13C Chemical Shifts of Propane Molecules Encaged in Structure II Clathrate Hydrate

Experimental NMR measurements for C-13 chemical shifts of propane molecules encaged in 16-hedral cages of structure II clathrate hydrate were conducted to investigate the effects of guest-host interaction of pure propane clathrate on the C-13 chemical shifts of propane guests. Experimental C-13 NMR measurerments revealed that the clathrate hydration of propane reverses the C-13 chemical shifts of methyl and methylene carbons in propane guests to gaseous propane at room temperature and atmospheric pressure or isolated propane, suggesting a change in magnetic environment around the propane guest by the clathrate hydration. Inversion of the C-13 chemical shifts of propane clathrate suggests that the deshielding effect of the water cage on the methyl carbons of the propane molecule encaged in the 16-hedral cage is greater than that on its methylene carbon.