Systematic survey on crystalline features of algal celluloses

Algal cellulose from different origins has been analysed with special reference to the crystalline features, such as allomorphism (I/I or triclinic/monoclinic two- phase model), dimension and uniplanar orientation behaviour of the specific crystallographic plane to the cell wall surface. Three types of cellulose were identified in the algal system: I-rich/broad microfibril/0.6 nm-oriented type; I- dominant/flat-ribbon/0.53 nm-oriented type; and I- dominant/small/random-oriented type. The first type appears to occur in more primitive organisms than the other types. The three types of algal cellulose correlate well with the arrangements of cellulose synthesizing complexes, i.e. multiple-row linear type, consolidated rosette type, and isolated rosette type, respectively. In Chara two types of crystals were found: an I-dominant/ribbon shaped/0.6 nm-oriented type and an I/narrow/random-oriented type. The former type, known to occur in some families of tunicates, was first identified in algal cellulose during this study. Reducing-end staining was successfully applied to microcrystal cellulose samples of Cladophorales and Zygnematales, showing that the cellulose microfibril has a parallel-chain structure for both cellulose I and cellulose I     

Cycloleonurinin, a cyclic peptide from Leonuri Fructus

From Leonuri Fructus, a cyclic peptide composed of twelve amino acid residues was isolated. The sequence of the residues was established by mass spectroscopy and by the use of a protein sequencer for the partial hydrolysates obtained by alpha-chymotrypsin.     

Polymerization of vinyl chloride in the presence of precipitants. II.

The kinetics of the radiation-induced polymerization of vinyl chloride in the presence of precipitants has been successfully described by a one-parameter equation as follows, where ?₀ is initial monomer volume fraction, X is conversion, t is time, and k is reaction constant. The equation was confirmed for extensive conditions of temperatures and monomer concentrations in the case of polymerization in methanol. The degree of polymerization was related with the reaction constant k, initial monomer volume fraction ?₀, monomer chain transfer constant C_m, conversion X, and the initiation rate I as follows, The factors which determine the value of the reaction constant k were elucidated through measurements of the reaction constant k and the degree of polymerization DP _n.     

Regioselective germylcupration of acetylenes

The reaction of terminal acetylenes with (Ph₃Ge)₂Cu(CN)Li₂ (1) or (Et₃Ge)₂Cu(SMe₂)Li (2) provides vinylgermanes in good yields. Whereas germylcupration of 1-dodecyne gives 2-germyl-1-dodecene as a main product, germylmetalation of phenylacetylene or 3-methyl-3-buten-1-yne affords 1-germyl compounds preferentially.     

The organic solvent effect on phosphomolybdic acid and its analytical application

The ultraviolet spectra of phosphomolybdic acid in aqueous and mixed solvent systems were studied. The spectra are profoundly affected by the addition of organic solvents such as tetrahydrofuran, ethanol and their homologues and eventually exhibit an absorption maximum at 310 run. The formation of phosphomolybdic acid was found to be quantitative even with low concentrations of molybdate ions (ca. 10(-4)M) at pH about 3. By using these facts, a simple method for direct spectrophotometric determination of phosphate ion has been developed.     

Reaction of alpha,alpha-dibromo oxime ethers with Grignard reagents: alkylative annulation providing a pyrimidine core

A convergent synthesis of a pyrimidine core has been achieved. Treatment of alpha,alpha-dibromo oxime ethers, which are easily derived from the corresponding esters, with a variety of Grignard reagents provides trisubstituted pyrimidines in good yields. This new method offers an easy access to functionalized pyrimidines.     

Polymerization of vinyl monomers in the presence of silica having surface functional groups

The surface of silica was modified by mercaptopropyl, chloropropyl, aminopropyl, and methacryloxypropyl groups by the treatment of silica with the corresponding silane coupling agents, and the effects of functional groups on the surface on the polymerization of vinyl monomers initiated by benzoyl peroxide or 2,2-azobisisobutyronitrile were investigated. Although the rate of the polymerization of vinyl monomers in the presence of silica was almost equal to that in the absence of silica, a part of polymer formed was grafted onto silica surface. The polymerization was considerably retarded in the presence of these functionalized silicas and the corresponding polymers were effectively grafted onto the surface. The molecular weight of ungrafted polymer formed in the presence of the functionalized silica was lower than that formed in the presence of unmodified silica. This indicates that the chain transfer reaction of growing polymer radical to functionalized silica surface forms radicals on the surface, which then couples with growing polymer radical and/or reinitiates the polymerization to give rise to the grafting of polymers onto the surface. In the case of silica having methacryloxypropyl groups, the grafting based on the copolymerization of vinyl monomer with the surface methacryloxypropyl groups was considered to successfully proceed.     

Radiation-induced polymerization of glass forming systems. VI. Polymerization rate at higher conversion in binary systems

The effect of temperature and composition on the inflection point in the time–conversion curve and the saturated conversion was investigated in the radiation-induced radical polymerization of binary systems consisting of a glass-forming monomer and a solvent. In the polymerization of completely homogeneous systems such as glycidyl methacrylate (GMA)–triacetin and hydroxyethyl methacrylate (HEMA)–propylene glycol systems, the time–conversion curve has an inflection point at polymerization temperatures between T_vm (T_v of monomer system) and T_vp (T_v of polymer system). Such conversions at the inflection point changed monotonically between 0 and 100% in this temperature range. T_v was found to be 30–50°C higher than T_g (glass transition temperature) and a monotonic function of composition (monomer–polymer–solvent). The acceleration effect continued to 100% conversion above T_vp, and no acceleration effect was observed below T_vm. The saturated conversion in homogeneous systems changed monotonically between 0 and 100% for polymerization temperatures between T_gm (T_g of monomer system) and T_gp (T_g of polymer system). T_g was also a monotonic function of composition. No saturation in conversion was observed above T_gp, and no polymerization occurred below T_gm. In the polymerization of completely heterogeneous systems such as HEMA–dioctyl phthalate, no acceleration effect was observed at any temperature and composition. The saturated conversion was 100% above T_g of pure HEMA, and no polymerization occurred below this temperature in this system.     

Solubilization of Polar Oils in Surfactant Self-Organized Structures

The cloud temperature of 2 wt% C(12)EO(8) aqueous solutions decreases upon addition of sarcosinate-lauroyl isopropyl (SLIP), 1-dodecanol, and m-xylene, whereas it increases in glycerol tris(2-ethylhexanoic) ester (TEH), isopropyl myristate (IPM), and saturated hydrocarbon systems. A three-phase microemulsion is formed at equal weights of water and oil in the IPM system, but a lamellar liquid crystal (L(alpha)) is present in the SLIP system at the balanced temperature. The effect of added oil on the phase transition of the hexagonal (H(1)) phase was also investigated by means of SAXS study. The H(1)-L(alpha) transition occurs upon addition of SLIP or 1-dodecanol whereas the H(1)-I(1) (discontinuous micellar cubic) phase transition takes place in TEH or IPM systems. These differences in phase behavior are attributed to the placement of solubilized oil in micelles: In the former systems, oil tends to penetrate in the surfactant palisade layer and induces the surfactant layer curvature in micelles to be less positive, while the penetration tendency is small and the opposite effect on the curvature is induced upon addition of the latter oils. Copyright 2001 Academic Press.     

Stereoregularity of poly(vinyl ether)

α-Methylvinyl isobutyl and methyl ethers were polymerized cationically and the structure of the polymers was studied by NMR. Poly(α-methylvinyl methyl ether) polymerized with iodine or ferric chloride as catalyst was found to be almost atactic, whereas poly(α-methylvinyl isobutyl ether) polymerized in toluene with BF₃OEt₂ or AlEt₂Cl as catalyst was found to be isotactic. In both cases, the addition of polar solvent resulted in the increase of syndiotactic structure as is the case with polymerization of alkyl vinyl ether. tert-Butyl vinyl ether was polymerized, and the polymer was converted into poly(vinyl acetate), the structure of which was studied by NMR. A nearly linear relationship between the optical density ratio D₇₂₂/D₇₃₆ in poly(tert-butyl vinyl ether) and the isotacticity of the converted poly(vinyl acetate) was observed.