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Related Concept Videos

Crown Ethers02:36

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.
Electrophilic Aromatic Substitution: Fluorination and Iodination of Benzene01:13

Electrophilic Aromatic Substitution: Fluorination and Iodination of Benzene

Bromination and chlorination of aromatic rings by electrophilic aromatic substitution reactions are easily achieved, but fluorination and iodination are difficult to achieve. Fluorine is so reactive that its reaction with benzene is difficult to control, resulting in poor yields of monofluoroaromatic products. To address this, Selectfluor reagent is used as a fluorine source in which a fluorine atom is bonded to a positively charged nitrogen.
Base-Catalyzed Ring-Opening of Epoxides02:26

Base-Catalyzed Ring-Opening of Epoxides

Due to their highly strained structures, epoxides can readily undergo ring-opening reactions through nucleophilic substitution, either in the presence of an acid or a base. The nucleophilic substitution reactions in the presence of acid are called acid-catalyzed ring-opening reactions, and nucleophilic substitution reactions in the presence of a base are called base-catalyzed ring-opening reactions. Epoxides undergo base-catalyzed ring-opening reactions in the presence of a strong nucleophile...
Acid-Catalyzed Ring-Opening of Epoxides02:24

Acid-Catalyzed Ring-Opening of Epoxides

Epoxides that are three-membered ring systems are more reactive than other cyclic and acyclic ethers. The high reactivity of epoxides originates from the strain present in the ring. This ring strain acts as a driving force for epoxides to undergo ring-opening reactions either with halogen acids or weak nucleophiles in the presence of mild acid. The acid catalyst converts the epoxide oxygen, a poor leaving group, into an oxonium ion, a better leaving group, making the reaction feasible. The...
Photoluminescence: Applications01:14

Photoluminescence: Applications

Photoluminescence offers a wide range of applications due to its inherent sensitivity and selectivity. This technique allows for both direct and indirect analyses of the analyte. Direct quantitative analysis is possible when the analyte exhibits a favorable quantum yield for fluorescence or phosphorescence. However, an indirect analysis may be feasible if the analyte is not fluorescent or phosphorescent, or if the quantum yield is unfavorable. Indirect methods include reacting the analyte with...
ortho–para-Directing Activators: –CH3, –OH, –⁠NH2, –OCH301:11

ortho–para-Directing Activators: –CH3, –OH, –⁠NH2, –OCH3

All ortho–para directors, excluding halogens, are activating groups. These groups donate electrons to the ring, making the ring carbons electron-rich. Consequently, the reactivity of the aromatic ring towards electrophilic substitution increases. For instance, the nitration of anisole is about 10,000 times faster than the nitration of benzene. The electron-donating effect of the methoxy group in anisole activates the ortho and para positions on the ring and stabilizes the corresponding...

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Synthesis of Cyclic Polymers and Characterization of Their Diffusive Motion in the Melt State at the Single Molecule Level
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Synthesis of Cyclic Polymers and Characterization of Their Diffusive Motion in the Melt State at the Single Molecule Level

Published on: September 26, 2016

Synthesis and analytical capabilities of fluorogenic ring-substituted crown ethers.

H Forrest1, G E Pacey

  • 1Department of Chemistry, Miami University, Oxford, OH 45056, U.S.A.

Talanta
|January 1, 1989
PubMed
Summary

Fluorogenic crown ethers show increased fluorescence upon complexation. However, this enhancement comes at the cost of reduced selectivity for specific alkali metals.

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Area of Science:

  • Analytical Chemistry
  • Supramolecular Chemistry
  • Organic Chemistry

Background:

  • Fluorogenic crown ethers are compounds that exhibit fluorescence.
  • Traditional fluorogenic crown ethers often lack sufficient signal for analytical applications.
  • Crown ethers are known for their ability to selectively bind metal cations.

Purpose of the Study:

  • To investigate the effect of incorporating fluorogens within the crown ether ring on fluorescence intensity.
  • To evaluate the selectivity of these modified fluorogenic crown ethers for alkali metals.

Main Methods:

  • Synthesis of fluorogenic crown ethers with integrated fluorogen units.
  • Spectroscopic analysis (fluorescence spectroscopy) to measure fluorescence intensity upon complexation with alkali metal ions.
  • Selectivity studies involving competition assays with various alkali metal ions.

Main Results:

  • Incorporating fluorogens into the crown ether ring significantly enhances fluorescence intensity (2-6 times the blank).
  • The modified fluorogenic crown ethers complex with a range of alkali metals.
  • A notable decrease in selectivity was observed, with broad complexation across different alkali metal ions.

Conclusions:

  • Fluorogen incorporation boosts the analytical signal of crown ethers.
  • The enhanced fluorescence comes with a trade-off, leading to diminished selectivity for specific alkali metal detection.
  • Further research may be needed to balance signal enhancement and selectivity in fluorogenic crown ether design.