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cis ‐cyclohexyl‐15‐crown‐5 ether: Dynamic stereochemistry in solution as studied by carbon‐13 NMR techniques
Author(s) -
Buchanan G. W.,
Bourque K.,
Diedrich G. K.,
Khan M. Z.
Publication year - 1987
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.1260250116
Subject(s) - chemistry , crown ether , ether , ion , potassium , carbon 13 nmr , sodium , ring flip , spin–lattice relaxation , crystallography , stereochemistry , medicinal chemistry , inorganic chemistry , ring (chemistry) , organic chemistry , nuclear magnetic resonance , physics , nuclear quadrupole resonance
Abstract 13 C NMR spectra of cis ‐cyclohexyl‐15‐crown‐5 ether in the temperature range 298–173 K have been recorded. A single degenerate conformational process, attributed to cyclohexyl ring inversion, has been detected with a barrier of ca 10.3 kcal mol‐ 1 . Sodium ion complexation increases this barrier by ca 0.5 kcal mol −1 , whereas potassium ion complexation has no measurable effect. Spin‐lattice relaxation time results also indicate more effective complexation of sodium ion than potassium ion by the macrocyclic crown ether system.