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
- National Research Council of Canada, Ottawa, Ontario (Canada)
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.
- OSTI ID:
- 6711720
- Journal Information:
- Journal of Physical Chemistry; (USA), Journal Name: Journal of Physical Chemistry; (USA) Vol. 94:1; ISSN 0022-3654; ISSN JPCHA
- Country of Publication:
- United States
- Language:
- English
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360602 -- Other Materials-- Structure & Phase Studies
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400202* -- Isotope Effects
Isotope Exchange
& Isotope Separation
CLATHRATES
DATA
DATA ANALYSIS
ELEMENTS
EVEN-ODD NUCLEI
EXPERIMENTAL DATA
FLUORINE 19
FLUORINE ISOTOPES
HYDRATES
HYDROGEN
INFORMATION
INTERMEDIATE MASS NUCLEI
ISOMERIC TRANSITION ISOTOPES
ISOTOPE EFFECTS
ISOTOPES
LIGHT NUCLEI
MAGNETIC RESONANCE
MEASURING INSTRUMENTS
MEASURING METHODS
NONMETALS
NUCLEAR MAGNETIC RESONANCE
NUCLEI
NUMERICAL DATA
ODD-EVEN NUCLEI
PHOSPHORUS 31
PHOSPHORUS ISOTOPES
RADIOISOTOPES
RESONANCE
SECONDS LIVING RADIOISOTOPES
SELENIUM 77
SELENIUM ISOTOPES
STABLE ISOTOPES