Densities, Sound Speed, and Viscosities of Some Amino Acids with Aqueous Tetra-Butyl Ammonium Iodide Solutions at Different Temperatures

Abstract

Apparent molar volumes (V ⌀ ), apparent molar isentropic compression (K ⌀,s ), and viscosity B coefficient of glycine, L-alanine, and L-valine in (0.01 and 0.03) mol·kg −1 aqueous tetrabutyl ammonium iodide (TBAI) solutions have been determined at temperatures (288.15, 293.15, 298.15, 303.15, and 308.15) K from their experimental density, ultrasonic speed, and flow time measurements, respectively. Partial molar volumes (V ⌀ 0 ) and partial molar isentropic compression (K ⌀,s 0 ) have been determined from the above measurements. Further, these data were used to calculate the corresponding transfer parameters (ΔV ⌀,s 0 and ΔK ⌀,s 0 ), hydration number (n H ), side chain group contributions of V ⌀ 0 , and viscosity B coefficients of the amino acids, partial molar expansibilities (E ⌀ 0 ), (dB/dT), and related parameters. The trends of variations of experimental and computed parameters have been discussed in terms of solute−solvent interactions with an emphasis on structure-making and structure-breaking ability of the above amino acids in the solvent mixture.

Volumetric Properties and Viscosity B-Coefficients for the Ternary Systems Epigallocatechin Gallate + MCl + H2O (M = Li, Na, K) at Temperatures 288.15–308.15 K

“…The calculated values of E φ 0 at T = 288.15–308.15 K are given in Table S2 in Supporting Information. E φ 0 was an important indicator of solute–solvent interactions. − These E φ 0 values were also employed in interpreting the structure making or breaking properties of various solutes. Table S2 in Supporting Information shows that the E φ 0 values were positive, which indicates that the partial molar volumes increased with the increase of temperature.…”

“…The E φ 0 values decreased with an increase in temperature. This may be attributed to the fact that molecular motions become fast through enhancement in temperature and the difference in water structure between solvation shell and bulk water become smaller and, consequently, the corresponding effect from the overlap of solvation shells become weaker. − …”

“…Hepler proposed a method that provided qualitative information about the structure making or breaking ability of a solute in eq − where C is only a mathematical parameter that is used in eq .…”

“…If the sign of (∂ E φ 0 /∂ T ) P is positive or its value is close to zero, the solute is a structure maker, otherwise it is a structure breaker. − The values of (∂ 2 V φ 0 /∂ T 2 ) P related to the studied solutions are listed in Table S2 in Supporting Information. It can be found that EGCG essentially acts as a structure maker.…”

Densities and Viscosities of Polyhydroxy Solutes in Aqueous Tetraethylammonium Bromide Solutions at Different Temperatures

“…Salt effects on water have been most commonly described in terms of their chaotropicity or kosmotropicity. Tetra- n -alkylammonium salts (R 4 NBr, R = CH 3 , C 2 H 5 ) are a separate class of electrolytes due to their unusual properties in solutions, apparently caused by their large size hydrophobic alkyl chains. − Tetra- n -alkylammonium halides destabilize lysozyme by interacting with the exposed hydrophobic groups of the denatured state and simultaneously weakening the hydrophobic interactions between the nonpolar groups of the protein. It has been reported that tetra- n -alkylammonium halides dissociate phycocyanin, a protein that exists in solution as several well characterized aggregates. − Hydrophobic interactions between the hydrophobic part of protein and bulky alkyl groups on R 4 N + ions play an essential role in inhibiting aggregation properties of this protein. , In view of increasing biological, pharmaceutical, and food applications, we have undertaken a systematic study of volumetric and rheological properties of some saccharides and their polyols in pure water and in Et 4 NBr (aq) solutions.…”