Thermodynamics of solvation and solvophobic effect in formamide

Using semi-adiabatic calorimetry, we measured the enthalpies of solution for various low-polar compounds including alkanes, aromatic hydrocarbons and their halogenated derivatives in formamide at temperature of 298 K. For the same compounds, the values of limiting activity coefficients in formamide were determined using GC headspace analysis at 298 K, and Gibbs free energies of solution and solvation were calculated. Based on these data and the available literature values of the Gibbs free energy of solvation in formamide for a number of other low-polar solutes, a study of the solvophobic effect in this solvent is performed, and its resemblance to the hydrophobic effect in aqueous solutions is demonstrated. It is shown that the contribution of the solvophobic effect into the solvation Gibbs free energy in formamide is much higher than that in aliphatic alcohols, but lower than that in water. Like in water, the magnitude of this contribution for different solutes linearly increases with the solute molecular volume. Solvophobic effect also significantly affects the enthalpies of dissolution in formamide, causing them to be more negative in the case of alkanes and more positive in the case of arenes.

/pdf/thermodynamics-of-solvation-and-solvophobic-effect-in-1jompu9jvh.pdf

Aggregation, adsorption, counterion binding, thermal and scattering behavior of metallosurfactant cis-[Co(en)2(C12H25NH2)Cl](NO3)2

Surface and bulk properties of anionic surfactant and sodium dodecyl sulfate (SDS), both in the absence and presence of co-solvent and co-solute, and its interaction with Bromocresol Green (BCG) in aqueous media were investigated, using surface tensiometry, conductometry, and UV-Visible spectroscopy at 303K. The main co-solvent and co-solute used in this work were ethanol and NaCl, respectively. Surface tensiometry and conductometry were used to detect the values of critical micelle concentration (CMC). The effect of ethanol and NaCl on the CMC and free energy of micellization ( ) was also studied. To enhance the scope of the present study, the interaction and solubilization behaviour of an amphiphilic organic dye, BCG, with SDS in aqueous media was also investigated. Simple, as well as differential, UV-Visible spectroscopy was used to study the solublization behavior of dye-surfactant (BCG-SDS) mixed systems. The partition coefficient (K x ) and the free energy of transfer ) of the dye from water to the hydrophobic interior of the micelle was calculated. The binding behavior of BCG in surfactant solution is reflected in terms of micelle-water partition coefficient (K x ). Low K x value shows that BCG is partitioned weakly from a polar to a non polar environment in the palisade layer of micelle. doi: 10.14456/WJST.2015.93

/pdf/the-interactions-of-co-solvent-co-solute-and-amphiphilic-4e798j02a5.pdf

The Interactions of Co-Solvent, Co-Solute and Amphiphilic Anionic Dye with Aqueous Solutions of Sodium Dodecyl Sulfate

The aggregation and adsorption properties of metallosurfactant, benzyldimethylhexadecylammonium tetrachloromanganate(II) (BDHA2[MnCl4], where BDHA represents benzyldimethylhexadecylammonium group) ...

Aggregation and adsorption properties of benzyldimethylhexadecylammonium tetrachloromanganate(II) metallosurfactant in water–ethylene glycol medium

The critical micelle concentration (CMC) of surfactant–Cr(III)–dodecylamine complexes of the type cis-α-[Cr(trien)(C12H25NH2)X]2+ (where trien = triethylenetetramine; X = F−, Cl−, Br−) has been studied in n-alcohol and in formamide at different temperatures, by electrical conductivity measurements. From the CMC values as a function of temperature, various thermodynamic properties have been evaluated: standard Gibbs energy changes (Δmic
 G
 0), standard enthalpy changes (Δmic
 H
 0) and standard entropy changes (Δmic
 S
 0) for micellization. Critical micelle concentrations have also been measured as a function of the percentage composition of alcohol added. The solvent composition dependences of these thermodynamic parameters were determined. It is suggested that alcohol addition leads to an increase in formamide penetration into the micellar interface that depends on the alcohol’s chain length. The results are discussed in terms of an increased hydrophobic effect, dielectric constant of the medium, the chain length of the alcohols, and the surfactant in the solvent mixture.

N. Kumaraguru

Papers

Studies on Thermodynamics of Micellization and Solvophobic Interactions of Novel Surfactant–Cr(III) Complexes in Non-aqueous Solvents