CCl4 Molecules Research Articles

Crystal and molecular structure of CCl4 III: A high pressure polymorph at 10 kbar

The crystal and molecular structure of a high pressure form of carbon tetrachloride (CCl4 III) was determined at approximately 10 kbar using a diamond-anvil beryllium pressure cell and a modified Buerger-type precession camera. CCl4 III crystallizes in the monoclinic system with a unit cell of the following dimensions: a=9.079± 0.012 Å, b=5.764± 0.003 Å, c=9.201± 0.004 Å, and β=104.29±0.05°. The space group is P21/c with four molecules per unit cell. Observed infrared spectra indicate that the CCl4 molecule exhibits regular tetrahedral symmetry at 10 kbar. By using an approximation to the repulsion energy in a least-squares refinement procedure considering only nonbonded Cl–Cl interactions, an approximate structure was obtained. Subsequent structure factor calculations using a grid-point sampling procedure yielded a final structure with a reliability factor of 9.56%. CCl4 III is isostructural with SnBr4, and contains closest nonbonded Cl–Cl distances of 3.49 Å, significantly less than the normal Van der Waals separation of 3.6 Å. Taking four molecules per unit cell, the calculated density is 2.190 g cm−3. A more compact phase than CCl4 III was predicted in the CCl4 system on the basis of packing efficiency and the predicted phase (CCl4 IV) was subsequently verified by visual observation in microscopic studies at pressures in the 35–40 kbar range and temperatures up to 500°C.

Differential Cross Sections for the Scattering of CCl4 by Isooctane

Differential cross sections for the scattering of CCl4 by isooctane (2,2,4-trimethylpentane) are reported for the range of relative kinetic energy Ē between 1.80 and 26.8 kcal mole−1. The faster beams are produced by adding the CCl4 to an excess of He which accelerates the heavier CCl4 molecules as the mixture flows from the source. The velocity selector has disks with narrow slots produced by chemical etching. The scattered CCl4 molecules are detected by their formation of negative ions at a hot Nb surface. The scattering at the higher energies shows rainbow structure which is used to determine parameters for an assumed form of the interaction potential. The disappearance of the rainbow maximum at low energies, attributed to the onset of orbiting, and the values of parameters derived indicate that the potential has a large central core. The decrease in the measured differential cross section at large angles implies the presence of a substantial amount of inelastic scattering.

The geometric configuration of molecules of adsorbing substances and the values of the elementary areas in the adsorption layer

1. The investigation of the adsorption of symmetrical molecules of methane, dimethyl ether and dioxane on the surface of A12O3 showed that the variations of the values of their elementary areas Ω are, considerably less than for unsymmetrical molecules of commensurate size (CH3OH, C5H11OH). This proves the influence of the orientation of the adsorbing molecules on the value of Ω. 2. The Ω values of the CCl4 molecule, which also has spherical symmetry, show greater inconsistancy than would be expected from its structure. Possible explanations of this fact are given.

Relative Intensities of the Raman Lines of Carbon Tetrachloride, Chloroform, and Methylene Chloride

The construction of a photoelectric Raman spectrometer is briefly described, and the procedure used to determine the intensities of Raman lines is given in detail. The relative intensities of the Raman lines of carbon tetrachloride, chloroform, and methylene chloride in the liquid state have been measured on a uniform scale. The values obtained for the individual molecules CCl4 and CHCl3 are in excellent agreement with those obtained previously by D. H. Rank [ J. Opt. Soc. Am.37, 798 ( 1947)] using the photoelectric method. The whole range of intensities on a uniform scale for the three molecules are also in good general agreement with those obtained by Welsh Crawford Thomas Love [ Can. J. Phys.30, 577 ( 1952)] in the gaseous phase using the photographic method. Only one out of thirteen strong lines has a significant intensity deviation of more than 15 percent from the mean values of the two sets of results. It is concluded that intensity measurements in the liquid phase for molecules with weak intermolecular forces may sometimes be adequate substitutes for the gaseous measurements that are strictly required for comparison with theoretical calculations.

The Normal Vibrations of Polyatomic Molecules as Treated by Urey-Bradley Field

A method of setting up the vibrational secular equation for polyatomic molecules of ``Urey-Bradley field'' type is described. By this method the vibration frequencies of CCl4, CBr4, CH4, CD4, CCl3Br, CCl2Br2, CClBr3, CCl3H, CCl2H2, CClH3, CCl3D, CCl2D2, CClD3, CH3D, CH2D2, and CHD3 molecules have been calculated. The 102 fundamental frequencies calculated using 28 distinct force constants are in satisfactory agreement with the observed, with a mean deviation of 1.4 percent.

The Chemical Effects of Ultrasonic Irradiation: Reaction between Carbon Tetrachloride and Water

Intense ultrasonic waves produce interesting physical and chemical effects, such as emulsification, luminescence, and chemical transformations. In an attempt to clarify the mechanism by which ultrasonic irradiation causes chemical reactions in liquid mixtures, a quantitative study was undertaken of the ultrasonic production of iodine in aqueous solutions of potassium iodide which contain some carbon tetrachloride. It was found that the amount of iodine liberated depends greatly on the dimensions and material of the container, but only slightly on the concentrations of potassium iodide and carbon tetrachloride. Frequencies of 400, 700, 1000, and 1500 kc gave varying results, but this is attributed to varying transparency of the test tube rather than to intrinsic frequency-sensitivity of the process. Although earlier investigators believed that dissolved oxygen is essential, the present work shows that nitrogen or helium serves nearly as well. As the power input is increased, no iodine is produced until cavitation occurs; then the yield increases almost linearly if the volume of solution is large enough, but for smaller volumes the yield first increases and then decreases sharply. The fundamental reaction is apparently that between water and dissolved carbon tetrachloride, caused by the large mechanical or electrical forces generated at the collapse of cavitation bubbles; the potassium iodide is primarily an indicator of the oxidizing chlorine set free. Rate studies suggest that the reaction takes place in two steps, each of which liberates two chlorines per CCl4 molecule; the first step is about ten times faster than the second.