Ionic Liquids: Dissecting the Enthalpies of Vaporization |
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| Authors: | Thorsten Köddermann Dietmar Paschek Dr Ralf Ludwig Prof Dr |
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| Institution: | 1. Institut für Chemie, Abteilung Physikalische Chemie, Universit?t Rostock, Dr.‐Lorenz‐Weg 1, 18059 Rostock, Germany, Fax: (+49)?381‐498‐6524;2. Fakult?t Chemie, Physikalische Chemie III, Technische Universit?t Dortmund, Otto‐Hahn‐Str. 6, 44221 Dortmund, Germany, Fax: (+49)?231‐755‐3748;3. Leibniz‐Institut für Katalyse, an der Universit?t Rostock, Albert‐Einstein‐Str. 29a, 18059 Rostock, Germany |
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| Abstract: | We calculate the heats of vaporisation for imidazolium‐based ionic liquids Cnmim]NTf2] with n=1, 2, 4, 6, 8 by means of molecular dynamics (MD) simulations and discuss their behavior with respect to temperature and the alkyl chain length. We use a force field developed recently. The different cohesive energies contributing to the overall heats of vaporisations are discussed in detail. With increasing alkyl chain length, the Coulomb contribution to the heat of vaporisation remains constant at around 80 kJ mol?1, whereas the van der Waals interaction increases continuously. The calculated increase of about 4.7 kJ mol?1 per CH2‐group of the van der Waals contribution in the ionic liquid exactly coincides with the increase in the heats of vaporisation for n‐alcohols and n‐alkanes, respectively. The results support the importance of van der Waals interactions even in systems completely composed of ions. |
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| Keywords: | cohesion energy enthalpies of vaporization ionic liquids molecular dynamics thermodynamics |
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