Intracavity Conformational Changes in Clathrate Hydrates

Acyclic hydrocarbon molecules favor the gauche or cis conformation, which are more stable in terms of molecular geometry when they are enclathrated in clathrate hydrates. Once they are captured, they maintain their conformations in the hydrate cavities. However, on the basis of Raman spectra and density functional theory (DFT) calculations, we observed conformational changes of an acyclic guest molecule (3-buten-2-one) occurring in the hydrate cavities induced by intercavity electron transfer after gamma-irradiation. This phenomenon is also accompanied by an enhanced thermodynamic stability of the clathrate hydrate phases. These results contribute to an understanding of the complex physicochemical properties of clathrate hydrates and suggest practical application for hydrate-based gas storage and separation.