Showing papers on "Tetrahedral molecular geometry published in 1968"

Infrared Study of Matrix‐Isolated Chlorinated Tetrahedral Molecules

Abstract: The infrared spectra of CH3Cl, CH3CH2CH2Cl, CH2Cl2, HCCl3, (CH3)–CCl3, FCCl3, BrCCl3, CCl4, and SiCl4 in an argon matrix at 20°K were studied. The chlorine isotopic splitting pattern of the bands in the 500–1300‐cm−1 region were recorded, and most of the isotopic frequencies were assigned. Normal‐coordinate calculations have been performed on these molecules to establish complete chlorine isotopic splitting patterns of all the fundamental vibration bands. Different isotopic species have different Fermi resonance interactions in the same band system; examples of this were observed in the spectra of FCCl3 and CCl4.

Molecular Association in TiCl4: Laser Raman Spectroscopy and Chlorine Isotope Effects

Abstract: Evidence for molecular association of liquid TiCl4 is presented. The chlorine isotope structure in the totally symmetric fundamental cannot have originated from a simple tetrahedral molecule belonging to the Td point group. High‐resolution measurements, which indicate an associated complex of lower symmetry, possibly D2h, C2h, or C2υ, are interpreted in terms of a chlorine‐bridged dimer structure. Additional support for an associative phenomenon rests upon some Raman data obtained for TiCl4 diluted with CCl4. The depolarization ratio (ρs) for the ν1 fundamental is 0.008, substantially greater than for ν1 of CCl4(0.004), but more than an order of magnitude smaller than previously reported (0.12). The ratio drops to 0.007 for a 25 mole % solution of TiCl4 in CCl4, but depolarized fundamentals have constant values of ρs = 0.75 as expected. Earlier results are reviewed and reinterpreted in terms of the new dimer model for liquid TiCl4.

Nuclear Radio-Frequency Spectra of a Series of Tetrahedral Molecules

Abstract: The molecular-beam magnetic-resonance method has been applied to a series of tetrahedral molecules. In each case, the radio-frequency spectrum was observed which corresponds to the reorientation of the total nuclear spin with respect to a large external magnetic field. In order to analyze these spectra, the energy levels of the complete spinrotation interaction and the direct dipole-dipole interaction have been calculated to first order in high-field perturbation theory by applying the recent group-theoretical treatment of Yi, Ozier, and Anderson. On the basis of these energy levels, the theoretical spectrum for each molecule has been constructed on a high-speed digital computer. By fitting this theoretical spectrum to the data, it has been found that: for where ${c}_{a}$ is the average spin-rotation constant and ${c}_{d}$ is the anisotropy in the spin-rotation matrix. Only the relative sign of these two constants was determined. Several earlier approximate methods of treating spherical rotor problems which involve the tensor part of the spin-rotation interaction are examined in the light of the present results.

Intermolecular forces in globular molecules VI: octopole moments of tetrahedral molecules

Abstract: Octopole moments for methane and carbon tetrafluoride derived from second virial coefficients temperature dependence, using spherical shell potential model

Vibrational analysis of free nine-atomic and bound five-atomic tetrahedral molecules

Abstract: A theoretical investigation of the vibrational motion of a free nine-atomic tetrahedral molecule is given using Wilson's. FG-matrix method. By going to the limit of infinite mass of the outermost atoms, the vibrational frequences of a bound five-atomic tetrahedral molecule are obtained. This limiting case is also alternatively treated by the explicit consideration of the hindered translational and rotational motions. Such a model would probably approximate the state of affairs for amorphous substances with a tetrahedral basic unit.