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cis-cyclohexyl-15-crown-5 ether: Dynamic stereochemistry in solution as studied by carbon-13 NMR techniques

✍ Scribed by G. W. Buchanan; K. Bourque; G. K. Diedrich; M. Z. Khan

Publisher: John Wiley and Sons
Year: 1987
Tongue: English
Weight: 324 KB
Volume: 25
Category: Article
ISSN: 0749-1581
DOI: 10.1002/mrc.1260250116

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✦ Synopsis

I3C 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-'. Sodium ion complexation increases this barrier by ca 0.5 kcal mol-', 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.

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Conformational Analysis of Crown Ether Analogs in Solution: cis-Cyclohexyl-10-crown-3 as Studied via Low-Temperature 1H and 13C NMR Spectroscopy

✍ G. W. Buchanan; M. Gerzain; K. Bourque 📂 Article 📅 1997 🏛 John Wiley and Sons 🌐 English ⚖ 434 KB 👁 2 views

Two conformations of cis-cyclohexyl-10-crown-3 were detected in solution below 250 K using 1H NMR at 400 MHz and 13C NMR at 100 MHz. Chemical shift assignments were facilitated by spectra of two dideuterio derivatives. From relative peak area measurements, the conformation with the unit OÈCH 2 ÈCH 2