Liquid Chloroform Research Articles

ChemInform Abstract: TEMPLATE SYNTHESIS AND IONOPHOROUS PROPERTIES OF SUBSTITUTED CROWN ETHERS TOWARDS ALKALI METAL IONS

AbstractEine Reihe substituierter Crownether (III) wurde nach einem neuen Verfahren unter Anwendung des Metall‐Ionen‐Templateffekts in relativ guten Ausb. (nur teilweise angegeben) dargestellt.

Structure of Liquid Chloroform. A Comparison between Computer Simulation and Neutron Scattering Results

AbstractThe intermolecular structure functions for liquid chloroform of various isotopic composition have been calculated from an MD simulation. Good agreement was found with the x‐ray measurement and four of the five experimental neutron structure functions. Strong disagreement, however, exists between the atom atom correlation functions derived from the neutron scattering experiments with the isotopic substitution method and the MD results. It seems possible that the atom atom correlation functions from the neutron scattering experiments, which are not without difficulties, might have suffered from experimental uncertainties.

Intermolecular nuclear relaxation and RISM pair-correlation function in liquids

The intermolecular proton-proton pair-correlation function (pcf) obtained from the reference interaction site model (RISM) is used as the equilibrium distribution and an effective force in spin relaxation theory. Agreement with experiments on proton dipolar relaxation in liquid acetonitrile, chloroform and ethane is obtained in this analysis. For molecules with non-uniformly distributed spin sites the pair-correlation effect may not be neglected in the treatment of relaxation theory. Aspects concerning uniform pair-distribution and orientational correlations in spin relaxations are briefly discussed.

The complete set of atom pair correlation functions of liquid chloroform as obtained from a final neutron scattering experiment with H/D isotopic substitution

A neutron scattering experiment has been performed on a CHCl3/CDCl3 sample with zero coherent scattering length for hydrogen. The study performed at 20°C with two different wavelengths (0·7 and 0·5 Å) allowed a detailed investigation of the data analysis procedure. In particular the inelasticity correction to self scattering has been computed on the basis of monoatomic gas model. One has also found that in the case of strong inelasticity the multiple scattering became angular dependent. The fully corrected coherent differential cross section was separated into an intra- and an intermolecular part from which the molecular parameters were determined. Combining the intermolecular contribution of CHCl3/CDCl3 with the results of experiments on CDCl3, CD 35Cl3, CD 37Cl3 and CHCl3 and using the known C-C atom pair correlation function, the complete set of atom pair correlation functions were computed and the most probable orientation between two chloroform molecules in the liquid phase was investigated. The most satisfactory figuration discovered up to now is one in which the molecule dipole axes are inclined with respect to each other and the hydrogen atom is tilted toward the hollow between two chlorine atoms of the next molecule.

Temperature dependence of ultrasound and relaxation in liquid chloroform

Spontaneous Brillouin scattering was used to determine the vibrational relaxation of liquid chloroform as a function of temperature. Comparison of experimental results with theoretical predictions leads to the conclusion that there is a simultaneous relaxation of all vibrational modes of the molecule.

Application of different spectroscopic methods to study the reorientation of molecules in liquid chloroform

The macroscopic dielectric relaxation time τ D and the Raman correlation time τ 2 for liquid chloroform were measured in the temperature range of 223 – 323 K. The values of these times together with the literature NMR results for τ 2 were used to discuss the applicability of the dielectric relaxation method to get the information about the microscopic single-particle correlations time τ 4.

Template synthesis and ionophorous properties of substituted crown ethers towards alkali-metal ions

A number of alkyl-substituted crown ethers of the type 2-R-12-crown-4, 2-R-15-crown-5, and 2-R-18-crown-6 (R = Me, Et, octyl, decyl, tetradecyl, icosyl, or Ph) have been prepared in relatively good yields by a novel synthetic route employing the metal-ion template effect. The ionophorous properties of these crown ethers with respect to the transport of lithium, sodium, and potassium picrates across a bulk liquid chloroform membrane were measured and have been compared to those of crown ethers already used as ionophores. Substitution of alkyl and phenyl groups on the crown ethers, making them more lipophilic, does not seem to assist the transport of Na+ and K+ as their picrate salts, but rather appears to make the ionophore more susceptible to remain in the chloroform phase, as the chain length increases, and thereby leads to a reduction in transport. Introduction of alkyl and other groups, however, does seem to assist the transport of Li+ as lithium picrate, although the overall rate of transport is considerably slower for Li+ than the rate for Na+.

Comparison of neutron scattering and molecular dynamics studies on liquid chloroform.

Comparison of neutron scattering and molecular dynamics studies on liquid chloroform.

A review and computer simulation of the structure and dynamics of liquid chloroform

Abstract Over a hundred recent papers on the structure and dynamics of liquid chloroform have been analysed using computer simulation to produce reference numerical data from a model of the pair potential. A considerable amount of the available experimental data is contradictory or restricted in scope. Particularly, there is confusion about the role of collision-induced scattering, the nature of the internal field correction, rotation-vibration coupling, vibrational cross-correlation, and the anisotropy of CHCl 3 molecular diffusion. The computer simulation suggests, for example, that the anisotropy of the rotational diffusion is opposite in sense to indications from NMR relaxation, based on the simple model of Langevin/Euler. Atom-atom p.d.f.′s from the simulation are compared with those of Bertagnolli [1] from neutron and X-ray diffraction. This is the first comparison of its kind and produces satisfactory, but not detailed, agreement. Data concerning orientational correlation times are summarised in tabular form from infra-red, far infra-red and dielectric absorption, Raman and Rayleigh scattering, NMR relaxation, Brillioun scattering and electric field induced anisotropy. These data are compared with results from the computer simulation. The data survey and simulation both point to the need for a coordinated effort at obtaining more accurate and wider ranging data, and to develop and improve the currently available theoretical and data-reduction methods .

Relaxation in liquid chloroform

Spontaneous Brillouin scattering has been used to determine the character of the vibrational relaxation present in liquid chloroform at 20 °C. The results indicated that the observed relaxation is explainable on the basis of a single relaxation theory. (AIP)

A two-component interpretation of the far infrared dielectric loss in liquid methyl chloroform

A possible interpretation of the so-called Poley absorption in polar liquids is that it is due to overlapping contributions from liquid- lattice bands together with a contribution from an inertially “rolled-off” Debye absorption. We propose a test involving the inertially similar but electrically very different molecules methyl chloroform and carbon tetrachloride. This test gives results which offer plausible support for the two-component interpretation.

High-overtone Spectra and Dipole Moment Functions for the C–H Stretching Vibration of Chloroform

Abstract The absorption spectra of liquid chloroform were observed for the C–H stretching fundamental vibration and its overtones up to v=←50. The spectral parameters were analyzed on the basis of the one-dimensional local mode representation, which led to the determination of the mechanical and electrical anharmonicities. The solvent effects on the absorption intensities are discussed from the viewpoint of the solvent effect on the dipole moment function. The finally obtained dipole moment function was compared with that obtained by the ab initio calculation.

A Structural Investigation of Liquid Chloroform

AbstractStarting from neutron scattering experiments on the species CDCl3, CD35Cl3, CD37Cl3 and CHCl3 the expansion coefficients of the generalized pair correlation function g00000(R), g00101(R), g00202(R), and g00110(R) are determined and analyzed quantitatively, thus providing preferred positions and orientations of the molecules in liquid chloroform. From the same set of experimental data the chlorine‐chlorine pair correlation function and the weighted sum of the chlorine‐hydrogen and chlorine‐carbon pair correlation functions are evaluated. The most probable configuration between two chloroform molecules in the liquid phase is derived from the position of the first peak of the corresponding pair correlation function. Both ways of description yield a consistent structural picture; namely the dipole axes are inclined and the hydrogen atoms point into the hollow between two chlorine atoms.

ChemInform Abstract: VIBRATIONAL‐TRANSLATIONAL RELAXATION IN LIQUID CHLOROFORM

Ultrasonic measurements were made in liquid chloroform over the frequency range from 3 MHz to 5 GHz by means of three experimental techniques, pulse‐echo overlap, high‐resolution Bragg reflection, and Brillouin scattering. The observed velocity dispersion revealed two relaxation processes, one at 650 MHz and the other at 5.1 GHz at 20 °C. They are interpreted in terms of vibrational–translational relaxation. Quantitative analysis of specific heat shows the lowest (261 cm−1) and the second lowest (366 cm−1) fundamental vibrational modes should have a common relaxation time at 50 ps and the group of all above the third mode (667 cm−1) at 290 ps. The present results are combined with recent data obtained by Laubereau et al. with the picosecond spectroscopy technique; a diagram illustrating V–T and V–V energy transfer is presented. A brief comment is given also on V–T and V–V processes in dichloromethane.

ChemInform Abstract: ISOTOPIC DILUTION STUDIES OF THE CHLOROFORM‐CHLOROFORM‐D SYSTEM BY RAMAN DIFFERENCE SPECTROSCOPY

Raman difference spectroscopy has been used to measure small frequency shifts in the ν1 and ν2 bands of CHCl3 and CDCl3 in various mixtures of liquid chloroform and deuterochloroform. The frequency shifts relative to the pure liquids vary linearly with concentration, and at infinitive dilution are determined to be for CHCl3: Δν1=+0.56 and Δν2=+1.92 cm−1; and for CDCl3: Δν1=+0.33 and Δν2=+1.82 cm−1. The fact that all frequency shifts are positive indicates that an exchange effect between like molecules is responsible for the phenomenon. The ν4 bands show no frequency shifts but narrow substantially in bandwidth upon isotopic dilution. The position of the composite (CHCl3+CDCl3) ν6 band relative to the pure liquids was also measured as a function of concentration. The data confirm that the frequency difference between this band in liquid CHCl3 and in CDCl3 is 1.05 cm−1. The ν6 frequency appear not to be significantly shifted by isotopic dilution.

Excess heat capacities and excess volumes of binary liquid mixtures of chloroform with cyclic ethers at 298.15 K

Molar excess heat capacities at constant pressure, C E p, of binary liquid mixtures chloroform + oxolane, chloroform + 1,3-dioxolane, chloroform + oxane, and chloroform + 1,4-dioxane have been determined at 298.15 K from measurements of volumetric heat capacities in a Picker flow microcalorimeter. A precision of ±0.04 J K −1 mole − was achieved by using the stepwise procedure. Experimental molar excess heat capacities are compared with values derived from H E results at different temperatures. Excess molar volumes, V E, for the same systems at 298.15 K have been determined by measuring the density of the pure liquids and solutions with a high-precision digital flow densimeter.

Vibrational–translational relaxation in liquid chloroform

Ultrasonic measurements were made in liquid chloroform over the frequency range from 3 MHz to 5 GHz by means of three experimental techniques, pulse-echo overlap, high-resolution Bragg reflection, and Brillouin scattering. The observed velocity dispersion revealed two relaxation processes, one at 650 MHz and the other at 5.1 GHz at 20 °C. They are interpreted in terms of vibrational–translational relaxation. Quantitative analysis of specific heat shows the lowest (261 cm−1) and the second lowest (366 cm−1) fundamental vibrational modes should have a common relaxation time at 50 ps and the group of all above the third mode (667 cm−1) at 290 ps. The present results are combined with recent data obtained by Laubereau et al. with the picosecond spectroscopy technique; a diagram illustrating V–T and V–V energy transfer is presented. A brief comment is given also on V–T and V–V processes in dichloromethane.

Isotopic dilution studies of the chloroform–chloroform-d system by Raman difference spectroscopy

Raman difference spectroscopy has been used to measure small frequency shifts in the ν1 and ν2 bands of CHCl3 and CDCl3 in various mixtures of liquid chloroform and deuterochloroform. The frequency shifts relative to the pure liquids vary linearly with concentration, and at infinitive dilution are determined to be for CHCl3: Δν1=+0.56 and Δν2=+1.92 cm−1; and for CDCl3: Δν1=+0.33 and Δν2=+1.82 cm−1. The fact that all frequency shifts are positive indicates that an exchange effect between like molecules is responsible for the phenomenon. The ν4 bands show no frequency shifts but narrow substantially in bandwidth upon isotopic dilution. The position of the composite (CHCl3+CDCl3) ν6 band relative to the pure liquids was also measured as a function of concentration. The data confirm that the frequency difference between this band in liquid CHCl3 and in CDCl3 is 1.05 cm−1. The ν6 frequency appear not to be significantly shifted by isotopic dilution.

Shapes of the ν1 Band of Liquid Chloroform and Intermolecular Interaction

Abstract The infrared absorption spectrum for the ν1 fundamental of chloroform or chloroform-d shows strong asymmetry, with a remarkable tailing on the high-frequency side. The observed band-width of the ν1 fundamental of chloroform-d is significantly narrower than that of chloroform. These asymmetric band profiles of the ν1 bands of chloroform and chloroform-d can be interpreted in terms of the existence of two different types of chloroform molecules. One is a molecule which interacts with another molecule, and the other is a non-interacting molecule. The isotope effect on the band-width can be explained in terms of the difference in the reduced mass for chloroform and chloroform-d.

Vibrational–translational energy exchange in liquid chloroform as a function of temperature as determined by Brillouin scattering

The temperature dependence of the vibrational relaxation time τvib of pure liquid CHCl3 was determined by Brillouin scattering between −5 and +55 °C. From the experimental results the number of intermolecular collisions Z10 necessary for the deactivation of the lowest vibrational mode has been calculated using the moving wall cell model. In contrast to other liquids no linear relationship between lnZ10 and (1/T)1/3 could be found. Different reasons for this behavior, which possibly is due to the weak dipole moment of CHCl3, are discussed.