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 zwitterion L-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 (h2) have been calculated. The h2 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 h2 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 h2 coefficients through their surface charge densities and hydration (or dehydration) abilities.

Compounds

#	Formula	Name
1	C7H15NO3	(R)-3-hydroxy-4-(trimethylammonio)butanoate
2	ClNa	sodium chloride
3	ClK	potassium chloride
4	BrNa	sodium bromide
5	H2O	water

Datasets

The table above is generated from the ThermoML associated json file (link above). POMD and RXND refer to PureOrMixture and Reaction Datasets. The compound numbers are included in properties, variables, and phases, if specificied; the numbers refer to the table of compounds on the left.
Type	Compound-#	Property	Variable	Constraint	Phase	Method	#Points
POMD	5	Mass density, kg/m3 ; Liquid	Pressure, kPa; Liquid Temperature, K; Liquid		Liquid	Vibrating tube method	1
POMD	2 5	Mass density, kg/m3 ; Liquid	Molality, mol/kg - 2; Liquid	Pressure, kPa; Liquid Temperature, K; Liquid	Liquid	Vibrating tube method	7
POMD	3 5	Mass density, kg/m3 ; Liquid	Molality, mol/kg - 3; Liquid	Pressure, kPa; Liquid Temperature, K; Liquid	Liquid	Vibrating tube method	7
POMD	4 5	Mass density, kg/m3 ; Liquid	Molality, mol/kg - 4; Liquid	Pressure, kPa; Liquid Temperature, K; Liquid	Liquid	Vibrating tube method	7
POMD	1 2 5	Mass density, kg/m3 ; Liquid	Solvent: Molality, mol/kg - 2; Liquid Molality, mol/kg - 1; Liquid	Pressure, kPa; Liquid Temperature, K; Liquid	Liquid	Vibrating tube method	7
POMD	1 3 5	Mass density, kg/m3 ; Liquid	Solvent: Molality, mol/kg - 3; Liquid Molality, mol/kg - 1; Liquid	Pressure, kPa; Liquid Temperature, K; Liquid	Liquid	Vibrating tube method	7
POMD	1 4 5	Mass density, kg/m3 ; Liquid	Solvent: Molality, mol/kg - 4; Liquid Molality, mol/kg - 1; Liquid	Pressure, kPa; Liquid Temperature, K; Liquid	Liquid	Vibrating tube method	7
POMD	1 5	Mass density, kg/m3 ; Liquid	Molality, mol/kg - 1; Liquid Pressure, kPa; Liquid Temperature, K; Liquid		Liquid	Vibrating tube method	1

Thermodynamics Research Center / ThermoML | Journal of Chemical Thermodynamics

Enthalpic pairwise self-association of L-carnitine in aqueous solutions of some alkali halides at T = 298.15 K

Wang, H.-Q.[Hua-Qin], Cheng, W.-N.[Wei-Na], Zhu, L.-Y.[Li-Yuan], Hu, X.-G.[Xin-Gen]

ABSTRACT