Catalysis of Electrophilic Addition of Alcohols to Alkoxyalkenes by Lithium Salts

Russian Journal of General Chemistry -     

Functional Methacryloyoxy Acetals: II. Electophilic Addition of Alcohols to Vinyloxyalkyl Methacrylates

Alcohols of various structures, in particular, ethylene, acetylene, fluorocontaining alcohols, add regio- and chemoselectively to the vinyloxy group of vinyloxyalkyl methacrylates at 20-40°C in the presence of catalytic quantities of trifluoroacetic acid affording functional acetalmethacrylates in high yield.     

Sulfur-containing polymer and carbon materials based on poly(vinyl chloride)

New sulfur-containing copolymers based on poly(vinyl chloride) have been prepared by the nucleophilic substitution of chlorine atoms by sulfur atoms using sodium tetra- and pentasulfides. It has been shown that these copolymers can be carbonized to produce sulfur-containing carbon materials with residual chlorine content about 2 wt %.     

Isomorphous substitutions of rare earth elements for calcium in synthetic hydroxyapatites

Polycrystalline hydroxyapatites Ca(10-x)REE(x)(PO(4))(6)(OH)(2-x)O(x) were synthesized and studied by X-ray powder diffraction, infrared absorption, diffuse-reflectance spectroscopy, and thermogravimetry. The solubility limits x(max) of rare earth elements (REE) in Ca hydroxyapatites decreases with an increasing REE atomic number from x(max) = 2.00 for La, Pr, and Nd to x(max) = 0.20 for Yb at 1100 °C. Refinements of X-ray diffraction patterns by the Rietveld method show that REE atoms substitute for Ca preferentially at the Ca(2) sites of the apatite structure. The substitution decreases the Ca(2)-O(4) atomic distances in the calcium coordination polyhedra and increases the Ca(2)-O(1,2,3) distances. This observation shows that interatomic distances depend not only on radii of the ions involved in the substitution but also on their charges.