Calorimetric properties of aqueous of alkanolamines

C. Romero1 and Y. Cruz1

1Departamento de Química, Universidad Nacional de Colombia. Bogota, Colombia

Keywords: enthalpy of dilution
property: pairwise coefficients, flow calorimetry
material: alkanolamines

The thermodynamic properties of aqueous solutions of alkanolamines are of special importance due to their industrial applications and for their importance in the elucidation of the nature of interactions between nonpolar and polar groups and water. Alkanolamines and their mixtures with water have an important a well-established industrial use as solvents, surfactants, in gas purification to absorb acid gases, primarily CO2 and SH2 among many others [1]. Eventhough there is a scientific interest to improve our understanding of molecular interactions, only few studies have been developed on the thermodynamic properties of these aqueous solutions [2-5]. It is well known that the increase of polar groups changes the hydrophobic–hydrophilic balance. This is especially important at low concentration where the interaction of the hydrophobic hydration sphere with the hydrophilic hydration sphere defines the behavior of the aqueous mixture. However, the complexity of interactions present in these systems means that the behavior of these solutes in water is not well understood. The aim of this work is to analyze the effect of the relationship between the number and relative position of the hydroxyl and amino groups in a hydrocarbon chain with three carbon atoms on the calorimetric properties of the aqueous solutions and its effect on the hydrophobic/hydrophilic character of alkanolamines. Dilution enthalpies of 3-amino-1-propanol, 1-amino-2-propanol, 2-amino-1-propanol, 3-amino-1,2-propanediol, 1,3-diamino-2-hidroxipropanol and 2-amino-1,3-propanediol in water were measured using an LKB flow microcalorimeter. Experimental data were treated according to the McMillan–Mayer theory to obtain the homotactic enthalpic interaction coefficients. The pair interaction coefficient hxx shows a clear dependence on the number and position of the polar groups groups The values of the interaction coefficients are discussed in terms of solute–solvent and solute–solute interactions and are used as indicative of hydrophobic behavior of the amino alcohols studied.

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  3. J. Aguila-Hernandez, A. Trejo, B. E. Garcıa-Flores. Colloids and Surfaces A: Physicochem. Eng. Aspects 308, 33 (2007).

  4. M. Mundhwa, A. Henni. J. Chem. Thermodynamics 39, 1439 (2007).

  5. L. Chiu, M. Li. J. Chem. Eng. Data, 44, 1396 (1999).

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