A theoretical investigation of the CO2-philicity of amides and carbamides

The knowledge of the interactions taking place at a molecular level can help the development of new technological procedures in Chemistry with low environmental impact. In organic, biochemical and pharmaceutical synthesis and in analytical chemistry, important advances in this domain are related to the use of solvents that can be valid alternatives to hazardous organic solvents. In the last decades, a large emphasis has been given to the use of carbon dioxide under supercritical conditions, since the mild temperature and pressure conditions of the fluid can easily be controlled to improve its capacity to solubilize small organic compounds. On the other hand, the solubility of larger molecules and of polar compounds in this medium is generally very low. This has motivated recent theoretical and experimental studies with the purpose of reaching a better understanding of the so-called CO2-philicity of molecules and materials, and very encouraging results have been reported. In this paper, we present an ab initio study of the intermolecular interactions between CO2 and amide and carbamide derivatives, performed on model 1: 1 complexes at the MP2/aug-cc-pVTZ//MP2/aug-cc-pVDZ level. Our findings shed some light on the key points to be considered in the design of large CO2-philic molecules, hinting at the use of solubilizer groups in which amide or urea bonds could be involved.