NOPR Collection:

Single-ion transfer energetics in some aqueous alkanols and the structuredness of aquo-organic solvents

Tue, 01 Jul 1997 00:00:00 GMT

Title: Single-ion transfer energetics in some aqueous alkanols and the structuredness of aquo-organic solvents Authors: Sinha, Rangana; Kundu, K K Abstract: Single-ion transfer energetics of some ions based on the widely used tetraphenylarsonium tetraphenylborate (TATB) reference electrolyte assumption have been determined in aqueous mixtures of 10, 20, 30, 50 & 70 wt% alkanols like ethanol (EtOH) and 2-propanol (2-PrOH) from solubility measurements of KPi, Ph₄AsPi, KPh₄B and Ph₄AsI [Pi-picrate, Ph = phenyl] at five equidistant temperatures in the range 15-35°C. Transfer free energies, ΔG (i), of the ions in aqueous EtOH and 2-PrOH as well as those in aqueous mixtures of methanol (MeOH) and z-butanol (t-BuOH), as obtained from the literature, after elimination of cavity effect and Born-type and ion-dipole-type electrostatic interacton effects, helped reveal acid-base typej interaction effect of solvents that dictate transfer chemical free energies of the ions, ΔG_{, ch} (i). On the other hand, transfer entropies, TΔS_,ch (i), obtained after due correction of cavity and Born-type electrostatic effects from TΔS (i) values, when analysed in the light of Kundu et al's four-step transfer process as well as the fact that increasing hydrophobicity of the I cosolvents helps increase the 3D-structuredness of these aquo-alkanolic solvents, led us to conclude that entropies of single ions rather than the complete electrolytes, serve as a better structural probe for aquo-organic solvents. This has also been substantiated from the corresponding behaviour of some small cations and anions in aqueous dimethyl sulphoxide (DMSO) and acetonitrile (ACN) solvents. Page(s): 541-559

Interaction studies of guanosine-DMSO-water system

Tue, 01 Jul 1997 00:00:00 GMT

Title: Interaction studies of guanosine-DMSO-water system Authors: Misra, K; Puri, A K; Shukla, A K; Haroon, S; Pandey, J D Abstract: Ultrasonic velocity, density and viscosity have been measured in ternary solution of guanosine-water- DMSO at 293, 298 and 303 K. Study of the temperature dependence of these systems clearly indicates the solute-solvent interactions. These interactions have also been studied in the light of thermodynamic properties, viz., the partial molal volume Φ⁰_v, the partial molal compressibility Φ⁰_v, viscosity Bvcoefficient of Jones-Dole equation and the solute activation parameters. All the thermodynamic parameters of guanosine-water-DMSO system have been deduced from the experimental values of ultrasonic velocity, density and viscosity. Transition state treatment advanced by Feakins has been applied to discuss the viscous flow mechanism in the biomolecule solutions under investigation. Page(s): 560-564

Solvation of N-chloranil and N-xylylene tagged cationic polyelectrolytes: Viscosity measurements in dimethylformamide and dimethyl sulphoxide

Tue, 01 Jul 1997 00:00:00 GMT

Title: Solvation of N-chloranil and N-xylylene tagged cationic polyelectrolytes: Viscosity measurements in dimethylformamide and dimethyl sulphoxide Authors: Singh, Meenakshi; Prasad, B B Abstract: Viscosity studies of four new types of cationic polyelectrolytes (mol. wt. 1167 to 6432), where quaternary nitrogens in the molecular chain are tagged with chloranil and xylylene moieties and are interspersed with ethylene, phenothiazine and bipyridyl (viologen) linkages, have been studied in the two dipolar aprotic solvents viz., dimethylformamide and dimethylsulphoxide at 298 ± 5 K. All results have been treated on the basis of Fuoss equation,η_sp/C=A/(1 +BÖC}, where (η_sp /C}_c-o led to an estimation of intrinsic viscosity ([η]).The [η] values signify not only the measure of molecular size of the polymer but also connote frictional resistances toward solution flow by the specific conformation of individual molecule in infinitely dilute solution. The increase in η_sp /C with dilution might not be due to chain expansion in all the cases. Thus, intrinsic viscosities in conjunction with other derived parameters, such as characteristic ratios (C_¥),maximum cross dimension (S), root mean square end-to-end distances (<R²_g> 1/2) and plane projection distances (P) at all temperatures have been invoked to propose the hydrodynamic models of polycations in the medium of intermediate permittivity. Page(s): 565-570

Classification of solvents on the basis of topology of the molecule

Tue, 01 Jul 1997 00:00:00 GMT

Title: Classification of solvents on the basis of topology of the molecule Authors: Kuanar, Minati; Mishra, Bijay K Abstract: Attempt has been made to classify the solvents on the basis of the topology of the molecule. The principal components of nine topological parameters for all the solvents have been determined. From the first principal component (PC₁.) the solvents have been classified into positive and negative principal component class, where most of the nonpolar solvents have negative PC₁ values and most of the polar solvents have positive PC₁ values. Page(s): 571-578