Enthalpic pairwise self-association of l-carnitine in aqueous solutions of some alkali halides at T = 298.15 K. (April 2016)

• Record Type: Journal Article
• Authors: Wang, Hua-Qin; Cheng, Wei-Na; Zhu, Li-Yuan; Hu, Xin-Gen
• Is Part Of: Journal of chemical thermodynamics. Volume 95(2016:Apr.)
• Page Start: 111
• Page End: 115
• Publication Date: 2016-04
• Subjects: l-Carnitine -- Alkali halides -- Dilution enthalpy -- The 2nd virial enthalpic coefficients -- Pairwise self-association -- Salt effects; Thermodynamics -- Periodicals; Thermochemistry -- Periodicals; Thermodynamique -- Périodiques; Thermochimie -- Périodiques; Thermochemistry; Thermodynamics; Periodicals; 541.369
• DOI: 10.1016/j.jct.2015.11.028
• Languages: English
• ISSNs: 0021-9614

Abstract

Graphical abstract: Highlights: Dilution enthalpies ofl -carnitine in aqueous alkali halide solutions by ITC. The second virial coefficients of enthalpy ( h 2 ) have been calculated. The values of h 2 increase with increasing molalities of aqueous salt solutions. The signs of h 2 turn from negative in pure water to positive in salt solutions. The trends is ascribed to the salt effects on pairwise self-associations. Abstract: Knowledge of the influence of ions of various nature on intermolecular hydrophilic and hydrophobic interactions in solutions is required in many research fields. In this paper, dilution enthalpies of zwitterionl -carnitine in aqueous NaCl, KCl and NaBr solutions of various molalities ( b = 0 to 3.0 mol · kg −1 ) have been determined respectively at T = (298.15 ± 0.01) K and p = (0.100 ± 0.005) MPa by isothermal titration calorimetry (ITC). In light of the MacMillan–Mayer theory, the 2nd virial enthalpic coefficients ( h 2 ) have been calculated. The h 2 coefficients increase gradually with increasing molality ( b ) of the three aqueous alkali halides solutions, from small negative values in pure water to relatively larger positive values in solution. The trends of h 2 coefficients are ascribed to the salt effects on the balance between hydrophilic and hydrophobic interactions in pairwise self-associations. It is considered that the size of cations and anions exert influences on h 2 coefficients through their surface charge densities and hydration (or dehydration) abilities.