The salting coefficient and size of alkylamines in saline media at different temperatures: estimation from Pitzer equations and the mean spherical approximation

The renewed theoretical interest in the proton transfer associated to the a mino group together with the scarcity of acid-base studies of amines in mod erate to concentrated saline media focussed our attention on the study of t he basicities of some alkylamines, namely monomethyl, dimethyl and trimethy lamine, in aqueous saline solutions of KCl at various temperatures. A non-conventional analysis of stoichiometric equilibrium constants versus ionic strength data is carried out. On one hand, Fitter's model is easily a pplied to calculate the salting coefficient and the thermodynamic equilibri um constant of the alkylamines. On the other hand, the mean spherical appro ximation has the advantage over the Debye-Huckel based theories that it can account for effects produced by species of different sizes. Here, it is ap plied to predict the dependence of the salting behavior on the size of the alkylamines. (C) 2001 Elsevier Science B.V. All rights reserved.