Effect of bromine substitution on the solubility of gases in hydrocarbons and fluorocarbons

The interactions of oxygen and of carbon dioxide with normal and brominated octane are studied by analysing original experimental gas solubility data as a function of temperature in the range between 288 and 313 K. The temperature dependence of the solubility yields the thermodynamic properties of solvation. The influence of bromine substitution was studied by comparing the present data with that for perfluorooctane and 1-bromoperfluorooctane. A molecular interpretation of the effects observed was done using atomistic simulation. In order to simulate 1-bromooctane, parameters of the molecular force field were developped for bromoalkanes within the OPLS-AA framework. In general, simulation provides correct predictions of the solubility and of its temperature dependence, except in cases where values are too close (within the error bars of the simulation). Structural aspects of the solvation of the two gases were analysed in light of the site–site solute–solvant radial distribution functions. The relative importance of electrostatic interactions is assessed by modifying the intermolecular potential models for the gases.