Classification of heavy-metal fluorides. fluorides with fluorite-like cation arrangement

The main feature of fluorite structure type is four families of crystallographic planes with dense trigon cation nets which are mutually oriented as the faces of a regular octahedron. A complicated cation composition may cause lowering of general symmetry to tetragonal (only one four-fold axis remains in the octahedral complex), rhombohedral (one three-fold axis), orthorhombic, and monoclinic. The geometric parameters of the cation sublattice remain constant. They are close to the parameters of the ideal face-centered cubic cation sublattice of fluorite (the measure of similarity is 1.00–0.81). This is true for all analyzed fluoride structures and some U⁴⁺, Th⁴⁺, Zr, and Ln oxyfluorides. Thus, the concept is confirmed that the crystalline state is determined by systems of parallel planes filled by dense heavy-atom nets. Institute of Inorganic Chemistry, Siberian Branch, Russian Academy of Sciences. Institute of Crystallography, Russian Academy of Sciences. Translated fromZhurnal Struktumoi Khimii, Vol. 35, No. 1, pp. 71–80, January–February, 1994. Translated by T. Yudanova     

Calculation of the gas hydrate HS-1 framework structure and its energy estimation

Using the Zimmennan-Pimentel potential, we have calculated the basic atomic coordinates of the unit cell of the gas hydrate HS-lframework. A minimum change in the strain energy of hydrogen bonh U_H fakes place in formation of this framework from ice Ih. The dependence of U_H on the lattice parameters is derived.Institute of Inorganic Chemistry, Siberian Branch, Russian Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 34, No. 5, pp. 175–178, September–October, 1993.Translated by T. Yudanova     

Two New and a Known Compound from Lawsonia inermis

A new obtusafuran derivative, lawsonicin ( 1 ), and a new naphthaquinone, lawsonadeem ( 2 ), along with a known constituent, vomifoliol ( 3 ), were isolated from the aerial parts of Lawsonia alba and characterized by chemical transformation and spectroscopic experiments, including 2D‐NMR techniques.     

Synthesis and polymerization of N-vinylindole

The reaction of indole with acetylene under pressure is investigated. It is shown that under the action of KOH in aqueous dioxane at 220° C, N-vinylindole C₁₀H₉N is formed in 66% yield, and that this compound undergoes free radical and cationic polymerization.