ISSN:
1573-1111
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
Notes:
Abstract At relatively high temperatures (200–270K), clathrate hydrate cages achieve their full crystallographic symmetry because of time averaging of different cage configurations which exist because of disorder in the water molecule orientations. The average orientation of guest molecules in the cages can be obtained from the NMR spectrum, in case of spin 1/2 nuclei from the nuclear shielding tensor, in case of spin 1 nuclei from the quadrupole coupling tensor. Guest molecules studied include carbon dioxide, carbonyl sulphide, methyl-d3 fluoride, methyl-d3 chloride, methyl-d3 bromide, ethane-d6, acetylene-d2 in the structure I hydrates, and methyl-d3 iodide in the structure II hydrate. For the slightly flattened large cage of structure I hydrate, the guest molecules rotate so that the plane which contains the long axis of the molecule is confined to be nearer to the equatorial plane of the cage than the axial regions. Since the structure II large cage has tetrahedral symmetry on time average, it exerts no orienting effect on guest molecules.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00663262
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