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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.
Thermal and Photochemical Electrocyclic Reactions: Overview01:26

Thermal and Photochemical Electrocyclic Reactions: Overview

Electrocyclic reactions are reversible reactions. They involve an intramolecular cyclization or ring-opening of a conjugated polyene. Shown below are two examples of electrocyclic reactions. In the first reaction, the formation of the cyclic product is favored. In contrast, in the second reaction, ring-opening is favored due to the high ring strain associated with cyclobutene formation.
Thermal Electrocyclic Reactions: Stereochemistry01:17

Thermal Electrocyclic Reactions: Stereochemistry

The stereochemistry of electrocyclic reactions is strongly influenced by the orbital symmetry of the polyene HOMO. Under thermal conditions, the reaction proceeds via the ground-state HOMO.
Selection Rules: Thermal Activation
Conjugated systems containing an even number of π-electron pairs undergo a conrotatory ring closure. For example, thermal electrocyclization of (2E,4E)-2,4-hexadiene, a conjugated diene containing two π-electron pairs, gives trans-3,4-dimethylcyclobutene.
Photochemical Electrocyclic Reactions: Stereochemistry01:26

Photochemical Electrocyclic Reactions: Stereochemistry

The absorption of UV–visible light by conjugated systems causes the promotion of an electron from the ground state to the excited state. Consequently, photochemical electrocyclic reactions proceed via the excited-state HOMO rather than the ground-state HOMO. Since the ground- and excited-state HOMOs have different symmetries, the stereochemical outcome of electrocyclic reactions depends on the mode of activation; i.e., thermal or photochemical.
Selection Rules: Photochemical Activation
Aromatic Hydrocarbon Cations: Structural Overview01:18

Aromatic Hydrocarbon Cations: Structural Overview

Cycloheptatriene is a neutral monocyclic unsaturated hydrocarbon that consists of an odd number of carbon atoms and an intervening sp3 carbon in the ring. The three double bonds in the ring correspond to 6 π electrons, which is a Huckel number, and therefore satisfies the criteria of 4n + 2 π electrons. However, the intervening sp3 carbon disrupts the continuous overlap of p orbitals. As a result, cycloheptatriene is not aromatic.
Removing one hydrogen from the intervening CH2 group with both...
Cationic Chain-Growth Polymerization: Mechanism00:57

Cationic Chain-Growth Polymerization: Mechanism

The cationic polymerization mechanism consists of three steps: initiation, propagation, and termination. In the initiation step of the polymerization process, the π bond of a monomer gets protonated by the Lewis acid catalyst, which is formed from boron trifluoride and water. The protonation of the π bond generates a carbocation stabilized by the electron‐donating group. In the propagation step, the π bond of the second monomer acts as a nucleophile and attacks the generated carbocation,...

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Related Experiment Video

Updated: Jun 26, 2026

Solid-state Graft Copolymer Electrolytes for Lithium Battery Applications
05:33

Solid-state Graft Copolymer Electrolytes for Lithium Battery Applications

Published on: August 12, 2013

Proton Conduction in Tröger's Base-Linked Poly(crown ether)s.

Hasmukh A Patel, John Selberg1, Dhafer Salah2

  • 1Department of Electrical Engineering , University of California Santa Cruz , Santa Cruz , California 95064 , United States.

ACS Applied Materials & Interfaces
|June 6, 2018
PubMed
Summary
This summary is machine-generated.

New polymers incorporating dibenzo[18]crown-6 (DB18C6) exhibit proton conductivity in humid conditions due to water adsorption and hydrogen bonding. These materials form stable membranes with potential applications in supramolecular chemistry.

Keywords:
Tröger’s basefuel cellmembranepoly(crown ether)proton conductionwater uptake

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Isotopic Effect in Double Proton Transfer Process of Porphycene Investigated by Enhanced QM/MM Method

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Area of Science:

  • Supramolecular Chemistry
  • Polymer Science
  • Materials Science

Background:

  • Dibenzo[18]crown-6 (DB18C6) is a key molecule in supramolecular and host-guest chemistry.
  • Proton conductivity is crucial for various energy applications.
  • Developing novel materials with tailored properties is an ongoing challenge.

Purpose of the Study:

  • To synthesize and characterize novel Tröger's base-linked polymers incorporating DB18C6.
  • To investigate the proton conductivity of these polymers under humid conditions.
  • To explore the potential applications of these new materials.

Main Methods:

  • Synthesis of poly(TBL-DB18C6)-t and poly(TBL-DB18C6)-c via in situ alkylation and cyclization.
  • Characterization of macromolecular structures using spectroscopic techniques and size-exclusion chromatography.
  • Measurement of water vapor adsorption and proton conductivity.

Main Results:

  • High-molecular-weight polymers with excellent solubility and film-forming ability were successfully synthesized.
  • The polymers exhibit significant water uptake (23 wt%) and retain adsorbed water under varying humidity.
  • Proton conductivity of 1.4 × 10⁻⁴ mS cm⁻¹ was achieved in humid environments, attributed to hydrogen bonding and proton hopping.

Conclusions:

  • Tröger's base-linked polymers with DB18C6 demonstrate promising proton conductivity for applications in humid environments.
  • The materials' robust film-forming ability and the presence of crown ether cavities open avenues for diverse applications.
  • This work expands the utility of DB18C6 in advanced functional materials.