On the encapsulation of hydrocarbon components of natural gas within molecular baskets in water. The role of C-H…π interactions and the host's conformational dynamics in the process of encapsulation

摘要

We examined the encapsulation of CH_4, C_2H_6, C_3H_8 and iso-C_4H_(10) in water, using four molecular baskets [1]-[4]. The baskets were shown to bind to hydrocarbon gases by forming favourable C-H…π contacts and, concurrently, adjusting the size of their cup-shaped platform. In the quest for sustainable and alternative sources of energy, natural gas plays an important role. The world reserves of this important resource are vast and maintained within the earth's crust, permafrost regions or at the bottom of the oceans. The dominant constituent of natural gas is methane (70-90%), while ethane, propane and butane (natural gas liquids, NGLs) represent minor components (0-20%). Indeed, small hydrocarbons are used for the generation of heat and electricity but also as a feedstock in the chemical industry whereby steam cracking, steam reforming, catalytic dehydrogenation and Fischer-Tropsch synthesis constitute important methods for obtaining valuable raw materials. Over the last decade, the exploitation of shale reserves of natural gas in North America, via so-called hydraulic fracturing, has spurred an additional interest toward developing effective and environmentally friendly ways for converting C1 through C4 hydrocarbons into functional chemicals.