Lithum ion complexation effects on stereochemical dynamics of 14-crown-4 ethers in solution as studied by 13C nuclear magnetic resonance
- 1 September 1988
- journal article
- research article
- Published by Canadian Science Publishing in Canadian Journal of Chemistry
- Vol. 66 (9) , 2204-2209
- https://doi.org/10.1139/v88-351
Abstract
The barrier to ring inversion for the cis-syn-cis isomer of dicyclohexano-14-crown-4 has been determined via 13C nuclear magnetic resonance coalescence temperature measurements to be 42.3 .+-. 0.8 kJ/mol. For the LiNCS complex of this isomer, the inversion barrier increases by ca. 5 kJ/mol. For the Li+ complex of the cis-anti-cis iosmer, evidence for two dynamic conformational processes in solution is presented, with Li complexation inducing an increase in the barrier to degenerate cyclohexane ring inversion similar to that found in the cis-syn-cis isomer. 13C Tl measurements indicate a substantial decrease in the mobilities of both isomers in the presence of Li+ ions in solution.Keywords
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