A detailed single-crystal structure analysis is reported for ethylene oxide hydrate. This confirms the polyhedral host lattice formed by 46 hydrogen-bonded water molecules in a cubic unit cell of 12.03 A with space-group symmetry Pm3n. Disordered ethylene oxide molecules occupy the six equivalent tetrakaidecahedral cavities, and their electron-density distribution suggests that they are hindered axial rotors. Additional guest molecules, either ethylene oxide, oxygen, or nitrogen molecules occupy the two dodecahedral cavities with high disorder and low statistical weight. The compound is therefore nonstoichiometric having the limiting formula 2M·6C2H.O·46H20, in which the percentage of M is variable. If M is assumed to be entirely ethylene oxide, as is likely from the method of preparation, the composition of the crystals obtained from an equilibrated aqueous solution of 8 mole % ethylene oxide at 9°C is 6.4C2H.O·46H20.• M. v. Stackelberg and W. Meinhold, Z. Electrochem. 58, 40 (1954); M. v. StackeJberg and H. Friihbuss, ibid., p. 99.

The structure of the tetrahydrofuran/hydrogen sulfide double hydrate has been determined from three-dimensional single-crystal data. The analysis confirmed the clathrate host lattice characteristic of 17-Å cubic (Type II) gas hydrates. The hexakaidecahedral voids enclose tetrahydrofuran molecules which appear to undergo free rotation. Statistically, 46% of the pentagonal dodecahedra are occupied by hydrogen sulfide molecules.

Lattice parameters for urea have been measured at seven temperatures in the range 12 to 173 K and the crystal structure has been determined at 12, 60 and 123 K from neutron diffraction data. With 342 reflections (sin 0/A <0.77 A -I) measured for an octant of reciprocal space, full-matrix least-squares refinement gave Rw(F2) = 0.030, 0.029 and 0.029 at 12, 60 and 123 K. The atomic anisotropic thermal parameters are consistent with overall rigid-body motion together with intramolecular librations of the NH2 groups.

Articles you may be interested inAtomic layer deposition of zirconium silicate films using zirconium tetrachloride and tetra-n-butyl orthosilicate J.The compounds [(n-C4H 9)4N+]"xn-·nyH.O have been prepared where X is F-, Cl-, Be, CHaCO:!-, cr04lr-, WO.lr-, C.O.2-, HCOs-, HPO.lr-, and y is approximately 32. They form an isomorphous crystal series which is tetragonal with a=23.65±0.15 A, c= 12.40±0.15 A.A similar series of the type [(i-C,HU)4N+]nXn-'ny'H 2 0 has been prepared where X is F-, Cl-, Cr042-, WO.2-, and y' is approximately 40. They also form an isomorphous group which is orthorhombic with a= 12.1O±0.1O A, b=21.50±0.15 A, c= 12.65±0.15 A.These compounds are believed to be of the clathrate type, similar in general character to the gas hydrates.

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