Beta-elimination of a phosphonate group from an alkoxy radical: an intramolecular acylation approach using an acylphosphonate as a carbonyl group acceptor

On the basis of facile beta-elimination of a phosphonate group from an alkoxy radical, intramolecular acylation reaction has been developed, in which an acylphosphonate is used as an excellent carbonyl group radical acceptor.     

Development of a novel granular detergent with an interspersion particle comprising an anionic surfactant and a polymeric polycarboxalate

This paper discusses a process for making a novel granular detergent with an interspersion particle comprising an anionic surfactant and a polymeric polycarboxalate. This process contains three steps to develop the interspersion particles with anionic surfactant and polymeric ploycarboxalate. The first step was to form a detergent particle by spray drying of an aqueous detergent slurry comprising anionic surfactant (liner alkyl benzene sulfonate) with the different levels of polymeric polycarboxalate. In the second step, the spray-dried granules were densified and ground by a roll compacter and a grinder. The ground particles were coated by nonionic and zeolite in a vertical batch type high shear mixer (third step). In this study, the feasibility to make better performance of granular detergent was discussed.     

Flow cell within an LED: a proposal for an optical absorption detector

Droplets formed at the tip of a tube under the same conditions possess extreme uniformity of form, volume and weight. These properties of liquid drop formation have been known for a long time and consequently many applications for the drop have been found in instrumentation and chemical analysis methods. In the present paper, we report on the analytical use of a dynamic LED-based flow-through optical absorption detector with optical path length controlled by continuous dropping of a solution. This arrangement consists of a flow cell built within a high-intensity red LED (λ _max = 630 nm). The feasibility of the detector is demonstrated by colorimetric determination of methylene blue, and ammonium by Berthelot’s reaction, in a flow-injection system. For ammonium, the reaction forms a blue dye (indophenol) with a maximum absorption at 630–650 nm. The detection limit, considered as 3 times the signal of the blank, is better than 125 μg l^-1. The small flow cell represents a good combination of optical path length, low volume and fast washout. This detector can be used advantageously in automated methods and can represent a solution to problems of optical detection involving gas bubbles and precipitation of particles in turbidimetric applications.     

The conversion of an aziridine plus an iminium salt to a 1,2-diamine

The conversion of an aziridine to a 1,2-diamine using lithium iodide and an iminium salt is discussed. We have found that when the aziridine is substituted by only alkyl groups, it is the less substituted carbonnitrogen bond that is broken; whereas, when the aziridine is substituted by a phenyl group at either the nitrogen or the carbon, it is the more substituted carbonnitrogen bond that is broken. For a 2,3-disubstituted aziridine, the reaction sequence goes with net retention of stereochemistry.     

Comparison of a jet separator and an open splitter as an interface between a multi-capillary gas chromatographic column and a time-of-flight mass spectrometer

A gas chromatographic/time-of-flight mass spectrometric (GC/TOFMS) interface is being developed for fast on-line analysis utilizing multi-capillary column technology. A variable gap-distance jet separator has been constructed and its performance compared with that of a commercially supplied post-column open splitter recommended for use between the multi-capillary column and a mass spectrometer. Both interfaces were found to be compatible with the GC/TOFMS system at high carrier gas flow-rates, facilitating high-speed and high-resolution separations. The systems were investigated and tested with a mixture of volatile organic compounds (VOCs) with molecular masses from 85 to 166: dichloromethane, toluene, m-dichlorobenzene, o-dichlorobenzene and tetrachloroethylene. The optimum tip-to-tip gap distance corresponding to the highest efficiency of the jet separator was found to be 0.030 mm for each compound at carrier gas flow-rates of 20, 40 and 60 ml min(-1) giving, in the ion source housing, ion gauge pressure readings of 1.6 x 10(-6), 5.0 x 10(-6) and 5.8 x 10(-6) mbar, respectively. The efficiency of the jet separator (10-30% yields) was significantly higher than that of the open splitter (6-9% yields). The observation that the open splitter did not provide a constant flow-rate to the ion source was not in agreement with the manufacturer's specifications. A method for measuring the gas flow-rates in all parts of the equipment is described. The correlation between yield in the jet separator and molecular mass for the heterogeneous set of compounds studied was found to be less linear than usually reported for homologous series of compounds in jet separator studies. The result suggests that the pressure conditions in the jet may be sufficient for the separation process to be partly controlled by diffusion rather than predominately by effusion. Copyright 2000 John Wiley & Sons, Ltd.     

Lateral spread of an amplification signal using an enzymatic system on a conductive surface

In this letter, we report a novel signal amplification phenomenon that rapidly and dramatically increases both the magnitude and the lateral extent of the original signal. This phenomenon utilizes an enzyme immobilized on a conductive surface to generate amplified signals at locations remote from the original site of enzyme activity. The result is demonstrated on a microfluidic platform using the established precipitating enzyme-substrate system of horseradish peroxidase (HRP) and 3,3',5,5'-tetramethylbenzidine (TMB) on a surface plasmon resonance (SPR) imaging system.     

On the stereochemistry of an alkylcuprate induced conversion of a bromoallene into an alkylallene

By preparing $\text{levorotatory}$$\text{2}$ following a route of known stereochemistry, we were able to elucidate the stereochemistry of the conversion of the levorotatory bromoallene $\text{1}$ into levorotatory $\text{2}$ by $\text{t}$-Bu(CN)CuLi: the reaction occurs with retention of configuration in the allenyl moiety.     

Dielectrophoresis of an inhomogeneous colloidal particle under an inhomogeneous field: a first-principles approach

In reality, colloidal particles often possess an arbitrary inhomogeneity profile. We present a first-principles approach to dielectrophoresis of such an inhomogeneous colloidal particle under an inhomogeneous field of an oscillating electric dipole moment. For numerical simulations, we treat the inhomogeneous particle as a specific graded one with a physically motivated dielectric model and conductivity profile. We find that both multipolar interactions and spatial fluctuations inside the particle can affect the dielectrophoretic spectrum of the particle significantly.     

Assembly of a polyoxometalate into an anisotropic gel

The self-assembly of the polyoxomolybdate [MnMo6O18[(OCH2)3CNHCO(4-C5H4N)]2]3- and [PdCl2(PhCN)2] yields a transparent and birefringent gel.     

Acceleration of a Diels-Alder reaction in an ultracentrifuge

The reaction rate for the Diels-Alder reaction between maleic anhydride and furan is increased when performed in an ultracentrifuge.     

Putting a brake on an autonomous DNA nanomotor

A strategy was developed to reversibly switch on/off an autonomous DNA nanomotor that contains a DNA enzyme. The multiple RNA cleavage of the DNAzyme powered the motor to move, and a strand displacement mechanism provided the basis for a reversible brake to the motor.     

From an electron micrograph to a postage stamp

Soon following Dan Shechtman’s discovery of quasicrystals, Ágnes Csanády and her associates started producing beautiful quasicrystals of flowerlike morphology. The image of one of their specimen appeared on the Israeli postage stamp honoring Shechtman’s discovery, his Nobel Prize, and the International Year of Crystallography.     

Adsorption of a double-chain surfactant on an oxide

Adsorption of surfactants on solids is affected by the intermolecular packing in the adsorbed layer besides the driving forces. The adsorption behavior of a double-chain surfactant on silica is studied here along with that of the single-chain one. Comparison of adsorption of these two surfactants is warranted since while the single-chain surfactants form spherical micelles, the double-chain ones form bilayered vesicles in solution. While the adsorption of the single-chain surfactant reaches the plateau in a wide concentration range, the adsorption of the double-chain one increases sharply in a concentration range 10⁻⁵ mol/L up to the plateau. The single chain is found to form 1.5 monolayers under saturation coverage suggesting adsorption with reverse orientation at high concentration. In contrast, the adsorption of the double-chain surfactant under saturation coverage is equivalent to a 0.9 monolayer. Fluorescence tests revealed the hydrophobicity change of the surface with increase in adsorption. However, the hydrophobicity tests show the solid surface to be hydrophilic in this range; the double-chain surfactant is proposed to form a partial bilayer.     

Photolysis of a 2-tetbazeio from an enehydrazine

Photolysis of the 2-tetrazene $\text{1}$ gives the triazole $\text{2}$ by homolysis of one single N,N-bond. The formation of the other products $\text{4}$ – $\text{13}$ can be rationalized by regarding the aza-allyl radical $\text{3}$ as a common precursor.