Guest–Host Hydrogen Bonding in Structure H Clathrate Hydrates

Molecular dynamics simulations of the structure H (sH) clathrate of tert‐butylmethylether show the prevalence of ether–water hydrogen bonding (see picture), absent in the neo‐hexane sH clathrate. This affects guest–cage dynamics and host–water dielectric relaxation dynamics. The 13C and 1H NMR relaxation times for both guests are measured, and the differences are explained in terms of guest–host interactions in the two clathrates. The formation of guest–host hydrogen bonds in structure H (sH) clathrate hydrates is studied herein. We contrast the structure and guest dynamics of the tert‐butylmethylether (TBME) and neohexane (NH) sH clathrates by performing molecular dynamics simulations on these two clathrates and measuring 1H and 13C NMR relaxation times of the guests. These two guests are isoelectronic and differ with respect to the presence of the ether oxygen atom in TBME and a CH2 group in NH. The TBME guest forms long‐lived hydrogen bonds with water molecules in the equatorial region of the large sH clathrate cage. These hydrogen bonds effectively tether the TBME guest to the side of the cage and restrict its rattling and rotational motions in the cage compared to NH, which does not become hydrogen bonded to the cage’s water molecules. Molecular dynamics simulations of the structure H (sH) clathrate of tert‐butylmethylether show the prevalence of ether–water hydrogen bonding (see picture), absent in the neo‐hexane sH clathrate. This affects guest–cage dynamics and host–water dielectric relaxation dynamics. The 13C and 1H NMR relaxation times for both guests are measured, and the differences are explained in terms of guest–host interactions in the two clathrates.