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It is well-known that, in general, fluorocarbons are highly soluble in liquid and supercritical CO 2 and fluorine substitution has been widely utilized as a method to make otherwise insoluble organic compounds more CO 2 -philic. In this work, we investigate the CO 2 -philicity of fluorinated compounds with varying numbers of fluorine atoms in the system by using simple quantum chemical calculations. We explore the fundamental nature of fluorocarbon and hydrocarbon interactions with CO 2 by examining the effects of stepwise fluorination on methane using correlated ab initio calculations. The results suggest an optimum density of fluorine atoms that can be viewed as a maximum CO 2 -philicity. As a charge-separated molecule, CO 2 is observed to act as a weak Lewis acid as well as a weak Lewis base in intermolecular interactions. In this work, we present evidence that CO 2 −fluorocarbon and CO 2 −hydrocarbon interactions are fundamentally different, although energetically comparable. Fluorocarbons interact through the carbon atom of CO 2, while hydrocarbons interact through the oxygen atoms. The results indicate that in the case of partially fluorinated hydrocarbons, there is a specific fluorine atom−CO 2 interaction. In these systems, the C−H bonds may also contribute to CO 2 -philicity through weak C−H···O interactions. The effect of fluorine substitution on the CO 2 -philicity of carbonyl containing CO 2 -philes is also investigated.
Raveendran et al. (2003) studied this question.