Nuclear magnetic resonance studies of guest species in clathrate hydrates: line-shape anisotropies, chemical shifts, and the determination of cage occupancy ratios and hydration numbers

• Published in: Journal of physical chemistry (1952) Vol. 94; no. 1; pp. 157 - 162
• Main Authors: Collins, M. J, Ratcliffe, C. I, Ripmeester, J. A
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 1990
• Subjects: 360602 > Other Materials > Structure & Phase Studies; CLATHRATES; Condensed matter: structure, mechanical and thermal properties; Crystal binding; cohesive energy; Crystalline state (including molecular motions in solids); DATA; DATA ANALYSIS; ELEMENTS; EVEN-ODD NUCLEI; Exact sciences and technology; EXPERIMENTAL DATA; FLUORINE 19; FLUORINE ISOTOPES; HYDRATES; HYDROGEN; INFORMATION; INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; INTERMEDIATE MASS NUCLEI; ISOMERIC TRANSITION ISOTOPES; ISOTOPE EFFECTS; ISOTOPES; LIGHT NUCLEI; MAGNETIC RESONANCE; MATERIALS SCIENCE; MEASURING INSTRUMENTS; MEASURING METHODS; NONMETALS; NUCLEAR MAGNETIC RESONANCE; NUCLEI; NUMERICAL DATA; ODD-EVEN NUCLEI; PHOSPHORUS 31; PHOSPHORUS ISOTOPES; Physics; RADIOISOTOPES; RESONANCE; SECONDS LIVING RADIOISOTOPES; SELENIUM 77; SELENIUM ISOTOPES; STABLE ISOTOPES 400202 > Isotope Effects, Isotope Exchange, & Isotope Separation; Structure of solids and liquids; crystallography; Acetylenic aliphatic compound; Hydrogen Selenides; Hydrogen Sulfides; Phosphine; Crystal chemistry; Ethylene; Clathrate; Ice; Experimental study; Acetylene; Inorganic compound; Ethylenic aliphatic compound; Chemical shift; Saturated aliphatic compound; NMR spectrum; Halogen Organic compounds
• ISSN: 0022-3654; 1541-5740
• DOI: 10.1021/j100364a024

NMR spectra of the guest molecules PH{sub 3}, H{sub 2}Se, D{sub 2}Se, D{sub 2}S, CD{sub 3}F, CD{sub 3}Cl, CD{sub 3}Br, C{sub 2}D{sub 2}, and C{sub 2}D{sub 4} in their structure I clathrate hydrates have been obtained by use of {sup 2}H, {sup 19}F, {sup 31}P, and {sup 77}Se nuclei. Components due to guests in the small and large cages have been distinguished by using isotropic chemical shift and static line-shape anisotropy differences. Low-temperature magic angle spinning was used in some cases to resolve the two components. Guests in the small cages are invariably found to have a lower field isotropic shift than those in the large cage. The static line shapes are isotropic for guests in the small spherical cages, whereas in the large oblate cages they have a residual anisotropy. Relative cage occupancy ratios {theta}{sub S}/{theta}{sub L} have been obtained from the observed NMR intensities, and together with similar results from previous NMR studies, these have been used to derive hydration numbers. This represents a new and nondestructive method of determining structure I hydrate compositions.