Clermont Université, Université Blaise Pascal, Institut de Chimie de Clermont-Ferrand, UMR 6296 CNRS, équipe Thermodynamique et Interactions Moléculaires, ICCF-TIM, BP 80026, F-63171 Aubière, France.
J Phys Chem B. 2013 Jun 20;117(24):7416-25. doi: 10.1021/jp403074z. Epub 2013 Jun 10.
The influence of the presence of imidazolium side chain unsaturation on the solubility of ethane and ethylene was studied in three ionic liquids: 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide-saturated alkyl side-chain in the cation; 1-methyl-3-(buten-3-yl)imidazolium bis(trifluorosulfonyl)imide-double bond in the side-chain of the cation; and 1-methyl-3-benzylimidazolium bis(trifluorosulfonyl)imide-benzyl group in the side-chain of the cation. The solubility of both gases decreases when the side-chain of the cations is functionalized with an unsaturated group. This can be explained by a less favorable enthalpy of solvation. The difference of solubility between ethane and ethylene can be explained from a balance of enthalpic and entropic factors: for the ionic liquid with the saturated alkyl side-chain and the benzyl-substituted side-chain, it is the favorable entropy of solvation that explains the larger ethylene solubility, whereas in the case of the saturated side-chain, it is the more favorable enthalpy of solvation. Molecular simulation allowed the identification of the mechanisms of solvation and the preferential solvation sites for each gas in the different ionic liquids. Simulations have shown that the entropy of solvation is more favorable when the presence of the gas weakens the cation-anion interactions or when the gas can be solvated near different sites of the ionic liquid.
阳离子中饱和烷基侧链的 1-丁基-3-甲基咪唑𬭩双（三氟甲磺酰基）酰胺；阳离子中侧链的 1-甲基-3-（丁烯-3-基）咪唑𬭩双（三氟磺酰基）酰亚胺-双键；阳离子中侧链的 1-甲基-3-苄基咪唑𬭩双（三氟磺酰基）酰亚胺-苄基。当阳离子侧链官能化有不饱和基团时，两种气体的溶解度都会降低。这可以用溶剂化焓不利来解释。乙烷和乙烯之间溶解度的差异可以从焓和熵因素的平衡来解释：对于具有饱和烷基侧链和苄基取代侧链的离子液体，是有利的溶剂化熵解释了较大的乙烯溶解度，而在饱和侧链的情况下，则是更有利的溶剂化焓。分子模拟允许确定每种气体在不同离子液体中的溶剂化机制和优先溶剂化位置。模拟表明，当气体存在削弱阳离子-阴离子相互作用时，或者当气体可以在离子液体的不同位置附近被溶剂化时，溶剂化熵更为有利。
