An application of plastic microchannel-microheater chips to a thermal synthetic reaction.

Polystyrol microchannel-microheater chips were fabricated on the basis of imprinting and photolithography techniques. The solution (i.e., methanol) temperature in the vicinity of the microheater (width = 100 or 200 microm and length = 100 microm) integrated in the channel (width = 100 microm and depth = 20 microm) was evaluated on the basis of the temperature-dependent fluorescence lifetime of Rhodamine B as a function of a flow rate and the voltage applied to the heater. The study demonstrated that the fabricated chip acted certainly as a microheater. The chip was then applied to the thermal reaction between benzaldehyde and malononitrile in methanol. Under optimum conditions, benzilidenemalononitrile as the product of the reaction was obtained in a 96% yield with the reaction time of 84 s.     

Measurement of thickness of a thin film by means of laser interference at many incident angles

An optical method for directly measuring the thickness of a thin transparent film has been proposed by means of multi-wave laser interference at many incident angles, and confirmed experimentally by means of equipment made on an experimental basis. Two methods are available: one can be used when an index of refraction of the film, a wavelength λ, and two successive angles of incidence at which the sinusoidal light intensity has minimum values, are known (Method I), and another can be used without an index of film refraction when three successive angles of incidence and a wavelength are known (Method II). The smallest measurable thickness is 1.43λ for Method I, and 2.5λ for Method II. The largest measurable thickness is about 100λ for both methods. The measurement error by means of numerical calculation is Δh/h−1.01×10⁻², and that obtained experimentally with an angular resolution of incident light of 0.3° is Δh/h7×10⁻² for Method I. The refractive index can also be measured by means of Method II.     

Synthesis of 9-(trifluoromethyl)pyrido[1′,2′:1,2]-imidazo[4,5-b]quinoxalines

9-(Trifluoromethyl)pyrido[1′,2′:1,2]imidazo[4,5-b]quinoxalines (9-CF₃-PIQs) were obtained from the cyclization of 2-amino-3-chloro-6-(trifluoromethyl)quinoxaline ( 1a ) with some substituted pyridines. 3-[2-(4-Pyridyl)ethenyl]-9-CF₃-PIQ, one of thus obtained 9-CF₃-PIQs, cyclized with another molecule of 1a to produce the dihydro bis-PIQ-ethene derivative.     

Solid Acid-Base Control of Inorganic/Organic Hybrids by Inorganic Components for Molecule-Selectivity

Solid acid-base properties of methylsiloxane-based inorganic/organic hybrids were controlled by incorporation of inorganic components other than Si into methylsiloxane networks. The effect of different inorganic components on the solid acid-base properties was estimated by first-principles calculations based on density functional theory (DFT). The deprotonation tends to occur in the order Si < Al < Nb inorganic components, suggesting that the acidity increases in the same order. Methylsiloxane-based hybrids with solid acid-base properties were also synthesized by incorporating inorganic components derived from metal alkoxides. Hammett indicators revealed that the solid acidity increased in the order Si < Al < Nb inorganic components, which was consistent with the results of first-principles calculations. Preliminary experiments revealed that the methylsiloxane-based hybrids also provided a solid basic nature by containing Ca and Y inorganic components derived from metal alkoxides. The acidic hybrids were found to have Brønsted acid sites from the FT-IR experiments of adsorbed pyridine on the hybrids.     

The use of a highly sulfated cyclodextrin for the simultaneous chiral separation of amphetamine-type stimulants by capillary electrophoresis

We investigated the simultaneous chiral separation of nine amphetamine type stimulants (dl-norephedrine, dl-norpseudoephedrine, dl-ephedrine, dl-pseudoephedrine, dl-amphetamine, dl-methamphetamine, dl-methylenedioxyamphetamine (MDA), dl-methylenedioxymethamphetamine (MDMA), and dl-methylenedioxyethylamphetamine (MDEA)) by capillary electrophoresis using highly sulfated gamma-cyclodextrin (SU(XIII)-gamma-CD) as a chiral selector. Three different approaches using SU(XIII)-gamma-CD with 50 mM phosphate background electrolyte were designed; (I) high CD concentration (10 mM SU(XIII)-gamma-CD) at neutral pH (pH 7.0) in the normal polarity mode, (II) low CD concentration (1.0 mM) at low pH (pH 2.6) in the normal polarity mode and (III) high CD concentration at low pH (pH 2.6) in the reversed-polarity mode. In mode (II), the effects of adding three neutral CDs (beta-CD, dimethyl-beta-CD and hydroxypropyl-beta-CD) were also investigated. The best separation was obtained after optimizing mode (III) as follows: run buffer of 10 mM SU(XIII)-gamma-CD with 50 mM phosphate background electrolyte at pH 2.6, applied voltage of -12 kV and capillary temperature of 15 degrees C.     

Semiempirical MO study on the abnormal bond orders of large networks of highly branched polyenes

The π-electronic structures of the ground state of linear and highly branched polyenes with up to 80 π-electrons are calculated with particular reference to the alternation of the bond orders. The MO methods adopted are HMO, PPP , variable-β, γ, and its improved version. The effect of the electron correlation through singly and doubly excited configurations is estimated with a second-order perturbation calculation. The calculated bond orders systematically vary with the degree of approximation used. Most of the bond order values can be grouped into either a single or double bond region. In certain series of highly branched polyenes the bond orders of double and single bonds at the root of branching, respectively, get smaller and larger as the size of the molecule increases and sometimes their difference gets diminishingly small. The origin of these abnormal bond orders is discussed in terms of the π-electron flow networks.     

Synthesis of polybenzimidazoles with sulfonic acid groups

2-Sulfoterephthalic acid (STA) and disulfoisophthalic acid (DSIA) were synthesized through the sulfonation and the oxidation of m- and p-xylene. The polycondensation reactions of STA and DSIA with aromatic tetraamines gave polybenzimidazoles which contained one or two sulfonic acid groups for each repeating unit. The polymer obtained was soluble in sulfuric acid, some organic solvents, and aqueous strong alkaline solution. The polymers were stable up to 400°C, but they gave polybenzimidazoles above 400°C by eliminating sulfonic acid groups, instead of ring closure.     

Dispersion behavior of oleic acid in aqueous media: from micelles to emulsions

 Dispersion behavior of aqueous solutions containing oleic acid (RH), sodium oleate (R^-Na⁺), and NaCl was investigated by turbidity and dynamic light-scattering measurements. Changes of the size of scattering particles in solution composed of 1 mM oleic acid and 100 mM NaCl were traced as a function of the degree of ionization α, in terms of radius of the equivalent hydrodynamic sphere. Large associated micelles with a radius of 30 nm appeared by a slight decline of α and existed at α higher than 0.75. They were responsible for the three-phase equilibrium (solution, micelle and aggregated micelle, and acid–soap, (R^-Na⁺)₃RH) characterized by a constant pH of 9.75. The appearance of a new phase, (R^-Na⁺)₃RH, contributed to increase both the turbidity and averaged scattering particle size. As the breakdown of the three-phase equilibrium, radius of scattering particles increased significantly. Finally, oleic acid oil droplets were separated from aqueous phase at low α. When the system was buffered by tris(hydroxymethyl)aminomethane (Tris), scattering particles with a weight-averaged hydrodynamic radius of 75 nm existed in a wide range of α from 0.85 to 0.65. In Tris buffered solution, turbidity formation was induced by the increase in the number of aggregated particles. Received: 12 November 1996 Accepted: 4 April 1997     

Effective consideration of ring structures in CAST/CNMR for highly accurate C NMR chemical shift prediction

A new function that effectively takes into account ring structural environments achieves extensive highly accurate prediction of ¹³C NMR chemical shift in the CAST/CNMR system. The approach adapts a fast and flexible ring perception algorithm and a new CAST coding method for the ring information. ¹³C NMR chemical shift prediction is performed for complicated polycyclic natural products and their synthetic intermediates as the demonstration, which shows the reliability of the function in extending the scope of the practically accurate ¹³C NMR prediction for wide range of organic compounds.     

Preparation of an intercalation compound of layered titanic acid H2Ti4O9 with methylene blue

Intercalation of methylene blue into layered titanic acid H₂Ti₄O₉ was examined by a guest exchange method using a propylammonium-H _x Ti₄O₉ intercalation compound as the intermediate. Methylene blue cations were arranged in the interlayer space obliquely to the layer surface. The visible spectrum of the intercalation compound suggested that the methylene blue cations were in an associated state in the interlayer space of H₂Ti₄₀₉. The intercalated methylene blue cations underwent a reversible electrochemical redox reaction in the dark, indicating that intercalation compounds of H₂Ti₄O₉ can be applied to a modified electrode.