In the case of [BMIm][Br], [Br] vdW parameters were adjusted to improve the agreement with the experimental ∆H vap . Since the parameters reproduced more attractive interactions, the vdW radius of the anion was slightly increased to compensate for this contribution, which resulted in minimal impact on the density. There is evidence that IL's formed by symmetric cations of the imidazolium family present lower ∆H vap than IL's composed of asymmetric cations. Figure shows the predicted heats of vaporization for IL's in this study whose ∆H vap has not been reported. The expected trend of lower ∆H vap as the temperature rises is followed in all the examples. The enthalpy values are observed to increase as a function of the molecular weight of cations (the size of the anion is similar) as expected.