Transient Voltammetry Under Hydrodynamic Conditions

The channel flow cell has been shown to be a powerful tool with which to study analytical, mechanistic and kinetic processes. In this article we describe a numerical strategy which provides an efficient and flexible alternative to previous computational techniques for simulating channel electrode problems. It is demonstrated that the finite element method can accurately simulate the transient currents measured in hydrodynamic systems under mass transport control, at both macro- and micro-electrodes. Results are compared to analytical theory where available, and to previously established methods of simulation.     

Asymmetric Organocatalysis Under Mechanochemical Conditions

Asymmetric organocatalysis is a robust methodology providing access to numerous valuable compounds while having green chemistry principles in mind. The realization of organocatalytic transformation under solvent-free mechanochemical conditions brings additional benefits in terms of yields, selectivities, and, last but not least overall improved sustainability. This overview describes developments in the use of mechanochemistry as a vehicle for asymmetric organocatalytic transformations. The material is organized according to main catalytic activation modes, starting with covalent activation and proceeding to non-covalent activation modes. The advantages of mechanochemical organocatalytic reactions are particularly highlighted, but in some cases also, limitations are mentioned. Possibilities for target compound synthesis are also discussed.     

Electrodeposition Under High Magnetic Field

The film growth under high magnetic field using a super-conducting magnet is discussed from the view point of a magnetization energy. The film configuration in nickel eletrodeposits with and without the high magnetic field was examined by means of the AFM (Atomic Force Microscopy), In the absence of magnetic field, the film surface appeared irregular structure. However, when the magnetic field was imposed in parallel to the cathode plate, nickel deposited shown clearly ordered stationary structure. The experimental results could be explained by nickel magnetic anisotropy. On the other hand, when the field was imposed in perpendicular to a cathode plate, deposition structure is controlled by the fluid motion induced by Lorentz force.     

Block Copolymers Under Shear Flow

Summary: Microphase separation transition in block copolymer melts and solutions in equilibrium and under shear flow is reviewed. The non‐equilibrium molecular dynamics (NEMD) computer simulation methodology is presented in detail including the derivation of the SLLOD equations of motion, Gaussian thermostat, and operator‐splitting symplectic integrators. Results of our recent NEMD computer simulation studies of diblock copolymers in a selective solvent under shear flow are presented. Shear‐dependent structural, rheological, and microscopical properties are described. New phase transitions are discovered. The parallel‐perpendicular orientational transition in a weak‐strong flow is revealed. Theoretical approaches are reviewed including the Edwards Hamiltonian, Landau‐Ginzburg model, self‐consistent mean field theory, field‐theoretic simulation, as well as the time‐dependent Landau‐Ginzburg framework and its application to the studies of complex fluids.

     

Transport of Pesticides Under Aquifer Conditions

Abstract

Pesticide transport was determined in a quarternary coarse grained aquifer which was characterized by low organic carbon content. Water spiked with the pesticides atrazine, chlortoluron, isoproturon, simazine and terbuthylazine and chloride salt as conservative tracer, was injected in the aquifer. Mean residence times (MRT) of pesticides were generally 1.5 to 3 times higher than the MRT of the tracer. Sediment retention capacity calculated from experimental data yielded generally small values below 250 ng/kg sediment. Retardation characteristics were in the order of magnitude expected from literature data on organic carbon/water partition coefficients. Transport of pesticides was due to convection and dispersion whereas adsorption and degradation was low.     

Dihalocyclopropanation of Phenylthio or Butylthiocycloalkenes Under Phase Transfer Conditions. Opening of Cyclopropanes Under Microwave Irradiation

Dihalocarbenes (X=C1,Br) generated under phase transfer conditions added to phenylthio or butylthiocylcloalkenes give corresponding 1,1-dihalo-2-thiobutyl or thiophenyl-cyclopropanes. The ring opening of dichlorophenylthiocyclopropanes (2a, 2b, 2c) was obtained by using silver tetrafluoborate on alumina under microwave irradiation.     

Tetrahydropyranylation of Alcohols Under Solvent-Free Conditions

A green, efficient, and large-scale method for tetrahydropyranylation of alcohols in the presence of a catalytic amount of pyridinium chloride at room temperature under solvent-free conditions is reported.     

Synthesis of Guanylhydrazones Under Microwave Irradiation

Abstract

The reaction of aromatic aldehydes and ketones with aminoguanidine hydrochloride under microwave irradiation (MWI) afforded guanylhydrazones in shorter reaction times and improved yield as compared to the conventional methodology.     

Synthesis of Thiosemicarbazones Under Microwave Irradiation

Thiosemicarbazones (3) are effectively synthesized in a few minutes by the condensation reaction of aldehydes with thiosemicarbazide under microwave irradiation.     

超声辐照法合成二氯苯基膦

超声辐照法合成二氯苯基膦;二氯苯基膦（DCPP）;合成;超声;络合剂     

利用微波辐射制备2-萘甲醚的合成实验

利用微波辐射的方法合成 2 萘甲醚 ,对微波辐射功率、微波辐射时间、催化剂的用量、反应物的配比对反应产率的影响进行讨论 ,该方法与传统合成方法相比具有反应时间短 ,反应条件温和 ,简单易行 ,无污染的特点     

The Suzuki Reaction Under Solvent-Free Conditions

The coupling reaction of diverse arylhalogenids with phenyl-boronic acid under solvent-free conditions has been performed using a palladium catalyst. The order of reactivity was complementary to the normal Suzuki reaction.     

Preparation of Chitin Hydrogel Under Mild Conditions

Both the amount of water and the number of calcium ions are main factors affecting the dissolution of chitin in calcium chloride dihydrate-saturated methanol (calcium solvent). The higher degree of N-acetylation of the chitin was also indicated by its higher solubility in calcium solvent. The chitin hydrogel was prepared by adding a large excess of water to the chitin solution with vigorous stirring, followed by extensive dialysis against water or by filtration to remove the methanol and calcium ions. The water content of the chitin hydrogel was approximately 94–96% (w/v) and could be controlled by centrifugation. The chitin gel was also prepared by the addition of a large excess of alcohol, such as ethanol and iso-propanol, and these protocols were found to be effective under anhydrous conditions because the alcohols were exchangeable with other organic solvents in solution. The chitin hydrogel was more susceptible to lysozyme than to chitinase, and showed and a poor susceptibility to chitosanase. A α-chitin-type crystalline structure was regenerated from chitin sheets prepared from both α-chitin and β-chitin solutions in calcium solvent, but the β-chitin-type sheet was formed from the β-chitin hydrogel prepared by mechanical agitation in water. The α-chitin hydrogel solidified when thawed after freezing, but the β-chitin hydrogel prepared by mechanical agitation maintained its gel form even after prolonged freezing. Animal studies revealed a low toxicity for the chitin sheet and an acceleration of epidermal cell regeneration.     

Non-Bonded Radii of the Atoms Under Compression

Abstract : We present quantum mechanical estimates for non-bonded, van der Waals-like, radii of 93 atoms in a pressure range from 0 to 300 gigapascal. Trends in radii are largely maintained under pressure, but atoms also change place in their relative size ordering. Multiple isobaric contractions of radii are predicted and are explained by pressure-induced changes to the electronic ground state configurations of the atoms. The presented radii are predictive of drastically different chemistry under high pressure and permit an extension of chemical thinking to different thermodynamic regimes. For example, they can aid in assignment of bonded and non-bonded contacts, for distinguishing molecular entities, and for estimating available space inside compressed materials. All data has been made available in an interactive web application.     

Fluorides of Silver Under Large Compression**

The silver-fluorine phase diagram has been scrutinized as a function of external pressure using theoretical methods. Our results indicate that two novel stoichiometries containing Ag⁺ and Ag²⁺ cations (Ag₃F₄ and Ag₂F₃) are thermodynamically stable at ambient and low pressure. Both are computed to be magnetic semiconductors under ambient pressure conditions. For Ag₂F₅, containing both Ag²⁺ and Ag³⁺, we find that strong 1D antiferromagnetic coupling is retained throughout the pressure-induced phase transition sequence up to 65 GPa. Our calculations show that throughout the entire pressure range of their stability the mixed-valence fluorides preserve a finite band gap at the Fermi level. We also confirm the possibility of synthesizing AgF₄ as a paramagnetic compound at high pressure. Our results indicate that this compound is metallic in its thermodynamic stability region. Finally, we present general considerations on the thermodynamic stability of mixed-valence compounds of silver at high pressure.     

Deprotonation-Alkylation of Alkyl Cyanides Under Sonochemical Conditions

Deprotonation-alkylation of n-alkyl cyanides can be readily effected by an alkyl halide in the presence of sodium in a one pot procedure. Yields are generally better than in the usual methods, and the overall reaction conditions have important advantages in terms of ease and simplicity compatible with preparative scale-up.     

Dehydrogenative Silylation of Alcohols Under Pd-Nanoparticle Catalysis

Pd-nanoparticle-catalyzed dehydrogenative coupling between various hydrosilanes and alcohols was shown to provide silyl ethers in good and reproducible yields. The synthetic methodology is effective for a wide range of simple and bulky silanes and secondary alcohols, while keeping various other functional groups intact. The procedure also exhibits high selectivity for the silylation of primary versus secondary alcohols in 1,2-diols, and allows the successive silylation of alkynols and hydrogenation of the triple bond to afford Z-alkenols in good yields.     

Improved Synthesis of Oxadiazoles Under Microwave Irradiation

Abstract

Amidoximes (1) reacted with isopropenyl acetate in presence of KSF under microwave irradiation and gave 1,2,4-oxadiazoles (2). 1,2,4-Oxadiazoles (4) can also be obtained by microwave irradiation from O-acylamidoximes (3) adsorbed on Alumina.

1,3,4-Oxadiazoles (6) were obtained by irradiation of bis (acyl) hydrazines (5) in thionyl chloride.