<i>cis</i>‐cyclohexyl‐15‐crown‐5 ether: Dynamic stereochemistry in solution as studied by carbon‐13 NMR techniques

Abstract

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.