Molecular Interactions In Liquids Research Articles

A Review of Ultrasonic Wave Propagation through Liquid Solutions

Abstract:: Understanding the molecular interactions in liquids or liquid mixtures of binary or ternary liquids is crucial for various applications. Numerous methods and tools exist to elucidate how atoms interact in such mixtures. This review examines multiple research papers investigating molecular interactions, focusing on the acoustic/ultrasonic technique. This technique employs ultrasonic waves to probe molecular interactions. Researchers utilized an ultrasonic interferometer to measure ultrasonic wave velocity, liquid den-sity can be determined by using a specific gravity bottle, and employed the Ostwald viscometer for viscosity measurements. Researchers derived several acoustic and thermodynamic parameters by evaluating ultrasonic wave velocity, liquid density, and viscosity. This comprehensive study dramatically contributes to understanding the molecular interactions within specific samples, with detailed explanations provided for the observed parameters. Ultra-sonic wave propagation influences the medium's physical characteristics; it includes knowledge of the physics of liquid and solution. How frequency and temperature affect thermo acoustical characteristics has been investigated. The nature of forces between molecules, including hydrogen bonds, charge transfer complexes, hydrogen bond breaking, and complexes, has been deduced from the investigations above.

Multicomponent Liquid−Liquid Equilibria Prediction for Aromatic Extraction Systems Using COSMO-RS

A novel method based on unimolecular quantum mechanical calculations has been used to predict the multicomponent liquid−liquid equilibria (LLE). The recently developed COnductor-like Screening MOdel (COSMO), along with the most common quantum chemical package of Gaussian03 has been used in this work. COSMO-RS combines the COSMO model calculations with exact statistical thermodynamics of pairwise interacting surface segments and has been used for the evaluation of molecular interactions in liquids. COSMO-RS has been used to predict the LLE for 158 multicomponent data sets, which consist of 80 ternary, 9 quaternary, and 4 quinary systems, several of which are examined at different temperatures. The effective contact surface area (aeff), the hydrogen-bonding coefficient (chb), and the cutoff surface charge density for hydrogen bonding (σhb) have been estimated simultaneously, using 10 ternary data sets that consist of 11 different functional groups (CH3, CH2, CH, CHCH2, C−CH3, OH, CH2O, C−(CH2), COO, C−Cl, CH2−CN) and 9 different solvents (sulfolane, dimethyl sulfoxide, N-methyl pyrrolidone, furfural, propylene carbonate, triethylene glycol, tetraethylene glycol, ethylene carbonate, dicyanobutane). Cavity radii (ri) values up to 1.17 times greater than the Bondi radius have been used. The prediction has been initially benchmarked on the octane−toluene−sulfolane system at three temperatures: 25, 35, 45 °C, for which the root-mean-square deviations (RMSDs) are <1% for mole fraction predictions. Thereafter, the LLE has been predicted for 158 multicomponent data sets. An important aspect of our work is that, for the first time, quaternary and quinary systems have been predicted using COSMO-RS. The overall RMSD is <5% for multicomponent systems, compared to ∼1% for NRTL and UNIQUAC models and 5% for UNIFAC models.

Prediction of Binary VLE for Imidazolium Based Ionic Liquid Systems Using COSMO-RS

A novel method based on unimolecular quantum mechanical calculation has been used to predict the binary vapor−liquid equilibria (VLE) of ionic liquids (ILs).The recently developed conductor-like screening model (COSMO), along with the most common quantum chemical package of GAUSSIAN 03, has been used in this work. These conductor-like screening model calculations combined with exact statistical thermodynamics provide the information necessary for the evaluation of molecular interactions in liquids. An effective parametrization has been done using 10 associated and 22 binary nonassociated systems; these 32 systems are all non-ILs. The effective contact surface area aeff and the hydrogen-bonding coefficient chb have been estimated using a sequential scheme. The root-mean-square error obtained for excess Gibb's free energy is ∼0.1 for aeff and chb. Values for α‘ (misfit constant), σhb (cutoff surface charge density for hydrogen bonding), and cavity radii (ri) as given in the literature have been used as defa...

Fast solvent screening via quantum chemistry: COSMO‐RS approach

AbstractCOSMO‐RS, a general and fast methodology for the a priori prediction of thermophysical data of liquids is presented. It is based on cheap unimolecular quantum chemical calculations, which, combined with exact statistical thermodynamics, provide the information necessary for the evaluation of molecular interactions in liquids. COSMO‐RS is an alternative to structure interpolating group contribution methods. The method is independent of experimental data and generally applicable. A methodological comparison with group contribution methods is given. The applicability of the COSMO‐RS method to the goal of solvent screening is demonstrated at various examples of vapor–liquid‐, liquid–liquid‐, solid–liquid‐equilibria and vapor‐pressure predictions.

COSMO-RS: a novel and efficient method for the a priori prediction of thermophysical data of liquids

A novel and very efficient method for the a priori prediction of thermophysical data of liquids is presented. It is based on unimolecular quantum chemical calculations that provide the necessary information for the evaluation of molecular interactions in liquids. Combined with a very fast and accurate statistical thermodynamics, the new method is an alternative to structure-interpolating group contribution methods (GCMs). The most important advantages are the essentially general applicability, the sound physical basis, and the graphicness of the procedure, which easily allows for chemical interpretation and understanding of thermophysical behaviour. A methodological comparison with GCMs is given. Example applications are presented.

Magnetooptical and light scattering effects in liquid binary solutions

The paper presents results of the magnetooptical Faraday and Cotton-Mouton effects measured for binary solutions of o-bromoanisole in benzene and p-xylene. These magnetooptical effects can provide information on molecular interactions in liquids. For very diluted solutions of o-bromoanisole (polar molecule) in benzene or p-xylene (nonpolar molecules) the aggregation processes of o-bromoanisole with nonpolar molecules are unambiguously evidenced by the Faraday and Cotton-Mouton effects. The choice of the magnetooptical method for studying molecular interactions in liquids follows from correlations in the theoretical description of the Cotton-Mouton, Faraday and light scattering effects. The results of the magnetooptical measurements have been used for determination of the degree of light depolarization in light scattering processes. The presented method for measurement of light depolarization degree does not require a direct observation of Rayleigh light scattering. Measurements have been performed in a pulse magnetic field of high intensity ( B = 20 T) and laser beam: λ = 488 nm.

Linear and nonlinear dielectric studies of intermolecular interactions in nitroalkane-benzene liquid solutions. 1. Experimental results

The paper is devoted to studies of molecular interactions and structure of the benzene solutions of nitroalkanes. Both linear and nonlinear electric polarization methods, were applied. These methods, when applied in conjunction, provide, in authors' opinion, one of the best source of information on weak, nonspecific molecular interactions in liquids. The results of measurements for the four lowest regular nitroalkanes and for 2-nitropropane and 2-methyl-2-nitropropane in benzene are presented. The measurements were performed for concentrations up to 0.6 molar fraction (mf) at three temperatures within the range 288–323 K. The results are presented as the temperature and concentration dependences of molar quantities (<μ 2 > and <μ 4 >. These results suggest the formation of weak molecular complexes with partially compensated dipole moments. The detailed quantitative analysis of the experimental data and their comparison with the results obtained with the quantum-mechanical calculations will be presented in the second part of this paper.

Walter Gordy: some memories and impressions

With the death of Walter Gordy it was clear to many physicists and chemists, and especially to those who knew him as a person, that the world of radiospectroscopy and molecular physics had lost one of its more versatile and colourful characters. For something like thirty years he was the dominant figure in the quest for scientifically usable radio waves at the shortest possible wavelengths, an objective which he pursued with dramatic success and with relentless energy. For a more complete picture of the man, however, we must also look into the ways in which this energy was also directed into various other areas of physics and chemistry. A scientist’s first research, and how he or she describes it, can often give keys to the person’s general approach to scientific problems, and indeed can often show a pattern of interests to be sustained over a long period. This applies in some degree to Gordy, but an examination of his early work leaves us aware, not for the only time, that generalizations such as that above do not apply well to him. Beginning in 1934 and continuing through the remainder of that decade, Gordy’s early publications were of infra-red spectroscopic studies of liquids and solutions. The early work was associated with the names of E.K. Plyler and Dudley Williams, at the Physics Department of the University of North Carolina, and continued in the later part of this period when Gordy was at the Mary Hardin-Baylor College in Belton, Texas. Perhaps it was during this time that he, a Southerner by birth and to some extent by temperament, became what he once described to me as “a Texas fan”. The frontier spirit of that state no doubt suited his approach to science and to life. In some thirty papers up to 1941, Gordy’s work shows a strong awareness of chemical bonding and structure. Mostly this was in relation to molecular interactions in liquids, particularly hydrogen bonding, spectroscopic studies of which were becoming recognized [ 11 as a very direct means to new clear-cut

Dielectric response of molecular interactions in liquids

A survey was carried out concerning chosen problems of dielectric behaviour of the solute—solute-solvent interaction. Special attention was paid to the dipole moments of molecular complexes and to the solvent effect upon them. Problems of the proton density distribution in hydrogen bonded systems and the so—called superpolarizability of hydrogen bridges was discussed in the light of contemporary views. The phenomenon of the non—linear dielectric effect and anomalous positive effect in hydrogen bonded systems seemed to be of particular interest. Attention was paid to the existing conceptions dealing with this problem, namely the equilibrium model, the significant structures model, and the proton—jumping conception. Finally, an attempt was made to present a general outlook on the problem of the dynamics in solution from the point of view of dielectric relaxation in the case of forming simple molecular complexes.

P.M.R. relaxation time studies in some binary liquid systems

Proton magnetic resonance relaxation time measurements have been carried out in mixtures of water with formic acid, acetic acid, propionic acid and n-butyric acid. On account of molecular association, the results reveal strong deviation of these mixtures from the ideal behaviour. The molecular association effect is discussed in some detail. The molecular association ratios determined from the present studies are in excellent agreement with those obtained by the ultrasonic absorption technique. It is further shown that N.M.R. relaxation time studies reveal more information about molecular interactions in liquids than the ultrasonic absorption studies.

Evidence of molecular interactions in liquids from anisotropic rayleigh light scattering

Revision of methods currently in use for measuring depolarization factors and Rayleigh ratios for scattering of light by liquids includes use of a helium-neon cw laser as the source of incident light, a fused silica cell with dielectric reflecting coating for double-pass illumination of the sample, and clarification of samples by filtration through silver membrane or microporous porcelain discs of approximately 0.2 micron pore size. Values of the molar Rayleigh ratio for λ = 6328 Å, R TOTAL m (cm 2 mole −1 × 10 4) referred to the absolute value determined by D. J. Coumou for benzene at λ = 5460 Å, and values of D u, the depolarization factor for unpolarized incident light, were determined for nine liquids at 25° ± 2°C, as follows: acetone: 1.66, 0.163; acetonitrile: 1.40, 0.313; benzene: 7.66, 0.423; carbon disulfide: 27.49, 0.651; carbon tetrachloride: 2.91, 0.042; chloroform: 3.11, 0.215; cyclohexane: 2.76, 0.047; nitrobenzene: 35.22, 0.753; nitromethane: 1.40, 0.394. Separation of the total Rayleigh ratio into isotropic and anisotropic parts is accomplished by use of the Cabannes factor. While the fluctuation theory of Einstein and Smoluchowski gives an exact theoretical expression for liquid isotropic scattering, there is no generally accepted expression yet developed which, utilizing the principal polarizability axes as measured for the free molecule, can give an equally satisfactory account of the isotropic and anisotropic light scattering. An expression for the effective electric field at the scattering molecule, as afforded by the Onsager-Scholte model, yields corrections to give the expected values for the square of the mean polarizability α ̄ OS 2 and the anisotropy of the polarizability β OS 2. These are compared with experimental values from measurements on pure liquids and solutions in carbon tetrachloride.

Use of ultrasonic measurements in the study of molecular interactions in liquids

1. The molecular velocity of sound does not remain constant in response to changes produced by pressure. 2. Rao's rule cannot be used to deduce the degree n to which the volume is raised in the repulsion law; instead, the velocity of sound as a function of pressure should be used. Then n is found as being close to 3 for many organic liquids. 3. Allowance should be made for the finite velocity of sound within the molecules. The velocity in the free gaps is dependent on the interaction between the particles and has a negative temperature coefficient. 4. The velocity of sound in a liquid is dependent on the degree of order of the molecules.