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Title: 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

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.
Authors:
; ;  [1]
  1. (National Research Council of Canada, Ottawa, Ontario (Canada))
Publication Date:
OSTI Identifier:
6711720
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Physical Chemistry; (USA); Journal Volume: 94:1
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; 36 MATERIALS SCIENCE; CLATHRATES; NUCLEAR MAGNETIC RESONANCE; DATA ANALYSIS; EXPERIMENTAL DATA; FLUORINE 19; HYDRATES; HYDROGEN; ISOTOPE EFFECTS; MEASURING INSTRUMENTS; MEASURING METHODS; PHOSPHORUS 31; SELENIUM 77; DATA; ELEMENTS; EVEN-ODD NUCLEI; FLUORINE ISOTOPES; INFORMATION; INTERMEDIATE MASS NUCLEI; ISOMERIC TRANSITION ISOTOPES; ISOTOPES; LIGHT NUCLEI; MAGNETIC RESONANCE; NONMETALS; NUCLEI; NUMERICAL DATA; ODD-EVEN NUCLEI; PHOSPHORUS ISOTOPES; RADIOISOTOPES; RESONANCE; SECONDS LIVING RADIOISOTOPES; SELENIUM ISOTOPES; STABLE ISOTOPES 400202* -- Isotope Effects, Isotope Exchange, & Isotope Separation; 360602 -- Other Materials-- Structure & Phase Studies