Aromatic nitrations by mixed acid. Slow liquid-liquid reaction regime

Aromatic nitrations by mixed acid have been selected as a specific case of a heterogeneous liquid-liquid reaction. An extensive experimental programme has been followed using adiabatic and heat-flow calorimetry and pilot reactor experiments, supported by chemical analysis. A series of nitration experiments has been carried out to study the influences of different initial and operating conditions such as temperature, stirring speed and sulphuric acid concentration. In parallel, a mathematical model to predict the overall conversion rate has been developed. In this paper the mathematical modelling and the implementation and experimental validation for benzene, toluene and chlorobenzene mononitration in the kinetic control regime (slow liquid-liquid reaction) are presented and discussed.     

Hybrid photocatalytic membranes embedding decatungstate for heterogeneous photooxygenation

The incorporation of decatungstate in polymeric membranes provides new heterogeneous photocatalysts for the oxidation of organic substrates under oxygen atmosphere at 25 °C. Photocatalytic membranes have been prepared yielding polymeric films with a high thermal, chemical and mechanical stability (PVDF, PDMS, Hyflon). Surface spectroscopy techniques including transmittance and reflectance UV-Vis and FT-IR have been used to assess the photocatalyst integrity within the polymeric support. Catalyst screening has been performed under both homogeneous and heterogeneous photooxygenation conditions. The photocatalyst activity has been evaluated in terms of the substrate conversion, turnover numbers, and recycling experiments. A membrane induced selectivity behavior has been evidenced by comparison with homogeneous oxidations.     

Ethoxylated fatty alcohols as corrosion inhibitors for dissolution of zinc in hydrochloric acid

The effect of some ethoxylated fatty alcohols, with different numbers of ethylene oxide units, on the corrosion of zinc in 0.5 M HCl has been studied using weight loss and polarization measurements. The inhibition efficiency was found to increase with increasing concentration, number of ethylene oxide units per molecule and with decreasing the temperature. Inhibition was explained on the basis of adsorption of ethoxylated fatty alcohols molecules on the metal surface through their ethoxy groups. The degree of surface coverage varied linearly with logarithm of inhibitor concentration fitting Temkin isotherm. The thermodynamic parameters were calculated for the tested system from the data obtained at different temperatures.     

氧气液相氧化一元取代甲苯制备芳香醛

研究了在酸碱不同体系下气氛液相氧化对氯甲苯、邻硝基甲苯制取相应芳香醛的反应 ,比较了反应温度、反应时间、氧气流量、底物浓度对各自反应的影响。初步研究了反应在酸碱不同条件下的反应机理 ,认为在醋酸体系下是自由基反应 ,而在有机胺体系下应是碳负离子反应。     

A generalized equation for surface tension from the triple point to the critical point

A three-parameter generalized equation is proposed for surface tension from the triple point to the critical point. This equation not only fits the data well but also is good for interpolation between the normal boiling point and the critical point. This equation is also good for extrapolation to the triple point. This equation has been tested using the surface tension of water from the triple point to the critical point. The constants of this equation obtained using orthobaric surface tensions are given for a number of compounds. The isobaric surface tensions determined at a pressure of 1 atm do not differ significantly from the orthobaric surface tensions. Such data also have been used in obtaining equations from the triple to the critical point.Nomenclature T _c Critical temperature, K - T _t Triple point, K - T _m Melting point, K - T _r Reduced temperature, K - X (T _c-T)/T _c - Surface tension, dyne · cm^–1;10^–3N · m^–1 - _m Surface tension at the melting point - _f Surface tension at T _r=0.9 - _t Surface tension at the triple point - Relative deviation 100[ _obsd– _calcd]/ _obsd - Standard deviation [( _obsd– _calcd)²/(No. points—No. parameters)]^0.5     

Characterization of Oleogels Based on Waxes and Their Hydrolyzates

In this paper, the structuring of liquid oils, also known as oleogelation, is systematically investigated for the first time using a quasi-quaternary mixing system approach. Native waxes with different quantities of wax esters (WE), n-alkanes (hydrocarbons (HC)), fatty acids (FA), and fatty alcohols (FaOH) are applied in mixtures with hydrolyzed waxes to systematically change the composition. Hydrolyzed waxes contain high levels of FA and FaOH. The model systems are investigated on microscopic level (brightfield light microscopy (BFM), cryogenic scanning electron microscopy (cryo-SEM)) as well as on their macroscopic properties (rheology, gel hardness) and calorimetric behavior (differential scanning calorimetry (DSC)). It is found that sunflower wax (SFW)-based gels (12% structurant) become less hard on any admixture. Beeswax (BW)-based gels show significant increases in hardness when 25% and 50% (w/w) hydrolyzate are admixed. This could be related to stepwise crystallization. Further analysis reveals that the dissolution/melting behavior of the wax ester mixtures can be surprisingly well described as ideal solubility of a single pseudocomponent. The approach to unravel the individual contributions of the different species present in waxes is successful and marks a first step to better understand the systematic of wax functionality as oleogelators. Practical Application: The substitution of hardstock fats in structured oil phases is of interest for two reasons. The improved nutritional profile oleogels offer are beneficial for public health while the elimination of palm oil based ingredients appears to be a general public desire. Among the technical solutions for non-TAG oil structuring waxes are very promising. This is primarily due to their availability, prior consumption, potentially low cost for functionality. Currently waxes are technically and scientifically wrongly treated as single components. In order to better utilize the potential of waxes and design future sourcing strategies it is necessary to understand the wax functionality at a compositional/molecular level. This contribution marks the first step into this direction by considering classes of molecules with respect to their contribution to functionality. This understanding is considered as a key for future compositional design.     

Study of the coupling reactions between electrochemically generated aromatic radical anions and methyl, alkyl and benzyl radicals

Alkyl radicals produced in the indirect reduction of alkyl halides or alkyldimethylsulfonium salts by electrochemically generated aromatic radical anions couple fast with the latter and alkylated or dialkylated dihydro compounds are formed. Rate constants measured for the coupling reaction between on one hand methyl, primary, secondary and tertiary alkyl radicals as well as benzyl and cumyl radicals and on the other hand a wide spectrum of electrochemically generated aromatic radical anions are found to be about 1×10⁹ M⁻¹ s⁻¹. Previous measurements of coupling rate constants for primary alkyl radicals have been re-evaluated since they were affected by the presence of an S_N2 reaction occurring between the alkyl halides used as radical precursors and the aromatic radical anions. New experiments are also included using alkyldimethylsulfonium salts as precursors in order to prevent such S_N2 artefacts. It is concluded that sterical hindrance does not play a significant role for the radical-radical anion coupling reactions. In general the rate constants for the coupling reactions are all close to 10⁹ M⁻¹ s⁻¹.     

尖晶石纳米催化剂应用于烯丙醇多相氧化制烯丙醛或烯丙酮

使用共沉淀法通过Ru对MeFe2O4的同晶取供制备了纳米级MnFe1.95Ru0.05O4催化剂。在通过过渡金属进一步改性该催化剂的过程中，发现MnFe1.95Ru0.05O4的催化剂性能优异于文献报道的其他多相醇氧化催化剂，XRD测试表明该催化剂仍保持尖晶石结构。该纳米催化剂能有效地将不同烯丙醇类氧化成烯丙醛类或烯丙酮类，与文献报道的其他多相氧化催化体系相比，该催化剂具有更高的活性转换数。借助于EXAFS等表征结果和1－辛醇与4－辛醇的竞争反应，判断出单核的Ru类反应的活性中心，EXAFS的表征同时表明由于Cu的添加而产生的Ru=0能加快反应速率。作者在此基础上提出反应机理，认为Ru在反应过程中形成醇化物，再经过β消除反应生成相应的醛或酮。     

Tasting green leaf volatiles by larvae and adults of Colorado potato beetle,Leptinotarsa decemlineata

Larvae and adults of the Colorado potato beetle,Leptinotarsa decemlineata (Say), are shown to have galeal gustatory cells that are highly sensitive to distillate of potato leaf extracts, (E)-2-hexen-1-ol, (E)-2-hexenal, and other saturated and unsaturated six-carbon alcohols. In larvae and adults, the sensory response patterns elicited by leaf homogenate, leaf distillate and a mixture of these two extracts differ in subtle ways. Beetle larvae feed most readily on Millipore disks treated with leaf homogenate and the mixture, but they did not feed on disks treated with leaf distillate. The differences in behavioral response and sensory input are used to derive a potential gustatory code that may stimulate different levels of feeding. This code may be disrupted by compounds present in nonhost leaves, thus leading to reduced feeding. Possible interactions of sapid leaf volatiles, amino acids, sugars, and potentially deterrent plant compounds are discussed.