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Crown Ethers

Crown Ethers

Crown ethers are cyclic polyethers that contain multiple oxygen atoms, usually arranged in a regular pattern. The first crown ether was synthesized by Charles Pederson while working at DuPont in 1967. For this work, Pedersen was co-awarded the 1987 Nobel Prize in Chemistry. Crown ethers are named using the formula x-crown-y, where x is the total number of atoms in the ring and y is the number of ether oxygen atoms. The term 'crown' refers to the crown-like shape that these ether molecules take.

¹H NMR of Conformationally Flexible Molecules: Temporal Resolution

¹H NMR of Conformationally Flexible Molecules: Temporal Resolution

At room temperature, the chair conformer of cyclohexane undergoes rapid ring flipping between two equivalent chair conformers at a rate of approximately 105 times per second. These two chair conformers are in equilibrium. The rapid ring flipping results in the interconversion of the axial proton to an equatorial proton and an equatorial to the axial proton. Such interconversions are too rapid and cannot be detected on the NMR timescale. Hence, the NMR spectrometer cannot distinguish between the...

¹H NMR of Conformationally Flexible Molecules: Variable-Temperature NMR

¹H NMR of Conformationally Flexible Molecules: Variable-Temperature NMR

The axial and equatorial protons in cyclohexane can be distinguished by performing a variable-temperature NMR experiment. In this process, except for one proton, the remaining eleven protons are replaced by deuterium. The deuterium substitution avoids the possible peak splitting caused by the spin-spin coupling between the adjacent protons. The remaining proton flips between the axial and equatorial positions.

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Related Experiment Video

Updated: Jun 13, 2026

Transport Properties of Ibuprofen Encapsulated in Cyclodextrin Nanosponge Hydrogels: A Proton HR-MAS NMR Spectroscopy Study

Transport Properties of Ibuprofen Encapsulated in Cyclodextrin Nanosponge Hydrogels: A Proton HR-MAS NMR Spectroscopy Study

Published on: August 15, 2016

The diffusion NMR studies of crown ethers-cyclodextrin complexation process.

Błazej Gierczyk¹, Barbara Nowak-Wydra, Grzegorz Schroeder

¹Faculty of Chemistry, A. Mickiewicz University, Grunwaldzka 6, 60 780 Poznań, Poland. hanuman@amu.edu.pl

Magnetic Resonance in Chemistry : MRC

|May 18, 2010

Summary

This summary is machine-generated.

Crown ethers and cyclodextrins form complexes, studied via diffusion measurements. Structural parameters like ring diameter and symmetry influence molecular interactions and complex formation.

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Area of Science:

Supramolecular Chemistry
Physical Chemistry

Background:

Crown ethers and cyclodextrins are macrocyclic hosts with significant applications.
Understanding host-guest complexation is crucial for molecular recognition and material science.

Purpose of the Study:

To investigate the formation and structure of complexes between crown ethers and cyclodextrins.
To elucidate the relationship between structural parameters and the interaction tendencies within these complexes.

Main Methods:

Utilized diffusion measurements to study complex formation.
Employed theoretical calculations to propose complex structures.

Main Results:

Diffusion measurements provided insights into the dynamics of complex formation.
Theoretical models successfully predicted complex structures based on experimental data.
Identified key structural parameters governing molecular interactions.

Conclusions:

Crown ether-cyclodextrin complexation is influenced by structural features.
Ring diameter and symmetry are critical determinants of interaction strength and complex stability.
This study enhances the understanding of supramolecular assembly in host-guest systems.