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Related Concept Videos

Radical Reactivity: Steric Effects01:10

Radical Reactivity: Steric Effects

The presence of electron-donating, electron-withdrawing, or conjugating groups adjacent to a radical center, imparts electronic stabilization to the radicals. Examples of such electronically-stabilized radicals are triphenylmethyl, tetramethylpiperidine‐N‐oxide, and 2,2‐diphenyl‐1‐picrylhydrazyl. These radicals are remarkably stable and are known as persistent radicals. Some of the persistent radicals can even be isolated and purified.
Along with electronic factors, steric factors also account...
Radicals: Electronic Structure and Geometry01:07

Radicals: Electronic Structure and Geometry

This lesson delves into the geometry of a radical, which is influenced by the electronic structure of the molecule. The principle is similar to that of a lone pair, where the unpaired electron influences the geometry at the radical center.
Accordingly, the structure of a trivalent radical lies between the geometries of carbocations and carbanions. An sp2-hybridized carbocation is trigonal planar, while an sp3-hybridized carbanion is trigonal pyramidal. Here, the difference in geometry is...
Radical Reactivity: Overview01:11

Radical Reactivity: Overview

Radicals, the highly reactive species, gain stability by undergoing three different reactions. The first reaction involves a radical-radical coupling, in which a radical combines with another radical, forming a spin‐paired molecule. The second reaction is between a radical and a spin‐paired molecule, generating a new radical and a new spin‐paired molecule. The third reaction is radical decomposition in a unimolecular reaction, forming a new radical and a spin‐paired molecule. These three...
Radical Halogenation: Stereochemistry01:33

Radical Halogenation: Stereochemistry

Stereochemistry is the study of the different spatial arrangements of atoms in a given molecule. The stereochemistry of radical halogenations can be understood from three different situations:
Halogenation to form a new chiral center:
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...
Radical Reactivity: Nucleophilic Radicals01:16

Radical Reactivity: Nucleophilic Radicals

Radicals adjacent to electron-donating groups are called nucleophilic radicals. These radicals readily react with electrophilic alkenes. The SOMO–LUMO interactions are the driving force for the reaction, where the high-energy SOMO of the electron-rich, nucleophilic radicals interacts with the low-energy LUMO of the electron-deficient, electrophilic alkenes. Such SOMO–LUMO interactions are the basis of reactive radical traps, affecting the selectivity in radical reactions. For instance, consider...

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Related Experiment Video

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Rapid Scan Electron Paramagnetic Resonance Opens New Avenues for Imaging Physiologically Important Parameters In Vivo
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Published on: September 26, 2016

Stable diarylnitroxide diradical with triplet ground state.

Andrzej Rajca1, Kouichi Shiraishi, Suchada Rajca

  • 1Department of Chemistry, University of Nebraska, Lincoln, NE 68588-0304, USA. arajca1@unl.edu

Chemical Communications (Cambridge, England)
|July 15, 2009
PubMed
Summary

Researchers isolated a stable nitroxide diradical, a diarylnitroxide diradical, which exhibits a triplet ground state and strong ferromagnetic coupling at room temperature.

Area of Science:

  • Organic chemistry
  • Materials science

Background:

  • Nitroxide radicals are known for their unique electronic properties.
  • The development of stable organic diradicals is a key area in radical chemistry.

Purpose of the Study:

  • To synthesize and characterize the first isolated diarylnitroxide diradical.
  • To investigate the magnetic properties and stability of this novel diradical.

Main Methods:

  • Isolation and purification of the diarylnitroxide diradical.
  • Solid-state stability studies at room temperature.
  • Magnetic susceptibility measurements to determine ground state and coupling.

Main Results:

  • The diarylnitroxide diradical was successfully isolated and found to be stable in the solid state at room temperature.

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  • The compound exhibits a triplet ground state.
  • Strong ferromagnetic coupling was observed in the diradical.

    • Conclusions:

    • The successful isolation of a stable diarylnitroxide diradical opens new avenues for organic radical materials.
    • The observed triplet ground state and ferromagnetic coupling highlight its potential applications in molecular magnetism.