Reaction of tetrahydrofurfuryl alcohol with dimethylamine and/or hydrogen

Conclusions 1-Pentanol, 1-dimethylaminopentane or 4-penten-1-o1, 1-pentanol, and 1,5-pentanediol are the major products of the hydroamination of tetrahydrofurfuryl alcohol by dimethylamine and the hydrogenation of this alcohol on a promoted, fused reduced iron catalyst.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2847–2849, December, 1987.The authors express their gratitude to V. G. Zaikin and A. I. Mikaya for assistance in interpreting the mass spectral data.     

Matrix polyelectrolyte microcapsules: new system for macromolecule encapsulation

A new approach to fabricate polyelectrolyte microcapsules is based on exploiting porous inorganic microparticles of calcium carbonate. Porous CaCO3 microparticles (4.5-5.0 microns) were synthesized and characterized by scanning electron microscopy and the Brunauer-Emmett-Teller method of nitrogen adsorption/desorption to get a surface area of 8.8 m2/g and an average pore size of 35 nm. These particles were used as templates for polyelectrolyte layer-by-layer assembly of two oppositely charged polyelectrolytes, poly(styrene sulfonate) and poly(allylamine hydrochloride). Calcium carbonate core dissolution resulted in formation ofpolyelectrolyte microcapsules with an internal matrix consisting of a polyelectrolyte complex. Microcapsules with an internal matrix were analyzed by confocal Raman spectroscopy, scanning electron microscopy, force microscopy, and confocal laser-scanning fluorescence microscopy. The structure was found to be dependent on a number of polyelectrolyte adsorption treatments. Capsules have a very high loading capacity for macromolecules, which can be incorporated into the capsules by capturing them from the surrounding medium into the capsules. In this paper, we investigated the loading by dextran and bovine serum albumin as macromolecules. The amount of entrapped macromolecules was determined by two independent methods and found to be up to 15 pg per microcapsule.     

Microgel-based engineered nanostructures and their applicability with template-directed layer-by-layer polyelectrolyte assembly in protein encapsulation

A novel strategy for the fabrication of microcapsules is elaborated by employing biomacromolecules and a dissolvable template. Calcium carbonate (CaCO(3)) microparticles were used as sacrificial templates for the two-step deposition of polyelectrolyte coatings by surface controlled precipitation (SCP) followed by the layer-by-layer (LbL) adsorption technique to form capsule shells. When sodium alginate was used for inner shell assembly, template decomposition with an acid resulted in simultaneous formation of microgel-like structures due to calcium ion-induced gelation. An extraction of the calcium after further LbL treatment resulted in microcapsules filled with the biopolymer. The hollow as well as the polymer-filled polyelectrolyte capsules were characterized using confocal laser scanning microscopy (CLSM), scanning electron microscopy (SEM), and scanning force microscopy (SFM). The results demonstrated multiple functionalities of the CaCO(3) core - as supporting template, porous core for increased polymer accommodation/immobilization, and as a source of shell-hardening material. The LbL treatment of the core-inner shell assembly resulted in further surface stabilization of the capsule wall and supplementation of a nanostructured diffusion barrier for encapsulated material. The polymer forming the inner shell governs the chemistry of the capsule interior and could be engineered to obtain a matrix for protein/drug encapsulation or immobilization. The outer shell could be used to precisely tune the properties of the capsule wall and exterior. [Diagram: see text] Confocal laser scanning microscopy (CLSM) image of microcapsules (insert is after treating with rhodamine 6G to stain the capsule wall).     

Evidence for 5-center 4-electron bonding in (C...H...C...H...C) array

This paper brings new independent evidence for 5-center 4-electron bonding, whose existence in (C...H...C...H...C) fragment of the molecule I was anticipated in the recent study by Tantillo and Hoffmann. The evidence is based on the applications of the so-called multicenter bond indices, recently proposed as new efficient tool for the detection and localization of multicenter bonding in molecules.     

Redundancy in string cone inequalities and multiplicities in potential functions on cluster varieties

Journal of Algebraic Combinatorics - We study defining inequalities of string cones via a potential function on a reduced double Bruhat cell. We give a necessary criterion for the potential...     

Upper bounds of best one-sided approximations of the classes WrLΨ in the metric of L

The lowest upper bound is obtained for best one-sided approximations of classes (r=1,2 ...) by trigonometric polynomials and splines of minimum deficiency with equidistant knots, in the metric of space L, where W^rL={f:f(x+2)=f(x), f^(r–1)(x) is absolutely continuous, f ^(r)L 1} and L is an Orlicz space.Translated from Matematicheskie Zametki, Vol. 22, No. 2, pp. 257–267, August, 1977.     

NMR studies of solid state—solvent and H/D isotope effects on hydrogen bond geometries of 1:1 complexes of collidine with carboxylic acids

¹H and ¹⁵N NMR spectra of 10 complexes exhibiting strong OHN hydrogen bonds formed by ¹⁵N-labeled collidine and different proton donors, partially deuterated in mobile proton sites, have been observed by low-temperature NMR spectroscopy using a low-freezing CDF₃/CDF₂Cl mixture as polar aprotic solvent. The following proton donors have been used: HCl, formic acid, acetic acid, various substituted benzoic acids and HBF₄. The slow hydrogen bond exchange regime could be reached below 140 K, which allowed us to resolve ¹⁵N signal splittings due to H/D isotopic substitution. The valence bond order model is used to link the observed NMR parameters to hydrogen bond geometries. The results are compared to those obtained previously [Magn. Reson. Chem. 39 (2001) S18] for the same complexes in the organic solids. The increase of the dielectric constant from the organic solids to the solution (30 at 130 K) leads to a change of the hydrogen bond geometries along the geometric correlation line towards the zwitterionic structures, where the proton is partially transferred from oxygen to nitrogen. Whereas the changes of spectroscopic and, hence, geometric parameters are small for the systems which are already zwitterionic in the solid state, large changes are observed for molecular complexes which exhibit almost a full proton transfer from oxygen to nitrogen in the polar liquid solvent.     

Texture–Strength Properties of the Alumina–Montmorillonite Composite

The texture characteristics and strength properties of the molded alumina–montmorillonite composite are studied. The mixture is obtained by mixing suspensions of activated clay and pseudoboehmite followed by drying (at 293 and 393 K) and calcination (at 873 K). It is a promising support for cracking and hydrotreating catalysts. The changes in the specific surface area; the volumes of micro-, meso-, macropore, and medium-size pores; and the strength of samples are studied by varying the montmorillonite concentration in the composite. The addition of 20–35 wt % clay largely results in a sharp in reduction of the macropore region and, correspondingly, provides the alumina oxide average strength of the extrudates of 10–12 MN/m², which is sufficient for industrial supports. This excludes the stage of standard acidic peptization from the technological scheme of alumina production. The complex study of the porous structure of the composite by adsorption and mercury porosimetry combined with elements of percolation theory makes it possible to predict the texture–strength properties of derivative materials.