Alternating copolymerization of isoprene and butadiene with acrylonitrile

Copolymerizations of acrylonitrile and isoprene or butadiene were carried out in the presence of a new catalytic system containing Cr(O-tert-Bu)₄ and AlEtCl₂. It was found that the copolymer compositions have a highly alternating structure, even with varying feed ratios of monomer. The nuclear magnetic resonance spectra of the copolymers obtained with this catalytic system were observed and are discussed in terms of the alternation.     

Distribution pattern of rare earth ions between water and montmorillonite and its relation to the sorbed species of the ions.

REE (rare earth element) distribution coefficients (Kd) between the aqueous phase and montmorillonite surface were obtained to investigate the relation between the REE distribution patterns and the species of REE sorbed on the solid-water interface. It was shown that the features in the REE patterns, such as the slope of the REE patterns, the tetrad effect, and the Y/Ho ratio, were closely related to the REE species at the montmorillonite-water interface. In a binary system (REE-montmorillonite) below pH 5, three features (a larger Kd value for a lighter REE, the absence of the tetrad effect, and the Y/Ho ratio being unchanged from its initial value) suggest that hydrated REE are directly sorbed as an outer-sphere complex at the montmorillonite-water interface. Above pH 5.5, the features in the REE patterns, the larger Kd value for heavier REE, the M-type tetrad effect, and the reduced Y/Ho ratio, showed the formation of an inner-sphere complex of REE with -OH group at the montmorillonite surface. In addition, the REE patterns in the presence of humic acid at pH 5.9 were also studied, where the REE patterns became flat, suggesting that the humate complex is dominant as both dissolved and sorbed species of REE in the ternary system. All of these results were consistent with the spectroscopic data (laser-induced fluorescence spectroscopy) showing the local structure of Eu(III) conducted in the same experimental system. The present results suggest that the features in the REE distribution patterns include information on the REE species at the solid-water interface.     

Binding of metal ions by polyethylenimine and its derivatives

Measurements have been made of the binding of divalent metal ions, Cu²⁺, Ni²⁺, Co²⁺, and Zn²⁺ ions, by polyethylenimine (PEI) and its acetyl or alkyl derivatives by the equilibriumdialysis technique. These metal ions, in particular the Cu²⁺ ion, exhibited tremendously remarkable binding affinity toward PEI. The extent of complexation of the polymer with the metal ions was decreased markedly by acetylation or alkylation of the polymer. PEI with no primary amine showed an appreciable decrease in its affinity for the metal ion. These results indicate the participation of the primary amine of the polymer in the formation of the complex. A cooperative binding isotherm was observed in PEI–metal ion complex formation, suggesting swelling or conformational change of the polymer induced by this coordination process. Binding of the Cu²⁺ ion by PEI was found to be essentially independent of temperature over the range 5–35°C.     

Evaluation of molecular structure in Langmuir monolayers of zinc stearate and zinc 12-hydroxystearate by IR external reflection spectroscopy

 In situ polarized Fourier transform IR external reflection spectra of Langmuir monolayers of zinc stearate and zinc 12-hydroxystearate on a water surface were recorded for various surface areas, and their molecular structures were estimated. In the zinc stearate monolayer, the wavenumbers and the absorbances of the antisymmetric and symmetric methylene stretching bands did not change during monolayer compression, which means that orientational and conformational changes of the hydrocarbon chain did not occur. However, wavenumber changes of the antisymmetric and symmetric carboxylate stretching bands were observed during surface compression. The change in the binding nature of the zinc cation to the carboxylate group was speculated. Moreover, it was elucidated that the structure of the hydrocarbon chain in the zinc 12-hydroxystearate monolayer was different from that in the zinc stearate monolayer. Received: 21 March 2001 Accepted: 6 July 2001     

An analytical expression for the approximate dependence of the degree of counterion binding on the composition of ionic-nonionic mixed micelles

A simple analytical expression is presented to describe the dependence of the degree of counterion binding beta of ionic-nonionic mixed micelles on the composition x(I) (the micelle mole fraction of the ionic species): 1/(1-beta)=1-x(I)+x(I)/[1-beta(x(I)=1)]. In the application of the relation, the value of beta for the pure ionic micelle, beta(x(I)=1), should be known in advance. An equivalent expression was first proposed by Hall et al. on purely empirical grounds but in the present study the relation is derived on the basis of the Poisson-Boltzmann equation of the plate model of micelles in a salt-free medium. The insensitive nature of beta toward a change in micelle concentration as well as to the addition of a salt is also derived under reasonable approximations. When the relation was applied to 12 mixed micelles both with and without added salt, it described quite well the observed composition dependencies of all examples examined. Two other simple analytical expressions are also derived, but they are much less satisfactory in describing the experimental data.     

Contracted polarization functions for B to Ar

Using optimal exponents for B through Ne given by Dunning and those for Al through Ar by Woon and Dunning, d-type contracted polarization functions (2d/1d), (3d/1d), and (3d/2d) are generated from natural orbitals of atomic single and double excitation configuration interaction (SDCI) calculations, where the numbers before and after the slash are those of the primitive and contracted Gaussian type functions. The resulting contracted functions are tested on N₂ and P₂ molecules by self-consistent field and SDCI calculations, which clarify characteristics of the present polarization functions. Received: 5 June 1997 / Accepted: 20 August 1997     

Ab initio MO Calculations of benzene + TCNE and naphthalene + TCNE complexes with STO-3G π-split basis set

Ab initio SCF MO calculations have been carried out on benzene + TCNE (tetracyanoethylene) and naphthalene + TCNE complexes with the STO -3G, STO -3G π-split (STO -3G for π orbitals and a split basis for π orbitals), and 4–31G basis sets. The interaction energy, gross charges, dipole moment, and the electron density in the middle plane of the complexes have also been evaluated. The STO -3G π-split basis set is appropriate for the calculation of large π–π stacking complexes from two points of view, production of reliable results and ease of computations. The approximation scheme based on the semiorthogonalized orgitals is revealed to be very efficient to save CPU time and storage in such calculations. The stable conformation and the charge-transfer interaction of the two complexes are discussed on the basis of the calculated quantities.     

Synthesis of 2-alkylidenetetrahydrofurans by Ru-catalyzed regio- and stereoselective codimerization of dihydrofurans with alpha,beta-unsaturated esters

2-(1-Alkoxycarbonyl)alkylidenetetrahydrofurans were readily synthesized by the codimerization of 2,3- or 2,5-dihydrofurans with alpha,beta-unsaturated esters using a zerovalent Ru catalyst, Ru(cod)(cot), with high regio- and stereoselectivity.     

Preparation of α-trialkylsilyl ketones from α-phenylseleno derivatives via their silyl enol ethers

On treatment with metallic lithium in the presence of dimethylaminonaphthalene, trialkylsilyl enol ethers of α-phenylseleno ketones were converted into the corresponding α-trialkylsilyl ketones in good yields.     

Polyesters containing ring units in main chains. I. Preparation and stereochemistry of monomers and polyesters

Cycloalkanone (C₅–C₈, C₁₂, and C₁₅) or cycloalkane (C₅ and C₆) ring-containing monomeric diesters and the polyesters derived from them were prepared, and their configurations were studied by ¹³C-NMR spectroscopy. Absolute configurations were determined for ring sizes 5, 6, and 7. Configurational change during reduction of a ketonic group of monomeric diesters with ring sizes 5 and 6 was discussed in terms of the steric effect of ring substituents on the ketonic group. In the polycondensation reaction epimerization of the ring units was observed in 5-, 6-, and 7-membered cycloalkanones and not in others, which is explained by steric hindrance by the ring substituents against attack of tetrabutyl titanate catalyst on the ketonic group.