Clathrate Ices—Recent Results
Abstract The last five years have seen an increasing interest in clathrate ices as a result of the discovery of extensive deposits of natural gas hydrates in permafrost regions. Twenty-six new clathrate hydrates have been identified, mainly by NMR, including a tetragonal hydrate of dimethyl ether. N...
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1978
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crcambridgeupr:10.1017/s0022143000033281 2024-09-15T18:15:38+00:00 Clathrate Ices—Recent Results Davidson, D. W. Ripmeester, J. A. 1978 http://dx.doi.org/10.1017/s0022143000033281 https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022143000033281 en eng Cambridge University Press (CUP) Journal of Glaciology volume 21, issue 85, page 33-49 ISSN 0022-1430 1727-5652 journal-article 1978 crcambridgeupr https://doi.org/10.1017/s0022143000033281 2024-07-24T04:03:07Z Abstract The last five years have seen an increasing interest in clathrate ices as a result of the discovery of extensive deposits of natural gas hydrates in permafrost regions. Twenty-six new clathrate hydrates have been identified, mainly by NMR, including a tetragonal hydrate of dimethyl ether. N -butane and neo pentane have been found to be enclathrated in natural gas hydrates, the former as a gauche conformer. As a result of their high symmetries, encaged neo pentane, CF 4 , SF 6 , and SeF 6 exhibit a Resing apparent-phase-change effect in the temperature range of NMR line narrowing. There is increasing evidence that reorientational jumps of water molecules are more frequent than translational jumps in clathrate ices. This is certainly so for ethylene oxide-d 4 and tetrahydrofuran-d 8 hydrates for which two regions of proton line narrowing and two T 1 ρ minima have been observed. The reorientational motions of most guest molecules in structure II hydrates only become isotropic on a time scale long enough to permit the cage configurations to be averaged to 4 3m symmetry by reorientation of the water molecules. The orientations of the water molecules remain disordered to the lowest temperatures. Article in Journal/Newspaper Journal of Glaciology permafrost Cambridge University Press Journal of Glaciology 21 85 33 49 |
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Cambridge University Press |
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English |
description |
Abstract The last five years have seen an increasing interest in clathrate ices as a result of the discovery of extensive deposits of natural gas hydrates in permafrost regions. Twenty-six new clathrate hydrates have been identified, mainly by NMR, including a tetragonal hydrate of dimethyl ether. N -butane and neo pentane have been found to be enclathrated in natural gas hydrates, the former as a gauche conformer. As a result of their high symmetries, encaged neo pentane, CF 4 , SF 6 , and SeF 6 exhibit a Resing apparent-phase-change effect in the temperature range of NMR line narrowing. There is increasing evidence that reorientational jumps of water molecules are more frequent than translational jumps in clathrate ices. This is certainly so for ethylene oxide-d 4 and tetrahydrofuran-d 8 hydrates for which two regions of proton line narrowing and two T 1 ρ minima have been observed. The reorientational motions of most guest molecules in structure II hydrates only become isotropic on a time scale long enough to permit the cage configurations to be averaged to 4 3m symmetry by reorientation of the water molecules. The orientations of the water molecules remain disordered to the lowest temperatures. |
format |
Article in Journal/Newspaper |
author |
Davidson, D. W. Ripmeester, J. A. |
spellingShingle |
Davidson, D. W. Ripmeester, J. A. Clathrate Ices—Recent Results |
author_facet |
Davidson, D. W. Ripmeester, J. A. |
author_sort |
Davidson, D. W. |
title |
Clathrate Ices—Recent Results |
title_short |
Clathrate Ices—Recent Results |
title_full |
Clathrate Ices—Recent Results |
title_fullStr |
Clathrate Ices—Recent Results |
title_full_unstemmed |
Clathrate Ices—Recent Results |
title_sort |
clathrate ices—recent results |
publisher |
Cambridge University Press (CUP) |
publishDate |
1978 |
url |
http://dx.doi.org/10.1017/s0022143000033281 https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022143000033281 |
genre |
Journal of Glaciology permafrost |
genre_facet |
Journal of Glaciology permafrost |
op_source |
Journal of Glaciology volume 21, issue 85, page 33-49 ISSN 0022-1430 1727-5652 |
op_doi |
https://doi.org/10.1017/s0022143000033281 |
container_title |
Journal of Glaciology |
container_volume |
21 |
container_issue |
85 |
container_start_page |
33 |
op_container_end_page |
49 |
_version_ |
1810453500412297216 |