Electronic states of an infinite polyene under local perturbations

A perturbation theory method is developed in the tight-binding LCAO MO treatment of a one-dimensional polymer under local perturbation with the aid of the Wannier function. As the first step, electronic states of an infinite polyene under a few of significant cases of perturbation are formulated in the scheme of the Hückel MO approach, giving the changes in total energies, electron densities, and bond orders of the perturbed systems.     

Precipitation of metal 8-hydroxyquinolates from homogeneous solution—II Thorium

A comparison has been made of the precipitation of thorium with 8-hydroxyquinoline by the direct method of addition of reagent and by precipitation from homogeneous solution by generation of the reagent from 8-acetoxyquinoline. The latter reagent produces a thorium precipitate with superior physical characteristics. Separation studies using cerium^III as a diverse ion also indicate the superiority of the method using 8-acetoxyquinoline. Further studies of thorium 8-hydroxyquinolate, precipitated by either method, indicate that ignition to thorium oxide is a reliable way to conclude the determination. Methods involving weighing or brominating the 8-hydroxyquinolate generally furnish erroneous results.     

Absolute structure of panaxytriol

Diastereomeric mixture at C-3 of (9R,10R)-panaxytriol acetonide (3) and (9S,10S)-panaxytriol acetonide (4) were enantioselectively acetylated to give (3R)-acetates (3a-Ac, 4a-Ac) and (3S)-alcohols (3b, 4b) by enzyme mediated-acetylation using CHIRAZYME and vinyl acetate, respectively. Hydrolysis of (3R)-acetate (3a-Ac, 4a-Ac) with CHIRAZYME and phosphate buffer afforded (3R)-alcohols (3a, 4a), respectively. Deprotection of panaxytriol acetonides (3a, 3b, 4a, 4b) gave panaxatriol and its isomers, respectively. Comparison of optical rotation values of the synthetic panaxatriols with that of the natural one confirmed that the absolute configuration of panaxytriol sould be 3R,9R,10R.     

Effect of solvent on radical polymerization of vinyl benzoate

Absolute rate constants of the vinyl benzoate polymerization have been measured by use of the intermittent illumination method in various aromatic solvents and ethyl acetate at 30°C. The determination of absolute rate constants showed that effects of solvent on the polymerization rate of vinyl benzoate were mainly ascribed to the variation of k_p values with solvents rather than that of k_t values. The k_p values for solvents used increased in the order: benzonitrile < ethyl benzoate < anisole < chlorobenzene < benzene < fluorobenzene < ethyl acetate. There was an eightfold difference between the largest and the smallest values The large variation among k_p values was explained neither by the copolymerization through solvents nor the chain transfer to solvents, but by a reversible complex formation between the propagating radical and aromatic solvents. This explanation was supported by a correlation between k_p values and calculated delocalization stabilizations for the complexes.     

Counting efficiency and colour quenching in measuring Cherenkov radiation

The counting efficiency of Cherenkov radiation by the liquid scintillation counter is studied in several solvents. The relation between the strength of the pulse height by the Cherenkov radiation and the maximum energy of -rays was fairly proportional. The colour quenching can be corrected by measuring the absorbance of solution.     

AxBAx‐Type Block–Graft Polymers with Soft Methacrylate Middle Segments and Hard Styrene Outer Grafts: Synthesis,Morphology, and Mechanical Properties

Novel copolymers with controlled architectures can function as new building blocks for well‐defined nanostructures on the basis of microphase separation, unlike conventional ABA triblock copolymers. A series of well‐defined A_xBA_x‐type block–graft copolymers consisting of soft middle segments (dodecyl methacrylate (DMA)) and hard outer graft chains (styrene (St)) were synthesized by ruthenium‐catalyzed living radical block and graft polymerization. NMR spectroscopy and size‐exclusion chromatography combined with multiangle laser light scattering confirmed the well‐defined structure of the A_xBA_x block–graft copolymers with backbones and graft chains of controlled lengths. Transmission electron microscopy and transmission electron microtomography revealed a series of morphologies for the copolymers. Morphological changes were observed from PSt “honeycomb” cylinders to lamellae and poly(DMA) cylinders with increasing PSt‐graft content, whereby the phase diagram was shifted significantly to lower volume fractions of the larger‐number component (St) relative to those of the corresponding ABA triblock copolymers. More specifically, poly(DMA) cylinders were observed even before the St content reached 50 wt %. The A_xBA_x and ABA copolymers with 17–30 wt % of St exhibited characteristics of a thermoplastic elastomer with tensile strengths of 1–6 MPa and elongations at break of 70–300 %. These mechanical properties can be related well to the microphase structures of the A_xBA_x and ABA copolymers.     

First example of memory of chirality in carbenium ion chemistry

The non-Kolbe reaction of N-benzoyloxazolidine derivatives 6 derived from L-serine gave optically active N,O-acetals 7 when graphite was used as an anode material. This reaction represents the first example of "memory of chirality" in carbenium ion chemistry. The material used for the anode was critical for the memory of chirality. The substitution of carboxyl group with methoxyl group was found to proceed with an inversion mechanism.     

Selective vinyl polymerization of 4-vinyl-1-cyclohexene with ziegler–natta catalyst

The polymerization of 4-vinyl-1-cyclohexene (4VCHE) with Ziegler–Natta catalysts was studied. The polymerization of 4VCHE by the vinyl group took place with TiCl₃–aluminum alkyls catalysts, while vinylene group of 4VCHE did not participate in the reaction, but it affected the polymerization rate of 4VCHE. The effects of aluminum alkyl and type of TiCl₃ on the polymerization were examined. The overall activation energy for the polymerization was estimated to be 41.9kJ/mol. Monomer-isomerization copolymerization of 4VCHE and trans-2-butene occurred with the TiCl₃-(i-C₄H₉)₃Al catalyst to give copolymers consisting of 4VCHE and 1-butene units.     

Comparison between theoretical values and simulation results of viscosity for the dissipative particle dynamics method

In order to investigate the validity of the dissipative particle dynamics method, which is a mesoscopic simulation technique, we have derived an expression for viscosity from the equation of motion of dissipative particles. In the concrete, we have shown the Fokker-Planck equation in phase space, and macroscopic conservation equations such as the equation of continuity and the equation of momentum conservation. The basic equations of the single-particle and pair distribution functions have been derived using the Fokker-Planck equation. The solutions of these distribution functions have approximately been solved by the perturbation method under the assumption of molecular chaos. The expressions of the viscosity due to momentum and dissipative forces have been obtained using the approximate solutions of the distribution functions. Also, we have conducted nonequilibrium dynamics simulations to investigate the influence of the parameters, which have appeared in defining the equation of motion in the dissipative particle dynamics method. The theoretical values of the viscosity due to dissipative forces in the Hoogerbrugge-Koelman theory are in good agreement with the simulation results obtained by the nonequilibrium dynamics method, except in the range of small number densities. There are restriction conditions for taking appropriate values of the number density, number of particles, time interval, shear rate, etc., to obtain physically reasonable results by means of dissipative particle dynamics simulations.