Determination of the vaporisation enthalpies for amino acid ionic liquids [C(n)mim][Ala](n=5, 6) and applications of the molar surface Gibbs energy

摘要

Amino acid ionic liquids (ILs) 1-alkyl-3-methylimidazolium alanine [C(n)mim][Ala] (n = 5,6) were prepared and characterized. The enthalpy of vaporisation at the average temperature, Delta H-g(1)m(o)(T-av), for the two ILs were determined by means of isothermogravimetrical analysis, and in terms of Delta C-g(1)p,m(o), the value of Delta H-g(1)m(o)(T-av) can be adjusted to Delta H-g(1)m(o)(2 9 8); then, the polarity, delta(mu), of the two ILs were estimated, in which the order of the delta(mu) is in consistent with our experiences. In terms of molar surface Gibbs energy, g(s), the traditional Eotvos equation was improved, the parameters of new Eotvos one have clear physical meanings: Its slope and intercept are the molar surface entropy, s, and the molar surface enthalpy, h, respectively. In addition, combining g(s) with Lorentz-Lorenz equation, an expression for predicting surface tension, gamma, of the ILs was obtained, and the predicted values of gamma are in good agreement with the experimental ones. (c) 2020 Elsevier Ltd.