From density measurements (25 °C) of aqueous solutions at various concentrations of solute, apparent molar volumes of some open-chain bifunctional amines, with the amine group being primary, secondary, and tertiary, have been determined. The compounds studied were 2-aminoethanol, 3-amino-1-propanol, 2-methoxyethylamine, 3-methoxy-l-propylaminee,t hylenediamine, 1,3-diaminopropane,2 -(methylamino)ethanol, 2-(ethylamino)ethanol, 2-(dimethylamino)ethanol, 2-(diethylamino)ethanol, and their mono- and dihydrochlorides. The volume changes for the first and second steps of proton ionization have been calculated from the limiting partial molar volumes. The volume change values of the above bifunctional amines are compared with the corresponding values for monofunctional amines. The difference in the volume changes caused by the introduction of the second hydrophilic center is discussed. The volumes and entropies of ionization of the amines and carboxylic acids are compared and the deviations of these functions from predictions based on simple electrostatic theories are considered.

Volume Changes In Proton Ionization of Amines In Water .2. Amino-alcohols, Amino Ethers, and Diamines

CABANI, SERGIO;MOLLICA, VINCENZO;
1977

Abstract

From density measurements (25 °C) of aqueous solutions at various concentrations of solute, apparent molar volumes of some open-chain bifunctional amines, with the amine group being primary, secondary, and tertiary, have been determined. The compounds studied were 2-aminoethanol, 3-amino-1-propanol, 2-methoxyethylamine, 3-methoxy-l-propylaminee,t hylenediamine, 1,3-diaminopropane,2 -(methylamino)ethanol, 2-(ethylamino)ethanol, 2-(dimethylamino)ethanol, 2-(diethylamino)ethanol, and their mono- and dihydrochlorides. The volume changes for the first and second steps of proton ionization have been calculated from the limiting partial molar volumes. The volume change values of the above bifunctional amines are compared with the corresponding values for monofunctional amines. The difference in the volume changes caused by the introduction of the second hydrophilic center is discussed. The volumes and entropies of ionization of the amines and carboxylic acids are compared and the deviations of these functions from predictions based on simple electrostatic theories are considered.
Cabani, Sergio; Mollica, Vincenzo; L., Lepori; S. T., Lobo
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11568/218144
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