Complexation of hydrazine with native cellulose in water and toluene

Adsorption–complexation of cellulose by hydrazine solutions in water and toluene was studied for native cellulose of varied crystallinity. Penetration of hydrazine into cellulose takes place more readily in hydrazine solution of higher concentration and with cellulose of lower crystallinity, but the equilibrium uptake was nearly independent of crystallinity. Complexation from toluene solution takes place at lower hydrazine concentration in toluene than in water, presumably because of the difference in hydrazine–solvent interaction. The adsorption isotherm of hydrazine in water is likely to be sigmoid, implying a cooperative sorption mechanism. It can presumably be ascribed to the disordered structure in the course of complexation.     

Formation and stability of cellulose–copper–NaOH crystalline complex

We investigated the crystal structure of alkali-celluloses, Na-cellulose IIA and II(Cu), formerly known as Na-cellulose IIB, by synchrotron X-ray diffraction. Na-cellulose IIA, formed from cellulose I by high-concentration NaOH treatment, has a fiber repeat of 15 Å and a threefold-like helical conformation. Na-cellulose II(Cu), prepared by treating cellulose I with copper-saturated alkali solution, also has a fiber repeat of 15 Å with threefold helical symmetry. Incorporation of Cu(II) ions into cellulose was confirmed by multiwavelength anomalous diffraction. Monitoring by X-ray diffraction revealed that the formation of this complex from cellulose I is remarkably slow, probably because of the involvement of copper ion. The stability of alkali-cellulose II(Cu) was tested to estimate the influence of the presence of copper in the crystal. Na-cellulose II(Cu) characteristically dissolved in aqueous ammonia solution, indicating strong coordination of copper ion to cellulose.     

Effects of lignin and hemicellulose contents on dissolution of wood pulp in aqueous NaOH/urea solution

Four species of delignified woodchips with about 1 % lignin content (Chlorite–Woodchips) and a series of softwood pulps with different lignin contents were prepared by sodium chlorite delignification. After mechanical defibration, some Chlorite–Woodchips were directly subjected to dissolution treatment in NaOH/urea solvent; the others were first treated with NaOH solution to remove the hemicellulose to obtain NaOH–Chlorite–Woodchips or oxidized with potassium permanganate (OPP) to remove lignin completely to obtain OPP–Chlorite–Woodchips, and then subjected to the dissolution in NaOH/urea solvent. The results showed that the dissolved proportion of the Chlorite–Woodchips ranged from 36 to 46 %, the dissolved proportion of glucan was within 12 %, and most of the hemicellulose was dissolved in NaOH/urea solvent. Compared with Chlorite–Woodchips, the dissolved proportion of NaOH–Chlorite–Woodchips was lower, but their dissolved proportion of glucan was higher. After further permanganate delignification, both the dissolved proportion of the OPP–Chlorite–Woodchips and the dissolved proportion of glucan of the OPP–Chlorite–Woodchips were higher than those of the Chlorite–Woodchips. However, the dissolved proportion of glucan was still limited to only 15–30 %. The effect of the lignin content of softwood pulps on their dissolution is complicated. With the decrease of the lignin content of softwood pulp from 6.9 to 2.8 %, the dissolved proportion of pulp increased from 14 to 26 %. However, further reduction of lignin content from 2.8 to 0.3 % led to a decrease in the dissolved proportion of pulp from 26 to 12 %. The dissolved proportion of glucan followed the same tendency. These results indicated that the dissolution of wood cellulose in NaOH/urea solvent is not simply controlled by the hemicellulose and lignin contents, but also by some other factors.     

Alternating cooligomerization of isoprene and propylene with vanadium catalyst

Alternating cooligomerization of isoprene with propylene has been investigated between ?30 and 0°C, VO(acac)₂–Et₃Al–Et₂AlCl being used as catalyst. In the presence of an excess of propylene, 2,4,7-trimethyl-1,4-octadiene and 2,4-dimethyl-1,4-nonadiene are selectively formed. The formation is explained by the alternating coordination of isoprene and propylene to the vanadium. When triphenylphosphine or pyridine is added to the catalyst, the cooligomerization is suppressed while the formation of the dimer and trimer of isoprene is high.     

Construction of a square-planar hydroperoxo-copper(II) complex inducing a higher catalytic reactivity

A novel hydroperoxo-copper(II) complex with a square-planar geometry has been prepared, which has exhibited a higher selectivity and catalytic reactivity for dimethyl sulfide, in contrast to that with a trigonal-bipyramidal one.     

Practical method for the synthesis of polysilanes using Mg and Lewis acid system

Reduction of dichlorosilanes with Mg metal in the presence of Lewis acid and LiCl was found to be the highly practical method for the synthesis of polysilanes.     

An application of fragment interaction analysis based on local MP2

We have developed a method named ‘fragment interaction analysis based on local MP2’ (abbreviated as FILM). This method enables us to decompose the interaction energy associated with dispersion interactions into contributions of localized occupied orbitals. In this study, the basis set dependence of the results derived from FILM was examined. The results suggested that the individual ratio of pair correlation energies of selected orbital pairs to the total dispersion interaction was almost independent of the basis set size. As an illustrative example, detailed analysis was performed on the human immunodeficiency virus type 1 protease complexed with lopinavir molecule.     

First-principles energy band calculation for undoped and N-doped InTaO4 with layered wolframite-type structure

The electronic structures of undoped and N-doped InTaO₄ with optimized structures are calculated within the framework of the density functional theory. Calculated lattice constants are in excellent agreement with experimental values, within a difference of 2%. The valence band maximum (VBM) is located near the middle point on the ZD line and the conduction band minimum (CBM) near the middle point on the DX line. This means that InTaO₄ is an indirect-gap material and a minimum theoretical gap between VBM and CBM is ca. 3.7 eV. The valence band in the range from −6.0 to 0 eV mainly consists of O 2p orbitals, where In 4d5s5p and Ta 5d orbitals are slightly hybridized with O 2p orbitals. On the other hand, the conduction band below 5.5 eV is mainly composed of the Ta 5d orbitals and the contributions of In and O orbitals are small. The band gap of N-doped InTaO₄ decreases by 0.3 eV than that of undoped InTaO₄, because new gap states originating from N 2p orbitals appear near the top of the valence band. This result indicates that doping of N atoms into metal oxides is a useful method to develop photocatalysts sensitive to visible light.     

Synthesis of unsymmetrically substituted pyrene derivatives through (6-bromo-3,8-dibutylpyren-1-yl)trimethylsilane

A straightforward route to unsymmetrically functionalized pyrene derivatives is described involving the synthesis of key precursor (6-bromo-3,8-dibutylpyren-1-yl)trimethylsilane 1. In a first step bromide 1 was successful in Suzuki-Miyaura, Sonogashira, and Buchwald-Hartwig cross-coupling reactions. Subsequent transformation of the trimethylsilyl group to bromide enabled the introduction of a second variable functional group onto the pyrene skeleton.