive functionalities in good to excellent yields at room temperature.