Solvation of 5‐fluorouracil in supercritical CO 2

The solvation properties of 5‐fluorouracil in supercritical carbon dioxide (SC‐CO 2 ) is investigated by means of molecular dynamics computer simulations using a force field that treats all atoms explicitly. Solvation shell distribution functions and solvent density maps around the solute were computed at different supercritical temperatures in the range 308–328 K and densities varying from 0.117 to 0.94 g/cm 3 . At the lowest density, we detect a strongly inhomogeneous local density augmentation effect manifested as the clustering of solvent molecules above and below the solute molecular plane and around its carbonyl and NH groups. The free‐energy benefit for a CO 2 molecule to be in the first solvation shell relative to the bulk is roughly twice the thermal energy at such conditions. The distribution of the relative orientation of CO 2 with respect to the solute suggests that local bond multipolar solute–solvent interactions are responsible for the solvent density enhancement in these systems. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008