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Radical Reactivity: Overview01:11

Radical Reactivity: Overview

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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...
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Radical Reactivity: Electrophilic Radicals01:02

Radical Reactivity: Electrophilic Radicals

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Radicals adjacent to electron‐withdrawing groups are called electrophilic radicals. These radicals readily react with nucleophilic alkenes. For example, the malonate radical, in which the radical center is flanked by two electron‐withdrawing groups, reacts readily with butyl vinyl ether, which consists of an electron‐donating oxygen substituent. The reaction between electrophilic malonate radical and nucleophilic vinyl ether is favored because the radical has a...
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Radical Reactivity: Steric Effects01:10

Radical Reactivity: Steric Effects

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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...
2.6K
Radical Chain-Growth Polymerization: Overview01:10

Radical Chain-Growth Polymerization: Overview

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Chain-growth or addition polymerization is successive addition reactions of monomers with a polymer chain. In radical chain-growth polymerization, the reaction proceeds via a free-radical intermediate. The free radical is formed from radical initiators, which spontaneously generate free radicals by homolytic fission. Organic peroxides (such as dibenzoyl peroxide, as shown in Figure 1) or azo compounds are popular radical initiators. A low concentration ratio of radical initiator to monomer is...
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Radical Reactivity: Nucleophilic Radicals01:16

Radical Reactivity: Nucleophilic Radicals

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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...
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Free-Radical Chain Reaction and Polymerization of Alkenes02:35

Free-Radical Chain Reaction and Polymerization of Alkenes

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The conversion of alkenes to macromolecules called polymers is a reaction of high commercial importance. The structure of the polymer is defined by a repeating unit, while the terminal groups are considered insignificant. The average degree of polymerization represents the number of repeating units in the polymer molecule and is denoted by the subscript n.
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Updated: Feb 24, 2026

Synthesis of pH Dependent Pyrazole, Imidazole, and Isoindolone Dipyrrinone Fluorophores using a Claisen-Schmidt Condensation Approach
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Poliradicaloides macrocíclicos basados en el fluorenilo

Xuefeng Lu1, Sangsu Lee2, Yongseok Hong2

  • 1Department of Chemistry, National University of Singapore , 3 Science Drive 3, 117543 Singapore.

Journal of the American Chemical Society
|August 26, 2017
PubMed
Resumen
Este resumen es generado por máquina.

Se sintetizaron poliradicaloides macrocíclicos estables con interacciones de espín ajustables. La geometría tiene un impacto significativo en sus propiedades electrónicas y ópticas, y algunas muestran antiaromaticidad.

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Área de la Ciencia:

  • Química orgánica
  • Ciencias de los materiales
  • Química supramolecular

Sus antecedentes:

  • El control de las interacciones espín-espín intramoleculares en los poliradicaloides es crucial para el desarrollo de materiales orgánicos avanzados.
  • Los poliradicaloides macrocíclicos estables y bien definidos son difíciles de sintetizar y caracterizar.

Objetivo del estudio:

  • Síntesis y caracterización de nuevos poliradicaloides macrocíclicos basados en el fluorenilo.
  • Investigar el efecto de la geometría molecular, incluida la presencia de espaciadores de etileno, en sus propiedades electrónicas y magnéticas.
  • Comparar las propiedades de los poliradicaloides macrocíclicos con sus homólogos lineales.

Principales métodos:

  • Desarrollo de tres vías sintéticas distintas para los polirradicaloides macrocíclicos.
  • Purificación mediante cromatografía en columna de gel de sílice estándar.
  • Análisis computacional mediante el método de giro en el espacio activo restringido (RASSF).
  • Caracterización de las propiedades magnéticas mediante mediciones de dispositivos de interferencia cuántica superconductores (SQUID).
  • Evaluación de las propiedades ópticas y electroquímicas.

Principales resultados:

  • Síntesis exitosa de dos series de poliradicaloides macrocíclicos estables basados en fluorenilo (FR-MCn y MC-FnAn).
  • Caracter poliradical moderado calculado debido a las interacciones antiferromagnéticas espín-espín.
  • Se ha demostrado la influencia significativa de la geometría (ángulo de distorsión, espaciador de etileno) en el carácter poliradical, las energías de excitación y las propiedades de absorción.
  • Caracter global antiaromático identificado en los tetrámeros macrocíclicos (FR-MC4 y MC-F4A4) resultantes de la conjugación cíclica π.

Conclusiones:

  • Las estrategias sintéticas proporcionan acceso a poliradicaloides macrocíclicos estables bajo condiciones ambientales.
  • La geometría molecular es un determinante clave de las propiedades electrónicas, ópticas y magnéticas de estos sistemas.
  • El descubrimiento de la antiaromaticidad en estructuras macrocíclicas específicas abre nuevas vías para explorar materiales electrónicos.